Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

34 files changed, 4942 insertions, 0 deletions

diff --git a/python/mozboot/.ruff.toml b/python/mozboot/.ruff.toml
new file mode 100644
index 0000000000..648a1255cc
--- /dev/null
+++ b/python/mozboot/.ruff.toml
@@ -0,0 +1,4 @@
+extend = "../../pyproject.toml"
+
+[isort]
+known-first-party = ["mozboot"]
diff --git a/python/mozboot/README.rst b/python/mozboot/README.rst
new file mode 100644
index 0000000000..97dc3c97b2
--- /dev/null
+++ b/python/mozboot/README.rst
@@ -0,0 +1,20 @@
+mozboot - Bootstrap your system to build Mozilla projects
+=========================================================
+
+This package contains code used for bootstrapping a system to build
+mozilla-central.
+
+This code is not part of the build system per se. Instead, it is related
+to everything up to invoking the actual build system.
+
+If you have a copy of the source tree, you run:
+
+    python bin/bootstrap.py
+
+If you don't have a copy of the source tree, you can run:
+
+    curl https://hg.mozilla.org/mozilla-central/raw-file/default/python/mozboot/bin/bootstrap.py -o bootstrap.py
+    python bootstrap.py
+
+The bootstrap script will download everything it needs from hg.mozilla.org
+automatically!
diff --git a/python/mozboot/bin/bootstrap.py b/python/mozboot/bin/bootstrap.py
new file mode 100755
index 0000000000..733042bbc5
--- /dev/null
+++ b/python/mozboot/bin/bootstrap.py
@@ -0,0 +1,439 @@
+#!/usr/bin/env python3
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This script provides one-line bootstrap support to configure systems to build
+# the tree. It does so by cloning the repo before calling directly into `mach
+# bootstrap`.
+
+# Note that this script can't assume anything in particular about the host
+# Python environment (except that it's run with a sufficiently recent version of
+# Python 3), so we are restricted to stdlib modules.
+
+import sys
+
+major, minor = sys.version_info[:2]
+if (major < 3) or (major == 3 and minor < 6):
+    print(
+        "Bootstrap currently only runs on Python 3.6+."
+        "Please try re-running with python3.6+."
+    )
+    sys.exit(1)
+
+import ctypes
+import os
+import shutil
+import subprocess
+import tempfile
+from optparse import OptionParser
+from pathlib import Path
+
+CLONE_MERCURIAL_PULL_FAIL = """
+Failed to pull from hg.mozilla.org.
+
+This is most likely because of unstable network connection.
+Try running `cd %s && hg pull https://hg.mozilla.org/mozilla-unified` manually,
+or download a mercurial bundle and use it:
+https://firefox-source-docs.mozilla.org/contributing/vcs/mercurial_bundles.html"""
+
+WINDOWS = sys.platform.startswith("win32") or sys.platform.startswith("msys")
+VCS_HUMAN_READABLE = {
+    "hg": "Mercurial",
+    "git": "Git",
+}
+
+
+def which(name):
+    """Python implementation of which.
+
+    It returns the path of an executable or None if it couldn't be found.
+    """
+    search_dirs = os.environ["PATH"].split(os.pathsep)
+    potential_names = [name]
+    if WINDOWS:
+        potential_names.insert(0, name + ".exe")
+
+    for path in search_dirs:
+        for executable_name in potential_names:
+            test = Path(path) / executable_name
+            if test.is_file() and os.access(test, os.X_OK):
+                return test
+
+    return None
+
+
+def validate_clone_dest(dest: Path):
+    dest = dest.resolve()
+
+    if not dest.exists():
+        return dest
+
+    if not dest.is_dir():
+        print(f"ERROR! Destination {dest} exists but is not a directory.")
+        return None
+
+    if not any(dest.iterdir()):
+        return dest
+    else:
+        print(f"ERROR! Destination directory {dest} exists but is nonempty.")
+        print(
+            f"To re-bootstrap the existing checkout, go into '{dest}' and run './mach bootstrap'."
+        )
+        return None
+
+
+def input_clone_dest(vcs, no_interactive):
+    repo_name = "mozilla-unified"
+    print(f"Cloning into {repo_name} using {VCS_HUMAN_READABLE[vcs]}...")
+    while True:
+        dest = None
+        if not no_interactive:
+            dest = input(
+                f"Destination directory for clone (leave empty to use "
+                f"default destination of {repo_name}): "
+            ).strip()
+        if not dest:
+            dest = repo_name
+        dest = validate_clone_dest(Path(dest).expanduser())
+        if dest:
+            return dest
+        if no_interactive:
+            return None
+
+
+def hg_clone_firefox(hg: Path, dest: Path, head_repo, head_rev):
+    # We create an empty repo then modify the config before adding data.
+    # This is necessary to ensure storage settings are optimally
+    # configured.
+    args = [
+        str(hg),
+        # The unified repo is generaldelta, so ensure the client is as
+        # well.
+        "--config",
+        "format.generaldelta=true",
+        "init",
+        str(dest),
+    ]
+    res = subprocess.call(args)
+    if res:
+        print("unable to create destination repo; please try cloning manually")
+        return None
+
+    # Strictly speaking, this could overwrite a config based on a template
+    # the user has installed. Let's pretend this problem doesn't exist
+    # unless someone complains about it.
+    with open(dest / ".hg" / "hgrc", "a") as fh:
+        fh.write("[paths]\n")
+        fh.write("default = https://hg.mozilla.org/mozilla-unified\n")
+        fh.write("\n")
+
+        # The server uses aggressivemergedeltas which can blow up delta chain
+        # length. This can cause performance to tank due to delta chains being
+        # too long. Limit the delta chain length to something reasonable
+        # to bound revlog read time.
+        fh.write("[format]\n")
+        fh.write("# This is necessary to keep performance in check\n")
+        fh.write("maxchainlen = 10000\n")
+
+    # Pulling a specific revision into an empty repository induces a lot of
+    # load on the Mercurial server, so we always pull from mozilla-unified (which,
+    # when done from an empty repository, is equivalent to a clone), and then pull
+    # the specific revision we want (if we want a specific one, otherwise we just
+    # use the "central" bookmark), at which point it will be an incremental pull,
+    # that the server can process more easily.
+    # This is the same thing that robustcheckout does on automation.
+    res = subprocess.call(
+        [str(hg), "pull", "https://hg.mozilla.org/mozilla-unified"], cwd=str(dest)
+    )
+    if not res and head_repo:
+        res = subprocess.call(
+            [str(hg), "pull", head_repo, "-r", head_rev], cwd=str(dest)
+        )
+    print("")
+    if res:
+        print(CLONE_MERCURIAL_PULL_FAIL % dest)
+        return None
+
+    head_rev = head_rev or "central"
+    print(f'updating to "{head_rev}" - the development head of Gecko and Firefox')
+    res = subprocess.call([str(hg), "update", "-r", head_rev], cwd=str(dest))
+    if res:
+        print(
+            f"error updating; you will need to `cd {dest} && hg update -r central` "
+            "manually"
+        )
+    return dest
+
+
+def git_clone_firefox(git: Path, dest: Path, watchman: Path, head_repo, head_rev):
+    tempdir = None
+    cinnabar = None
+    env = dict(os.environ)
+    try:
+        cinnabar = which("git-cinnabar")
+        if not cinnabar:
+            from urllib.request import urlopen
+
+            cinnabar_url = "https://github.com/glandium/git-cinnabar/"
+            # If git-cinnabar isn't installed already, that's fine; we can
+            # download a temporary copy. `mach bootstrap` will install a copy
+            # in the state dir; we don't want to copy all that logic to this
+            # tiny bootstrapping script.
+            tempdir = Path(tempfile.mkdtemp())
+            with open(tempdir / "download.py", "wb") as fh:
+                shutil.copyfileobj(
+                    urlopen(f"{cinnabar_url}/raw/master/download.py"), fh
+                )
+
+            subprocess.check_call(
+                [sys.executable, str(tempdir / "download.py")],
+                cwd=str(tempdir),
+            )
+            env["PATH"] = str(tempdir) + os.pathsep + env["PATH"]
+            print(
+                "WARNING! git-cinnabar is required for Firefox development  "
+                "with git. After the clone is complete, the bootstrapper "
+                "will ask if you would like to configure git; answer yes, "
+                "and be sure to add git-cinnabar to your PATH according to "
+                "the bootstrapper output."
+            )
+
+        # We're guaranteed to have `git-cinnabar` installed now.
+        # Configure git per the git-cinnabar requirements.
+        subprocess.check_call(
+            [
+                str(git),
+                "clone",
+                "--no-checkout",
+                "hg::https://hg.mozilla.org/mozilla-unified",
+                str(dest),
+            ],
+            env=env,
+        )
+        subprocess.check_call(
+            [str(git), "config", "fetch.prune", "true"], cwd=str(dest), env=env
+        )
+        subprocess.check_call(
+            [str(git), "config", "pull.ff", "only"], cwd=str(dest), env=env
+        )
+
+        if head_repo:
+            subprocess.check_call(
+                [str(git), "cinnabar", "fetch", f"hg::{head_repo}", head_rev],
+                cwd=str(dest),
+                env=env,
+            )
+
+        subprocess.check_call(
+            [str(git), "checkout", "FETCH_HEAD" if head_rev else "bookmarks/central"],
+            cwd=str(dest),
+            env=env,
+        )
+
+        watchman_sample = dest / ".git/hooks/fsmonitor-watchman.sample"
+        # Older versions of git didn't include fsmonitor-watchman.sample.
+        if watchman and watchman_sample.exists():
+            print("Configuring watchman")
+            watchman_config = dest / ".git/hooks/query-watchman"
+            if not watchman_config.exists():
+                print(f"Copying {watchman_sample} to {watchman_config}")
+                copy_args = [
+                    "cp",
+                    ".git/hooks/fsmonitor-watchman.sample",
+                    ".git/hooks/query-watchman",
+                ]
+                subprocess.check_call(copy_args, cwd=str(dest))
+
+            config_args = [
+                str(git),
+                "config",
+                "core.fsmonitor",
+                ".git/hooks/query-watchman",
+            ]
+            subprocess.check_call(config_args, cwd=str(dest), env=env)
+        return dest
+    finally:
+        if tempdir:
+            shutil.rmtree(str(tempdir))
+
+
+def add_microsoft_defender_antivirus_exclusions(dest, no_system_changes):
+    if no_system_changes:
+        return
+
+    if not WINDOWS:
+        return
+
+    powershell_exe = which("powershell")
+
+    if not powershell_exe:
+        return
+
+    def print_attempt_exclusion(path):
+        print(
+            f"Attempting to add exclusion path to Microsoft Defender Antivirus for: {path}"
+        )
+
+    powershell_exe = str(powershell_exe)
+    paths = []
+
+    # mozilla-unified / clone dest
+    repo_dir = Path.cwd() / dest
+    paths.append(repo_dir)
+    print_attempt_exclusion(repo_dir)
+
+    # MOZILLABUILD
+    mozillabuild_dir = os.getenv("MOZILLABUILD")
+    if mozillabuild_dir:
+        paths.append(mozillabuild_dir)
+        print_attempt_exclusion(mozillabuild_dir)
+
+    # .mozbuild
+    mozbuild_dir = Path.home() / ".mozbuild"
+    paths.append(mozbuild_dir)
+    print_attempt_exclusion(mozbuild_dir)
+
+    args = ";".join(f"Add-MpPreference -ExclusionPath '{path}'" for path in paths)
+    command = f'-Command "{args}"'
+
+    # This will attempt to run as administrator by triggering a UAC prompt
+    # for admin credentials. If "No" is selected, no exclusions are added.
+    ctypes.windll.shell32.ShellExecuteW(None, "runas", powershell_exe, command, None, 0)
+
+
+def clone(options):
+    vcs = options.vcs
+    no_interactive = options.no_interactive
+    no_system_changes = options.no_system_changes
+
+    if vcs == "hg":
+        hg = which("hg")
+        if not hg:
+            print("Mercurial is not installed. Mercurial is required to clone Firefox.")
+            try:
+                # We're going to recommend people install the Mercurial package with
+                # pip3. That will work if `pip3` installs binaries to a location
+                # that's in the PATH, but it might not be. To help out, if we CAN
+                # import "mercurial" (in which case it's already been installed),
+                # offer that as a solution.
+                import mercurial  # noqa: F401
+
+                print(
+                    "Hint: have you made sure that Mercurial is installed to a "
+                    "location in your PATH?"
+                )
+            except ImportError:
+                print("Try installing hg with `pip3 install Mercurial`.")
+            return None
+        binary = hg
+    else:
+        binary = which(vcs)
+        if not binary:
+            print("Git is not installed.")
+            print("Try installing git using your system package manager.")
+            return None
+
+    dest = input_clone_dest(vcs, no_interactive)
+    if not dest:
+        return None
+
+    add_microsoft_defender_antivirus_exclusions(dest, no_system_changes)
+
+    print(f"Cloning Firefox {VCS_HUMAN_READABLE[vcs]} repository to {dest}")
+
+    head_repo = os.environ.get("GECKO_HEAD_REPOSITORY")
+    head_rev = os.environ.get("GECKO_HEAD_REV")
+
+    if vcs == "hg":
+        return hg_clone_firefox(binary, dest, head_repo, head_rev)
+    else:
+        watchman = which("watchman")
+        return git_clone_firefox(binary, dest, watchman, head_repo, head_rev)
+
+
+def bootstrap(srcdir: Path, application_choice, no_interactive, no_system_changes):
+    args = [sys.executable, "mach"]
+
+    if no_interactive:
+        # --no-interactive is a global argument, not a command argument,
+        # so it needs to be specified before "bootstrap" is appended.
+        args += ["--no-interactive"]
+
+    args += ["bootstrap"]
+
+    if application_choice:
+        args += ["--application-choice", application_choice]
+    if no_system_changes:
+        args += ["--no-system-changes"]
+
+    print("Running `%s`" % " ".join(args))
+    return subprocess.call(args, cwd=str(srcdir))
+
+
+def main(args):
+    parser = OptionParser()
+    parser.add_option(
+        "--application-choice",
+        dest="application_choice",
+        help='Pass in an application choice (see "APPLICATIONS" in '
+        "python/mozboot/mozboot/bootstrap.py) instead of using the "
+        "default interactive prompt.",
+    )
+    parser.add_option(
+        "--vcs",
+        dest="vcs",
+        default="hg",
+        choices=["git", "hg"],
+        help="VCS (hg or git) to use for downloading the source code, "
+        "instead of using the default interactive prompt.",
+    )
+    parser.add_option(
+        "--no-interactive",
+        dest="no_interactive",
+        action="store_true",
+        help="Answer yes to any (Y/n) interactive prompts.",
+    )
+    parser.add_option(
+        "--no-system-changes",
+        dest="no_system_changes",
+        action="store_true",
+        help="Only executes actions that leave the system " "configuration alone.",
+    )
+
+    options, leftover = parser.parse_args(args)
+    try:
+        srcdir = clone(options)
+        if not srcdir:
+            return 1
+        print("Clone complete.")
+        print(
+            "If you need to run the tooling bootstrapping again, "
+            "then consider running './mach bootstrap' instead."
+        )
+        if not options.no_interactive:
+            remove_bootstrap_file = input(
+                "Unless you are going to have more local copies of Firefox source code, "
+                "this 'bootstrap.py' file is no longer needed and can be deleted. "
+                "Clean up the bootstrap.py file? (Y/n)"
+            )
+            if not remove_bootstrap_file:
+                remove_bootstrap_file = "y"
+        if options.no_interactive or remove_bootstrap_file == "y":
+            try:
+                Path(sys.argv[0]).unlink()
+            except FileNotFoundError:
+                print("File could not be found !")
+        return bootstrap(
+            srcdir,
+            options.application_choice,
+            options.no_interactive,
+            options.no_system_changes,
+        )
+    except Exception:
+        print("Could not bootstrap Firefox! Consider filing a bug.")
+        raise
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))
diff --git a/python/mozboot/mozboot/__init__.py b/python/mozboot/mozboot/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/python/mozboot/mozboot/__init__.py
diff --git a/python/mozboot/mozboot/android-avds/arm.json b/python/mozboot/mozboot/android-avds/arm.json
new file mode 100644
index 0000000000..756018631c
--- /dev/null
+++ b/python/mozboot/mozboot/android-avds/arm.json
@@ -0,0 +1,27 @@
+{
+    "emulator_package": "system-images;android-24;default;armeabi-v7a",
+    "emulator_avd_name": "mozemulator-armeabi-v7a",
+    "emulator_extra_args": [
+        "-skip-adb-auth",
+        "-verbose",
+        "-show-kernel",
+        "-ranchu",
+        "-selinux", "permissive",
+        "-memory", "3072",
+        "-cores", "4",
+        "-skin", "800x1280",
+        "-gpu", "on",
+        "-no-snapstorage",
+        "-no-snapshot",
+        "-no-window",
+        "-no-accel",
+        "-prop", "ro.test_harness=true"
+    ],
+    "emulator_extra_config": {
+        "hw.keyboard": "yes",
+        "hw.lcd.density": "320",
+        "disk.dataPartition.size": "4000MB",
+        "sdcard.size": "600M"
+    },
+    "emulator_prewarm": false
+}
diff --git a/python/mozboot/mozboot/android-avds/arm64.json b/python/mozboot/mozboot/android-avds/arm64.json
new file mode 100644
index 0000000000..767f9299d4
--- /dev/null
+++ b/python/mozboot/mozboot/android-avds/arm64.json
@@ -0,0 +1,27 @@
+{
+    "emulator_package": "system-images;android-30;default;arm64-v8a",
+    "emulator_avd_name": "mozemulator-arm64",
+    "emulator_extra_args": [
+        "-skip-adb-auth",
+        "-verbose",
+        "-show-kernel",
+        "-ranchu",
+        "-selinux", "permissive",
+        "-memory", "3072",
+        "-cores", "4",
+        "-skin", "800x1280",
+        "-gpu", "on",
+        "-no-snapstorage",
+        "-no-snapshot",
+        "-no-window",
+        "-no-accel",
+        "-prop", "ro.test_harness=true"
+    ],
+    "emulator_extra_config": {
+        "hw.keyboard": "yes",
+        "hw.lcd.density": "320",
+        "disk.dataPartition.size": "4000MB",
+        "sdcard.size": "600M"
+    },
+    "emulator_prewarm": false
+}
diff --git a/python/mozboot/mozboot/android-avds/x86_64.json b/python/mozboot/mozboot/android-avds/x86_64.json
new file mode 100644
index 0000000000..68f99a9937
--- /dev/null
+++ b/python/mozboot/mozboot/android-avds/x86_64.json
@@ -0,0 +1,26 @@
+{
+    "emulator_package": "system-images;android-24;default;x86_64",
+    "emulator_avd_name": "mozemulator-x86_64",
+    "emulator_extra_args": [
+        "-skip-adb-auth",
+        "-verbose",
+        "-show-kernel",
+        "-ranchu",
+        "-selinux", "permissive",
+        "-memory", "3072",
+        "-cores", "4",
+        "-skin", "800x1280",
+        "-gpu", "on",
+        "-no-snapstorage",
+        "-no-snapshot",
+        "-no-window",
+        "-no-accel",
+        "-prop", "ro.test_harness=true"
+    ],
+    "emulator_extra_config": {
+        "hw.keyboard": "yes",
+        "hw.lcd.density": "320",
+        "disk.dataPartition.size": "4000MB",
+        "sdcard.size": "600M"
+    }
+}
diff --git a/python/mozboot/mozboot/android-emulator-packages.txt b/python/mozboot/mozboot/android-emulator-packages.txt
new file mode 100644
index 0000000000..3e782df670
--- /dev/null
+++ b/python/mozboot/mozboot/android-emulator-packages.txt
@@ -0,0 +1,2 @@
+platform-tools
+emulator
diff --git a/python/mozboot/mozboot/android-packages.txt b/python/mozboot/mozboot/android-packages.txt
new file mode 100644
index 0000000000..e36a300d83
--- /dev/null
+++ b/python/mozboot/mozboot/android-packages.txt
@@ -0,0 +1,4 @@
+emulator
+platform-tools
+build-tools;33.0.1
+platforms;android-33
diff --git a/python/mozboot/mozboot/android-system-images-packages.txt b/python/mozboot/mozboot/android-system-images-packages.txt
new file mode 100644
index 0000000000..86069f7680
--- /dev/null
+++ b/python/mozboot/mozboot/android-system-images-packages.txt
@@ -0,0 +1 @@
+emulator
diff --git a/python/mozboot/mozboot/android.py b/python/mozboot/mozboot/android.py
new file mode 100644
index 0000000000..26929da696
--- /dev/null
+++ b/python/mozboot/mozboot/android.py
@@ -0,0 +1,886 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this,
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import errno
+import json
+import os
+import stat
+import subprocess
+import sys
+import time
+from pathlib import Path
+from typing import Optional, Union
+
+import requests
+from tqdm import tqdm
+
+# We need the NDK version in multiple different places, and it's inconvenient
+# to pass down the NDK version to all relevant places, so we have this global
+# variable.
