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[ELF] -r: fix crash when processing a SHT_REL[A] that relocates a SHF_MERGE after D67504/r372734 

Fix PR43767

In -r mode, when processing a SHT_REL[A] that relocates a SHF_MERGE, sec->getRelocatedSection() is a
MergeInputSection and its parent is an OutputSection but is asserted to
be a SyntheticSection (MergeSyntheticSection) in LinkerScript.cpp:addInputSec().
 ##
The code path is not exercised in non -r mode because the relocated
section changed from MergeInputSection to InputSection.

Reorder the code to make the non -r logic apply to -r as well, thus fix
the crash.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D69364
This commit is contained in:
Fangrui Song 2019-10-24 10:52:19 -07:00
parent 267cc3292e
commit 56d81104f1
2 changed files with 33 additions and 10 deletions
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20
lld/ELF/InputFiles.cpp
View File

@ -838,6 +838,16 @@ InputSectionBase *ObjFile<ELFT>::createInputSection(const Elf_Shdr &sec) {
if (!target)
return nullptr;
// ELF spec allows mergeable sections with relocations, but they are
// rare, and it is in practice hard to merge such sections by contents,
// because applying relocations at end of linking changes section
// contents. So, we simply handle such sections as non-mergeable ones.
// Degrading like this is acceptable because section merging is optional.
if (auto *ms = dyn_cast<MergeInputSection>(target)) {
target = toRegularSection(ms);
this->sections[sec.sh_info] = target;
}
// This section contains relocation information.
// If -r is given, we do not interpret or apply relocation
// but just copy relocation sections to output.
@ -856,16 +866,6 @@ InputSectionBase *ObjFile<ELFT>::createInputSection(const Elf_Shdr &sec) {
fatal(toString(this) +
": multiple relocation sections to one section are not supported");
// ELF spec allows mergeable sections with relocations, but they are
// rare, and it is in practice hard to merge such sections by contents,
// because applying relocations at end of linking changes section
// contents. So, we simply handle such sections as non-mergeable ones.
// Degrading like this is acceptable because section merging is optional.
if (auto *ms = dyn_cast<MergeInputSection>(target)) {
target = toRegularSection(ms);
this->sections[sec.sh_info] = target;
}
if (sec.sh_type == SHT_RELA) {
ArrayRef<Elf_Rela> rels = CHECK(getObj().relas(&sec), this);
target->firstRelocation = rels.begin();

23
lld/test/ELF/merge-relocatable.s Normal file
View File

@ -0,0 +1,23 @@
# REQUIRES: x86
## Test that we keep a SHT_REL[A] section which relocates a SHF_MERGE section
## in -r mode. The relocated SHF_MERGE section is handled as non-mergeable.
# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
# RUN: ld.lld -r %t.o -o %t
# RUN: llvm-readobj -S %t | FileCheck %s
# CHECK: Name: .rodata.cst8
# CHECK-NOT: }
# CHECK: Size: 16
# CHECK: Name: .rela.rodata.cst8
# CHECK-NOT: }
# CHECK: Size: 48
foo:
.section .rodata.cst8,"aM",@progbits,8,unique,0
.quad foo
.section .rodata.cst8,"aM",@progbits,8,unique,1
.quad foo