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-rw-r--r--build/unix/elfhack/inject.c136
-rw-r--r--build/unix/elfhack/inject/copy_source.py10
-rw-r--r--build/unix/elfhack/inject/moz.build40
3 files changed, 186 insertions, 0 deletions
diff --git a/build/unix/elfhack/inject.c b/build/unix/elfhack/inject.c
new file mode 100644
index 0000000000..9e8399a1d1
--- /dev/null
+++ b/build/unix/elfhack/inject.c
@@ -0,0 +1,136 @@
+/* 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/. */
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <elf.h>
+
+/* The Android NDK headers define those */
+#undef Elf_Ehdr
+#undef Elf_Addr
+
+#if defined(__LP64__)
+# define Elf_Ehdr Elf64_Ehdr
+# define Elf_Addr Elf64_Addr
+#else
+# define Elf_Ehdr Elf32_Ehdr
+# define Elf_Addr Elf32_Addr
+#endif
+
+// On ARM, PC-relative function calls have a limit in how far they can jump,
+// which might not be enough for e.g. libxul.so. The easy way out would be
+// to use the long_call attribute, which forces the compiler to generate code
+// that can call anywhere, but clang doesn't support the attribute yet
+// (https://bugs.llvm.org/show_bug.cgi?id=40623), and while the command-line
+// equivalent does exist, it's currently broken
+// (https://bugs.llvm.org/show_bug.cgi?id=40624). So we create a manual
+// trampoline, corresponding to the code GCC generates with long_call.
+#ifdef __arm__
+__attribute__((section(".text._init_trampoline"), naked)) int init_trampoline(
+ int argc, char** argv, char** env) {
+ __asm__ __volatile__(
+ // thumb doesn't allow to use r12/ip with ldr, and thus would require an
+ // additional push/pop to save/restore the modified register, which would
+ // also change the call into a blx. It's simpler to switch to arm.
+ ".arm\n"
+ " ldr ip, .LADDR\n"
+ ".LAFTER:\n"
+ " add ip, pc, ip\n"
+ " bx ip\n"
+ ".LADDR:\n"
+ " .word real_original_init-(.LAFTER+8)\n");
+}
+#endif
+
+extern __attribute__((visibility("hidden"))) void original_init(int argc,
+ char** argv,
+ char** env);
+
+extern __attribute__((visibility("hidden"))) Elf_Addr relhack[];
+extern __attribute__((visibility("hidden"))) Elf_Ehdr elf_header;
+
+extern __attribute__((visibility("hidden"))) int (*mprotect_cb)(void* addr,
+ size_t len,
+ int prot);
+extern __attribute__((visibility("hidden"))) long (*sysconf_cb)(int name);
+extern __attribute__((visibility("hidden"))) char relro_start[];
+extern __attribute__((visibility("hidden"))) char relro_end[];
+
+static inline __attribute__((always_inline)) void do_relocations(void) {
+ Elf_Addr* ptr;
+ for (Elf_Addr* entry = relhack; *entry; entry++) {
+ if ((*entry & 1) == 0) {
+ ptr = (Elf_Addr*)((intptr_t)&elf_header + *entry);
+ *ptr += (intptr_t)&elf_header;
+ } else {
+ size_t remaining = (8 * sizeof(Elf_Addr) - 1);
+ Elf_Addr bits = *entry;
+ do {
+ bits >>= 1;
+ remaining--;
+ ptr++;
+ if (bits & 1) {
+ *ptr += (intptr_t)&elf_header;
+ }
+ } while (bits);
+ ptr += remaining;
+ }
+ }
+}
+
+__attribute__((section(".text._init_noinit"))) int init_noinit(int argc,
+ char** argv,
+ char** env) {
+ do_relocations();
+ return 0;
+}
+
+__attribute__((section(".text._init"))) int init(int argc, char** argv,
+ char** env) {
+ do_relocations();
+ original_init(argc, argv, env);
+ // Ensure there is no tail-call optimization, avoiding the use of the
+ // B.W instruction in Thumb for the call above.