+from mozboot.bootstrap import MOZCONFIG_SUGGESTION_TEMPLATE
+
+NDK_VERSION = "r23c"
+CMDLINE_TOOLS_VERSION_STRING = "9.0"
+CMDLINE_TOOLS_VERSION = "9477386"
+
+BUNDLETOOL_VERSION = "1.14.1"
+
+# We expect the emulator AVD definitions to be platform agnostic
+LINUX_X86_64_ANDROID_AVD = "linux64-android-avd-x86_64-repack"
+LINUX_ARM_ANDROID_AVD = "linux64-android-avd-arm-repack"
+
+MACOS_X86_64_ANDROID_AVD = "linux64-android-avd-x86_64-repack"
+MACOS_ARM_ANDROID_AVD = "linux64-android-avd-arm-repack"
+MACOS_ARM64_ANDROID_AVD = "linux64-android-avd-arm64-repack"
+
+WINDOWS_X86_64_ANDROID_AVD = "linux64-android-avd-x86_64-repack"
+WINDOWS_ARM_ANDROID_AVD = "linux64-android-avd-arm-repack"
+
+AVD_MANIFEST_X86_64 = Path(__file__).resolve().parent / "android-avds/x86_64.json"
+AVD_MANIFEST_ARM = Path(__file__).resolve().parent / "android-avds/arm.json"
+AVD_MANIFEST_ARM64 = Path(__file__).resolve().parent / "android-avds/arm64.json"
+
+JAVA_VERSION_MAJOR = "17"
+JAVA_VERSION_MINOR = "0.7"
+JAVA_VERSION_PATCH = "7"
+
+ANDROID_NDK_EXISTS = """
+Looks like you have the correct version of the Android NDK installed at:
+%s
+"""
+
+ANDROID_SDK_EXISTS = """
+Looks like you have the Android SDK installed at:
+%s
+We will install all required Android packages.
+"""
+
+ANDROID_SDK_TOO_OLD = """
+Looks like you have an outdated Android SDK installed at:
+%s
+I can't update outdated Android SDKs to have the required 'sdkmanager'
+tool.  Move it out of the way (or remove it entirely) and then run
+bootstrap again.
+"""
+
+INSTALLING_ANDROID_PACKAGES = """
+We are now installing the following Android packages:
+%s
+You may be prompted to agree to the Android license. You may see some of
+output as packages are downloaded and installed.
+"""
+
+MOBILE_ANDROID_MOZCONFIG_TEMPLATE = """
+# Build GeckoView/Firefox for Android:
+ac_add_options --enable-project=mobile/android
+
+# Targeting the following architecture.
+# For regular phones, no --target is needed.
+# For x86 emulators (and x86 devices, which are uncommon):
+# ac_add_options --target=i686
+# For newer phones or Apple silicon
+# ac_add_options --target=aarch64
+# For x86_64 emulators (and x86_64 devices, which are even less common):
+# ac_add_options --target=x86_64
+
+{extra_lines}
+"""
+
+MOBILE_ANDROID_ARTIFACT_MODE_MOZCONFIG_TEMPLATE = """
+# Build GeckoView/Firefox for Android Artifact Mode:
+ac_add_options --enable-project=mobile/android
+ac_add_options --enable-artifact-builds
+
+{extra_lines}
+# Write build artifacts to:
+mk_add_options MOZ_OBJDIR=./objdir-frontend
+"""
+
+
+class GetNdkVersionError(Exception):
+    pass
+
+
+def install_mobile_android_sdk_or_ndk(url, path: Path):
+    """
+    Fetch an Android SDK or NDK from |url| and unpack it into the given |path|.
+
+    We use, and 'requests' respects, https. We could also include SHAs for a
+    small improvement in the integrity guarantee we give. But this script is
+    bootstrapped over https anyway, so it's a really minor improvement.
+
+    We keep a cache of the downloaded artifacts, writing into |path|/mozboot.
+    We don't yet clean the cache; it's better to waste some disk space and
+    not require a long re-download than to wipe the cache prematurely.
+    """
+
+    download_path = path / "mozboot"
+    try:
+        download_path.mkdir(parents=True)
+    except OSError as e:
+        if e.errno == errno.EEXIST and download_path.is_dir():
+            pass
+        else:
+            raise
+
+    file_name = url.split("/")[-1]
+    download_file_path = download_path / file_name
+    download(url, download_file_path)
+
+    if file_name.endswith(".tar.gz") or file_name.endswith(".tgz"):
+        cmd = ["tar", "zxf", str(download_file_path)]
+    elif file_name.endswith(".tar.bz2"):
+        cmd = ["tar", "jxf", str(download_file_path)]
+    elif file_name.endswith(".zip"):
+        cmd = ["unzip", "-q", str(download_file_path)]
+    elif file_name.endswith(".bin"):
+        # Execute the .bin file, which unpacks the content.
+        mode = os.stat(path).st_mode
+        download_file_path.chmod(mode | stat.S_IXUSR)
+        cmd = [str(download_file_path)]
+    else:
+        raise NotImplementedError(f"Don't know how to unpack file: {file_name}")
+
+    print(f"Unpacking {download_file_path}...")
+
+    with open(os.devnull, "w") as stdout:
+        # These unpack commands produce a ton of output; ignore it.  The
+        # .bin files are 7z archives; there's no command line flag to quiet
+        # output, so we use this hammer.
+        subprocess.check_call(cmd, stdout=stdout, cwd=str(path))
+
+    print(f"Unpacking {download_file_path}... DONE")
+    # Now delete the archive
+    download_file_path.unlink()
+
+
+def download(
+    url,
+    download_file_path: Path,
+):
+    with requests.Session() as session:
+        request = session.head(url, allow_redirects=True)
+        request.raise_for_status()
+        remote_file_size = int(request.headers["content-length"])
+
+        if download_file_path.is_file():
+            local_file_size = download_file_path.stat().st_size
+
+            if local_file_size == remote_file_size:
+                print(
+                    f"{download_file_path.name} already downloaded. Skipping download..."
+                )
+            else:
+                print(f"Partial download detected. Resuming download of {url}...")
+                download_internal(
+                    download_file_path,
+                    session,
+                    url,
+                    remote_file_size,
+                    local_file_size,
+                )
+        else:
+            print(f"Downloading {url}...")
+            download_internal(download_file_path, session, url, remote_file_size)
+
+
+def download_internal(
+    download_file_path: Path,
+    session,
+    url,
+    remote_file_size,
+    resume_from_byte_pos: int = None,
+):
+    """
+    Handles both a fresh SDK/NDK download, as well as resuming a partial one
+    """
+    # "ab" will behave same as "wb" if file does not exist
+    with open(download_file_path, "ab") as file:
+        # 64 KB/s should be fine on even the slowest internet connections
+        chunk_size = 1024 * 64
+        # https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Range#directives
+        resume_header = (
+            {"Range": f"bytes={resume_from_byte_pos}-"}
+            if resume_from_byte_pos
+            else None
+        )
+
+        request = session.get(
+            url, stream=True, allow_redirects=True, headers=resume_header
+        )
+
+        with tqdm(
+            total=int(remote_file_size),
+            unit="B",
+            unit_scale=True,
+            unit_divisor=1024,
+            desc=download_file_path.name,
+            initial=resume_from_byte_pos if resume_from_byte_pos else 0,
+        ) as progress_bar:
+            for chunk in request.iter_content(chunk_size):
+                file.write(chunk)
+                progress_bar.update(len(chunk))
+
+
+def get_ndk_version(ndk_path: Union[str, Path]):
+    """Given the path to the NDK, return the version as a 3-tuple of (major,
+    minor, human).
+    """
+    ndk_path = Path(ndk_path)
+    with open(ndk_path / "source.properties", "r") as f:
+        revision = [line for line in f if line.startswith("Pkg.Revision")]
+        if not revision:
+            raise GetNdkVersionError(
+                "Cannot determine NDK version from source.properties"
+            )
+        if len(revision) != 1:
+            raise GetNdkVersionError("Too many Pkg.Revision lines in source.properties")
+
+        (_, version) = revision[0].split("=")
+        if not version:
+            raise GetNdkVersionError(
+                "Unexpected Pkg.Revision line in source.properties"
+            )
+
+        (major, minor, revision) = version.strip().split(".")
+        if not major or not minor:
+            raise GetNdkVersionError("Unexpected NDK version string: " + version)
+
+        # source.properties contains a $MAJOR.$MINOR.$PATCH revision number,
+        # but the more common nomenclature that Google uses is alphanumeric
+        # version strings like "r20" or "r19c".  Convert the source.properties
+        # notation into an alphanumeric string.
+        int_minor = int(minor)
+        alphas = "abcdefghijklmnop"
+        ascii_minor = alphas[int_minor] if int_minor > 0 else ""
+        human = "r%s%s" % (major, ascii_minor)
+        return (major, minor, human)
+
+
+def get_paths(os_name):
+    mozbuild_path = Path(
+        os.environ.get("MOZBUILD_STATE_PATH", Path("~/.mozbuild").expanduser())
+    )
+    sdk_path = Path(
+        os.environ.get("ANDROID_SDK_HOME", mozbuild_path / f"android-sdk-{os_name}"),
+    )
+    ndk_path = Path(
+        os.environ.get(
+            "ANDROID_NDK_HOME", mozbuild_path / f"android-ndk-{NDK_VERSION}"
+        ),
+    )
+    avd_home_path = Path(
+        os.environ.get("ANDROID_AVD_HOME", mozbuild_path / "android-device" / "avd")
+    )
+    return mozbuild_path, sdk_path, ndk_path, avd_home_path
+
+
+def sdkmanager_tool(sdk_path: Path):
+    # sys.platform is win32 even if Python/Win64.
+    sdkmanager = "sdkmanager.bat" if sys.platform.startswith("win") else "sdkmanager"
+    return (
+        sdk_path / "cmdline-tools" / CMDLINE_TOOLS_VERSION_STRING / "bin" / sdkmanager
+    )
+
+
+def avdmanager_tool(sdk_path: Path):
+    # sys.platform is win32 even if Python/Win64.
+    sdkmanager = "avdmanager.bat" if sys.platform.startswith("win") else "avdmanager"
+    return (
+        sdk_path / "cmdline-tools" / CMDLINE_TOOLS_VERSION_STRING / "bin" / sdkmanager
+    )
+
+
+def adb_tool(sdk_path: Path):
+    adb = "adb.bat" if sys.platform.startswith("win") else "adb"
+    return sdk_path / "platform-tools" / adb
+
+
+def emulator_tool(sdk_path: Path):
+    emulator = "emulator.bat" if sys.platform.startswith("win") else "emulator"
+    return sdk_path / "emulator" / emulator
+
+
+def ensure_android(
+    os_name,
+    os_arch,
+    artifact_mode=False,
+    ndk_only=False,
+    system_images_only=False,
+    emulator_only=False,
+    avd_manifest_path: Optional[Path] = None,
+    prewarm_avd=False,
+    no_interactive=False,
+    list_packages=False,
+):
+    """
+    Ensure the Android SDK (and NDK, if `artifact_mode` is falsy) are
+    installed.  If not, fetch and unpack the SDK and/or NDK from the
+    given URLs.  Ensure the required Android SDK packages are
+    installed.
+
+    `os_name` can be 'linux', 'macosx' or 'windows'.
+    """
+    # The user may have an external Android SDK (in which case we
+    # save them a lengthy download), or they may have already
+    # completed the download. We unpack to
+    # ~/.mozbuild/{android-sdk-$OS_NAME, android-ndk-$VER}.
+    mozbuild_path, sdk_path, ndk_path, avd_home_path = get_paths(os_name)
+
+    if os_name == "macosx":
+        os_tag = "mac"
+    elif os_name == "windows":
+        os_tag = "win"
+    else:
+        os_tag = os_name
+
+    sdk_url = "https://dl.google.com/android/repository/commandlinetools-{0}-{1}_latest.zip".format(  # NOQA: E501
+        os_tag, CMDLINE_TOOLS_VERSION
+    )
+    ndk_url = android_ndk_url(os_name)
+    bundletool_url = "https://github.com/google/bundletool/releases/download/{v}/bundletool-all-{v}.jar".format(  # NOQA: E501
+        v=BUNDLETOOL_VERSION
+    )
+
+    ensure_android_sdk_and_ndk(
+        mozbuild_path,
+        os_name,
+        sdk_path=sdk_path,
+        sdk_url=sdk_url,
+        ndk_path=ndk_path,
+        ndk_url=ndk_url,
+        bundletool_url=bundletool_url,
+        artifact_mode=artifact_mode,
+        ndk_only=ndk_only,
+        emulator_only=emulator_only,
+    )
+
+    if ndk_only:
+        return
+
+    avd_manifest = None
+    if avd_manifest_path is not None:
+        with open(avd_manifest_path) as f:
+            avd_manifest = json.load(f)
+        # Some AVDs cannot be prewarmed in CI because they cannot run on linux64
+        # (like the arm64 AVD).
+        if "emulator_prewarm" in avd_manifest:
+            prewarm_avd = prewarm_avd and avd_manifest["emulator_prewarm"]
+
+    # We expect the |sdkmanager| tool to be at
+    # ~/.mozbuild/android-sdk-$OS_NAME/tools/cmdline-tools/$CMDLINE_TOOLS_VERSION_STRING/bin/sdkmanager. # NOQA: E501
+    ensure_android_packages(
+        os_name,
+        os_arch,
+        sdkmanager_tool=sdkmanager_tool(sdk_path),
+        emulator_only=emulator_only,
+        system_images_only=system_images_only,
+        avd_manifest=avd_manifest,
+        no_interactive=no_interactive,
+        list_packages=list_packages,
+    )
+
+    if emulator_only or system_images_only:
+        return
+
+    ensure_android_avd(
+        avdmanager_tool=avdmanager_tool(sdk_path),
+        adb_tool=adb_tool(sdk_path),
+        emulator_tool=emulator_tool(sdk_path),
+        avd_home_path=avd_home_path,
+        sdk_path=sdk_path,
+        no_interactive=no_interactive,
+        avd_manifest=avd_manifest,
+        prewarm_avd=prewarm_avd,
+    )
+
+
+def ensure_android_sdk_and_ndk(
+    mozbuild_path: Path,
+    os_name,
+    sdk_path: Path,
+    sdk_url,
+    ndk_path: Path,
+    ndk_url,
+    bundletool_url,
+    artifact_mode,
+    ndk_only,
+    emulator_only,
+):
+    """
+    Ensure the Android SDK and NDK are found at the given paths.  If not, fetch
+    and unpack the SDK and/or NDK from the given URLs into
+    |mozbuild_path/{android-sdk-$OS_NAME,android-ndk-$VER}|.
+    """
+
+    # It's not particularly bad to overwrite the NDK toolchain, but it does take
+    # a while to unpack, so let's avoid the disk activity if possible.  The SDK
+    # may prompt about licensing, so we do this first.
+    # Check for Android NDK only if we are not in artifact mode.
+    if not artifact_mode and not emulator_only:
+        install_ndk = True
+        if ndk_path.is_dir():
+            try:
+                _, _, human = get_ndk_version(ndk_path)
+                if human == NDK_VERSION:
+                    print(ANDROID_NDK_EXISTS % ndk_path)
+                    install_ndk = False
+            except GetNdkVersionError:
+                pass  # Just do the install.
+        if install_ndk:
+            # The NDK archive unpacks into a top-level android-ndk-$VER directory.
+            install_mobile_android_sdk_or_ndk(ndk_url, mozbuild_path)
+
+    if ndk_only:
+        return
+
+    # We don't want to blindly overwrite, since we use the
+    # |sdkmanager| tool to install additional parts of the Android
+    # toolchain.  If we overwrite, we lose whatever Android packages
+    # the user may have already installed.
+    if sdkmanager_tool(sdk_path).is_file():
+        print(ANDROID_SDK_EXISTS % sdk_path)
+    elif sdk_path.is_dir():
+        raise NotImplementedError(ANDROID_SDK_TOO_OLD % sdk_path)
+    else:
+        # The SDK archive used to include a top-level
+        # android-sdk-$OS_NAME directory; it no longer does so.  We
+        # preserve the old convention to smooth detecting existing SDK
+        # installations.
+        cmdline_tools_path = mozbuild_path / f"android-sdk-{os_name}" / "cmdline-tools"
+        install_mobile_android_sdk_or_ndk(sdk_url, cmdline_tools_path)
+        # The tools package *really* wants to be in
+        # <sdk>/cmdline-tools/$CMDLINE_TOOLS_VERSION_STRING
+        (cmdline_tools_path / "cmdline-tools").rename(
+            cmdline_tools_path / CMDLINE_TOOLS_VERSION_STRING
+        )
+        download(bundletool_url, mozbuild_path / "bundletool.jar")
+
+
+def get_packages_to_install(packages_file_content, avd_manifest):
+    packages = []
+    packages += map(lambda package: package.strip(), packages_file_content)
+    if avd_manifest is not None:
+        packages += [avd_manifest["emulator_package"]]
+    return packages
+
+
+def ensure_android_avd(
+    avdmanager_tool: Path,
+    adb_tool: Path,
+    emulator_tool: Path,
+    avd_home_path: Path,
+    sdk_path: Path,
+    no_interactive=False,
+    avd_manifest=None,
+    prewarm_avd=False,
+):
+    """
+    Use the given sdkmanager tool (like 'sdkmanager') to install required
+    Android packages.
+    """
+    if avd_manifest is None:
+        return
+
+    avd_home_path.mkdir(parents=True, exist_ok=True)
+    # The AVD needs this folder to boot, so make sure it exists here.
+    (sdk_path / "platforms").mkdir(parents=True, exist_ok=True)
+
+    avd_name = avd_manifest["emulator_avd_name"]
+    args = [
+        str(avdmanager_tool),
+        "--verbose",
+        "create",
+        "avd",
+        "--force",
+        "--name",
+        avd_name,
+        "--package",
+        avd_manifest["emulator_package"],
+    ]
+
+    if not no_interactive:
+        subprocess.check_call(args)
+        return
+
+    # Flush outputs before running sdkmanager.
+    sys.stdout.flush()
+    env = os.environ.copy()
+    env["ANDROID_AVD_HOME"] = str(avd_home_path)
+    proc = subprocess.Popen(args, stdin=subprocess.PIPE, env=env)
+    proc.communicate("no\n".encode("UTF-8"))
+
+    retcode = proc.poll()
+    if retcode:
+        cmd = args[0]
+        e = subprocess.CalledProcessError(retcode, cmd)
+        raise e
+
+    avd_path = avd_home_path / (str(avd_name) + ".avd")
+    config_file_name = avd_path / "config.ini"
+
+    print(f"Writing config at {config_file_name}")
+
+    if config_file_name.is_file():
+        with open(config_file_name, "a") as config:
+            for key, value in avd_manifest["emulator_extra_config"].items():
+                config.write("%s=%s\n" % (key, value))
+    else:
+        raise NotImplementedError(
+            f"Could not find config file at {config_file_name}, something went wrong"
+        )
+    if prewarm_avd:
+        run_prewarm_avd(adb_tool, emulator_tool, env, avd_name, avd_manifest)
+    # When running in headless mode, the emulator does not run the cleanup
+    # step, and thus doesn't delete lock files. On some platforms, left-over
+    # lock files can cause the emulator to not start, so we remove them here.
+    for lock_file in ["hardware-qemu.ini.lock", "multiinstance.lock"]:
+        lock_file_path = avd_path / lock_file
+        try:
+            lock_file_path.unlink()
+            print(f"Removed lock file {lock_file_path}")
+        except OSError:
+            # The lock file is not there, nothing to do.
+            pass
+
+
+def run_prewarm_avd(
+    adb_tool: Path,
+    emulator_tool: Path,
+    env,
+    avd_name,
+    avd_manifest,
+):
+    """
+    Ensures the emulator is fully booted to save time on future iterations.
+    """
+    args = [str(emulator_tool), "-avd", avd_name] + avd_manifest["emulator_extra_args"]
+
+    # Flush outputs before running emulator.
+    sys.stdout.flush()
+    proc = subprocess.Popen(args, env=env)
+
+    booted = False
+    for i in range(100):
+        boot_completed_cmd = [str(adb_tool), "shell", "getprop", "sys.boot_completed"]
+        completed_proc = subprocess.Popen(
+            boot_completed_cmd, env=env, stdout=subprocess.PIPE
+        )
+        try:
+            out, err = completed_proc.communicate(timeout=30)
+            boot_completed = out.decode("UTF-8").strip()
+            print("sys.boot_completed = %s" % boot_completed)
+            time.sleep(30)
+            if boot_completed == "1":
+                booted = True
+                break
+        except subprocess.TimeoutExpired:
+            # Sometimes the adb command hangs, that's ok
+            print("sys.boot_completed = Timeout")
+
+    if not booted:
+        raise NotImplementedError("Could not prewarm emulator")
+
+    # Wait until the emulator completely shuts down
+    subprocess.Popen([str(adb_tool), "emu", "kill"], env=env).wait()
+    proc.wait()
+
+
+def ensure_android_packages(
+    os_name,
+    os_arch,
+    sdkmanager_tool: Path,
+    emulator_only=False,
+    system_images_only=False,
+    avd_manifest=None,
+    no_interactive=False,
+    list_packages=False,
+):
+    """
+    Use the given sdkmanager tool (like 'sdkmanager') to install required
+    Android packages.
+    """
+
+    # This tries to install all the required Android packages.  The user
+    # may be prompted to agree to the Android license.
+    if system_images_only:
+        packages_file_name = "android-system-images-packages.txt"
+    elif emulator_only:
+        packages_file_name = "android-emulator-packages.txt"
+    else:
+        packages_file_name = "android-packages.txt"
+
+    packages_file_path = (Path(__file__).parent / packages_file_name).resolve()
+
+    with open(packages_file_path) as packages_file:
+        packages_file_content = packages_file.readlines()
+
+    packages = get_packages_to_install(packages_file_content, avd_manifest)
+    print(INSTALLING_ANDROID_PACKAGES % "\n".join(packages))
+
+    args = [str(sdkmanager_tool)]
+    if os_name == "macosx" and os_arch == "arm64":
+        # Support for Apple Silicon is still in nightly
+        args.append("--channel=3")
+    args.extend(packages)
+
+    # sdkmanager needs JAVA_HOME
+    java_bin_path = ensure_java(os_name, os_arch)
+    env = os.environ.copy()
+    env["JAVA_HOME"] = str(java_bin_path.parent)
+
+    if not no_interactive:
+        subprocess.check_call(args, env=env)
+        return
+
+    # Flush outputs before running sdkmanager.
