[lld] r238115 - [ELF] Fix lld when no unique sections is used

Sean Silva chisophugis at gmail.com
Tue May 26 16:26:56 PDT 2015 

On Tue, May 26, 2015 at 2:18 PM, Rui Ueyama <ruiu at google.com> wrote:

> On Tue, May 26, 2015 at 2:08 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>>
>>
>> On Sun, May 24, 2015 at 9:19 AM, Simon Atanasyan <simon at atanasyan.com>
>> wrote:
>>
>>> Author: atanasyan
>>> Date: Sun May 24 11:19:27 2015
>>> New Revision: 238115
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=238115&view=rev
>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject-3Frev-3D238115-26view-3Drev&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=nm8yYFCvY6T4fBGwvJlJKypGmFjwiY6IcWkt8P5Ign4&s=r2vswq3ecSih5seNV2g18GrKLqyg7y7hZxy5FPdrk3Y&e=>
>>> Log:
>>> [ELF] Fix lld when no unique sections is used
>>>
>>> Original patch of Shankar Easwaran with additional test case.
>>> The yaml2obj does not allow to create an object file with non-unique
>>> sections names
>>
>>
>> Should we fix yaml2obj?
>>
>
> Yes we should fix it if it can't handle valid objects, but I think we
> probably start considering checking in object files (as opposed to checking
> in yaml files) is the right thing, as IIRC Rafael said before. Object files
> are the input for the linker, so in order to get a precise control over the
> input, it's better to use object files themselves.
>

Rafael was referring to using a binary as essentially an integration test "
to test that lld can work with a binary produced by a current clang". For
the bulk of testing that is definitely the wrong thing to do.

The idea that we need "precise control" in general is patently false.

For a given test input, we expect the same behavior on a class of
equivalent object files. What is considered equivalent is determined by
what transformations can be made to an object file that will result in the
same interpretation by the code being tested. For example, we can rearrange
the string table with no effect on the interpretation of the object file.

When testing a particular piece of code by feeding an input, the only
important thing is that we provide an input that falls into a class of
equivalent object files that exercise the code in the way we want. It is in
that sense that the output of yaml2obj is useful for testing. It is the
same reason that the .ll format is useful for testing. The .ll format
cannot represent all .bc files, nor can it represent all in-memory
Module's, but that is a *good thing*, because for most of the things that
we want to test, it *is* able to be transformed into a member of the
equivalence class of in-memory Module's that we need for testing, while
being substantially more readable (and other good properties).

