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[ELF] Fallback to sh_link=0 if neither .dynsym nor .symtab exists 

Summary: .rela.plt may only contain R_*_{,I}RELATIVE relocations and not need a symbol table link. bfd/gold fallbacks to sh_link=0 in this case. Without this patch, ld.lld --strip-all caused lld to dereference a null pointer.

Reviewers: ruiu, grimar, espindola

Reviewed By: ruiu

Subscribers: emaste, arichardson, llvm-commits

Differential Revision: https://reviews.llvm.org/D53881

llvm-svn: 345648
This commit is contained in:
Fangrui Song 2018-10-30 20:54:54 +00:00
parent 4c39dfc91e
commit e0799a7268
2 changed files with 18 additions and 12 deletions
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14
lld/ELF/SyntheticSections.cpp
View File

@ -1491,11 +1491,15 @@ void RelocationBaseSection::addReloc(const DynamicReloc &Reloc) {
}
void RelocationBaseSection::finalizeContents() {
// If all relocations are R_*_RELATIVE they don't refer to any
// dynamic symbol and we don't need a dynamic symbol table. If that
// is the case, just use the index of the regular symbol table section.
getParent()->Link = In.DynSymTab ? In.DynSymTab->getParent()->SectionIndex
: In.SymTab->getParent()->SectionIndex;
// If all relocations are R_*_{,I}RELATIVE they don't refer to any dynamic
// symbol and we don't need a dynamic symbol table. If that is the case, use
// the index of the regular symbol table section (if exists) or 0.
if (In.DynSymTab)
getParent()->Link = In.DynSymTab->getParent()->SectionIndex;
else if (In.SymTab)
getParent()->Link = In.SymTab->getParent()->SectionIndex;
else
getParent()->Link = 0;
if (In.RelaIplt == this || In.RelaPlt == this)
getParent()->Info = In.GotPlt->getParent()->SectionIndex;

16
lld/test/ELF/gnu-ifunc-relative.s
View File

@ -1,7 +1,9 @@
// REQUIRES: x86
// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
// RUN: ld.lld -static %t.o -o %tout
// RUN: llvm-readobj -r -t %tout | FileCheck %s
// RUN: ld.lld --strip-all %t.o -o %t
// RUN: llvm-readobj -r %t | FileCheck %s
// RUN: ld.lld %t.o -o %t
// RUN: llvm-readobj -r -t %t | FileCheck %s --check-prefixes=CHECK,SYM
.type foo STT_GNU_IFUNC
.globl foo
@ -16,8 +18,8 @@ _start:
// CHECK-NEXT: R_X86_64_IRELATIVE - 0x[[ADDR:.*]]
// CHECK-NEXT: }
// CHECK: Name: foo
// CHECK-NEXT: Value: 0x[[ADDR]]
// CHECK-NEXT: Size: 0
// CHECK-NEXT: Binding: Global
// CHECK-NEXT: Type: GNU_IFunc
// SYM: Name: foo
// SYM-NEXT: Value: 0x[[ADDR]]
// SYM-NEXT: Size: 0
// SYM-NEXT: Binding: Global
// SYM-NEXT: Type: GNU_IFunc