+    sys.stdout.flush()
+    sys.stderr.flush()
+    # Emulate yes.  For a discussion of passing input to check_output,
+    # see https://stackoverflow.com/q/10103551.
+    yes = "\n".join(["y"] * 100).encode("UTF-8")
+    proc = subprocess.Popen(args, stdin=subprocess.PIPE, env=env)
+    proc.communicate(yes)
+
+    retcode = proc.poll()
+    if retcode:
+        cmd = args[0]
+        e = subprocess.CalledProcessError(retcode, cmd)
+        raise e
+    if list_packages:
+        subprocess.check_call([str(sdkmanager_tool), "--list"])
+
+
+def generate_mozconfig(os_name, artifact_mode=False):
+    moz_state_dir, sdk_path, ndk_path, avd_home_path = get_paths(os_name)
+
+    extra_lines = []
+    if extra_lines:
+        extra_lines.append("")
+
+    if artifact_mode:
+        template = MOBILE_ANDROID_ARTIFACT_MODE_MOZCONFIG_TEMPLATE
+    else:
+        template = MOBILE_ANDROID_MOZCONFIG_TEMPLATE
+
+    kwargs = dict(
+        sdk_path=sdk_path,
+        ndk_path=ndk_path,
+        avd_home_path=avd_home_path,
+        moz_state_dir=moz_state_dir,
+        extra_lines="\n".join(extra_lines),
+    )
+    return template.format(**kwargs).strip()
+
+
+def android_ndk_url(os_name, ver=NDK_VERSION):
+    # Produce a URL like
+    # 'https://dl.google.com/android/repository/android-ndk-$VER-linux.zip
+    base_url = "https://dl.google.com/android/repository/android-ndk"
+
+    if os_name == "macosx":
+        # |mach bootstrap| uses 'macosx', but Google uses 'darwin'.
+        os_name = "darwin"
+
+    return "%s-%s-%s.zip" % (base_url, ver, os_name)
+
+
+def main(argv):
+    import optparse  # No argparse, which is new in Python 2.7.
+    import platform
+
+    parser = optparse.OptionParser()
+    parser.add_option(
+        "-a",
+        "--artifact-mode",
+        dest="artifact_mode",
+        action="store_true",
+        help="If true, install only the Android SDK (and not the Android NDK).",
+    )
+    parser.add_option(
+        "--jdk-only",
+        dest="jdk_only",
+        action="store_true",
+        help="If true, install only the Java JDK.",
+    )
+    parser.add_option(
+        "--ndk-only",
+        dest="ndk_only",
+        action="store_true",
+        help="If true, install only the Android NDK (and not the Android SDK).",
+    )
+    parser.add_option(
+        "--system-images-only",
+        dest="system_images_only",
+        action="store_true",
+        help="If true, install only the system images for the AVDs.",
+    )
+    parser.add_option(
+        "--no-interactive",
+        dest="no_interactive",
+        action="store_true",
+        help="Accept the Android SDK licenses without user interaction.",
+    )
+    parser.add_option(
+        "--emulator-only",
+        dest="emulator_only",
+        action="store_true",
+        help="If true, install only the Android emulator (and not the SDK or NDK).",
+    )
+    parser.add_option(
+        "--avd-manifest",
+        dest="avd_manifest_path",
+        help="If present, generate AVD from the manifest pointed by this argument.",
+    )
+    parser.add_option(
+        "--prewarm-avd",
+        dest="prewarm_avd",
+        action="store_true",
+        help="If true, boot the AVD and wait until completed to speed up subsequent boots.",
+    )
+    parser.add_option(
+        "--list-packages",
+        dest="list_packages",
+        action="store_true",
+        help="If true, list installed packages.",
+    )
+
+    options, _ = parser.parse_args(argv)
+
+    if options.artifact_mode and options.ndk_only:
+        raise NotImplementedError("Use no options to install the NDK and the SDK.")
+
+    if options.artifact_mode and options.emulator_only:
+        raise NotImplementedError("Use no options to install the SDK and emulators.")
+
+    os_name = None
+    if platform.system() == "Darwin":
+        os_name = "macosx"
+    elif platform.system() == "Linux":
+        os_name = "linux"
+    elif platform.system() == "Windows":
+        os_name = "windows"
+    else:
+        raise NotImplementedError(
+            "We don't support bootstrapping the Android SDK (or Android "
+            "NDK) on {0} yet!".format(platform.system())
+        )
+
+    os_arch = platform.machine()
+
+    if options.jdk_only:
+        ensure_java(os_name, os_arch)
+        return 0
+
+    avd_manifest_path = (
+        Path(options.avd_manifest_path) if options.avd_manifest_path else None
+    )
+
+    ensure_android(
+        os_name,
+        os_arch,
+        artifact_mode=options.artifact_mode,
+        ndk_only=options.ndk_only,
+        system_images_only=options.system_images_only,
+        emulator_only=options.emulator_only,
+        avd_manifest_path=avd_manifest_path,
+        prewarm_avd=options.prewarm_avd,
+        no_interactive=options.no_interactive,
+        list_packages=options.list_packages,
+    )
+    mozconfig = generate_mozconfig(os_name, options.artifact_mode)
+
+    # |./mach bootstrap| automatically creates a mozconfig file for you if it doesn't
+    # exist. However, here, we don't know where the "topsrcdir" is, and it's not worth
+    # pulling in CommandContext (and its dependencies) to find out.
+    # So, instead, we'll politely ask users to create (or update) the file themselves.
+    suggestion = MOZCONFIG_SUGGESTION_TEMPLATE % ("$topsrcdir/mozconfig", mozconfig)
+    print("\n" + suggestion)
+
+    return 0
+
+
+def ensure_java(os_name, os_arch):
+    mozbuild_path, _, _, _ = get_paths(os_name)
+
+    if os_name == "macosx":
+        os_tag = "mac"
+    else:
+        os_tag = os_name
+
+    if os_arch == "x86_64":
+        arch = "x64"
+    elif os_arch == "arm64":
+        arch = "aarch64"
+    else:
+        arch = os_arch
+
+    ext = "zip" if os_name == "windows" else "tar.gz"
+
+    java_path = java_bin_path(os_name, mozbuild_path)
+    if not java_path:
+        raise NotImplementedError(f"Could not bootstrap java for {os_name}.")
+
+    if not java_path.exists():
+        # e.g. https://github.com/adoptium/temurin17-binaries/releases/
+        #      download/jdk-17.0.7%2B7/OpenJDK17U-jre_x64_linux_hotspot_17.0.7_7.tar.gz
+        java_url = (
+            "https://github.com/adoptium/temurin{major}-binaries/releases/"
+            "download/jdk-{major}.{minor}%2B{patch}/"
+            "OpenJDK{major}U-jdk_{arch}_{os}_hotspot_{major}.{minor}_{patch}.{ext}"
+        ).format(
+            major=JAVA_VERSION_MAJOR,
+            minor=JAVA_VERSION_MINOR,
+            patch=JAVA_VERSION_PATCH,
+            os=os_tag,
+            arch=arch,
+            ext=ext,
+        )
+        install_mobile_android_sdk_or_ndk(java_url, mozbuild_path / "jdk")
+    return java_path
+
+
+def java_bin_path(os_name, toolchain_path: Path):
+    # Like jdk-17.0.7+7
+    jdk_folder = "jdk-{major}.{minor}+{patch}".format(
+        major=JAVA_VERSION_MAJOR, minor=JAVA_VERSION_MINOR, patch=JAVA_VERSION_PATCH
+    )
+
+    java_path = toolchain_path / "jdk" / jdk_folder
+
+    if os_name == "macosx":
+        return java_path / "Contents" / "Home" / "bin"
+    elif os_name == "linux":
+        return java_path / "bin"
+    elif os_name == "windows":
+        return java_path / "bin"
+    else:
+        return None
+
+
+def locate_java_bin_path(host_kernel, toolchain_path: Union[str, Path]):
+    if host_kernel == "WINNT":
+        os_name = "windows"
+    elif host_kernel == "Darwin":
+        os_name = "macosx"
+    elif host_kernel == "Linux":
+        os_name = "linux"
+    else:
+        # Default to Linux
+        os_name = "linux"
+    path = java_bin_path(os_name, Path(toolchain_path))
+    if not path.is_dir():
+        raise JavaLocationFailedException(
+            f"Could not locate Java at {path}, please run "
+            "./mach bootstrap --no-system-changes"
+        )
+    return str(path)
+
+
+class JavaLocationFailedException(Exception):
+    pass
+
+
+if __name__ == "__main__":
+    sys.exit(main(sys.argv))
diff --git a/python/mozboot/mozboot/archlinux.py b/python/mozboot/mozboot/archlinux.py
new file mode 100644
index 0000000000..391bd3e3ff
--- /dev/null
+++ b/python/mozboot/mozboot/archlinux.py
@@ -0,0 +1,33 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import sys
+
+from mozboot.base import BaseBootstrapper
+from mozboot.linux_common import LinuxBootstrapper
+
+
+class ArchlinuxBootstrapper(LinuxBootstrapper, BaseBootstrapper):
+    """Archlinux experimental bootstrapper."""
+
+    def __init__(self, version, dist_id, **kwargs):
+        print("Using an experimental bootstrapper for Archlinux.", file=sys.stderr)
+        BaseBootstrapper.__init__(self, **kwargs)
+
+    def install_packages(self, packages):
+        # watchman is not available via pacman
+        packages = [p for p in packages if p != "watchman"]
+        self.pacman_install(*packages)
+
+    def upgrade_mercurial(self, current):
+        self.pacman_install("mercurial")
+
+    def pacman_install(self, *packages):
+        command = ["pacman", "-S", "--needed"]
+        if self.no_interactive:
+            command.append("--noconfirm")
+
+        command.extend(packages)
+
+        self.run_as_root(command)
diff --git a/python/mozboot/mozboot/base.py b/python/mozboot/mozboot/base.py
new file mode 100644
index 0000000000..c32946c4eb
--- /dev/null
+++ b/python/mozboot/mozboot/base.py
@@ -0,0 +1,733 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import re
+import subprocess
+import sys
+from pathlib import Path
+
+from mach.util import to_optional_path, win_to_msys_path
+from mozbuild.bootstrap import bootstrap_all_toolchains_for, bootstrap_toolchain
+from mozfile import which
+from packaging.version import Version
+
+from mozboot import rust
+from mozboot.util import (
+    MINIMUM_RUST_VERSION,
+    get_mach_virtualenv_binary,
+    http_download_and_save,
+)
+
+NO_MERCURIAL = """
+Could not find Mercurial (hg) in the current shell's path. Try starting a new
+shell and running the bootstrapper again.
+"""
+
+MERCURIAL_UNABLE_UPGRADE = """
+You are currently running Mercurial %s. Running %s or newer is
+recommended for performance and stability reasons.
+
+Unfortunately, this bootstrapper currently does not know how to automatically
+upgrade Mercurial on your machine.
+
+You can usually install Mercurial through your package manager or by
+downloading a package from http://mercurial.selenic.com/.
+"""
+
+MERCURIAL_UPGRADE_FAILED = """
+We attempted to upgrade Mercurial to a modern version (%s or newer).
+However, you appear to have version %s still.
+
+It's possible your package manager doesn't support a modern version of
+Mercurial. It's also possible Mercurial is not being installed in the search
+path for this shell. Try creating a new shell and run this bootstrapper again.
+
+If it continues to fail, consider installing Mercurial by following the
+instructions at http://mercurial.selenic.com/.
+"""
+
+MERCURIAL_INSTALL_PROMPT = """
+Mercurial releases a new version every 3 months and your distro's package
+may become out of date. This may cause incompatibility with some
+Mercurial extensions that rely on new Mercurial features. As a result,
+you may not have an optimal version control experience.
+
+To have the best Mercurial experience possible, we recommend installing
+Mercurial via the "pip" Python packaging utility. This will likely result
+in files being placed in /usr/local/bin and /usr/local/lib.
+
+How would you like to continue?
+  1. Install a modern Mercurial via pip [default]
+  2. Install a legacy Mercurial via the distro package manager
+  3. Do not install Mercurial
+Your choice: """
+
+PYTHON_UNABLE_UPGRADE = """
+You are currently running Python %s. Running %s or newer (but
+not 3.x) is required.
+
+Unfortunately, this bootstrapper does not currently know how to automatically
+upgrade Python on your machine.
+
+Please search the Internet for how to upgrade your Python and try running this
+bootstrapper again to ensure your machine is up to date.
+"""
+
+RUST_INSTALL_COMPLETE = """
+Rust installation complete. You should now have rustc and cargo
+in %(cargo_bin)s
+
+The installer tries to add these to your default shell PATH, so
+restarting your shell and running this script again may work.
+If it doesn't, you'll need to add the new command location
+manually.
+
+If restarting doesn't work, edit your shell initialization
+script, which may be called ~/.bashrc or ~/.bash_profile or
+~/.profile, and add the following line:
+
+    %(cmd)s
+
+Then restart your shell and run the bootstrap script again.
+"""
+
+RUST_NOT_IN_PATH = """
+You have some rust files in %(cargo_bin)s
+but they're not part of this shell's PATH.
+
+To add these to the PATH, edit your shell initialization
+script, which may be called ~/.bashrc or ~/.bash_profile or
+~/.profile, and add the following line:
+
+    %(cmd)s
+
+Then restart your shell and run the bootstrap script again.
+"""
+
+RUSTUP_OLD = """
+We found an executable called `rustup` which we normally use to install
+and upgrade Rust programming language support, but we didn't understand
+its output. It may be an old version, or not be the installer from
+https://rustup.rs/
+
+Please move it out of the way and run the bootstrap script again.
+Or if you prefer and know how, use the current rustup to install
+a compatible version of the Rust programming language yourself.
+"""
+
+RUST_UPGRADE_FAILED = """
+We attempted to upgrade Rust to a modern version (%s or newer).
+However, you appear to still have version %s.
+
+It's possible rustup failed. It's also possible the new Rust is not being
+installed in the search path for this shell. Try creating a new shell and
+run this bootstrapper again.
+
+If this continues to fail and you are sure you have a modern Rust on your
+system, ensure it is on the $PATH and try again. If that fails, you'll need to
+install Rust manually.
+
+We recommend the installer from https://rustup.rs/ for installing Rust,
+but you may be able to get a recent enough version from a software install
+tool or package manager on your system, or directly from https://rust-lang.org/
+"""
+
+BROWSER_ARTIFACT_MODE_MOZCONFIG = """
+# Automatically download and use compiled C++ components:
+ac_add_options --enable-artifact-builds
+""".strip()
+
+JS_MOZCONFIG_TEMPLATE = """\
+# Build only the SpiderMonkey JS test shell
+ac_add_options --enable-project=js
+"""
+
+# Upgrade Mercurial older than this.
+# This should match the OLDEST_NON_LEGACY_VERSION in
+# version-control-tools/hgext/configwizard/__init__.py.
+MODERN_MERCURIAL_VERSION = Version("4.9")
+
+# Upgrade rust older than this.
+MODERN_RUST_VERSION = Version(MINIMUM_RUST_VERSION)
+
+
+class BaseBootstrapper(object):
+    """Base class for system bootstrappers."""
+
+    def __init__(self, no_interactive=False, no_system_changes=False):
+        self.package_manager_updated = False
+        self.no_interactive = no_interactive
+        self.no_system_changes = no_system_changes
+        self.state_dir = None
+        self.srcdir = None
+
+    def validate_environment(self):
+        """
+        Called once the current firefox checkout has been detected.
+        Platform-specific implementations should check the environment and offer advice/warnings
+        to the user, if necessary.
+        """
+
+    def suggest_install_distutils(self):
+        """Called if distutils.{sysconfig,spawn} can't be imported."""
+        print(
+            "Does your distro require installing another package for distutils?",
+            file=sys.stderr,
+        )
+
+    def suggest_install_pip3(self):
+        """Called if pip3 can't be found."""
+        print(
+            "Try installing pip3 with your system's package manager.", file=sys.stderr
+        )
+
+    def install_system_packages(self):
+        """
+        Install packages shared by all applications. These are usually
+        packages required by the development (like mercurial) or the
+        build system (like autoconf).
+        """
+        raise NotImplementedError(
+            "%s must implement install_system_packages()" % __name__
+        )
+
+    def install_browser_packages(self, mozconfig_builder):
+        """
+        Install packages required to build Firefox for Desktop (application
+        'browser').
+        """
+        raise NotImplementedError(
+            "Cannot bootstrap Firefox for Desktop: "
+            "%s does not yet implement install_browser_packages()" % __name__
+        )
+
+    def ensure_browser_packages(self):
+        """
+        Install pre-built packages needed to build Firefox for Desktop (application 'browser')
+
+        Currently this is not needed and kept for compatibility with Firefox for Android.
+        """
+        pass
+
+    def ensure_js_packages(self):
+        """
+        Install pre-built packages needed to build SpiderMonkey JavaScript Engine
+
+        Currently this is not needed and kept for compatibility with Firefox for Android.
+        """
+        pass
+
+    def ensure_browser_artifact_mode_packages(self):
+        """
+        Install pre-built packages needed to build Firefox for Desktop (application 'browser')
+
+        Currently this is not needed and kept for compatibility with Firefox for Android.
+        """
+        pass
+
+    def generate_browser_mozconfig(self):
+        """
+        Print a message to the console detailing what the user's mozconfig
+        should contain.
+
+        Firefox for Desktop can in simple cases determine its build environment
+        entirely from configure.
+        """
+        pass
+
+    def install_js_packages(self, mozconfig_builder):
+        """
+        Install packages required to build SpiderMonkey JavaScript Engine
+        (application 'js').
+        """
+        return self.install_browser_packages(mozconfig_builder)
+
+    def generate_js_mozconfig(self):
+        """
+        Create a reasonable starting point for a JS shell build.
+        """
+        return JS_MOZCONFIG_TEMPLATE
+
+    def install_browser_artifact_mode_packages(self, mozconfig_builder):
+        """
+        Install packages required to build Firefox for Desktop (application
+        'browser') in Artifact Mode.
+        """
+        raise NotImplementedError(
+            "Cannot bootstrap Firefox for Desktop Artifact Mode: "
+            "%s does not yet implement install_browser_artifact_mode_packages()"
+            % __name__
+        )
+
+    def generate_browser_artifact_mode_mozconfig(self):
+        """
+        Print a message to the console detailing what the user's mozconfig
+        should contain.
+
+        Firefox for Desktop Artifact Mode needs to enable artifact builds and
+        a path where the build artifacts will be written to.
+        """
+        return BROWSER_ARTIFACT_MODE_MOZCONFIG
+
+    def install_mobile_android_packages(self, mozconfig_builder):
+        """
+        Install packages required to build GeckoView (application
+        'mobile/android').
+        """
+        raise NotImplementedError(
+            "Cannot bootstrap GeckoView/Firefox for Android: "
+            "%s does not yet implement install_mobile_android_packages()" % __name__
+        )
+
+    def ensure_mobile_android_packages(self):
+        """
+        Install pre-built packages required to run GeckoView (application 'mobile/android')
+        """
+        raise NotImplementedError(
+            "Cannot bootstrap GeckoView/Firefox for Android: "
+            "%s does not yet implement ensure_mobile_android_packages()" % __name__
+        )
+
+    def ensure_mobile_android_artifact_mode_packages(self):
+        """
+        Install pre-built packages required to run GeckoView Artifact Build
+        (application 'mobile/android')
+        """
+        self.ensure_mobile_android_packages()
+
+    def generate_mobile_android_mozconfig(self):
+        """
+        Print a message to the console detailing what the user's mozconfig
+        should contain.
+
+        GeckoView/Firefox for Android needs an application and an ABI set, and it needs
+        paths to the Android SDK and NDK.
+        """
+        raise NotImplementedError(
+            "%s does not yet implement generate_mobile_android_mozconfig()" % __name__
+        )
+
+    def install_mobile_android_artifact_mode_packages(self, mozconfig_builder):
+        """
+        Install packages required to build GeckoView/Firefox for Android (application
+        'mobile/android', also known as Fennec) in Artifact Mode.
+        """
+        raise NotImplementedError(
+            "Cannot bootstrap GeckoView/Firefox for Android Artifact Mode: "
+            "%s does not yet implement install_mobile_android_artifact_mode_packages()"
+            % __name__
+        )
+
+    def generate_mobile_android_artifact_mode_mozconfig(self):
+        """
+        Print a message to the console detailing what the user's mozconfig
+        should contain.
+
+        GeckoView/Firefox for Android Artifact Mode needs an application and an ABI set,
+        and it needs paths to the Android SDK.
+        """
+        raise NotImplementedError(
+            "%s does not yet implement generate_mobile_android_artifact_mode_mozconfig()"
+            % __name__
+        )
+
+    def ensure_sccache_packages(self):
+        """
+        Install sccache.
