[lld] r322259 - [ELF] Fix SysV hash tables with --no-rosegment

Wed Jan 17 05:00:01 PST 2018

Merged in r322642.

On Thu, Jan 11, 2018 at 8:05 AM, Rui Ueyama <ruiu at google.com> wrote:
> Approved.
>
> On Wed, Jan 10, 2018 at 10:58 PM, Shoaib Meenai <smeenai at fb.com> wrote:
>>
>> Requesting a merge to 6.0.
>>
>>
>>
>> From: llvm-commits <llvm-commits-bounces at lists.llvm.org> on behalf of
>> Shoaib Meenai via llvm-commits <llvm-commits at lists.llvm.org>
>> Reply-To: Shoaib Meenai <smeenai at fb.com>
>> Date: Wednesday, January 10, 2018 at 10:58 PM
>> To: "llvm-commits at lists.llvm.org" <llvm-commits at lists.llvm.org>
>> Subject: [lld] r322259 - [ELF] Fix SysV hash tables with --no-rosegment
>>
>>
>>
>> Author: smeenai
>>
>> Date: Wed Jan 10 22:57:01 2018
>>
>> New Revision: 322259
>>
>>
>>
>> URL:
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject-3Frev-3D322259-26view-3Drev&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=TzrIlS-6umMNRBVgupRbtxnFD-cXXbaxjd-gc8JgZcw&s=3Y89oPU0NvdG7K6lOFdJV5V8EZeTYfpNxkgb3JOIiEQ&e=
>>
>> Log:
>>
>> [ELF] Fix SysV hash tables with --no-rosegment
>>
>>
>>
>> When setting up the chain, we copy over the bucket's previous symbol
>>
>> index, assuming that this index will be 0 (STN_UNDEF) for an unused
>>
>> bucket (marking the end of the chain). When linking with --no-rosegment,
>>
>> however, unused buckets will in fact contain the padding value, and so
>>
>> the hash table will end up containing invalid chains. Zero out the hash
>>
>> table section explicitly to avoid this, similar to what's already done
>>
>> for GNU hash sections.
>>
>>
>>
>> Differential Revision:
>> https://urldefense.proofpoint.com/v2/url?u=https-3A__reviews.llvm.org_D41928&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=TzrIlS-6umMNRBVgupRbtxnFD-cXXbaxjd-gc8JgZcw&s=8qLiJg_KJkyadNiH7iVdh1Ab9J2tTu3wPrSxx_VYhGk&e=
>>
>>
>>
>> Added:
>>
>>     lld/trunk/test/ELF/sysv-hash-no-rosegment.s
>>
>> Modified:
>>
>>     lld/trunk/ELF/SyntheticSections.cpp
>>
>>
>>
>> Modified: lld/trunk/ELF/SyntheticSections.cpp
>>
>> URL:
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_lld_trunk_ELF_SyntheticSections.cpp-3Frev-3D322259-26r1-3D322258-26r2-3D322259-26view-3Ddiff&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=TzrIlS-6umMNRBVgupRbtxnFD-cXXbaxjd-gc8JgZcw&s=Csr47xs-UR1RtF4_oipHeeHvguaFAWBjbu_BF-eGMmY&e=
>>
>>
>> ==============================================================================
>>
>> --- lld/trunk/ELF/SyntheticSections.cpp (original)
>>
>> +++ lld/trunk/ELF/SyntheticSections.cpp Wed Jan 10 22:57:01 2018
>>
>> @@ -1836,6 +1836,9 @@ void HashTableSection::finalizeContents(
>>
>> }
>>
>> void HashTableSection::writeTo(uint8_t *Buf) {
>>
>> +  // See comment in GnuHashTableSection::writeTo.
>>
>> +  memset(Buf, 0, Size);
>>
>> +
>>
>>    unsigned NumSymbols = InX::DynSymTab->getNumSymbols();
>>
>>    uint32_t *P = reinterpret_cast<uint32_t *>(Buf);
>>
>>
>>
>> Added: lld/trunk/test/ELF/sysv-hash-no-rosegment.s
>>
>> URL:
>> https://urldefense.proofpoint.com/v2/url?u=http-3A__llvm.org_viewvc_llvm-2Dproject_lld_trunk_test_ELF_sysv-2Dhash-2Dno-2Drosegment.s-3Frev-3D322259-26view-3Dauto&d=DwIGaQ&c=5VD0RTtNlTh3ycd41b3MUw&r=o3kDXzdBUE3ljQXKeTWOMw&m=TzrIlS-6umMNRBVgupRbtxnFD-cXXbaxjd-gc8JgZcw&s=0bbiAHcIR4yTXv2MSkubnqN6lLXgm4QYw7TElwgAPKk&e=
>>
>>
>> ==============================================================================
>>
>> --- lld/trunk/test/ELF/sysv-hash-no-rosegment.s (added)
>>
>> +++ lld/trunk/test/ELF/sysv-hash-no-rosegment.s Wed Jan 10 22:57:01 2018
>>
>> @@ -0,0 +1,13 @@
>>
>> +# REQUIRES: x86
>>
>> +# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
>>
>> +# RUN: ld.lld -shared --no-rosegment -o %t %t.o
>>
>> +# RUN: llvm-readobj -hash-table %t | FileCheck %s
>>
>> +
>>
>> +# CHECK:      HashTable {
>>
>> +# CHECK-NEXT:   Num Buckets: 2
>>
>> +# CHECK-NEXT:   Num Chains: 2
>>
>> +# CHECK-NEXT:   Buckets: [1, 0]
>>
>> +# CHECK-NEXT:   Chains: [0, 0]
>>
>> +# CHECK-NEXT: }
>>
>> +
>>
>> +callq undef at PLT
>>
>>
>>
>>
>>
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>>
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>>
>>
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