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[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://reviews.llvm.org/D41928

llvm-svn: 322259
This commit is contained in:
Shoaib Meenai 2018-01-11 06:57:01 +00:00
parent bb9c6fc3bc
commit d79bbf4474
2 changed files with 16 additions and 0 deletions
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3
lld/ELF/SyntheticSections.cpp
View File

@ -1836,6 +1836,9 @@ void HashTableSection::finalizeContents() {
} }
void HashTableSection::writeTo(uint8_t *Buf) { void HashTableSection::writeTo(uint8_t *Buf) {
// See comment in GnuHashTableSection::writeTo.
memset(Buf, 0, Size);
unsigned NumSymbols = InX::DynSymTab->getNumSymbols(); unsigned NumSymbols = InX::DynSymTab->getNumSymbols();
uint32_t *P = reinterpret_cast<uint32_t *>(Buf); uint32_t *P = reinterpret_cast<uint32_t *>(Buf);

13
lld/test/ELF/sysv-hash-no-rosegment.s Normal file
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@ -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@PLT