+        """
+        pass
+
+    def install_toolchain_artifact(self, toolchain_job, no_unpack=False):
+        if no_unpack:
+            return self.install_toolchain_artifact_impl(
+                self.state_dir, toolchain_job, no_unpack
+            )
+        bootstrap_toolchain(toolchain_job)
+
+    def install_toolchain_artifact_impl(
+        self, install_dir: Path, toolchain_job, no_unpack=False
+    ):
+        if type(self.srcdir) is str:
+            mach_binary = Path(self.srcdir) / "mach"
+        else:
+            mach_binary = (self.srcdir / "mach").resolve()
+        if not mach_binary.exists():
+            raise ValueError(f"mach not found at {mach_binary}")
+
+        if not self.state_dir:
+            raise ValueError(
+                "Need a state directory (e.g. ~/.mozbuild) to download " "artifacts"
+            )
+        python_location = get_mach_virtualenv_binary()
+        if not python_location.exists():
+            raise ValueError(f"python not found at {python_location}")
+
+        cmd = [
+            str(python_location),
+            str(mach_binary),
+            "artifact",
+            "toolchain",
+            "--bootstrap",
+            "--from-build",
+            toolchain_job,
+        ]
+
+        if no_unpack:
+            cmd += ["--no-unpack"]
+
+        subprocess.check_call(cmd, cwd=str(install_dir))
+
+    def auto_bootstrap(self, application, exclude=[]):
+        args = ["--with-ccache=sccache"]
+        if application.endswith("_artifact_mode"):
+            args.append("--enable-artifact-builds")
+            application = application[: -len("_artifact_mode")]
+        args.append("--enable-project={}".format(application.replace("_", "/")))
+        if exclude:
+            args.append(
+                "--enable-bootstrap={}".format(",".join(f"-{x}" for x in exclude))
+            )
+        bootstrap_all_toolchains_for(args)
+
+    def run_as_root(self, command, may_use_sudo=True):
+        if os.geteuid() != 0:
+            if may_use_sudo and which("sudo"):
+                command.insert(0, "sudo")
+            else:
+                command = ["su", "root", "-c", " ".join(command)]
+
+        print("Executing as root:", subprocess.list2cmdline(command))
+
+        subprocess.check_call(command, stdin=sys.stdin)
+
+    def prompt_int(self, prompt, low, high, default=None):
+        """Prompts the user with prompt and requires an integer between low and high.
+
+        If the user doesn't select an option and a default isn't provided, then
+        the lowest option is used. This is because some option must be implicitly
+        selected if mach is invoked with "--no-interactive"
+        """
+        if default is not None:
+            assert isinstance(default, int)
+            assert low <= default <= high
+        else:
+            default = low
+
+        if self.no_interactive:
+            print(prompt)
+            print('Selecting "{}" because context is not interactive.'.format(default))
+            return default
+
+        while True:
+            choice = input(prompt)
+            if choice == "" and default is not None:
+                return default
+            try:
+                choice = int(choice)
+                if low <= choice <= high:
+                    return choice
+            except ValueError:
+                pass
+            print("ERROR! Please enter a valid option!")
+
+    def prompt_yesno(self, prompt):
+        """Prompts the user with prompt and requires a yes/no answer."""
+        if self.no_interactive:
+            print(prompt)
+            print('Selecting "Y" because context is not interactive.')
+            return True
+
+        while True:
+            choice = input(prompt + " (Yn): ").strip().lower()[:1]
+            if choice == "":
+                return True
+            elif choice in ("y", "n"):
+                return choice == "y"
+
+            print("ERROR! Please enter y or n!")
+
+    def _ensure_package_manager_updated(self):
+        if self.package_manager_updated:
+            return
+
+        self._update_package_manager()
+        self.package_manager_updated = True
+
+    def _update_package_manager(self):
+        """Updates the package manager's manifests/package list.
+
+        This should be defined in child classes.
+        """
+
+    def _parse_version_impl(self, path: Path, name, env, version_param):
+        """Execute the given path, returning the version.
+
+        Invokes the path argument with the --version switch
+        and returns a Version representing the output
+        if successful. If not, returns None.
+
+        An optional name argument gives the expected program
+        name returned as part of the version string, if it's
+        different from the basename of the executable.
+
+        An optional env argument allows modifying environment
+        variable during the invocation to set options, PATH,
+        etc.
+        """
+        if not name:
+            name = path.name
+        if name.lower().endswith(".exe"):
+            name = name[:-4]
+
+        process = subprocess.run(
+            [str(path), version_param],
+            env=env,
+            universal_newlines=True,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT,
+        )
+        if process.returncode != 0:
+            # This can happen e.g. if the user has an inactive pyenv shim in
+            # their path. Just silently treat this as a failure to parse the
+            # path and move on.
+            return None
+
+        match = re.search(name + " ([a-z0-9\.]+)", process.stdout)
+        if not match:
+            print("ERROR! Unable to identify %s version." % name)
+            return None
+
+        return Version(match.group(1))
+
+    def _parse_version(self, path: Path, name=None, env=None):
+        return self._parse_version_impl(path, name, env, "--version")
+
+    def _hg_cleanenv(self, load_hgrc=False):
+        """Returns a copy of the current environment updated with the HGPLAIN
+        and HGRCPATH environment variables.
+
+        HGPLAIN prevents Mercurial from applying locale variations to the output
+        making it suitable for use in scripts.
+
+        HGRCPATH controls the loading of hgrc files. Setting it to the empty
+        string forces that no user or system hgrc file is used.
+        """
+        env = os.environ.copy()
+        env["HGPLAIN"] = "1"
+        if not load_hgrc:
+            env["HGRCPATH"] = ""
+
+        return env
+
+    def is_mercurial_modern(self):
+        hg = to_optional_path(which("hg"))
+        if not hg:
+            print(NO_MERCURIAL)
+            return False, False, None
+
+        our = self._parse_version(hg, "version", self._hg_cleanenv())
+        if not our:
+            return True, False, None
+
+        return True, our >= MODERN_MERCURIAL_VERSION, our
+
+    def ensure_mercurial_modern(self):
+        installed, modern, version = self.is_mercurial_modern()
+
+        if modern:
+            print("Your version of Mercurial (%s) is sufficiently modern." % version)
+            return installed, modern
+
+        self._ensure_package_manager_updated()
+
+        if installed:
+            print("Your version of Mercurial (%s) is not modern enough." % version)
+            print(
+                "(Older versions of Mercurial have known security vulnerabilities. "
+                "Unless you are running a patched Mercurial version, you may be "
+                "vulnerable."
+            )
+        else:
+            print("You do not have Mercurial installed")
+
+        if self.upgrade_mercurial(version) is False:
+            return installed, modern
+
+        installed, modern, after = self.is_mercurial_modern()
+
+        if installed and not modern:
+            print(MERCURIAL_UPGRADE_FAILED % (MODERN_MERCURIAL_VERSION, after))
+
+        return installed, modern
+
+    def upgrade_mercurial(self, current):
+        """Upgrade Mercurial.
+
+        Child classes should reimplement this.
+
+        Return False to not perform a version check after the upgrade is
+        performed.
+        """
+        print(MERCURIAL_UNABLE_UPGRADE % (current, MODERN_MERCURIAL_VERSION))
+
+    def warn_if_pythonpath_is_set(self):
+        if "PYTHONPATH" in os.environ:
+            print(
+                "WARNING: Your PYTHONPATH environment variable is set. This can "
+                "cause flaky installations of the requirements, and other unexpected "
+                "issues with mach. It is recommended to unset this variable."
+            )
+
+    def is_rust_modern(self, cargo_bin: Path):
+        rustc = to_optional_path(which("rustc", extra_search_dirs=[str(cargo_bin)]))
+        if not rustc:
+            print("Could not find a Rust compiler.")
+            return False, None
+
+        our = self._parse_version(rustc)
+        if not our:
+            return False, None
+
+        return our >= MODERN_RUST_VERSION, our
+
+    def cargo_home(self):
+        cargo_home = Path(os.environ.get("CARGO_HOME", Path("~/.cargo").expanduser()))
+        cargo_bin = cargo_home / "bin"
+        return cargo_home, cargo_bin
+
+    def print_rust_path_advice(self, template, cargo_home: Path, cargo_bin: Path):
+        # Suggest ~/.cargo/env if it exists.
+        if (cargo_home / "env").exists():
+            cmd = f"source {cargo_home}/env"
+        else:
+            # On Windows rustup doesn't write out ~/.cargo/env
+            # so fall back to a manual PATH update. Bootstrap
+            # only runs under msys, so a unix-style shell command
+            # is appropriate there.
+            cargo_bin = win_to_msys_path(cargo_bin)
+            cmd = f"export PATH={cargo_bin}:$PATH"
+        print(template % {"cargo_bin": cargo_bin, "cmd": cmd})
+
+    def ensure_rust_modern(self):
+        cargo_home, cargo_bin = self.cargo_home()
+        modern, version = self.is_rust_modern(cargo_bin)
+
+        rustup = to_optional_path(which("rustup", extra_search_dirs=[str(cargo_bin)]))
+
+        if modern:
+            print("Your version of Rust (%s) is new enough." % version)
+
+        elif version:
+            print("Your version of Rust (%s) is too old." % version)
+
+        if rustup and not modern:
+            rustup_version = self._parse_version(rustup)
+            if not rustup_version:
+                print(RUSTUP_OLD)
+                sys.exit(1)
+            print("Found rustup. Will try to upgrade.")
+            self.upgrade_rust(rustup)
+
+            modern, after = self.is_rust_modern(cargo_bin)
+            if not modern:
+                print(RUST_UPGRADE_FAILED % (MODERN_RUST_VERSION, after))
+                sys.exit(1)
+        elif not rustup:
+            # No rustup. Download and run the installer.
+            print("Will try to install Rust.")
+            self.install_rust()
+            modern, version = self.is_rust_modern(cargo_bin)
+            rustup = to_optional_path(
+                which("rustup", extra_search_dirs=[str(cargo_bin)])
+            )
+
+        self.ensure_rust_targets(rustup, version)
+
+    def ensure_rust_targets(self, rustup: Path, rust_version):
+        """Make sure appropriate cross target libraries are installed."""
+        target_list = subprocess.check_output(
+            [str(rustup), "target", "list"], universal_newlines=True
+        )
+        targets = [
+            line.split()[0]
+            for line in target_list.splitlines()
+            if "installed" in line or "default" in line
+        ]
+        print("Rust supports %s targets." % ", ".join(targets))
+
+        # Support 32-bit Windows on 64-bit Windows.
+        win32 = "i686-pc-windows-msvc"
+        win64 = "x86_64-pc-windows-msvc"
+        if rust.platform() == win64 and win32 not in targets:
+            subprocess.check_call([str(rustup), "target", "add", win32])
+
+        if "mobile_android" in self.application:
+            # Let's add the most common targets.
+            if rust_version < Version("1.33"):
+                arm_target = "armv7-linux-androideabi"
+            else:
+                arm_target = "thumbv7neon-linux-androideabi"
+            android_targets = (
+                arm_target,
+                "aarch64-linux-android",
+                "i686-linux-android",
+                "x86_64-linux-android",
+            )
+            for target in android_targets:
+                if target not in targets:
+                    subprocess.check_call([str(rustup), "target", "add", target])
+
+    def upgrade_rust(self, rustup: Path):
+        """Upgrade Rust.
+
+        Invoke rustup from the given path to update the rust install."""
+        subprocess.check_call([str(rustup), "update"])
+        # This installs rustfmt when not already installed, or nothing
+        # otherwise, while the update above would have taken care of upgrading
+        # it.
+        subprocess.check_call([str(rustup), "component", "add", "rustfmt"])
+
+    def install_rust(self):
+        """Download and run the rustup installer."""
+        import errno
+        import stat
+        import tempfile
+
+        platform = rust.platform()
+        url = rust.rustup_url(platform)
+        checksum = rust.rustup_hash(platform)
+        if not url or not checksum:
+            print("ERROR: Could not download installer.")
+            sys.exit(1)
+        print("Downloading rustup-init... ", end="")
+        fd, rustup_init = tempfile.mkstemp(prefix=Path(url).name)
+        rustup_init = Path(rustup_init)
+        os.close(fd)
+        try:
+            http_download_and_save(url, rustup_init, checksum)
+            mode = rustup_init.stat().st_mode
+            rustup_init.chmod(mode | stat.S_IRWXU)
+            print("Ok")
+            print("Running rustup-init...")
+            subprocess.check_call(
+                [
+                    str(rustup_init),
+                    "-y",
+                    "--default-toolchain",
+                    "stable",
+                    "--default-host",
+                    platform,
+                    "--component",
+                    "rustfmt",
+                ]
+            )
+            cargo_home, cargo_bin = self.cargo_home()
+            self.print_rust_path_advice(RUST_INSTALL_COMPLETE, cargo_home, cargo_bin)
+        finally:
+            try:
+                rustup_init.unlink()
+            except OSError as e:
+                if e.errno != errno.ENOENT:
+                    raise
diff --git a/python/mozboot/mozboot/bootstrap.py b/python/mozboot/mozboot/bootstrap.py
new file mode 100644
index 0000000000..e57f496f29
--- /dev/null
+++ b/python/mozboot/mozboot/bootstrap.py
@@ -0,0 +1,776 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import platform
+import re
+import shutil
+import stat
+import subprocess
+import sys
+import time
+from collections import OrderedDict
+from pathlib import Path
+from typing import Optional
+
+# Use distro package to retrieve linux platform information
+import distro
+from mach.site import MachSiteManager
+from mach.telemetry import initialize_telemetry_setting
+from mach.util import (
+    UserError,
+    get_state_dir,
+    to_optional_path,
+    to_optional_str,
+    win_to_msys_path,
+)
+from mozbuild.base import MozbuildObject
+from mozfile import which
+from packaging.version import Version
+
+from mozboot.archlinux import ArchlinuxBootstrapper
+from mozboot.base import MODERN_RUST_VERSION
+from mozboot.centosfedora import CentOSFedoraBootstrapper
+from mozboot.debian import DebianBootstrapper
+from mozboot.freebsd import FreeBSDBootstrapper
+from mozboot.gentoo import GentooBootstrapper
+from mozboot.mozconfig import MozconfigBuilder
+from mozboot.mozillabuild import MozillaBuildBootstrapper
+from mozboot.openbsd import OpenBSDBootstrapper
+from mozboot.opensuse import OpenSUSEBootstrapper
+from mozboot.osx import OSXBootstrapper, OSXBootstrapperLight
+from mozboot.solus import SolusBootstrapper
+from mozboot.void import VoidBootstrapper
+from mozboot.windows import WindowsBootstrapper
+
+APPLICATION_CHOICE = """
+Note on Artifact Mode:
+
+Artifact builds download prebuilt C++ components rather than building
+them locally. Artifact builds are faster!
+
+Artifact builds are recommended for people working on Firefox or
+Firefox for Android frontends, or the GeckoView Java API. They are unsuitable
+for those working on C++ code. For more information see:
+https://firefox-source-docs.mozilla.org/contributing/build/artifact_builds.html.
+
+Please choose the version of Firefox you want to build (see note above):
+%s
+Your choice: """
+
+APPLICATIONS = OrderedDict(
+    [
+        ("Firefox for Desktop Artifact Mode", "browser_artifact_mode"),
+        ("Firefox for Desktop", "browser"),
+        ("GeckoView/Firefox for Android Artifact Mode", "mobile_android_artifact_mode"),
+        ("GeckoView/Firefox for Android", "mobile_android"),
+        ("SpiderMonkey JavaScript engine", "js"),
+    ]
+)
+
+FINISHED = """
+Your system should be ready to build %s!
+"""
+
+MOZCONFIG_SUGGESTION_TEMPLATE = """
+Paste the lines between the chevrons (>>> and <<<) into
+%s:
+
+>>>
+%s
+<<<
+"""
+
+MOZCONFIG_MISMATCH_WARNING_TEMPLATE = """
+WARNING! Mismatch detected between the selected build target and the
+mozconfig file %s:
+
+Current config
+>>>
+%s
+<<<
+
+Expected config
+>>>
+%s
+<<<
+"""
+
+CONFIGURE_MERCURIAL = """
+Mozilla recommends a number of changes to Mercurial to enhance your
+experience with it.
+
+Would you like to run a configuration wizard to ensure Mercurial is
+optimally configured? (This will also ensure 'version-control-tools' is up-to-date)"""
+
+CONFIGURE_GIT = """
+Mozilla recommends using git-cinnabar to work with mozilla-central (or
+mozilla-unified).
+
+Would you like to run a few configuration steps to ensure Git is
+optimally configured?"""
+
+DEBIAN_DISTROS = (
+    "debian",
+    "ubuntu",
+    "linuxmint",
+    "elementary",
+    "neon",
+    "pop",
+    "kali",
+    "devuan",
+    "pureos",
+    "deepin",
+    "tuxedo",
+)
+
+FEDORA_DISTROS = (
+    "centos",
+    "fedora",
+    "rocky",
+    "oracle",
+)
+
+ADD_GIT_CINNABAR_PATH = """
+To add git-cinnabar to the PATH, edit your shell initialization script, which
+may be called {prefix}/.bash_profile or {prefix}/.profile, and add the following
+lines:
+
+    export PATH="{cinnabar_dir}:$PATH"
+
+Then restart your shell.
+"""
+
+
+OLD_REVISION_WARNING = """
+WARNING! You appear to be running `mach bootstrap` from an old revision.
+bootstrap is meant primarily for getting developer environments up-to-date to
+build the latest version of tree. Running bootstrap on old revisions may fail
+and is not guaranteed to bring your machine to any working state in particular.
+Proceed at your own peril.
+"""
+
+
+# Version 2.24 changes the "core.commitGraph" setting to be "True" by default.
+MINIMUM_RECOMMENDED_GIT_VERSION = Version("2.24")
+OLD_GIT_WARNING = """
+You are running an older version of git ("{old_version}").
+We recommend upgrading to at least version "{minimum_recommended_version}" to improve
+performance.
+""".strip()
+
+
+class Bootstrapper(object):
+    """Main class that performs system bootstrap."""
+
+    def __init__(
+        self,
+        choice=None,
+        no_interactive=False,
+        hg_configure=False,
+        no_system_changes=False,
+        exclude=[],
+        mach_context=None,
+    ):
+        self.instance = None
+        self.choice = choice
+        self.hg_configure = hg_configure
+        self.no_system_changes = no_system_changes
+        self.exclude = exclude
+        self.mach_context = mach_context
+        cls = None
+        args = {
+            "no_interactive": no_interactive,
+            "no_system_changes": no_system_changes,
+        }
+
+        if sys.platform.startswith("linux"):
+            # distro package provides reliable ids for popular distributions so
+            # we use those instead of the full distribution name
+            dist_id, version, codename = distro.linux_distribution(
+                full_distribution_name=False
+            )
+
+            if dist_id in FEDORA_DISTROS:
+                cls = CentOSFedoraBootstrapper
+                args["distro"] = dist_id
+            elif dist_id in DEBIAN_DISTROS:
+                cls = DebianBootstrapper
+                args["distro"] = dist_id
+                args["codename"] = codename
+            elif dist_id in ("gentoo", "funtoo"):
+                cls = GentooBootstrapper
+            elif dist_id in ("solus"):
+                cls = SolusBootstrapper
+            elif dist_id in ("arch") or Path("/etc/arch-release").exists():
+                cls = ArchlinuxBootstrapper
+            elif dist_id in ("void"):
+                cls = VoidBootstrapper
+            elif dist_id in (
+                "opensuse",
+                "opensuse-leap",
+                "opensuse-tumbleweed",
+                "suse",
+            ):
+                cls = OpenSUSEBootstrapper
+            else:
+                raise NotImplementedError(
+                    "Bootstrap support for this Linux "
+                    "distro not yet available: " + dist_id
+                )
+
+            args["version"] = version
+            args["dist_id"] = dist_id
+
+        elif sys.platform.startswith("darwin"):
+            # TODO Support Darwin platforms that aren't OS X.
+            osx_version = platform.mac_ver()[0]
+            if platform.machine() == "arm64" or _macos_is_running_under_rosetta():
+                cls = OSXBootstrapperLight
+            else:
+                cls = OSXBootstrapper
+            args["version"] = osx_version
+
+        elif sys.platform.startswith("openbsd"):
+            cls = OpenBSDBootstrapper
+            args["version"] = platform.uname()[2]
+
+        elif sys.platform.startswith(("dragonfly", "freebsd", "netbsd")):
+            cls = FreeBSDBootstrapper
+            args["version"] = platform.release()
+            args["flavor"] = platform.system()
+
+        elif sys.platform.startswith("win32") or sys.platform.startswith("msys"):
+            if "MOZILLABUILD" in os.environ:
+                cls = MozillaBuildBootstrapper
+            else:
+                cls = WindowsBootstrapper
+        if cls is None:
+            raise NotImplementedError(
+                "Bootstrap support is not yet available " "for your OS."
+            )
+
+        self.instance = cls(**args)
+
+    def maybe_install_private_packages_or_exit(self, application, checkout_type):
+        # Install the clang packages needed for building the style system, as
+        # well as the version of NodeJS that we currently support.
+        # Also install the clang static-analysis package by default
+        # The best place to install our packages is in the state directory
+        # we have.  We should have created one above in non-interactive mode.
+        self.instance.auto_bootstrap(application, self.exclude)
+        self.instance.install_toolchain_artifact("fix-stacks")
+        self.instance.install_toolchain_artifact("minidump-stackwalk")
+        if not self.instance.artifact_mode:
+            self.instance.install_toolchain_artifact("clang-tools/clang-tidy")
+            self.instance.ensure_sccache_packages()
+        # Like 'ensure_browser_packages' or 'ensure_mobile_android_packages'
+        getattr(self.instance, "ensure_%s_packages" % application)()
+
+    def check_code_submission(self, checkout_root: Path):
+        if self.instance.no_interactive or which("moz-phab"):
+            return
+
+        # Skip moz-phab install until bug 1696357 is fixed and makes it to a moz-phab
+        # release.
