[lld] r319367 - Don't crash on broken debug info.

[Rafael Avila de Espindola via llvm-commits]

Should be fixed in r319385.

I then added a check for alignment in llvm in r319392.

Cheers,
Rafael

Matt Morehouse <mascasa at google.com> writes:

> Hi Rafael,
>
> This test is failing under UBSan.  See
> http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/10690.
>
> ******************** TEST 'lld :: ELF/undef-broken-debug.test' FAILED
> ********************
> Script:
> --
> /b/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/bin/yaml2obj
> /b/sanitizer-x86_64-linux-fast/build/llvm/tools/lld/test/ELF/undef-broken-debug.test
> -o /b/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/tools/lld/test/ELF/Output/undef-broken-debug.test.tmp.o
> not /b/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/bin/ld.lld
> --full-shutdown
> /b/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/tools/lld/test/ELF/Output/undef-broken-debug.test.tmp.o
> -o /b/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/tools/lld/test/ELF/Output/undef-broken-debug.test.tmp.exe
> 2>&1 | /b/sanitizer-x86_64-linux-fast/build/llvm_build_ubsan/bin/FileCheck
> /b/sanitizer-x86_64-linux-fast/build/llvm/tools/lld/test/ELF/undef-broken-debug.test
> --
> Exit Code: 1
>
> Command Output (stderr):
> --
> /b/sanitizer-x86_64-linux-fast/build/llvm/tools/lld/test/ELF/undef-broken-debug.test:8:10:
> error: expected string not found in input
> # CHECK: error: undefined symbol: bar
>          ^
> <stdin>:1:1: note: scanning from here
> /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/bits/predefined_ops.h:147:24:
> runtime error: reference binding to misaligned address 0x000007d9cdd7
> for type 'const
> llvm::object::Elf_Rel_Impl<llvm::object::ELFType<llvm::support::endianness::little,
> true>, true>', which requires 2 byte alignment
> ^
>
>
>
>
>
> On Wed, Nov 29, 2017 at 2:09 PM, Rafael Espindola via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: rafael
>> Date: Wed Nov 29 14:09:16 2017
>> New Revision: 319367
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=319367&view=rev
>> Log:
>> Don't crash on broken debug info.
>>
>> Added:
>>     lld/trunk/test/ELF/undef-broken-debug.test
>> Modified:
>>     lld/trunk/ELF/GdbIndex.cpp
>>
>> Modified: lld/trunk/ELF/GdbIndex.cpp
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/
>> GdbIndex.cpp?rev=319367&r1=319366&r2=319367&view=diff
>> ============================================================
>> ==================
>> --- lld/trunk/ELF/GdbIndex.cpp (original)
>> +++ lld/trunk/ELF/GdbIndex.cpp Wed Nov 29 14:09:16 2017
>> @@ -68,14 +68,17 @@ LLDDwarfObj<ELFT>::findAux(const InputSe
>>    uint32_t SymIndex = Rel.getSymbol(Config->IsMips64EL);
>>    const typename ELFT::Sym &Sym = File->getELFSyms()[SymIndex];
>>    uint32_t SecIndex = File->getSectionIndex(Sym);
>> -  Symbol &B = File->getRelocTargetSym(Rel);
>> -  auto &DR = cast<Defined>(B);
>> -  uint64_t Val = DR.Value + getAddend<ELFT>(Rel);
>> +
>> +  // Broken debug info can point to a non-Defined symbol, just ignore it.
>> +  auto *DR = dyn_cast<Defined>(&File->getRelocTargetSym(Rel));
>> +  if (!DR)
>> +    return None;
>> +  uint64_t Val = DR->Value + getAddend<ELFT>(Rel);
>>
>>    // FIXME: We should be consistent about always adding the file
>>    // offset or not.
>> -  if (DR.Section->Flags & ELF::SHF_ALLOC)
>> -    Val += cast<InputSection>(DR.Section)->getOffsetInFile();
>> +  if (DR->Section->Flags & ELF::SHF_ALLOC)
>> +    Val += cast<InputSection>(DR->Section)->getOffsetInFile();
>>
>>    return RelocAddrEntry{SecIndex, Val};
>>  }
>>
>> Added: lld/trunk/test/ELF/undef-broken-debug.test
>> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/
>> undef-broken-debug.test?rev=319367&view=auto
>> ============================================================
>> ==================
>> --- lld/trunk/test/ELF/undef-broken-debug.test (added)
>> +++ lld/trunk/test/ELF/undef-broken-debug.test Wed Nov 29 14:09:16 2017
>> @@ -0,0 +1,44 @@
>> +# REQUIRES: x86
>> +# RUN: yaml2obj %s -o %t.o
>> +# RUN: not ld.lld %t.o -o %t.exe 2>&1 | FileCheck %s
>> +
>> +# The debug info has a broken relocation. Check that we don't crash
>> +# and still report the undefined symbol.
>> +
>> +# CHECK: error: undefined symbol: bar
>> +
>> +--- !ELF
>> +FileHeader:
>> +  Class:           ELFCLASS64
>> +  Data:            ELFDATA2LSB
>> +  Type:            ET_REL
>> +  Machine:         EM_X86_64
>> +Sections:
>> +  - Name:            .text
>> +    Type:            SHT_PROGBITS
>> +    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
>> +    Content:         '0000000000000000'
>> +  - Name:            .rela.text
>> +    Type:            SHT_RELA
>> +    Link:            .symtab
>> +    Info:            .text
>> +    Relocations:
>> +      - Offset:          0x0000000000000000
>> +        Symbol:          bar
>> +        Type:            R_X86_64_64
>> +  - Name:            .debug_line
>> +    Type:            SHT_PROGBITS
>> +    Content:         3300000002001C0000000101FB0E0D
>> 000101010100000001000001006162632E73000000000000090200000000
>> 00000000140208000101
>> +  - Name:            .rela.debug_line
>> +    Type:            SHT_RELA
>> +    Link:            .symtab
>> +    Info:            .debug_line
>> +    Relocations:
>> +      - Offset:          0x0000000000000029
>> +        Symbol:          bar
>> +        Type:            R_X86_64_64
>> +Symbols:
>> +  Global:
>> +    - Name:            _start
>> +      Section:         .text
>> +    - Name:            bar
>>
>>
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