Open ELF core dumps with more than 64K sections
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
2017-02-01 07:09:46 +08:00
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//===-- TestELFHeader.cpp ---------------------------------------*- C++ -*-===//
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//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "Plugins/ObjectFile/ELF/ELFHeader.h"
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2017-03-04 09:30:05 +08:00
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#include "lldb/Utility/DataExtractor.h"
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Open ELF core dumps with more than 64K sections
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
2017-02-01 07:09:46 +08:00
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#include "gtest/gtest.h"
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using namespace lldb;
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using namespace lldb_private;
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TEST(ELFHeader, ParseHeaderExtension) {
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uint8_t data[] = {
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// e_ident
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0x7f, 0x45, 0x4c, 0x46, 0x02, 0x01, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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// e_type, e_machine, e_version, e_entry
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0x03, 0x00, 0x3e, 0x00, 0x01, 0x00, 0x00, 0x00, 0x90, 0x48, 0x40, 0x00,
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0x00, 0x00, 0x00, 0x00,
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// e_phoff, e_shoff
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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// e_flags, e_ehsize, e_phentsize, e_phnum, e_shentsize, e_shnum,
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// e_shstrndx
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0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x38, 0x00, 0xff, 0xff, 0x40, 0x00,
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0x00, 0x00, 0xff, 0xff,
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// sh_name, sh_type, sh_flags
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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// sh_addr, sh_offset
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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// sh_size, sh_link, sh_info
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0x23, 0x45, 0x67, 0x00, 0x00, 0x00, 0x00, 0x00, 0x34, 0x56, 0x78, 0x00,
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0x12, 0x34, 0x56, 0x00,
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// sh_addralign, sh_entsize
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00,
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};
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DataExtractor extractor(data, sizeof data, eByteOrderLittle, 8);
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elf::ELFHeader header;
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offset_t offset = 0;
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ASSERT_TRUE(header.Parse(extractor, &offset));
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EXPECT_EQ(0x563412u, header.e_phnum);
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EXPECT_EQ(0x785634u, header.e_shstrndx);
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EXPECT_EQ(0x674523u, header.e_shnum);
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}
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