+        if sys.platform.startswith("darwin") and platform.machine() == "arm64":
+            return
+
+        if not self.instance.prompt_yesno("Will you be submitting commits to Mozilla?"):
+            return
+
+        mach_binary = checkout_root / "mach"
+        subprocess.check_call((sys.executable, str(mach_binary), "install-moz-phab"))
+
+    def bootstrap(self, settings):
+        if self.choice is None:
+            applications = APPLICATIONS
+            # Like ['1. Firefox for Desktop', '2. Firefox for Android Artifact Mode', ...].
+            labels = [
+                "%s. %s" % (i, name) for i, name in enumerate(applications.keys(), 1)
+            ]
+            choices = ["  {} [default]".format(labels[0])]
+            choices += ["  {}".format(label) for label in labels[1:]]
+            prompt = APPLICATION_CHOICE % "\n".join(choices)
+            prompt_choice = self.instance.prompt_int(
+                prompt=prompt, low=1, high=len(applications)
+            )
+            name, application = list(applications.items())[prompt_choice - 1]
+        elif self.choice in APPLICATIONS.keys():
+            name, application = self.choice, APPLICATIONS[self.choice]
+        elif self.choice in APPLICATIONS.values():
+            name, application = next(
+                (k, v) for k, v in APPLICATIONS.items() if v == self.choice
+            )
+        else:
+            raise Exception(
+                "Please pick a valid application choice: (%s)"
+                % "/".join(APPLICATIONS.keys())
+            )
+
+        mozconfig_builder = MozconfigBuilder()
+        self.instance.application = application
+        self.instance.artifact_mode = "artifact_mode" in application
+
+        self.instance.warn_if_pythonpath_is_set()
+
+        if sys.platform.startswith("darwin") and not os.environ.get(
+            "MACH_I_DO_WANT_TO_USE_ROSETTA"
+        ):
+            # If running on arm64 mac, check whether we're running under
+            # Rosetta and advise against it.
+            if _macos_is_running_under_rosetta():
+                print(
+                    "Python is being emulated under Rosetta. Please use a native "
+                    "Python instead. If you still really want to go ahead, set "
+                    "the MACH_I_DO_WANT_TO_USE_ROSETTA environment variable.",
+                    file=sys.stderr,
+                )
+                return 1
+
+        state_dir = Path(get_state_dir())
+        self.instance.state_dir = state_dir
+
+        hg = to_optional_path(which("hg"))
+
+        # We need to enable the loading of hgrc in case extensions are
+        # required to open the repo.
+        (checkout_type, checkout_root) = current_firefox_checkout(
+            env=self.instance._hg_cleanenv(load_hgrc=True),
+            hg=hg,
+        )
+        self.instance.srcdir = checkout_root
+        self.instance.validate_environment()
+        self._validate_python_environment(checkout_root)
+
+        if self.instance.no_system_changes:
+            self.maybe_install_private_packages_or_exit(application, checkout_type)
+            self._output_mozconfig(application, mozconfig_builder)
+            sys.exit(0)
+
+        self.instance.install_system_packages()
+
+        # Like 'install_browser_packages' or 'install_mobile_android_packages'.
+        getattr(self.instance, "install_%s_packages" % application)(mozconfig_builder)
+
+        if not self.instance.artifact_mode:
+            self.instance.ensure_rust_modern()
+
+        git = to_optional_path(which("git"))
+
+        # Possibly configure Mercurial, but not if the current checkout or repo
+        # type is Git.
+        hg_installed = bool(hg)
+        if checkout_type == "hg":
+            hg_installed, hg_modern = self.instance.ensure_mercurial_modern()
+
+        if hg_installed and checkout_type == "hg":
+            if not self.instance.no_interactive:
+                configure_hg = self.instance.prompt_yesno(prompt=CONFIGURE_MERCURIAL)
+            else:
+                configure_hg = self.hg_configure
+
+            if configure_hg:
+                configure_mercurial(hg, state_dir)
+
+        # Offer to configure Git, if the current checkout or repo type is Git.
+        elif git and checkout_type == "git":
+            should_configure_git = False
+            if not self.instance.no_interactive:
+                should_configure_git = self.instance.prompt_yesno(prompt=CONFIGURE_GIT)
+            else:
+                # Assuming default configuration setting applies to all VCS.
+                should_configure_git = self.hg_configure
+
+            if should_configure_git:
+                configure_git(
+                    git,
+                    to_optional_path(which("git-cinnabar")),
+                    state_dir,
+                    checkout_root,
+                )
+
+        self.maybe_install_private_packages_or_exit(application, checkout_type)
+        self.check_code_submission(checkout_root)
+        # Wait until after moz-phab setup to check telemetry so that employees
+        # will be automatically opted-in.
+        if not self.instance.no_interactive and not settings.mach_telemetry.is_set_up:
+            initialize_telemetry_setting(settings, str(checkout_root), str(state_dir))
+
+        self._output_mozconfig(application, mozconfig_builder)
+
+        print(FINISHED % name)
+        if not (
+            which("rustc")
+            and self.instance._parse_version(Path("rustc")) >= MODERN_RUST_VERSION
+        ):
+            print(
+                "To build %s, please restart the shell (Start a new terminal window)"
+                % name
+            )
+
+    def _default_mozconfig_path(self):
+        return Path(self.mach_context.topdir) / "mozconfig"
+
+    def _read_default_mozconfig(self):
+        path = self._default_mozconfig_path()
+        with open(path, "r") as mozconfig_file:
+            return mozconfig_file.read()
+
+    def _write_default_mozconfig(self, raw_mozconfig):
+        path = self._default_mozconfig_path()
+        with open(path, "w") as mozconfig_file:
+            mozconfig_file.write(raw_mozconfig)
+            print(f'Your requested configuration has been written to "{path}".')
+
+    def _show_mozconfig_suggestion(self, raw_mozconfig):
+        suggestion = MOZCONFIG_SUGGESTION_TEMPLATE % (
+            self._default_mozconfig_path(),
+            raw_mozconfig,
+        )
+        print(suggestion, end="")
+
+    def _check_default_mozconfig_mismatch(
+        self, current_mozconfig_info, expected_application, expected_raw_mozconfig
+    ):
+        current_raw_mozconfig = self._read_default_mozconfig()
+        current_application = current_mozconfig_info["project"][0].replace("/", "_")
+        if current_mozconfig_info["artifact-builds"]:
+            current_application += "_artifact_mode"
+
+        if expected_application == current_application:
+            if expected_raw_mozconfig == current_raw_mozconfig:
+                return
+
+            # There's minor difference, show the suggestion.
+            self._show_mozconfig_suggestion(expected_raw_mozconfig)
+            return
+
+        warning = MOZCONFIG_MISMATCH_WARNING_TEMPLATE % (
+            self._default_mozconfig_path(),
+            current_raw_mozconfig,
+            expected_raw_mozconfig,
+        )
+        print(warning)
+
+        if not self.instance.prompt_yesno("Do you want to overwrite the config?"):
+            return
+
+        self._write_default_mozconfig(expected_raw_mozconfig)
+
+    def _output_mozconfig(self, application, mozconfig_builder):
+        # Like 'generate_browser_mozconfig' or 'generate_mobile_android_mozconfig'.
+        additional_mozconfig = getattr(
+            self.instance, "generate_%s_mozconfig" % application
+        )()
+        if additional_mozconfig:
+            mozconfig_builder.append(additional_mozconfig)
+        raw_mozconfig = mozconfig_builder.generate()
+
+        current_mozconfig_info = MozbuildObject.get_base_mozconfig_info(
+            self.mach_context.topdir, None, ""
+        )
+        current_mozconfig_path = current_mozconfig_info["mozconfig"]["path"]
+
+        if current_mozconfig_path:
+            # mozconfig file exists
+            if self._default_mozconfig_path().exists() and Path.samefile(
+                Path(current_mozconfig_path), self._default_mozconfig_path()
+            ):
+                # This mozconfig file may be created by bootstrap.
+                self._check_default_mozconfig_mismatch(
+                    current_mozconfig_info, application, raw_mozconfig
+                )
+            elif raw_mozconfig:
+                # The mozconfig file is created by user.
+                self._show_mozconfig_suggestion(raw_mozconfig)
+        elif raw_mozconfig:
+            # No mozconfig file exists yet
+            self._write_default_mozconfig(raw_mozconfig)
+
+    def _validate_python_environment(self, topsrcdir):
+        valid = True
+        try:
+            # distutils is singled out here because some distros (namely Ubuntu)
+            # include it in a separate package outside of the main Python
+            # installation.
+            import distutils.spawn
+            import distutils.sysconfig
+
+            assert distutils.sysconfig is not None and distutils.spawn is not None
+        except ImportError as e:
+            print("ERROR: Could not import package %s" % e.name, file=sys.stderr)
+            self.instance.suggest_install_distutils()
+            valid = False
+        except AssertionError:
+            print("ERROR: distutils is not behaving as expected.", file=sys.stderr)
+            self.instance.suggest_install_distutils()
+            valid = False
+        pip3 = to_optional_path(which("pip3"))
+        if not pip3:
+            print("ERROR: Could not find pip3.", file=sys.stderr)
+            self.instance.suggest_install_pip3()
+            valid = False
+        if not valid:
+            print(
+                "ERROR: Your Python installation will not be able to run "
+                "`mach bootstrap`. `mach bootstrap` cannot maintain your "
+                "Python environment for you; fix the errors shown here, and "
+                "then re-run `mach bootstrap`.",
+                file=sys.stderr,
+            )
+            sys.exit(1)
+
+        mach_site = MachSiteManager.from_environment(
+            topsrcdir,
+            lambda: os.path.normpath(get_state_dir(True, topsrcdir=topsrcdir)),
+        )
+        mach_site.attempt_populate_optional_packages()
+
+
+def update_vct(hg: Path, root_state_dir: Path):
+    """Ensure version-control-tools in the state directory is up to date."""
+    vct_dir = root_state_dir / "version-control-tools"
+
+    # Ensure the latest revision of version-control-tools is present.
+    update_mercurial_repo(
+        hg, "https://hg.mozilla.org/hgcustom/version-control-tools", vct_dir, "@"
+    )
+
+    return vct_dir
+
+
+def configure_mercurial(hg: Optional[Path], root_state_dir: Path):
+    """Run the Mercurial configuration wizard."""
+    vct_dir = update_vct(hg, root_state_dir)
+
+    hg = to_optional_str(hg)
+
+    # Run the config wizard from v-c-t.
+    args = [
+        hg,
+        "--config",
+        f"extensions.configwizard={vct_dir}/hgext/configwizard",
+        "configwizard",
+    ]
+    subprocess.call(args)
+
+
+def update_mercurial_repo(hg: Path, url, dest: Path, revision):
+    """Perform a clone/pull + update of a Mercurial repository."""
+    # Disable common extensions whose older versions may cause `hg`
+    # invocations to abort.
+    pull_args = [str(hg)]
+    if dest.exists():
+        pull_args.extend(["pull", url])
+        cwd = dest
+    else:
+        pull_args.extend(["clone", "--noupdate", url, str(dest)])
+        cwd = "/"
+
+    update_args = [str(hg), "update", "-r", revision]
+
+    print("=" * 80)
+    print(f"Ensuring {url} is up to date at {dest}")
+
+    env = os.environ.copy()
+    env.update({"HGPLAIN": "1"})
+
+    try:
+        subprocess.check_call(pull_args, cwd=str(cwd), env=env)
+        subprocess.check_call(update_args, cwd=str(dest), env=env)
+    finally:
+        print("=" * 80)
+
+
+def current_firefox_checkout(env, hg: Optional[Path] = None):
+    """Determine whether we're in a Firefox checkout.
+
+    Returns one of None, ``git``, or ``hg``.
+    """
+    HG_ROOT_REVISIONS = set(
+        [
+            # From mozilla-unified.
+            "8ba995b74e18334ab3707f27e9eb8f4e37ba3d29"
+        ]
+    )
+
+    path = Path.cwd()
+    while path:
+        hg_dir = path / ".hg"
+        git_dir = path / ".git"
+        known_file = path / "config" / "milestone.txt"
+        if hg and hg_dir.exists():
+            # Verify the hg repo is a Firefox repo by looking at rev 0.
+            try:
+                node = subprocess.check_output(
+                    [str(hg), "log", "-r", "0", "--template", "{node}"],
+                    cwd=str(path),
+                    env=env,
+                    universal_newlines=True,
+                )
+                if node in HG_ROOT_REVISIONS:
+                    _warn_if_risky_revision(path)
+                    return "hg", path
+                # Else the root revision is different. There could be nested
+                # repos. So keep traversing the parents.
+            except subprocess.CalledProcessError:
+                pass
+
+        # Just check for known-good files in the checkout, to prevent attempted
+        # foot-shootings.  Determining a canonical git checkout of mozilla-unified
+        # is...complicated
+        elif git_dir.exists() or hg_dir.exists():
+            if known_file.exists():
+                _warn_if_risky_revision(path)
+                return ("git" if git_dir.exists() else "hg"), path
+        elif known_file.exists():
+            return "SOURCE", path
+
+        if not len(path.parents):
+            break
+        path = path.parent
+
+    raise UserError(
+        "Could not identify the root directory of your checkout! "
+        "Are you running `mach bootstrap` in an hg or git clone?"
+    )
+
+
+def update_git_tools(git: Optional[Path], root_state_dir: Path):
+    """Update git tools, hooks and extensions"""
+    # Ensure git-cinnabar is up to date.
+    cinnabar_dir = root_state_dir / "git-cinnabar"
+    cinnabar_exe = cinnabar_dir / "git-cinnabar"
+
+    if sys.platform.startswith(("win32", "msys")):
+        cinnabar_exe = cinnabar_exe.with_suffix(".exe")
+
+    # Previously, this script would do a full clone of the git-cinnabar
+    # repository. It now only downloads prebuilt binaries, so if we are
+    # updating from an old setup, remove the repository and start over.
+    if (cinnabar_dir / ".git").exists():
+        # git sets pack files read-only, which causes problems removing
+        # them on Windows. To work around that, we use an error handler
+        # on rmtree that retries to remove the file after chmod'ing it.
+        def onerror(func, path, exc):
+            if func == os.unlink:
+                os.chmod(path, stat.S_IRWXU)
+                func(path)
+            else:
+                raise
+
+        shutil.rmtree(str(cinnabar_dir), onerror=onerror)
+
+    # If we already have an executable, ask it to update itself.
+    exists = cinnabar_exe.exists()
+    if exists:
+        try:
+            subprocess.check_call([str(cinnabar_exe), "self-update"])
+        except subprocess.CalledProcessError as e:
+            print(e)
+
+    # git-cinnabar 0.6.0rc1 self-update had a bug that could leave an empty
+    # file. If that happens, install from scratch.
+    if not exists or cinnabar_exe.stat().st_size == 0:
+        from urllib.request import urlopen
+
+        import certifi
+
+        if not cinnabar_dir.exists():
+            cinnabar_dir.mkdir()
+
+        cinnabar_url = "https://github.com/glandium/git-cinnabar/"
+        download_py = cinnabar_dir / "download.py"
+        with open(download_py, "wb") as fh:
+            shutil.copyfileobj(
+                urlopen(
+                    f"{cinnabar_url}/raw/master/download.py", cafile=certifi.where()
+                ),
+                fh,
+            )
+
+        try:
+            subprocess.check_call(
+                [sys.executable, str(download_py)], cwd=str(cinnabar_dir)
+            )
+        except subprocess.CalledProcessError as e:
+            print(e)
+        finally:
+            download_py.unlink()
+
+    return cinnabar_dir
+
+
+def configure_git(
+    git: Optional[Path],
+    cinnabar: Optional[Path],
+    root_state_dir: Path,
+    top_src_dir: Path,
+):
+    """Run the Git configuration steps."""
+
+    git_str = to_optional_str(git)
+
+    match = re.search(
+        r"(\d+\.\d+\.\d+)",
+        subprocess.check_output([git_str, "--version"], universal_newlines=True),
+    )
+    if not match:
+        raise Exception("Could not find git version")
+    git_version = Version(match.group(1))
+
+    if git_version < MINIMUM_RECOMMENDED_GIT_VERSION:
+        print(
+            OLD_GIT_WARNING.format(
+                old_version=git_version,
+                minimum_recommended_version=MINIMUM_RECOMMENDED_GIT_VERSION,
+            )
+        )
+
+    if git_version >= Version("2.17"):
+        # "core.untrackedCache" has a bug before 2.17
+        subprocess.check_call(
+            [git_str, "config", "core.untrackedCache", "true"], cwd=str(top_src_dir)
+        )
+
+    cinnabar_dir = str(update_git_tools(git, root_state_dir))
+
+    if not cinnabar:
+        if "MOZILLABUILD" in os.environ:
+            # Slightly modify the path on Windows to be correct
+            # for the copy/paste into the .bash_profile
+            cinnabar_dir = win_to_msys_path(cinnabar_dir)
+
+            print(
+                ADD_GIT_CINNABAR_PATH.format(
+                    prefix="%USERPROFILE%", cinnabar_dir=cinnabar_dir
+                )
+            )
+        else:
+            print(ADD_GIT_CINNABAR_PATH.format(prefix="~", cinnabar_dir=cinnabar_dir))
+
+
+def _warn_if_risky_revision(path: Path):
+    # Warn the user if they're trying to bootstrap from an obviously old
+    # version of tree as reported by the version control system (a month in
+    # this case). This is an approximate calculation but is probably good
+    # enough for our purposes.
+    NUM_SECONDS_IN_MONTH = 60 * 60 * 24 * 30
+    from mozversioncontrol import get_repository_object
+
+    repo = get_repository_object(path)
+    if (time.time() - repo.get_commit_time()) >= NUM_SECONDS_IN_MONTH:
+        print(OLD_REVISION_WARNING)
+
+
+def _macos_is_running_under_rosetta():
+    proc = subprocess.run(
+        ["sysctl", "-n", "sysctl.proc_translated"],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.DEVNULL,
+    )
+    return (
+        proc.returncode == 0 and proc.stdout.decode("ascii", "replace").strip() == "1"
+    )
diff --git a/python/mozboot/mozboot/centosfedora.py b/python/mozboot/mozboot/centosfedora.py
new file mode 100644
index 0000000000..37aa0e8eaa
--- /dev/null
+++ b/python/mozboot/mozboot/centosfedora.py
@@ -0,0 +1,80 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import subprocess
+
+from mozfile import which
+
+from mozboot.base import BaseBootstrapper
+from mozboot.linux_common import LinuxBootstrapper
+
+
+class CentOSFedoraBootstrapper(LinuxBootstrapper, BaseBootstrapper):
+    def __init__(self, distro, version, dist_id, **kwargs):
+        BaseBootstrapper.__init__(self, **kwargs)
+
+        self.distro = distro
+        self.version = int(version.split(".")[0])
+        self.dist_id = dist_id
+
+    def install_packages(self, packages):
+        if self.version >= 33 and "perl" in packages:
+            packages.append("perl-FindBin")
+        # watchman is not available on centos/rocky
+        if self.distro in ("centos", "rocky", "oracle"):
+            packages = [p for p in packages if p != "watchman"]
+        self.dnf_install(*packages)
+
+    def upgrade_mercurial(self, current):
+        if current is None:
+            self.dnf_install("mercurial")
+        else:
+            self.dnf_update("mercurial")
+
+    def dnf_install(self, *packages):
+        if which("dnf"):
+
+            def not_installed(package):
+                # We could check for "Error: No matching Packages to list", but
+                # checking `dnf`s exit code is sufficent.
+                # Ideally we'd invoke dnf with '--cacheonly', but there's:
+                # https://bugzilla.redhat.com/show_bug.cgi?id=2030255
+                is_installed = subprocess.run(
+                    ["dnf", "list", "--installed", package],
+                    stdout=subprocess.PIPE,
+                    stderr=subprocess.STDOUT,
+                )
+                if is_installed.returncode not in [0, 1]:
+                    stdout = is_installed.stdout
+                    raise Exception(
+                        f'Failed to determine whether package "{package}" is installed: "{stdout}"'
+                    )
+                return is_installed.returncode != 0
+
+            packages = list(filter(not_installed, packages))
+            if len(packages) == 0:
+                # avoid sudo prompt (support unattended re-bootstrapping)
+                return
+
+            command = ["dnf", "install"]
+        else:
+            command = ["yum", "install"]
+
+        if self.no_interactive:
+            command.append("-y")
+        command.extend(packages)
+
+        self.run_as_root(command)
+
+    def dnf_update(self, *packages):
+        if which("dnf"):
+            command = ["dnf", "update"]
+        else:
+            command = ["yum", "update"]
+
+        if self.no_interactive:
+            command.append("-y")
+        command.extend(packages)
+
+        self.run_as_root(command)
diff --git a/python/mozboot/mozboot/debian.py b/python/mozboot/mozboot/debian.py
new file mode 100644
index 0000000000..34e328586e
--- /dev/null
+++ b/python/mozboot/mozboot/debian.py
@@ -0,0 +1,83 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import sys
+
+from mozboot.base import MERCURIAL_INSTALL_PROMPT, BaseBootstrapper
+from mozboot.linux_common import LinuxBootstrapper
+
+
+class DebianBootstrapper(LinuxBootstrapper, BaseBootstrapper):
+    def __init__(self, distro, version, dist_id, codename, **kwargs):
+        BaseBootstrapper.__init__(self, **kwargs)
+
+        self.distro = distro
+        self.version = version
+        self.dist_id = dist_id
+        self.codename = codename
+
+    def suggest_install_distutils(self):
+        print(
+            "HINT: Try installing distutils with "
+            "`apt-get install python3-distutils`.",
+            file=sys.stderr,
+        )
+
+    def suggest_install_pip3(self):
+        print(
+            "HINT: Try installing pip3 with `apt-get install python3-pip`.",
+            file=sys.stderr,
+        )
+
+    def install_packages(self, packages):
+        try:
+            if int(self.version) < 11:
+                # watchman is only available starting from Debian 11.
