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Diffstat (limited to '')
-rw-r--r-- | vendor/backtrace/src/symbolize/gimli/libs_macos.rs | 146 |
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, + }) +} |