+ return 0;
+}
+
+static inline __attribute__((always_inline)) void do_relocations_with_relro(
+ void) {
+ long page_size = sysconf_cb(_SC_PAGESIZE);
+ uintptr_t aligned_relro_start = ((uintptr_t)relro_start) & ~(page_size - 1);
+ // The relro segment may not end at a page boundary. If that's the case, the
+ // remainder of the page needs to stay read-write, so the last page is never
+ // set read-only. Thus the aligned relro end is page-rounded down.
+ uintptr_t aligned_relro_end = ((uintptr_t)relro_end) & ~(page_size - 1);
+ // By the time the injected code runs, the relro segment is read-only. But
+ // we want to apply relocations in it, so we set it r/w first. We'll restore
+ // it to read-only in relro_post.
+ mprotect_cb((void*)aligned_relro_start,
+ aligned_relro_end - aligned_relro_start, PROT_READ | PROT_WRITE);
+
+ do_relocations();
+
+ mprotect_cb((void*)aligned_relro_start,
+ aligned_relro_end - aligned_relro_start, PROT_READ);
+ // mprotect_cb and sysconf_cb are allocated in .bss, so we need to restore
+ // them to a NULL value.
+ mprotect_cb = NULL;
+ sysconf_cb = NULL;
+}
+
+__attribute__((section(".text._init_noinit_relro"))) int init_noinit_relro(
+ int argc, char** argv, char** env) {
+ do_relocations_with_relro();
+ return 0;
+}
+
+__attribute__((section(".text._init_relro"))) int init_relro(int argc,
+ char** argv,
+ char** env) {
+ do_relocations_with_relro();
+ original_init(argc, argv, env);
+ return 0;
+}
diff --git a/build/unix/elfhack/inject/copy_source.py b/build/unix/elfhack/inject/copy_source.py
new file mode 100644
index 0000000000..02b4f6237e
--- /dev/null
+++ b/build/unix/elfhack/inject/copy_source.py
@@ -0,0 +1,10 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+
+def copy(out_file, in_path):
+ with open(in_path, "r") as fh:
+ out_file.write(fh.read())
diff --git a/build/unix/elfhack/inject/moz.build b/build/unix/elfhack/inject/moz.build
new file mode 100644
index 0000000000..6f57d743f5
--- /dev/null
+++ b/build/unix/elfhack/inject/moz.build
@@ -0,0 +1,40 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+# dummy library name to avoid skipping building the source here, which
+# we only need the object for.
+Library("elfhack_inject")
+
+DIST_INSTALL = False
+
+cpu = CONFIG["CPU_ARCH"]
+
+gen_src = "%s.c" % cpu
+GeneratedFile(
+ gen_src, script="copy_source.py", entry_point="copy", inputs=["../inject.c"]
+)
+
+SOURCES += [
+ "!%s" % gen_src,
+]
+
+NO_PGO = True
+
+for v in ("OS_CPPFLAGS", "OS_CFLAGS", "DEBUG", "CLANG_PLUGIN", "OPTIMIZE", "FRAMEPTR"):
+ flags = []
+ idx = 0
+ for flag in COMPILE_FLAGS[v]:
+ if flag == "-isystem":
+ flags.append("".join(COMPILE_FLAGS[v][idx : idx + 2]))
+ elif flag.startswith(("-m", "-I", "-isystem", "--sysroot=")) or flag == "-fPIC":
+ flags.append(flag)
+ idx += 1
+ COMPILE_FLAGS[v] = flags
+
+COMPILE_FLAGS["OS_CFLAGS"] += ["-O2", "-fno-stack-protector", "-fno-lto"]
+
+AllowCompilerWarnings()
+NoVisibilityFlags()
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-16 19:02:55 +0000