+                packages = [p for p in packages if p != "watchman"]
+        except ValueError:
+            pass
+
+        self.apt_install(*packages)
+
+    def _update_package_manager(self):
+        self.apt_update()
+
+    def upgrade_mercurial(self, current):
+        """Install Mercurial from pip because Debian packages typically lag."""
+        if self.no_interactive:
+            # Install via Apt in non-interactive mode because it is the more
+            # conservative option and less likely to make people upset.
+            self.apt_install("mercurial")
+            return
+
+        res = self.prompt_int(MERCURIAL_INSTALL_PROMPT, 1, 3)
+
+        # Apt.
+        if res == 2:
+            self.apt_install("mercurial")
+            return False
+
+        # No Mercurial.
+        if res == 3:
+            print("Not installing Mercurial.")
+            return False
+
+        # pip.
+        assert res == 1
+        self.run_as_root(["pip3", "install", "--upgrade", "Mercurial"])
+
+    def apt_install(self, *packages):
+        command = ["apt-get", "install"]
+        if self.no_interactive:
+            command.append("-y")
+        command.extend(packages)
+
+        self.run_as_root(command)
+
+    def apt_update(self):
+        command = ["apt-get", "update"]
+        if self.no_interactive:
+            command.append("-y")
+
+        self.run_as_root(command)
diff --git a/python/mozboot/mozboot/freebsd.py b/python/mozboot/mozboot/freebsd.py
new file mode 100644
index 0000000000..f4d6d1847b
--- /dev/null
+++ b/python/mozboot/mozboot/freebsd.py
@@ -0,0 +1,70 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import sys
+
+from mozfile import which
+
+from mozboot.base import BaseBootstrapper
+
+
+class FreeBSDBootstrapper(BaseBootstrapper):
+    def __init__(self, version, flavor, **kwargs):
+        BaseBootstrapper.__init__(self, **kwargs)
+        self.version = int(version.split(".")[0])
+        self.flavor = flavor.lower()
+
+        self.packages = [
+            "gmake",
+            "gtar",
+            "m4",
+            "npm",
+            "pkgconf",
+            "py%d%d-sqlite3" % sys.version_info[0:2],
+            "rust",
+            "watchman",
+        ]
+
+        self.browser_packages = [
+            "dbus-glib",
+            "libXt",
+            "nasm",
+            "pulseaudio",
+        ]
+
+        if not which("as"):
+            self.packages.append("binutils")
+
+        if not which("unzip"):
+            self.packages.append("unzip")
+
+    def pkg_install(self, *packages):
+        if sys.platform.startswith("netbsd"):
+            command = ["pkgin", "install"]
+        else:
+            command = ["pkg", "install"]
+        if self.no_interactive:
+            command.append("-y")
+
+        command.extend(packages)
+        self.run_as_root(command)
+
+    def install_system_packages(self):
+        self.pkg_install(*self.packages)
+
+    def install_browser_packages(self, mozconfig_builder, artifact_mode=False):
+        # TODO: Figure out what not to install for artifact mode
+        packages = self.browser_packages.copy()
+        if not artifact_mode:
+            if sys.platform.startswith("netbsd"):
+                packages.extend(["brotli", "gtk3+", "libv4l", "cbindgen"])
+            else:
+                packages.extend(["gtk3", "mesa-dri", "v4l_compat", "rust-cbindgen"])
+        self.pkg_install(*packages)
+
+    def install_browser_artifact_mode_packages(self, mozconfig_builder):
+        self.install_browser_packages(mozconfig_builder, artifact_mode=True)
+
+    def upgrade_mercurial(self, current):
+        self.pkg_install("mercurial")
diff --git a/python/mozboot/mozboot/gentoo.py b/python/mozboot/mozboot/gentoo.py
new file mode 100644
index 0000000000..4ddf86696f
--- /dev/null
+++ b/python/mozboot/mozboot/gentoo.py
@@ -0,0 +1,29 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from mozboot.base import BaseBootstrapper
+from mozboot.linux_common import LinuxBootstrapper
+
+
+class GentooBootstrapper(LinuxBootstrapper, BaseBootstrapper):
+    def __init__(self, version, dist_id, **kwargs):
+        BaseBootstrapper.__init__(self, **kwargs)
+
+        self.version = version
+        self.dist_id = dist_id
+
+    def install_packages(self, packages):
+        DISAMBIGUATE = {
+            "gzip": "app-arch/gzip",
+            "tar": "app-arch/tar",
+        }
+        # watchman is available but requires messing with USEs.
+        packages = [DISAMBIGUATE.get(p, p) for p in packages if p != "watchman"]
+        self.run_as_root(["emerge", "--noreplace"] + packages)
+
+    def _update_package_manager(self):
+        self.run_as_root(["emerge", "--sync"])
+
+    def upgrade_mercurial(self, current):
+        self.run_as_root(["emerge", "--update", "mercurial"])
diff --git a/python/mozboot/mozboot/linux_common.py b/python/mozboot/mozboot/linux_common.py
new file mode 100644
index 0000000000..c6751d333b
--- /dev/null
+++ b/python/mozboot/mozboot/linux_common.py
@@ -0,0 +1,93 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# An easy way for distribution-specific bootstrappers to share the code
+# needed to install Stylo and Node dependencies.  This class must come before
+# BaseBootstrapper in the inheritance list.
+
+import platform
+
+
+def is_non_x86_64():
+    return platform.machine() != "x86_64"
+
+
+class MobileAndroidBootstrapper(object):
+    def __init__(self, **kwargs):
+        pass
+
+    def install_mobile_android_packages(self, mozconfig_builder, artifact_mode=False):
+        from mozboot import android
+
+        os_arch = platform.machine()
+        android.ensure_android(
+            "linux",
+            os_arch,
+            artifact_mode=artifact_mode,
+            no_interactive=self.no_interactive,
+        )
+        android.ensure_android(
+            "linux",
+            os_arch,
+            artifact_mode=artifact_mode,
+            no_interactive=self.no_interactive,
+            system_images_only=True,
+            avd_manifest_path=android.AVD_MANIFEST_X86_64,
+        )
+        android.ensure_android(
+            "linux",
+            os_arch,
+            artifact_mode=artifact_mode,
+            no_interactive=self.no_interactive,
+            system_images_only=True,
+            avd_manifest_path=android.AVD_MANIFEST_ARM,
+        )
+
+    def install_mobile_android_artifact_mode_packages(self, mozconfig_builder):
+        self.install_mobile_android_packages(mozconfig_builder, artifact_mode=True)
+
+    def ensure_mobile_android_packages(self):
+        from mozboot import android
+
+        android.ensure_java("linux", platform.machine())
+        self.install_toolchain_artifact(android.LINUX_X86_64_ANDROID_AVD)
+        self.install_toolchain_artifact(android.LINUX_ARM_ANDROID_AVD)
+
+    def generate_mobile_android_mozconfig(self, artifact_mode=False):
+        from mozboot import android
+
+        return android.generate_mozconfig("linux", artifact_mode=artifact_mode)
+
+    def generate_mobile_android_artifact_mode_mozconfig(self):
+        return self.generate_mobile_android_mozconfig(artifact_mode=True)
+
+
+class LinuxBootstrapper(MobileAndroidBootstrapper):
+    def __init__(self, **kwargs):
+        pass
+
+    def ensure_sccache_packages(self):
+        pass
+
+    def install_system_packages(self):
+        self.install_packages(
+            [
+                "bash",
+                "findutils",  # contains xargs
+                "gzip",
+                "libxml2",  # used by bootstrapped clang
+                "m4",
+                "make",
+                "perl",
+                "tar",
+                "unzip",
+                "watchman",
+            ]
+        )
+
+    def install_browser_packages(self, mozconfig_builder, artifact_mode=False):
+        pass
+
+    def install_browser_artifact_mode_packages(self, mozconfig_builder):
+        pass
diff --git a/python/mozboot/mozboot/mach_commands.py b/python/mozboot/mozboot/mach_commands.py
new file mode 100644
index 0000000000..02cc69f54b
--- /dev/null
+++ b/python/mozboot/mozboot/mach_commands.py
@@ -0,0 +1,119 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this,
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import errno
+import sys
+from pathlib import Path
+
+from mach.decorators import Command, CommandArgument
+
+from mozboot.bootstrap import APPLICATIONS
+
+
+@Command(
+    "bootstrap",
+    category="devenv",
+    description="Install required system packages for building.",
+)
+@CommandArgument(
+    "--application-choice",
+    choices=list(APPLICATIONS.keys()) + list(APPLICATIONS.values()),
+    default=None,
+    help="Pass in an application choice instead of using the default "
+    "interactive prompt.",
+)
+@CommandArgument(
+    "--no-system-changes",
+    dest="no_system_changes",
+    action="store_true",
+    help="Only execute actions that leave the system configuration alone.",
+)
+@CommandArgument(
+    "--exclude",
+    nargs="+",
+    help="A list of bootstrappable elements not to bootstrap.",
+)
+def bootstrap(
+    command_context, application_choice=None, no_system_changes=False, exclude=[]
+):
+    """Bootstrap system and mach for optimal development experience."""
+    from mozboot.bootstrap import Bootstrapper
+
+    bootstrapper = Bootstrapper(
+        choice=application_choice,
+        no_interactive=not command_context._mach_context.is_interactive,
+        no_system_changes=no_system_changes,
+        exclude=exclude,
+        mach_context=command_context._mach_context,
+    )
+    bootstrapper.bootstrap(command_context.settings)
+
+
+@Command(
+    "vcs-setup",
+    category="devenv",
+    description="Help configure a VCS for optimal development.",
+)
+@CommandArgument(
+    "-u",
+    "--update-only",
+    action="store_true",
+    help="Only update recommended extensions, don't run the wizard.",
+)
+def vcs_setup(command_context, update_only=False):
+    """Ensure a Version Control System (Mercurial or Git) is optimally
+    configured.
+
+    This command will inspect your VCS configuration and
+    guide you through an interactive wizard helping you configure the
+    VCS for optimal use on Mozilla projects.
+
+    User choice is respected: no changes are made without explicit
+    confirmation from you.
+
+    If "--update-only" is used, the interactive wizard is disabled
+    and this command only ensures that remote repositories providing
+    VCS extensions are up to date.
+    """
+    import mozversioncontrol
+    from mach.util import to_optional_path
+    from mozfile import which
+
+    import mozboot.bootstrap as bootstrap
+
+    repo = mozversioncontrol.get_repository_object(command_context._mach_context.topdir)
+    tool = "hg"
+    if repo.name == "git":
+        tool = "git"
+
+    # "hg" is an executable script with a shebang, which will be found by
+    # which. We need to pass a win32 executable to the function because we
+    # spawn a process from it.
+    if sys.platform in ("win32", "msys"):
+        tool += ".exe"
+
+    vcs = to_optional_path(which(tool))
+    if not vcs:
+        raise OSError(errno.ENOENT, "Could not find {} on $PATH".format(tool))
+
+    if update_only:
+        if repo.name == "git":
+            bootstrap.update_git_tools(
+                vcs,
+                Path(command_context._mach_context.state_dir),
+            )
+        else:
+            bootstrap.update_vct(vcs, Path(command_context._mach_context.state_dir))
+    else:
+        if repo.name == "git":
+            bootstrap.configure_git(
+                vcs,
+                to_optional_path(which("git-cinnabar")),
+                Path(command_context._mach_context.state_dir),
+                Path(command_context._mach_context.topdir),
+            )
+        else:
+            bootstrap.configure_mercurial(
+                vcs, Path(command_context._mach_context.state_dir)
+            )
diff --git a/python/mozboot/mozboot/mozconfig.py b/python/mozboot/mozboot/mozconfig.py
new file mode 100644
index 0000000000..a1ae4c8523
--- /dev/null
+++ b/python/mozboot/mozboot/mozconfig.py
@@ -0,0 +1,156 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import filecmp
+import os
+from pathlib import Path
+from typing import Union
+
+MOZ_MYCONFIG_ERROR = """
+The MOZ_MYCONFIG environment variable to define the location of mozconfigs
+is deprecated. If you wish to define the mozconfig path via an environment
+variable, use MOZCONFIG instead.
+""".strip()
+
+MOZCONFIG_LEGACY_PATH_ERROR = """
+You currently have a mozconfig at %s. This implicit location is no longer
+supported. Please move it to %s/.mozconfig or set an explicit path
+via the $MOZCONFIG environment variable.
+""".strip()
+
+DEFAULT_TOPSRCDIR_PATHS = (".mozconfig", "mozconfig")
+DEPRECATED_TOPSRCDIR_PATHS = ("mozconfig.sh", "myconfig.sh")
+DEPRECATED_HOME_PATHS = (".mozconfig", ".mozconfig.sh", ".mozmyconfig.sh")
+
+
+class MozconfigFindException(Exception):
+    """Raised when a mozconfig location is not defined properly."""
+
+
+class MozconfigBuilder(object):
+    def __init__(self):
+        self._lines = []
+
+    def append(self, block):
+        self._lines.extend([line.strip() for line in block.split("\n") if line.strip()])
+
+    def generate(self):
+        return "".join(line + "\n" for line in self._lines)
+
+
+def find_mozconfig(topsrcdir: Union[str, Path], env=os.environ):
+    """Find the active mozconfig file for the current environment.
+
+    This emulates the logic in mozconfig-find.
+
+    1) If ENV[MOZCONFIG] is set, use that
+    2) If $TOPSRCDIR/mozconfig or $TOPSRCDIR/.mozconfig exists, use it.
+    3) If both exist or if there are legacy locations detected, error out.
+
+    The absolute path to the found mozconfig will be returned on success.
+    None will be returned if no mozconfig could be found. A
+    MozconfigFindException will be raised if there is a bad state,
+    including conditions from #3 above.
+    """
+    topsrcdir = Path(topsrcdir)
+
+    # Check for legacy methods first.
+    if "MOZ_MYCONFIG" in env:
+        raise MozconfigFindException(MOZ_MYCONFIG_ERROR)
+
+    env_path = env.get("MOZCONFIG", None) or None
+
+    if env_path is not None:
+        env_path = Path(env_path)
+
+    if env_path is not None:
+        if not env_path.is_absolute():
+            potential_roots = [topsrcdir, Path.cwd()]
+            # Attempt to eliminate duplicates for e.g.
+            # self.topsrcdir == Path.cwd().
+            potential_roots_strings = set(str(p.resolve()) for p in potential_roots)
+            existing = [
+                root
+                for root in potential_roots_strings
+                if (Path(root) / env_path).exists()
+            ]
+            if len(existing) > 1:
+                # There are multiple files, but we might have a setup like:
+                #
+                # somedirectory/
+                #   srcdir/
+                #   objdir/
+                #
+                # MOZCONFIG=../srcdir/some/path/to/mozconfig
+                #
+                # and be configuring from the objdir.  So even though we
+                # have multiple existing files, they are actually the same
+                # file.
+                mozconfigs = [root / env_path for root in existing]
+                if not all(
+                    map(
+                        lambda p1, p2: filecmp.cmp(p1, p2, shallow=False),
+                        mozconfigs[:-1],
+                        mozconfigs[1:],
+                    )
+                ):
+                    raise MozconfigFindException(
+                        "MOZCONFIG environment variable refers to a path that "
+                        + "exists in more than one of "
+                        + ", ".join(potential_roots_strings)
+                        + ". Remove all but one."
+                    )
+            elif not existing:
+                raise MozconfigFindException(
+                    "MOZCONFIG environment variable refers to a path that "
+                    + "does not exist in any of "
+                    + ", ".join(potential_roots_strings)
+                )
+
+            env_path = existing[0] / env_path
+        elif not env_path.exists():  # non-relative path
+            raise MozconfigFindException(
+                "MOZCONFIG environment variable refers to a path that "
+                f"does not exist: {env_path}"
+            )
+
+        if not env_path.is_file():
+            raise MozconfigFindException(
+                "MOZCONFIG environment variable refers to a " f"non-file: {env_path}"
+            )
+
+    srcdir_paths = [topsrcdir / p for p in DEFAULT_TOPSRCDIR_PATHS]
+    existing = [p for p in srcdir_paths if p.is_file()]
+
+    if env_path is None and len(existing) > 1:
+        raise MozconfigFindException(
+            "Multiple default mozconfig files "
+            "present. Remove all but one. " + ", ".join(str(p) for p in existing)
+        )
+
+    path = None
+
+    if env_path is not None:
+        path = env_path
+    elif len(existing):
+        assert len(existing) == 1
+        path = existing[0]
+
+    if path is not None:
+        return Path.cwd() / path
+
+    deprecated_paths = [topsrcdir / s for s in DEPRECATED_TOPSRCDIR_PATHS]
+
+    home = env.get("HOME", None)
+    if home is not None:
+        home = Path(home)
+        deprecated_paths.extend([home / s for s in DEPRECATED_HOME_PATHS])
+
+    for path in deprecated_paths:
+        if path.exists():
+            raise MozconfigFindException(
+                MOZCONFIG_LEGACY_PATH_ERROR % (path, topsrcdir)
+            )
+
+    return None
diff --git a/python/mozboot/mozboot/mozillabuild.py b/python/mozboot/mozboot/mozillabuild.py
new file mode 100644
index 0000000000..c783809656
--- /dev/null
+++ b/python/mozboot/mozboot/mozillabuild.py
@@ -0,0 +1,235 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import ctypes
+import os
+import platform
+import subprocess
+import sys
+from pathlib import Path
+
+from mozbuild.util import mozilla_build_version
+from packaging.version import Version
+
+from mozboot.base import BaseBootstrapper
+
+
+def is_aarch64_host():
+    from ctypes import wintypes
+
+    kernel32 = ctypes.windll.kernel32
+    IMAGE_FILE_MACHINE_UNKNOWN = 0
+    IMAGE_FILE_MACHINE_ARM64 = 0xAA64
+
+    try:
+        iswow64process2 = kernel32.IsWow64Process2
+    except Exception:
+        # If we can't access the symbol, we know we're not on aarch64.
+        return False
+
+    currentProcess = kernel32.GetCurrentProcess()
+    processMachine = wintypes.USHORT(IMAGE_FILE_MACHINE_UNKNOWN)
+    nativeMachine = wintypes.USHORT(IMAGE_FILE_MACHINE_UNKNOWN)
+
+    gotValue = iswow64process2(
+        currentProcess, ctypes.byref(processMachine), ctypes.byref(nativeMachine)
+    )
+    # If this call fails, we have no idea.
+    if not gotValue:
+        return False
+
+    return nativeMachine.value == IMAGE_FILE_MACHINE_ARM64
+
+
+def get_is_windefender_disabled():
+    import winreg
+
+    try:
+        with winreg.OpenKeyEx(
+            winreg.HKEY_LOCAL_MACHINE, r"SOFTWARE\Microsoft\Windows Defender"
+        ) as windefender_key:
+            is_antivirus_disabled, _ = winreg.QueryValueEx(
+                windefender_key, "DisableAntiSpyware"
+            )
+            # is_antivirus_disabled is either 0 (False) or 1 (True)
+            return bool(is_antivirus_disabled)
+    except FileNotFoundError:
+        return True
+
+
+def get_windefender_exclusion_paths():
+    import winreg
+
+    paths = []
+    try:
+        with winreg.OpenKeyEx(
+            winreg.HKEY_LOCAL_MACHINE,
+            r"SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths",
+        ) as exclusions_key:
+            _, values_count, __ = winreg.QueryInfoKey(exclusions_key)
+            for i in range(0, values_count):
+                path, _, __ = winreg.EnumValue(exclusions_key, i)
+                paths.append(Path(path))
+    except FileNotFoundError:
+        pass
+
+    return paths
+
+
+def is_windefender_affecting_srcdir(src_dir: Path):
+    if get_is_windefender_disabled():
+        return False
+
+    # When there's a match, but path cases aren't the same between srcdir and exclusion_path,
+    # commonpath will use the casing of the first path provided.
+    # To avoid surprises here, we normcase(...) so we don't get unexpected breakage if we change
+    # the path order.
+    src_dir = src_dir.resolve()
+
+    try:
+        exclusion_paths = get_windefender_exclusion_paths()
+    except OSError as e:
+        if e.winerror == 5:
+            # A version of Windows 10 released in 2021 raises an "Access is denied"
+            # error (ERROR_ACCESS_DENIED == 5) to un-elevated processes when they
+            # query Windows Defender's exclusions. Skip the exclusion path checking.
+            return
+        raise
+
+    for exclusion_path in exclusion_paths:
+        exclusion_path = exclusion_path.resolve()
+        try:
+            if Path(os.path.commonpath((exclusion_path, src_dir))) == exclusion_path:
+                # exclusion_path is an ancestor of srcdir
+                return False
+        except ValueError:
+            # ValueError: Paths don't have the same drive - can't be ours
+            pass
+    return True
+
+
+class MozillaBuildBootstrapper(BaseBootstrapper):
+    """Bootstrapper for MozillaBuild to install rustup."""
+
+    def __init__(self, no_interactive=False, no_system_changes=False):
+        BaseBootstrapper.__init__(
+            self, no_interactive=no_interactive, no_system_changes=no_system_changes
+        )
+
+    def validate_environment(self):
+        if self.application.startswith("mobile_android"):
+            print(
+                "WARNING!!! Building Firefox for Android on Windows is not "
+                "fully supported. See https://bugzilla.mozilla.org/show_bug."