-- Sean Silva


>
>
>>
>>> so the fix uses a binary input object file in the test
>>> case.
>>>
>>> Added:
>>>     lld/trunk/test/elf/Inputs/no-unique-section-names.x86-64
>>>     lld/trunk/test/elf/no-unique-section-names.test
>>> Modified:
>>>     lld/trunk/lib/ReaderWriter/ELF/ELFFile.cpp
>>>     lld/trunk/lib/ReaderWriter/ELF/ELFFile.h
>>>
>>> Modified: lld/trunk/lib/ReaderWriter/ELF/ELFFile.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/ELFFile.cpp?rev=238115&r1=238114&r2=238115&view=diff
>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_lld_trunk_lib_ReaderWriter_ELF_ELFFile.cpp-3Frev-3D238115-26r1-3D238114-26r2-3D238115-26view-3Ddiff&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=nm8yYFCvY6T4fBGwvJlJKypGmFjwiY6IcWkt8P5Ign4&s=FWqH6lrsv4BIAIIzFDzBysqCu1e44RJJZ1EU3RMuTm4&e=>
>>>
>>> ==============================================================================
>>> --- lld/trunk/lib/ReaderWriter/ELF/ELFFile.cpp (original)
>>> +++ lld/trunk/lib/ReaderWriter/ELF/ELFFile.cpp Sun May 24 11:19:27 2015
>>> @@ -143,7 +143,7 @@ std::error_code ELFFile<ELFT>::createAto
>>>        auto rai(_objFile->begin_rela(&section));
>>>        auto rae(_objFile->end_rela(&section));
>>>
>>> -      _relocationAddendReferences[*sectionName] = make_range(rai, rae);
>>> +      _relocationAddendReferences[sHdr] = make_range(rai, rae);
>>>        totalRelocs += std::distance(rai, rae);
>>>      } else if (section.sh_type == llvm::ELF::SHT_REL) {
>>>        auto sHdr = _objFile->getSection(section.sh_info);
>>> @@ -155,7 +155,7 @@ std::error_code ELFFile<ELFT>::createAto
>>>        auto ri(_objFile->begin_rel(&section));
>>>        auto re(_objFile->end_rel(&section));
>>>
>>> -      _relocationReferences[*sectionName] = make_range(ri, re);
>>> +      _relocationReferences[sHdr] = make_range(ri, re);
>>>        totalRelocs += std::distance(ri, re);
>>>      } else {
>>>        _sectionSymbols[&section];
>>> @@ -554,12 +554,12 @@ ELFDefinedAtom<ELFT> *ELFFile<ELFT>::cre
>>>    unsigned int referenceStart = _references.size();
>>>
>>>    // Add Rela (those with r_addend) references:
>>> -  auto rari = _relocationAddendReferences.find(sectionName);
>>> +  auto rari = _relocationAddendReferences.find(section);
>>>    if (rari != _relocationAddendReferences.end())
>>>      createRelocationReferences(symbol, symContent, rari->second);
>>>
>>>    // Add Rel references.
>>> -  auto rri = _relocationReferences.find(sectionName);
>>> +  auto rri = _relocationReferences.find(section);
>>>    if (rri != _relocationReferences.end())
>>>      createRelocationReferences(symbol, symContent, secContent,
>>> rri->second);
>>>
>>>
>>> Modified: lld/trunk/lib/ReaderWriter/ELF/ELFFile.h
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/lld/trunk/lib/ReaderWriter/ELF/ELFFile.h?rev=238115&r1=238114&r2=238115&view=diff
>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_lld_trunk_lib_ReaderWriter_ELF_ELFFile.h-3Frev-3D238115-26r1-3D238114-26r2-3D238115-26view-3Ddiff&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=nm8yYFCvY6T4fBGwvJlJKypGmFjwiY6IcWkt8P5Ign4&s=abVSyiw2dvEwfgW3QPePDhBHZDrYyxZdjtzP8WAlWWI&e=>
>>>
>>> ==============================================================================
>>> --- lld/trunk/lib/ReaderWriter/ELF/ELFFile.h (original)
>>> +++ lld/trunk/lib/ReaderWriter/ELF/ELFFile.h Sun May 24 11:19:27 2015
>>> @@ -345,10 +345,10 @@ protected:
>>>    /// list of relocations references.  In ELF, if a section named,
>>> ".text" has
>>>    /// relocations will also have a section named ".rel.text" or
>>> ".rela.text"
>>>    /// which will hold the entries.
>>> -  std::unordered_map<StringRef, range<Elf_Rela_Iter>>
>>> +  std::unordered_map<const Elf_Shdr *, range<Elf_Rela_Iter>>
>>>    _relocationAddendReferences;
>>>    MergedSectionMapT _mergedSectionMap;
>>> -  std::unordered_map<StringRef, range<Elf_Rel_Iter>>
>>> _relocationReferences;
>>> +  std::unordered_map<const Elf_Shdr *, range<Elf_Rel_Iter>>
>>> _relocationReferences;
>>>    std::vector<ELFReference<ELFT> *> _references;
>>>    llvm::DenseMap<const Elf_Sym *, Atom *> _symbolToAtomMapping;
>>>    llvm::DenseMap<const ELFReference<ELFT> *, const Elf_Sym *>
>>>
>>> Added: lld/trunk/test/elf/Inputs/no-unique-section-names.x86-64
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf/Inputs/no-unique-section-names.x86-64?rev=238115&view=auto
>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_lld_trunk_test_elf_Inputs_no-2Dunique-2Dsection-2Dnames.x86-2D64-3Frev-3D238115-26view-3Dauto&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=nm8yYFCvY6T4fBGwvJlJKypGmFjwiY6IcWkt8P5Ign4&s=mMAHzxi4jojRJPdLeaObNFp1S8NTPlGpY6BUbz-zHI4&e=>
>>>
>>> ==============================================================================
>>> Binary files lld/trunk/test/elf/Inputs/no-unique-section-names.x86-64
>>> (added) and lld/trunk/test/elf/Inputs/no-unique-section-names.x86-64 Sun
>>> May 24 11:19:27 2015 differ
>>>
>>> Added: lld/trunk/test/elf/no-unique-section-names.test
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf/no-unique-section-names.test?rev=238115&view=auto
>>> <https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_lld_trunk_test_elf_no-2Dunique-2Dsection-2Dnames.test-3Frev-3D238115-26view-3Dauto&d=AwMFaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=mQ4LZ2PUj9hpadE3cDHZnIdEwhEBrbAstXeMaFoB9tg&m=nm8yYFCvY6T4fBGwvJlJKypGmFjwiY6IcWkt8P5Ign4&s=ZKn31z8Tw14hzsGV0zQUG0qg5YHdfSRjiPuvZifBzSE&e=>
>>>
>>> ==============================================================================
>>> --- lld/trunk/test/elf/no-unique-section-names.test (added)
>>> +++ lld/trunk/test/elf/no-unique-section-names.test Sun May 24 11:19:27
>>> 2015
>>> @@ -0,0 +1,19 @@
>>> +# Check handling object files with non-unique named sections.
>>> +
>>> +RUN: lld -flavor gnu -target x86_64-linux -shared -o %t \
>>> +RUN:     %p/Inputs/no-unique-section-names.x86-64
>>> +RUN: llvm-objdump -s %p/Inputs/no-unique-section-names.x86-64 %t \
>>> +RUN:   | FileCheck %s
>>> +
>>> +CHECK:      Contents of section .group:
>>> +CHECK-NEXT:  0000 01000000 08000000
>>> +CHECK-NEXT: Contents of section .text:
>>> +CHECK-NEXT:  0000 [[A1:[0-9a-f]+]] [[A2:[0-9a-f]+]] [[A3:[0-9a-f]+]]
>>> +CHECK-NEXT: Contents of section .group:
>>> +CHECK-NEXT:  0000 01000000 0a000000
>>> +CHECK-NEXT: Contents of section .text:
>>> +CHECK-NEXT:  0000 [[B1:[0-9a-f]+]] [[B2:[0-9a-f]+]] [[B3:[0-9a-f]+]]
>>> +
>>> +CHECK:      Contents of section .text:
>>> +CHECK:       {{[0-9a-f]+}} [[A1]] [[A2]] [[A3]]
>>> +CHECK-NEXT:  {{[0-9a-f]+}} [[B1]] [[B2]] [[B3]]
>>>
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>>>
>>
>>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150526/f2f8756c/attachment.html>

More information about the llvm-commits mailing list