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linux, dump_syms: Filter module entries outside specified ranges

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Partitioned libraries generated with lld and llvm-objcopy currently
contain a superset of debug information, beyond what applies to the
library itself. This is because objcopy cannot split up debug
information by partition - instead, it places a copy of all debug
information into each partition.

In lieu of potential future support for lld or objcopy becoming able to
split up debug information, let dump_syms do the next best thing:

- Find the address ranges of all PT_LOAD segments in the lib.
- Supply these to the Module being generated.
- Filter additions to the Module based on these ranges.

Bug: 990190
Change-Id: Ib5f279f42e3f6ea79eed9665efbcc23c3c5d25dc
Reviewed-on: https://chromium-review.googlesource.com/c/breakpad/breakpad/+/1884699
Reviewed-by: Joshua Peraza <jperaza@chromium.org>
This commit is contained in:
Christopher Grant 2019-10-29 14:56:38 -04:00 • committed by Joshua Peraza
parent 17958ef62c
commit 862c9f47ef
4 changed files with 120 additions and 0 deletions
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25
src/common/linux/dump_symbols.cc
View file

@ -182,6 +182,23 @@ typename ElfClass::Addr GetLoadingAddress(
return 0;
}
// Find the set of address ranges for all PT_LOAD segments.
template <typename ElfClass>
vector<Module::Range> GetPtLoadSegmentRanges(
const typename ElfClass::Phdr* program_headers,
int nheader) {
typedef typename ElfClass::Phdr Phdr;
vector<Module::Range> ranges;
for (int i = 0; i < nheader; ++i) {
const Phdr& header = program_headers[i];
if (header.p_type == PT_LOAD) {
ranges.push_back(Module::Range(header.p_vaddr, header.p_memsz));
}
}
return ranges;
}
#ifndef NO_STABS_SUPPORT
template<typename ElfClass>
bool LoadStabs(const typename ElfClass::Ehdr* elf_header,
@ -649,6 +666,14 @@ bool LoadSymbols(const string& obj_file,
module->SetLoadAddress(loading_addr);
info->set_loading_addr(loading_addr, obj_file);
// Allow filtering of extraneous debug information in partitioned libraries.
// Such libraries contain debug information for all libraries extracted from
// the same combined library, implying extensive duplication.
vector<Module::Range> address_ranges = GetPtLoadSegmentRanges<ElfClass>(
GetOffset<ElfClass, Phdr>(elf_header, elf_header->e_phoff),
elf_header->e_phnum);
module->SetAddressRanges(address_ranges);
const Shdr* sections =
GetOffset<ElfClass, Shdr>(elf_header, elf_header->e_shoff);
const Shdr* section_names = sections + elf_header->e_shstrndx;