+                "cgi?id=1169873 for details.",
+                file=sys.stderr,
+            )
+
+        if is_windefender_affecting_srcdir(self.srcdir):
+            print(
+                "Warning: the Firefox checkout directory is currently not in the "
+                "Windows Defender exclusion list. This can cause the build process "
+                "to be dramatically slowed or broken. To resolve this, follow the "
+                "directions here: "
+                "https://firefox-source-docs.mozilla.org/setup/windows_build.html"
+                "#antivirus-performance",
+                file=sys.stderr,
+            )
+
+    def install_system_packages(self):
+        pass
+
+    def upgrade_mercurial(self, current):
+        # Mercurial upstream sometimes doesn't upload wheels, and building
+        # from source requires MS Visual C++ 9.0. So we force pip to install
+        # the last version that comes with wheels.
+        if mozilla_build_version() >= Version("4.0"):
+            pip_dir = (
+                Path(os.environ["MOZILLABUILD"]) / "python3" / "Scripts" / "pip.exe"
+            )
+        else:
+            pip_dir = (
+                Path(os.environ["MOZILLABUILD"]) / "python" / "Scripts" / "pip.exe"
+            )
+
+        command = [
+            str(pip_dir),
+            "install",
+            "--upgrade",
+            "mercurial",
+            "--only-binary",
+            "mercurial",
+        ]
+        self.run(command)
+
+    def install_browser_packages(self, mozconfig_builder):
+        pass
+
+    def install_browser_artifact_mode_packages(self, mozconfig_builder):
+        pass
+
+    def _os_arch(self):
+        os_arch = platform.machine()
+        if os_arch == "AMD64":
+            # On Windows, x86_64 is reported as AMD64 but we use x86_64
+            # everywhere else, so let's normalized it here.
+            return "x86_64"
+        return os_arch
+
+    def install_mobile_android_packages(self, mozconfig_builder, artifact_mode=False):
+        from mozboot import android
+
+        os_arch = self._os_arch()
+        android.ensure_android(
+            "windows",
+            os_arch,
+            artifact_mode=artifact_mode,
+            no_interactive=self.no_interactive,
+        )
+        android.ensure_android(
+            "windows",
+            os_arch,
+            system_images_only=True,
+            artifact_mode=artifact_mode,
+            no_interactive=self.no_interactive,
+            avd_manifest_path=android.AVD_MANIFEST_X86_64,
+        )
+        android.ensure_android(
+            "windows",
+            os_arch,
+            system_images_only=True,
+            artifact_mode=artifact_mode,
+            no_interactive=self.no_interactive,
+            avd_manifest_path=android.AVD_MANIFEST_ARM,
+        )
+
+    def ensure_mobile_android_packages(self):
+        from mozboot import android
+
+        android.ensure_java("windows", self._os_arch())
+        self.install_toolchain_artifact(android.WINDOWS_X86_64_ANDROID_AVD)
+        self.install_toolchain_artifact(android.WINDOWS_ARM_ANDROID_AVD)
+
+    def install_mobile_android_artifact_mode_packages(self, mozconfig_builder):
+        self.install_mobile_android_packages(mozconfig_builder, artifact_mode=True)
+
+    def generate_mobile_android_mozconfig(self, artifact_mode=False):
+        from mozboot import android
+
+        return android.generate_mozconfig("windows", artifact_mode=artifact_mode)
+
+    def generate_mobile_android_artifact_mode_mozconfig(self):
+        return self.generate_mobile_android_mozconfig(artifact_mode=True)
+
+    def ensure_sccache_packages(self):
+        from mozboot import sccache
+
+        self.install_toolchain_artifact(sccache.RUSTC_DIST_TOOLCHAIN, no_unpack=True)
+        self.install_toolchain_artifact(sccache.CLANG_DIST_TOOLCHAIN, no_unpack=True)
+
+    def _update_package_manager(self):
+        pass
+
+    def run(self, command):
+        subprocess.check_call(command, stdin=sys.stdin)
diff --git a/python/mozboot/mozboot/openbsd.py b/python/mozboot/mozboot/openbsd.py
new file mode 100644
index 0000000000..a862525ece
--- /dev/null
+++ b/python/mozboot/mozboot/openbsd.py
@@ -0,0 +1,34 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from mozboot.base import BaseBootstrapper
+
+
+class OpenBSDBootstrapper(BaseBootstrapper):
+    def __init__(self, version, **kwargs):
+        BaseBootstrapper.__init__(self, **kwargs)
+
+        self.packages = ["gmake", "gtar", "rust", "unzip"]
+
+        self.browser_packages = [
+            "llvm",
+            "cbindgen",
+            "nasm",
+            "node",
+            "gtk+3",
+            "dbus-glib",
+            "pulseaudio",
+        ]
+
+    def install_system_packages(self):
+        # we use -z because there's no other way to say "any autoconf-2.13"
+        self.run_as_root(["pkg_add", "-z"] + self.packages)
+
+    def install_browser_packages(self, mozconfig_builder, artifact_mode=False):
+        # TODO: Figure out what not to install for artifact mode
+        # we use -z because there's no other way to say "any autoconf-2.13"
+        self.run_as_root(["pkg_add", "-z"] + self.browser_packages)
+
+    def install_browser_artifact_mode_packages(self, mozconfig_builder):
+        self.install_browser_packages(mozconfig_builder, artifact_mode=True)
diff --git a/python/mozboot/mozboot/opensuse.py b/python/mozboot/mozboot/opensuse.py
new file mode 100644
index 0000000000..051ee97f4b
--- /dev/null
+++ b/python/mozboot/mozboot/opensuse.py
@@ -0,0 +1,63 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from mozboot.base import MERCURIAL_INSTALL_PROMPT, BaseBootstrapper
+from mozboot.linux_common import LinuxBootstrapper
+
+
+class OpenSUSEBootstrapper(LinuxBootstrapper, BaseBootstrapper):
+    """openSUSE experimental bootstrapper."""
+
+    def __init__(self, version, dist_id, **kwargs):
+        print("Using an experimental bootstrapper for openSUSE.")
+        BaseBootstrapper.__init__(self, **kwargs)
+
+    def install_packages(self, packages):
+        ALTERNATIVE_NAMES = {
+            "libxml2": "libxml2-2",
+        }
+        # watchman is not available
+        packages = [ALTERNATIVE_NAMES.get(p, p) for p in packages if p != "watchman"]
+        self.zypper_install(*packages)
+
+    def _update_package_manager(self):
+        self.zypper_update()
+
+    def upgrade_mercurial(self, current):
+        """Install Mercurial from pip because system packages could lag."""
+        if self.no_interactive:
+            # Install via zypper in non-interactive mode because it is the more
+            # conservative option and less likely to make people upset.
+            self.zypper_install("mercurial")
+            return
+
+        res = self.prompt_int(MERCURIAL_INSTALL_PROMPT, 1, 3)
+
+        # zypper.
+        if res == 2:
+            self.zypper_install("mercurial")
+            return False
+
+        # No Mercurial.
+        if res == 3:
+            print("Not installing Mercurial.")
+            return False
+
+        # pip.
+        assert res == 1
+        self.run_as_root(["pip3", "install", "--upgrade", "Mercurial"])
+
+    def zypper(self, *args):
+        if self.no_interactive:
+            command = ["zypper", "-n", *args]
+        else:
+            command = ["zypper", *args]
+
+        self.run_as_root(command)
+
+    def zypper_install(self, *packages):
+        self.zypper("install", *packages)
+
+    def zypper_update(self, *packages):
+        self.zypper("update", *packages)
diff --git a/python/mozboot/mozboot/osx.py b/python/mozboot/mozboot/osx.py
new file mode 100644
index 0000000000..8cd180f4ab
--- /dev/null
+++ b/python/mozboot/mozboot/osx.py
@@ -0,0 +1,310 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import platform
+import subprocess
+import sys
+import tempfile
+from urllib.request import urlopen
+
+import certifi
+from mach.util import to_optional_path, to_optional_str
+from mozfile import which
+from packaging.version import Version
+
+from mozboot.base import BaseBootstrapper
+
+HOMEBREW_BOOTSTRAP = (
+    "https://raw.githubusercontent.com/Homebrew/install/master/install.sh"
+)
+
+BREW_INSTALL = """
+We will install the Homebrew package manager to install required packages.
+
+You will be prompted to install Homebrew with its default settings. If you
+would prefer to do this manually, hit CTRL+c, install Homebrew yourself, ensure
+"brew" is in your $PATH, and relaunch bootstrap.
+"""
+
+BREW_PACKAGES = """
+We are now installing all required packages via Homebrew. You will see a lot of
+output as packages are built.
+"""
+
+NO_BREW_INSTALLED = "It seems you don't have Homebrew installed."
+
+
+class OSXAndroidBootstrapper(object):
+    def install_mobile_android_packages(self, mozconfig_builder, artifact_mode=False):
+        os_arch = platform.machine()
+        if os_arch != "x86_64" and os_arch != "arm64":
+            raise Exception(
+                "You need a 64-bit version of Mac OS X to build "
+                "GeckoView/Firefox for Android."
+            )
+
+        from mozboot import android
+
+        android.ensure_android(
+            "macosx",
+            os_arch,
+            artifact_mode=artifact_mode,
+            no_interactive=self.no_interactive,
+        )
+
+        if os_arch == "x86_64" or os_arch == "x86":
+            android.ensure_android(
+                "macosx",
+                os_arch,
+                system_images_only=True,
+                artifact_mode=artifact_mode,
+                no_interactive=self.no_interactive,
+                avd_manifest_path=android.AVD_MANIFEST_X86_64,
+            )
+            android.ensure_android(
+                "macosx",
+                os_arch,
+                system_images_only=True,
+                artifact_mode=artifact_mode,
+                no_interactive=self.no_interactive,
+                avd_manifest_path=android.AVD_MANIFEST_ARM,
+            )
+        else:
+            android.ensure_android(
+                "macosx",
+                os_arch,
+                system_images_only=True,
+                artifact_mode=artifact_mode,
+                no_interactive=self.no_interactive,
+                avd_manifest_path=android.AVD_MANIFEST_ARM64,
+            )
+
+    def ensure_mobile_android_packages(self):
+        from mozboot import android
+
+        arch = platform.machine()
+        android.ensure_java("macosx", arch)
+
+        if arch == "x86_64" or arch == "x86":
+            self.install_toolchain_artifact(android.MACOS_X86_64_ANDROID_AVD)
+            self.install_toolchain_artifact(android.MACOS_ARM_ANDROID_AVD)
+        elif arch == "arm64":
+            # The only emulator supported on Apple Silicon is the Arm64 one.
+            self.install_toolchain_artifact(android.MACOS_ARM64_ANDROID_AVD)
+
+    def install_mobile_android_artifact_mode_packages(self, mozconfig_builder):
+        self.install_mobile_android_packages(mozconfig_builder, artifact_mode=True)
+
+    def generate_mobile_android_mozconfig(self):
+        return self._generate_mobile_android_mozconfig()
+
+    def generate_mobile_android_artifact_mode_mozconfig(self):
+        return self._generate_mobile_android_mozconfig(artifact_mode=True)
+
+    def _generate_mobile_android_mozconfig(self, artifact_mode=False):
+        from mozboot import android
+
+        return android.generate_mozconfig("macosx", artifact_mode=artifact_mode)
+
+
+def ensure_command_line_tools():
+    # We need either the command line tools or Xcode (one is sufficient).
+    # Python 3, required to run this code, is not installed by default on macos
+    # as of writing (macos <= 11.x).
+    # There are at least 5 different ways to obtain it:
+    # - macports
+    # - homebrew
+    # - command line tools
+    # - Xcode
+    # - python.org
+    # The first two require to install the command line tools.
+    # So only in the last case we may not have command line tools or xcode
+    # available.
+    # When the command line tools are installed, `xcode-select --print-path`
+    # prints their path.
+    # When Xcode is installed, `xcode-select --print-path` prints its path.
+    # When neither is installed, `xcode-select --print-path` prints an error
+    # to stderr and nothing to stdout.
+    # So in the rare case where we detect neither the command line tools or
+    # Xcode is installed, we trigger an intall of the command line tools
+    # (via `xcode-select --install`).
+    proc = subprocess.run(
+        ["xcode-select", "--print-path"],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.DEVNULL,
+    )
+    if not proc.stdout:
+        subprocess.run(["xcode-select", "--install"], check=True)
+        # xcode-select --install triggers a separate process to be started by
+        # launchd, and tracking its successful outcome would require something
+        # like figuring its pid and using kqueue to get a notification when it
+        # finishes. Considering how unlikely it is that someone would end up
+        # here in the first place, we just bail out.
+        print("Please follow the command line tools installer instructions")
+        print("and rerun `./mach bootstrap` when it's finished.")
+        sys.exit(1)
+
+
+class OSXBootstrapperLight(OSXAndroidBootstrapper, BaseBootstrapper):
+    def __init__(self, version, **kwargs):
+        BaseBootstrapper.__init__(self, **kwargs)
+
+    def install_system_packages(self):
+        ensure_command_line_tools()
+
+    # All the installs below are assumed to be handled by mach configure/build by
+    # default, which is true for arm64.
+    def install_browser_packages(self, mozconfig_builder):
+        pass
+
+    def install_browser_artifact_mode_packages(self, mozconfig_builder):
+        pass
+
+
+class OSXBootstrapper(OSXAndroidBootstrapper, BaseBootstrapper):
+    def __init__(self, version, **kwargs):
+        BaseBootstrapper.__init__(self, **kwargs)
+
+        self.os_version = Version(version)
+
+        if self.os_version < Version("10.6"):
+            raise Exception("OS X 10.6 or above is required.")
+
+        self.minor_version = version.split(".")[1]
+
+    def install_system_packages(self):
+        ensure_command_line_tools()
+
+        self.ensure_homebrew_installed()
+        _, hg_modern, _ = self.is_mercurial_modern()
+        if not hg_modern:
+            print(
+                "Mercurial wasn't found or is not sufficiently modern. "
+                "It will be installed with brew"
+            )
+
+        packages = ["git", "gnu-tar", "terminal-notifier", "watchman"]
+        if not hg_modern:
+            packages.append("mercurial")
+        self._ensure_homebrew_packages(packages)
+
+    def install_browser_packages(self, mozconfig_builder):
+        pass
+
+    def install_browser_artifact_mode_packages(self, mozconfig_builder):
+        pass
+
+    def _ensure_homebrew_found(self):
+        self.brew = to_optional_path(which("brew"))
+
+        return self.brew is not None
+
+    def _ensure_homebrew_packages(self, packages, is_for_cask=False):
+        package_type_flag = "--cask" if is_for_cask else "--formula"
+        self.ensure_homebrew_installed()
+
+        def create_homebrew_cmd(*parameters):
+            base_cmd = [to_optional_str(self.brew)]
+            base_cmd.extend(parameters)
+            return base_cmd + [package_type_flag]
+
+        installed = set(
+            subprocess.check_output(
+                create_homebrew_cmd("list"), universal_newlines=True
+            ).split()
+        )
+        outdated = set(
+            subprocess.check_output(
+                create_homebrew_cmd("outdated", "--quiet"), universal_newlines=True
+            ).split()
+        )
+
+        to_install = set(package for package in packages if package not in installed)
+        to_upgrade = set(package for package in packages if package in outdated)
+
+        if to_install or to_upgrade:
+            print(BREW_PACKAGES)
+        if to_install:
+            subprocess.check_call(create_homebrew_cmd("install") + list(to_install))
+        if to_upgrade:
+            subprocess.check_call(create_homebrew_cmd("upgrade") + list(to_upgrade))
+
+    def _ensure_homebrew_casks(self, casks):
+        self._ensure_homebrew_found()
+
+        known_taps = subprocess.check_output([to_optional_str(self.brew), "tap"])
+
+        # Ensure that we can access old versions of packages.
+        if b"homebrew/cask-versions" not in known_taps:
+            subprocess.check_output(
+                [to_optional_str(self.brew), "tap", "homebrew/cask-versions"]
+            )
+
+        # "caskroom/versions" has been renamed to "homebrew/cask-versions", so
+        # it is safe to remove the old tap. Removing the old tap is necessary
+        # to avoid the error "Cask [name of cask] exists in multiple taps".
+        # See https://bugzilla.mozilla.org/show_bug.cgi?id=1544981
+        if b"caskroom/versions" in known_taps:
+            subprocess.check_output(
+                [to_optional_str(self.brew), "untap", "caskroom/versions"]
+            )
+
+        self._ensure_homebrew_packages(casks, is_for_cask=True)
+
+    def ensure_homebrew_browser_packages(self):
+        # TODO: Figure out what not to install for artifact mode
+        packages = ["yasm"]
+        self._ensure_homebrew_packages(packages)
+
+    def ensure_homebrew_installed(self):
+        """
+        Search for Homebrew in sys.path, if not found, prompt the user to install it.
+        Then assert our PATH ordering is correct.
+        """
+        homebrew_found = self._ensure_homebrew_found()
+        if not homebrew_found:
+            self.install_homebrew()
+
+    def ensure_sccache_packages(self):
+        from mozboot import sccache
+
+        self.install_toolchain_artifact(sccache.RUSTC_DIST_TOOLCHAIN, no_unpack=True)
+        self.install_toolchain_artifact(sccache.CLANG_DIST_TOOLCHAIN, no_unpack=True)
+
+    def install_homebrew(self):
+        print(BREW_INSTALL)
+        bootstrap = urlopen(
+            url=HOMEBREW_BOOTSTRAP, cafile=certifi.where(), timeout=20
+        ).read()
+        with tempfile.NamedTemporaryFile() as tf:
+            tf.write(bootstrap)
+            tf.flush()
+
+            subprocess.check_call(["bash", tf.name])
+
+        homebrew_found = self._ensure_homebrew_found()
+        if not homebrew_found:
+            print(
+                "Homebrew was just installed but can't be found on PATH. "
+                "Please file a bug."
+            )
+            sys.exit(1)
+
+    def _update_package_manager(self):
+        subprocess.check_call([to_optional_str(self.brew), "-v", "update"])
+
+    def _upgrade_package(self, package):
+        self._ensure_homebrew_installed()
+
+        try:
+            subprocess.check_output(
+                [to_optional_str(self.brew), "-v", "upgrade", package],
+                stderr=subprocess.STDOUT,
+            )
+        except subprocess.CalledProcessError as e:
+            if b"already installed" not in e.output:
+                raise
+
+    def upgrade_mercurial(self, current):
+        self._upgrade_package("mercurial")
diff --git a/python/mozboot/mozboot/rust.py b/python/mozboot/mozboot/rust.py
new file mode 100644
index 0000000000..90607fccff
--- /dev/null
+++ b/python/mozboot/mozboot/rust.py
@@ -0,0 +1,185 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this,
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import platform as platform_mod
+import sys
+
+# Base url for pulling the rustup installer.
+RUSTUP_URL_BASE = "https://static.rust-lang.org/rustup"
+
+# Pull this to get the lastest stable version number.
+RUSTUP_MANIFEST = RUSTUP_URL_BASE + "/release-stable.toml"
+
+# We bake in a known version number so we can verify a checksum.
+RUSTUP_VERSION = "1.23.1"
+
+# SHA-256 checksums of the installers, per platform.
+RUSTUP_HASHES = {
+    "x86_64-unknown-freebsd": "3fb56018ec6009c5a3e345f07d7ea2fbc67d4c6768e528c6d990c7ebe2388d09",
+    "aarch64-apple-darwin": "6d56735284181b2eb804ed7f57f76cf5ff924251e8ab69d9b5822c3be1ca1dc7",
+    "x86_64-apple-darwin": "39101feb178a7e3e4443b09b36338e794a9e00385e5f44a2f7789aefb91354a9",
+    "x86_64-unknown-linux-gnu": "ed7773edaf1d289656bdec2aacad12413b38ad0193fff54b2231f5140a4b07c5",
+    "x86_64-pc-windows-msvc": "a586cf9de3e4aa791fd5796b6a5f99ca05591ccef8bb94e53af5b69f0261fb03",
+    "x86_64-unknown-netbsd": "8b29918e765f2cec3b81a911652b164471c42f8f31241f7401bb89582d6a3ed5",
+}
+
+NO_PLATFORM = """
+Sorry, we have no installer configured for your platform.
+
+Please try installing rust for your system from https://rustup.rs/
+or from https://rust-lang.org/ or from your package manager.
+"""
+
+
+def rustup_url(host, version=RUSTUP_VERSION):
+    """Download url for a particular version of the installer."""
+    return "%(base)s/archive/%(version)s/%(host)s/rustup-init%(ext)s" % {
+        "base": RUSTUP_URL_BASE,
+        "version": version,
+        "host": host,
+        "ext": exe_suffix(host),
+    }
+
+
+def rustup_hash(host):
+    """Look up the checksum for the given installer."""
+    return RUSTUP_HASHES.get(host, None)
+
+
+def platform():
+    """Determine the appropriate rust platform string for the current host"""
+    if sys.platform.startswith("darwin"):
+        if platform_mod.machine() == "arm64":
+            return "aarch64-apple-darwin"
+        return "x86_64-apple-darwin"
+    elif sys.platform.startswith(("win32", "msys")):
+        # Bravely assume we'll be building 64-bit Firefox.
+        return "x86_64-pc-windows-msvc"
+    elif sys.platform.startswith("linux"):
+        return "x86_64-unknown-linux-gnu"
+    elif sys.platform.startswith("freebsd"):
+        return "x86_64-unknown-freebsd"
+    elif sys.platform.startswith("netbsd"):
+        return "x86_64-unknown-netbsd"
+
+    return None
+
+
+def exe_suffix(host=None):
+    if not host:
+        host = platform()
+    if "windows" in host:
+        return ".exe"
+    return ""
+
+
+USAGE = """
+python rust.py [--update]
+
+Pass the --update option print info for the latest release of rustup-init.
