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mac: Accept modules in 10.13’s dyld shared cache

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In 10.13, modules loaded from the dyld shared cache appear with __TEXT
segments that have a nonzero “fileoff” (file offset). Previously, the
fileoff was always 0. Previously, the fileoff for segments in the dyld
shared cache was the actual offset into the shared cache (not 0), but
special consideration was given to __TEXT segments which were forced to
0. See 10.12.4 dyld-433.5/interlinked-dylibs/OptimizerLinkedit.cpp
LinkeditOptimizer<>::updateLoadCommands(). Note the comment there where
the __TEXT segment’s apparent fileoff is set to 0:

// HACK until lldb fixed in: <rdar://problem/20357466>
// DynamicLoaderMacOSXDYLD fixes for Monarch dyld shared cache

Refer also to the lldb commit that references the above,
http://llvm.org/viewvc/llvm-project?view=revision&revision=233714.

Evidently, update_dyld_shared_cache has been revised to no longer apply
this hack in 10.13. Crashpad’s sanity check for __TEXT segments having a
fileoff of 0 is no longer valid, and causes it to reject modules loaded
from the dyld shared cache.

Since this was just a sanity check, remove it entirely.

This caused module information for modules loaded from the dyld shared
cache to be missing from minidumps produced on 10.13, which in turn
prevented symbolization in frames belonging to most system libraries.
For reasons not yet understood, I don’t see this problem in Chrome on
10.13db1 17A264c on a test virtual machine (HFS+ filesystem), although I
do see it on actual hardware (APFS filesystem), and I do see it in
Crashpad’s tests and reduced testcases on both as well.

Bug: crashpad:185, crashpad:189
Test: crashpad_snapshot_test MachOImageReader.Self_DyldImages:ProcessReader.SelfModules:ProcessReader.ChildModules:ProcessTypes.DyldImagesSelf
Change-Id: I8b0a22c55c33ce920804a879f6fab67272f3556e
Reviewed-on: https://chromium-review.googlesource.com/535576
Reviewed-by: Robert Sesek <rsesek@chromium.org>
This commit is contained in:
Mark Mentovai 2017-06-14 15:01:53 -04:00
parent 6108d25232
commit 890ad441b3
1 changed files with 2 additions and 10 deletions
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10
snapshot/mac/mach_o_image_reader.cc
View File

@ -555,22 +555,14 @@ bool MachOImageReader::ReadSegmentCommand(
return false;
}
if (segment_name == SEG_TEXT) {
mach_vm_size_t vmsize = segment->vmsize();
if (segment_name == SEG_TEXT) {
if (vmsize == 0) {
LOG(WARNING) << "zero-sized " SEG_TEXT " segment" << load_command_info;
return false;
}
mach_vm_size_t fileoff = segment->fileoff();
if (fileoff != 0) {
LOG(WARNING) << base::StringPrintf(
SEG_TEXT " segment has unexpected fileoff 0x%llx",
fileoff) << load_command_info;
return false;
}
size_ = vmsize;
// The slide is computed as the difference between the __TEXT segment’s