1 files changed, 146 insertions, 0 deletions
diff --git a/vendor/backtrace/src/symbolize/gimli/libs_macos.rs b/vendor/backtrace/src/symbolize/gimli/libs_macos.rs
new file mode 100644
index 000000000..17703b88a
--- /dev/null
+++ b/vendor/backtrace/src/symbolize/gimli/libs_macos.rs
@@ -0,0 +1,146 @@
+#![allow(deprecated)]
+
+use super::mystd::ffi::{CStr, OsStr};
+use super::mystd::os::unix::prelude::*;
+use super::mystd::prelude::v1::*;
+use super::{Library, LibrarySegment};
+use core::convert::TryInto;
+use core::mem;
+
+pub(super) fn native_libraries() -> Vec<Library> {
+    let mut ret = Vec::new();
+    let images = unsafe { libc::_dyld_image_count() };
+    for i in 0..images {
+        ret.extend(native_library(i));
+    }
+    return ret;
+}
+
+fn native_library(i: u32) -> Option<Library> {
+    use object::macho;
+    use object::read::macho::{MachHeader, Segment};
+    use object::NativeEndian;
+
+    // Fetch the name of this library which corresponds to the path of
+    // where to load it as well.
+    let name = unsafe {
+        let name = libc::_dyld_get_image_name(i);
+        if name.is_null() {
+            return None;
+        }
+        CStr::from_ptr(name)
+    };
+
+    // Load the image header of this library and delegate to `object` to
+    // parse all the load commands so we can figure out all the segments
+    // involved here.
+    let (mut load_commands, endian) = unsafe {
+        let header = libc::_dyld_get_image_header(i);
+        if header.is_null() {
+            return None;
+        }
+        match (*header).magic {
+            macho::MH_MAGIC => {
+                let endian = NativeEndian;
+                let header = &*(header as *const macho::MachHeader32<NativeEndian>);
+                let data = core::slice::from_raw_parts(
+                    header as *const _ as *const u8,
+                    mem::size_of_val(header) + header.sizeofcmds.get(endian) as usize,
+                );
+                (header.load_commands(endian, data, 0).ok()?, endian)
+            }
+            macho::MH_MAGIC_64 => {
+                let endian = NativeEndian;
+                let header = &*(header as *const macho::MachHeader64<NativeEndian>);
+                let data = core::slice::from_raw_parts(
+                    header as *const _ as *const u8,
+                    mem::size_of_val(header) + header.sizeofcmds.get(endian) as usize,
+                );
+                (header.load_commands(endian, data, 0).ok()?, endian)
+            }
+            _ => return None,
+        }
+    };
+
+    // Iterate over the segments and register known regions for segments
+    // that we find. Additionally record information bout text segments
+    // for processing later, see comments below.
+    let mut segments = Vec::new();
+    let mut first_text = 0;
+    let mut text_fileoff_zero = false;
+    while let Some(cmd) = load_commands.next().ok()? {
+        if let Some((seg, _)) = cmd.segment_32().ok()? {
+            if seg.name() == b"__TEXT" {
+                first_text = segments.len();
+                if seg.fileoff(endian) == 0 && seg.filesize(endian) > 0 {
+                    text_fileoff_zero = true;
+                }
+            }
+            segments.push(LibrarySegment {
+                len: seg.vmsize(endian).try_into().ok()?,
+                stated_virtual_memory_address: seg.vmaddr(endian).try_into().ok()?,
+            });
+        }
+        if let Some((seg, _)) = cmd.segment_64().ok()? {
+            if seg.name() == b"__TEXT" {
+                first_text = segments.len();
+                if seg.fileoff(endian) == 0 && seg.filesize(endian) > 0 {
+                    text_fileoff_zero = true;
+                }
+            }
+            segments.push(LibrarySegment {
+                len: seg.vmsize(endian).try_into().ok()?,
+                stated_virtual_memory_address: seg.vmaddr(endian).try_into().ok()?,
+            });
+        }
+    }
+
+    // Determine the "slide" for this library which ends up being the
+    // bias we use to figure out where in memory objects are loaded.
+    // This is a bit of a weird computation though and is the result of
+    // trying a few things in the wild and seeing what sticks.
+    //
+    // The general idea is that the `bias` plus a segment's
+    // `stated_virtual_memory_address` is going to be where in the
+    // actual address space the segment resides. The other thing we rely
+    // on though is that a real address minus the `bias` is the index to
+    // look up in the symbol table and debuginfo.
+    //
+    // It turns out, though, that for system loaded libraries these
+    // calculations are incorrect. For native executables, however, it
+    // appears correct. Lifting some logic from LLDB's source it has
+    // some special-casing for the first `__TEXT` section loaded from
+    // file offset 0 with a nonzero size. For whatever reason when this
+    // is present it appears to mean that the symbol table is relative
+    // to just the vmaddr slide for the library. If it's *not* present
+    // then the symbol table is relative to the the vmaddr slide plus
+    // the segment's stated address.
+    //
+    // To handle this situation if we *don't* find a text section at
+    // file offset zero then we increase the bias by the first text
+    // sections's stated address and decrease all stated addresses by
+    // that amount as well. That way the symbol table is always appears
+    // relative to the library's bias amount. This appears to have the
+    // right results for symbolizing via the symbol table.
+    //
+    // Honestly I'm not entirely sure whether this is right or if
+    // there's something else that should indicate how to do this. For
+    // now though this seems to work well enough (?) and we should
+    // always be able to tweak this over time if necessary.
+    //
+    // For some more information see #318
+    let mut slide = unsafe { libc::_dyld_get_image_vmaddr_slide(i) as usize };
+    if !text_fileoff_zero {
+        let adjust = segments[first_text].stated_virtual_memory_address;
+        for segment in segments.iter_mut() {
+            segment.stated_virtual_memory_address -= adjust;
+        }
+        slide += adjust;
+    }
+
+    Some(Library {
+        name: OsStr::from_bytes(name.to_bytes()).to_owned(),
+        segments,
+        bias: slide,
+    })
+}