+
+When invoked without the --update option, it queries the latest version
+and verifies the current stored checksums against the distribution server,
+but doesn't update the version installed by `mach bootstrap`.
+"""
+
+
+def unquote(s):
+    """Strip outer quotation marks from a string."""
+    return s.strip("'").strip('"')
+
+
+def rustup_latest_version():
+    """Query the latest version of the rustup installer."""
+    import requests
+
+    r = requests.get(RUSTUP_MANIFEST)
+    # The manifest is toml, but we might not have the toml4 python module
+    # available, so use ad-hoc parsing to obtain the current release version.
+    #
+    # The manifest looks like:
+    #
+    # schema-version = '1'
+    # version = '0.6.5'
+    #
+    for line in r.iter_lines():
+        line = line.decode("utf-8")
+        key, value = map(str.strip, line.split("=", 2))
+        if key == "schema-version":
+            schema = int(unquote(value))
+            if schema != 1:
+                print("ERROR: Unknown manifest schema %s" % value)
+                sys.exit(1)
+        elif key == "version":
+            return unquote(value)
+    return None
+
+
+def http_download_and_hash(url):
+    import hashlib
+
+    import requests
+
+    h = hashlib.sha256()
+    r = requests.get(url, stream=True)
+    for data in r.iter_content(4096):
+        h.update(data)
+    return h.hexdigest()
+
+
+def make_checksums(version, validate=False):
+    hashes = []
+    for platform in RUSTUP_HASHES.keys():
+        if validate:
+            print("Checking %s... " % platform, end="", flush=True)
+        else:
+            print("Fetching %s... " % platform, end="", flush=True)
+        checksum = http_download_and_hash(rustup_url(platform, version))
+        if validate and checksum != rustup_hash(platform):
+            print(
+                "mismatch:\n  script: %s\n  server: %s"
+                % (RUSTUP_HASHES[platform], checksum)
+            )
+        else:
+            print("OK")
+        hashes.append((platform, checksum))
+    return hashes
+
+
+if __name__ == "__main__":
+    """Allow invoking the module as a utility to update checksums."""
+
+    update = False
+    if len(sys.argv) > 1:
+        if sys.argv[1] == "--update":
+            update = True
+        else:
+            print(USAGE)
+            sys.exit(1)
+
+    print("Checking latest installer version... ", end="", flush=True)
+    version = rustup_latest_version()
+    if not version:
+        print("ERROR: Could not query current rustup installer version.")
+        sys.exit(1)
+    print(version)
+
+    if version == RUSTUP_VERSION:
+        print("We're up to date. Validating checksums.")
+        make_checksums(version, validate=True)
+        exit()
+
+    if not update:
+        print("Out of date. We use %s. Validating checksums." % RUSTUP_VERSION)
+        make_checksums(RUSTUP_VERSION, validate=True)
+        exit()
+
+    print("Out of date. We use %s. Calculating checksums." % RUSTUP_VERSION)
+    hashes = make_checksums(version)
+    print("")
+    print("RUSTUP_VERSION = '%s'" % version)
+    print("RUSTUP_HASHES = {")
+    for item in hashes:
+        print("    '%s':\n        '%s'," % item)
+    print("}")
diff --git a/python/mozboot/mozboot/sccache.py b/python/mozboot/mozboot/sccache.py
new file mode 100644
index 0000000000..b3cc9fbae9
--- /dev/null
+++ b/python/mozboot/mozboot/sccache.py
@@ -0,0 +1,9 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# sccache-dist currently expects clients to provide toolchains when
+# distributing from macOS or Windows, so we download linux binaries capable
+# of cross-compiling for these cases.
+RUSTC_DIST_TOOLCHAIN = "rustc-dist-toolchain"
+CLANG_DIST_TOOLCHAIN = "clang-dist-toolchain"
diff --git a/python/mozboot/mozboot/solus.py b/python/mozboot/mozboot/solus.py
new file mode 100644
index 0000000000..664b5285aa
--- /dev/null
+++ b/python/mozboot/mozboot/solus.py
@@ -0,0 +1,32 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from mozboot.base import BaseBootstrapper
+from mozboot.linux_common import LinuxBootstrapper
+
+
+class SolusBootstrapper(LinuxBootstrapper, BaseBootstrapper):
+    """Solus experimental bootstrapper."""
+
+    def __init__(self, version, dist_id, **kwargs):
+        print("Using an experimental bootstrapper for Solus.")
+        BaseBootstrapper.__init__(self, **kwargs)
+
+    def install_packages(self, packages):
+        self.package_install(*packages)
+
+    def _update_package_manager(self):
+        pass
+
+    def upgrade_mercurial(self, current):
+        self.package_install("mercurial")
+
+    def package_install(self, *packages):
+        command = ["eopkg", "install"]
+        if self.no_interactive:
+            command.append("--yes-all")
+
+        command.extend(packages)
+
+        self.run_as_root(command)
diff --git a/python/mozboot/mozboot/test/python.ini b/python/mozboot/mozboot/test/python.ini
new file mode 100644
index 0000000000..4947f160f5
--- /dev/null
+++ b/python/mozboot/mozboot/test/python.ini
@@ -0,0 +1,4 @@
+[DEFAULT]
+subsuite = mozbuild
+
+[test_mozconfig.py]
diff --git a/python/mozboot/mozboot/test/test_mozconfig.py b/python/mozboot/mozboot/test/test_mozconfig.py
new file mode 100644
index 0000000000..b7375e8529
--- /dev/null
+++ b/python/mozboot/mozboot/test/test_mozconfig.py
@@ -0,0 +1,229 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import os
+import sys
+import unittest
+from pathlib import Path
+from shutil import rmtree
+from tempfile import gettempdir, mkdtemp
+
+import pytest
+from mozunit import main
+
+from mozboot.mozconfig import (
+    DEFAULT_TOPSRCDIR_PATHS,
+    DEPRECATED_HOME_PATHS,
+    DEPRECATED_TOPSRCDIR_PATHS,
+    MozconfigFindException,
+    find_mozconfig,
+)
+
+
+class TestFindMozconfig(unittest.TestCase):
+    def setUp(self):
+        self._old_env = dict(os.environ)
+        os.environ.pop("MOZCONFIG", None)
+        os.environ.pop("MOZ_OBJDIR", None)
+        os.environ.pop("CC", None)
+        os.environ.pop("CXX", None)
+        self._temp_dirs = set()
+
+    def tearDown(self):
+        os.environ.clear()
+        os.environ.update(self._old_env)
+
+        for temp_dir in self._temp_dirs:
+            rmtree(str(temp_dir))
+
+    def get_temp_dir(self):
+        new_temp_dir = Path(mkdtemp())
+        self._temp_dirs.add(new_temp_dir)
+
+        return new_temp_dir
+
+    def test_find_legacy_env(self):
+        """Ensure legacy mozconfig path definitions result in error."""
+
+        os.environ["MOZ_MYCONFIG"] = "/foo"
+
+        with self.assertRaises(MozconfigFindException) as e:
+            find_mozconfig(self.get_temp_dir())
+
+        self.assertTrue(str(e.exception).startswith("The MOZ_MYCONFIG"))
+
+    def test_find_multiple_configs(self):
+        """Ensure multiple relative-path MOZCONFIGs result in error."""
+        relative_mozconfig = ".mconfig"
+        os.environ["MOZCONFIG"] = relative_mozconfig
+
+        src_dir = self.get_temp_dir()
+        cur_dir = self.get_temp_dir()
+        dirs = [src_dir, cur_dir]
+        for iter_dir in dirs:
+            path = iter_dir / relative_mozconfig
+            with open(path, "w") as file:
+                file.write(str(path))
+
+        orig_dir = Path.cwd()
+        try:
+            os.chdir(cur_dir)
+            with self.assertRaises(MozconfigFindException) as e:
+                find_mozconfig(src_dir)
+        finally:
+            os.chdir(orig_dir)
+
+        self.assertIn("exists in more than one of", str(e.exception))
+        for iter_dir in dirs:
+            self.assertIn(str(iter_dir.resolve()), str(e.exception))
+
+    def test_find_multiple_but_identical_configs(self):
+        """Ensure multiple relative-path MOZCONFIGs pointing at the same file are OK."""
+        relative_mozconfig = "../src/.mconfig"
+        os.environ["MOZCONFIG"] = relative_mozconfig
+
+        top_dir = self.get_temp_dir()
+        src_dir = top_dir / "src"
+        src_dir.mkdir()
+        cur_dir = top_dir / "obj"
+        cur_dir.mkdir()
+
+        path = src_dir / relative_mozconfig
+        with open(path, "w"):
+            pass
+
+        orig_dir = Path.cwd()
+        try:
+            os.chdir(cur_dir)
+            self.assertEqual(Path(find_mozconfig(src_dir)).resolve(), path.resolve())
+        finally:
+            os.chdir(orig_dir)
+
+    def test_find_no_relative_configs(self):
+        """Ensure a missing relative-path MOZCONFIG is detected."""
+        relative_mozconfig = ".mconfig"
+        os.environ["MOZCONFIG"] = relative_mozconfig
+
+        src_dir = self.get_temp_dir()
+        cur_dir = self.get_temp_dir()
+        dirs = [src_dir, cur_dir]
+
+        orig_dir = Path.cwd()
+        try:
+            os.chdir(cur_dir)
+            with self.assertRaises(MozconfigFindException) as e:
+                find_mozconfig(src_dir)
+        finally:
+            os.chdir(orig_dir)
+
+        self.assertIn("does not exist in any of", str(e.exception))
+        for iter_dir in dirs:
+            self.assertIn(str(iter_dir.resolve()), str(e.exception))
+
+    def test_find_relative_mozconfig(self):
+        """Ensure a relative MOZCONFIG can be found in the srcdir."""
+        relative_mozconfig = ".mconfig"
+        os.environ["MOZCONFIG"] = relative_mozconfig
+
+        src_dir = Path(self.get_temp_dir())
+        cur_dir = Path(self.get_temp_dir())
+
+        path = src_dir / relative_mozconfig
+        with open(path, "w"):
+            pass
+
+        orig_dir = Path.cwd()
+        try:
+            os.chdir(cur_dir)
+            self.assertEqual(
+                str(Path(find_mozconfig(src_dir)).resolve()), str(path.resolve())
+            )
+        finally:
+            os.chdir(orig_dir)
+
+    @pytest.mark.skipif(
+        sys.platform.startswith("win"),
+        reason="This test uses unix-style absolute paths, since we now use Pathlib, and "
+        "`is_absolute()` always returns `False` on Windows if there isn't a drive"
+        " letter, this test is invalid for Windows.",
+    )
+    def test_find_abs_path_not_exist(self):
+        """Ensure a missing absolute path is detected."""
+        os.environ["MOZCONFIG"] = "/foo/bar/does/not/exist"
+
+        with self.assertRaises(MozconfigFindException) as e:
+            find_mozconfig(self.get_temp_dir())
+
+        self.assertIn("path that does not exist", str(e.exception))
+        self.assertIn("/foo/bar/does/not/exist", str(e.exception))
+
+    def test_find_path_not_file(self):
+        """Ensure non-file paths are detected."""
+
+        os.environ["MOZCONFIG"] = gettempdir()
+
+        with self.assertRaises(MozconfigFindException) as e:
+            find_mozconfig(self.get_temp_dir())
+
+        self.assertIn("refers to a non-file", str(e.exception))
+        self.assertTrue(str(e.exception).endswith(gettempdir()))
+
+    def test_find_default_files(self):
+        """Ensure default paths are used when present."""
+        for default_dir in DEFAULT_TOPSRCDIR_PATHS:
+            temp_dir = self.get_temp_dir()
+            path = temp_dir / default_dir
+
+            with open(path, "w"):
+                pass
+
+            self.assertEqual(Path(find_mozconfig(temp_dir)), path)
+
+    def test_find_multiple_defaults(self):
+        """Ensure we error when multiple default files are present."""
+        self.assertGreater(len(DEFAULT_TOPSRCDIR_PATHS), 1)
+
+        temp_dir = self.get_temp_dir()
+        for default_dir in DEFAULT_TOPSRCDIR_PATHS:
+            with open(temp_dir / default_dir, "w"):
+                pass
+
+        with self.assertRaises(MozconfigFindException) as e:
+            find_mozconfig(temp_dir)
+
+        self.assertIn("Multiple default mozconfig files present", str(e.exception))
+
+    def test_find_deprecated_path_srcdir(self):
+        """Ensure we error when deprecated path locations are present."""
+        for deprecated_dir in DEPRECATED_TOPSRCDIR_PATHS:
+            temp_dir = self.get_temp_dir()
+            with open(temp_dir / deprecated_dir, "w"):
+                pass
+
+            with self.assertRaises(MozconfigFindException) as e:
+                find_mozconfig(temp_dir)
+
+            self.assertIn("This implicit location is no longer", str(e.exception))
+            self.assertIn(str(temp_dir), str(e.exception))
+
+    def test_find_deprecated_home_paths(self):
+        """Ensure we error when deprecated home directory paths are present."""
+
+        for deprecated_path in DEPRECATED_HOME_PATHS:
+            home = self.get_temp_dir()
+            os.environ["HOME"] = str(home)
+            path = home / deprecated_path
+
+            with open(path, "w"):
+                pass
+
+            with self.assertRaises(MozconfigFindException) as e:
+                find_mozconfig(self.get_temp_dir())
+
+            self.assertIn("This implicit location is no longer", str(e.exception))
+            self.assertIn(str(path), str(e.exception))
+
+
+if __name__ == "__main__":
+    main()
diff --git a/python/mozboot/mozboot/util.py b/python/mozboot/mozboot/util.py
new file mode 100644
index 0000000000..583c08bf76
--- /dev/null
+++ b/python/mozboot/mozboot/util.py
@@ -0,0 +1,49 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import hashlib
+import os
+from pathlib import Path
+from urllib.request import urlopen
+
+import certifi
+from mach.site import PythonVirtualenv
+from mach.util import get_state_dir
+
+MINIMUM_RUST_VERSION = "1.66.0"
+
+
+def get_tools_dir(srcdir=False):
+    if os.environ.get("MOZ_AUTOMATION") and "MOZ_FETCHES_DIR" in os.environ:
+        return os.environ["MOZ_FETCHES_DIR"]
+    return get_state_dir(srcdir)
+
+
+def get_mach_virtualenv_root():
+    return Path(get_state_dir(specific_to_topsrcdir=True)) / "_virtualenvs" / "mach"
+
+
+def get_mach_virtualenv_binary():
+    root = get_mach_virtualenv_root()
+    return Path(PythonVirtualenv(str(root)).python_path)
+
+
+def http_download_and_save(url, dest: Path, hexhash, digest="sha256"):
+    """Download the given url and save it to dest.  hexhash is a checksum
+    that will be used to validate the downloaded file using the given
+    digest algorithm.  The value of digest can be any value accepted by
+    hashlib.new.  The default digest used is 'sha256'."""
+    f = urlopen(url, cafile=certifi.where())
+    h = hashlib.new(digest)
+    with open(dest, "wb") as out:
+        while True:
+            data = f.read(4096)
+            if data:
+                out.write(data)
+                h.update(data)
+            else:
+                break
+    if h.hexdigest() != hexhash:
+        dest.unlink()
+        raise ValueError("Hash of downloaded file does not match expected hash")
diff --git a/python/mozboot/mozboot/void.py b/python/mozboot/mozboot/void.py
new file mode 100644
index 0000000000..8ae0198ace
--- /dev/null
+++ b/python/mozboot/mozboot/void.py
@@ -0,0 +1,41 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from mozboot.base import BaseBootstrapper
+from mozboot.linux_common import LinuxBootstrapper
+
+
+class VoidBootstrapper(LinuxBootstrapper, BaseBootstrapper):
+    def __init__(self, version, dist_id, **kwargs):
+        BaseBootstrapper.__init__(self, **kwargs)
+
+        self.distro = "void"
+        self.version = version
+        self.dist_id = dist_id
+
+    def run_as_root(self, command):
+        # VoidLinux doesn't support users sudo'ing most commands by default because of the group
+        # configuration.
+        super().run_as_root(command, may_use_sudo=False)
+
+    def xbps_install(self, *packages):
+        command = ["xbps-install"]
+        if self.no_interactive:
+            command.append("-y")
+        command.extend(packages)
+
+        self.run_as_root(command)
+
+    def xbps_update(self):
+        command = ["xbps-install", "-Su"]
+        if self.no_interactive:
+            command.append("-y")
+
+        self.run_as_root(command)
+
+    def install_packages(self, packages):
+        self.xbps_install(*packages)
+
+    def _update_package_manager(self):
+        self.xbps_update()
diff --git a/python/mozboot/mozboot/windows.py b/python/mozboot/mozboot/windows.py
new file mode 100644
index 0000000000..8f70a70b2f
--- /dev/null
+++ b/python/mozboot/mozboot/windows.py
@@ -0,0 +1,127 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import ctypes
+import os
+import subprocess
+import sys
+
+from mozfile import which
+
+from mozboot.base import BaseBootstrapper
+
+
+def is_aarch64_host():
+    from ctypes import wintypes
+
+    kernel32 = ctypes.windll.kernel32
+    IMAGE_FILE_MACHINE_UNKNOWN = 0
+    IMAGE_FILE_MACHINE_ARM64 = 0xAA64
+
+    try:
+        iswow64process2 = kernel32.IsWow64Process2
+    except Exception:
+        # If we can't access the symbol, we know we're not on aarch64.
+        return False
+
+    currentProcess = kernel32.GetCurrentProcess()
+    processMachine = wintypes.USHORT(IMAGE_FILE_MACHINE_UNKNOWN)
+    nativeMachine = wintypes.USHORT(IMAGE_FILE_MACHINE_UNKNOWN)
+
+    gotValue = iswow64process2(
+        currentProcess, ctypes.byref(processMachine), ctypes.byref(nativeMachine)
+    )
+    # If this call fails, we have no idea.
+    if not gotValue:
+        return False
+
+    return nativeMachine.value == IMAGE_FILE_MACHINE_ARM64
+
+
+class WindowsBootstrapper(BaseBootstrapper):
+    """Bootstrapper for msys2 based environments for building in Windows."""
+
+    SYSTEM_PACKAGES = [
+        "mingw-w64-x86_64-make",
+        "mingw-w64-x86_64-perl",
+        "patch",
+        "patchutils",
+        "diffutils",
+        "tar",
+        "unzip",
+        "mingw-w64-x86_64-toolchain",  # TODO: Remove when Mercurial is installable from a wheel.
+        "mingw-w64-i686-toolchain",
+    ]
+
+    BROWSER_PACKAGES = ["mingw-w64-x86_64-nasm", "mingw-w64-i686-nsis"]
+
+    def __init__(self, **kwargs):
+        if (
+            "MOZ_WINDOWS_BOOTSTRAP" not in os.environ
+            or os.environ["MOZ_WINDOWS_BOOTSTRAP"] != "1"
+        ):
+            raise NotImplementedError(
+                "Bootstrap support for Windows is under development. For "
+                "now use MozillaBuild to set up a build environment on "
+                "Windows. If you are testing Windows Bootstrap support, "
+                "try `export MOZ_WINDOWS_BOOTSTRAP=1`"
+            )
+        BaseBootstrapper.__init__(self, **kwargs)
+        if not which("pacman"):
+            raise NotImplementedError(
+                "The Windows bootstrapper only works with msys2 with "
+                "pacman. Get msys2 at http://msys2.github.io/"
+            )
+        print("Using an experimental bootstrapper for Windows.")
+
+    def install_system_packages(self):
+        self.pacman_install(*self.SYSTEM_PACKAGES)
+
+    def upgrade_mercurial(self, current):
+        self.pip_install("mercurial")
+
+    def install_browser_packages(self, mozconfig_builder):
+        self.pacman_install(*self.BROWSER_PACKAGES)
+
+    def install_mobile_android_packages(self, mozconfig_builder):
+        raise NotImplementedError(
+            "We do not support building Android on Windows. Sorry!"
+        )
+
+    def ensure_mobile_android_packages(self):
+        raise NotImplementedError(
+            "We do not support building Android on Windows. Sorry!"
+        )
+
+    def install_mobile_android_artifact_mode_packages(self, mozconfig_builder):
+        raise NotImplementedError(
+            "We do not support building Android on Windows. Sorry!"
+        )
+
+    def _update_package_manager(self):
+        self.pacman_update()
+
+    def run(self, command):
+        subprocess.check_call(command, stdin=sys.stdin)
+
+    def pacman_update(self):
+        command = ["pacman", "--sync", "--refresh"]
+        self.run(command)
+
+    def pacman_upgrade(self):
+        command = ["pacman", "--sync", "--refresh", "--sysupgrade"]
+        self.run(command)
+
+    def pacman_install(self, *packages):
+        command = ["pacman", "--sync", "--needed"]
+        if self.no_interactive:
+            command.append("--noconfirm")
+
+        command.extend(packages)
+        self.run(command)
+
+    def pip_install(self, *packages):
+        command = ["pip", "install", "--upgrade"]
+        command.extend(packages)
+        self.run(command)
diff --git a/python/mozboot/setup.py b/python/mozboot/setup.py
new file mode 100644
index 0000000000..234650dc8a
--- /dev/null
+++ b/python/mozboot/setup.py
@@ -0,0 +1,16 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from distutils.core import setup
+
+VERSION = "0.1"
+
+setup(
+    name="mozboot",
+    description="System bootstrap for building Mozilla projects.",
+    license="MPL 2.0",
+    packages=["mozboot"],
+    version=VERSION,
+    scripts=["bin/bootstrap.py"],
+)