caio/clang-p2996
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Open ELF core dumps with more than 64K sections

Browse Source 
Summary:
Problem:

There are three filelds in the ELF header - e_phnum, e_shnum, and e_shstrndx -
that could be bigger than 64K and therefore do not fit in 16 bits reserved for
them in the header. If this happens, pretty often there is a special section at
index 0 which contains their real values for these fields in the section header
in the fields sh_info, sh_size, and sh_link respectively.

Fix:

- Rename original fields in the header declaration. We want to have them around
just in case.

- Reintroduce these fields as 32-bit members at the end of the header. By default
they are initialized from the header in Parse() method.

- In Parse(), detect the situation when the header might have been extended into
section info #0 and try to read it from the same data source.

- ObjectFileELF::GetModuleSpecifications accesses some of these fields but the
original parse uses too small data source. Re-parse the header if necessary
using bigger data source.

- ProcessElfCore::CreateInstance uses header with potentially sentinel values,
but it does not access these fields, so a comment here is enough.

Reviewers: labath

Reviewed By: labath

Subscribers: davidb, lldb-commits, mgorny

Differential Revision: https://reviews.llvm.org/D29095
Author: Eugene Birukov <eugenebi@hotmail.com>

llvm-svn: 293714
This commit is contained in:
Pavel Labath
2017-01-31 23:09:46 +00:00
parent 06fcea4cd9
commit 23ccc29197
8 changed files with 161 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
View File

@@ -610,7 +610,8 @@ size_t ObjectFileELF::GetModuleSpecifications(
DataExtractor data;
data.SetData(data_sp);
elf::ELFHeader header;
if (header.Parse(data, &data_offset)) {
lldb::offset_t header_offset = data_offset;
if (header.Parse(data, &header_offset)) {
if (data_sp) {
ModuleSpec spec(file);
@@ -645,10 +646,24 @@ size_t ObjectFileELF::GetModuleSpecifications(
__FUNCTION__, file.GetPath().c_str());
}
// In case there is header extension in the section #0, the header
// we parsed above could have sentinel values for e_phnum, e_shnum,
// and e_shstrndx. In this case we need to reparse the header
// with a bigger data source to get the actual values.
size_t section_header_end = header.e_shoff + header.e_shentsize;
if (header.HasHeaderExtension() &&
section_header_end > data_sp->GetByteSize()) {
data_sp = file.MemoryMapFileContentsIfLocal (file_offset,
section_header_end);
data.SetData(data_sp);
lldb::offset_t header_offset = data_offset;
header.Parse(data, &header_offset);
}
// Try to get the UUID from the section list. Usually that's at the
// end, so
// map the file in if we don't have it already.
size_t section_header_end =
section_header_end =
header.e_shoff + header.e_shnum * header.e_shentsize;
if (section_header_end > data_sp->GetByteSize()) {
data_sp = file.MemoryMapFileContentsIfLocal(file_offset,
@@ -3067,10 +3082,10 @@ void ObjectFileELF::DumpELFHeader(Stream *s, const ELFHeader &header) {
s->Printf("e_flags = 0x%8.8x\n", header.e_flags);
s->Printf("e_ehsize = 0x%4.4x\n", header.e_ehsize);
s->Printf("e_phentsize = 0x%4.4x\n", header.e_phentsize);
s->Printf("e_phnum = 0x%4.4x\n", header.e_phnum);
s->Printf("e_phnum = 0x%8.8x\n", header.e_phnum);
s->Printf("e_shentsize = 0x%4.4x\n", header.e_shentsize);
s->Printf("e_shnum = 0x%4.4x\n", header.e_shnum);
s->Printf("e_shstrndx = 0x%4.4x\n", header.e_shstrndx);
s->Printf("e_shnum = 0x%8.8x\n", header.e_shnum);
s->Printf("e_shstrndx = 0x%8.8x\n", header.e_shstrndx);
}
//----------------------------------------------------------------------