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[ELF2] getLocalRelTarget should handle R_PPC64_TOC directly 

R_PPC64_TOC does not have an associated symbol, but does have a non-zero VA
that target-specific code must compute using some non-trivial rule. We
handled this as a special case in PPC64TargetInfo::relocateOne, where
we knew to write this special address, but that did not work when creating shared
libraries. The special TOC address needs to be the subject of a
R_PPC64_RELATIVE relocation, and so we also need to know how to encode this
special address in the addend of that relocation.

Thus, some target-specific logic is necessary when creating R_PPC64_RELATIVE as
well. To solve this problem, we teach getLocalRelTarget to handle R_PPC64_TOC
as a special case. This allows us to remove the special case in
PPC64TargetInfo::relocateOne (simplifying code there), and naturally allows the
existing logic to do the right thing when creating associated R_PPC64_RELATIVE
relocations for shared libraries.

llvm-svn: 250555
This commit is contained in:
Hal Finkel 2015-10-16 21:55:40 +00:00
parent 3d5b48c480
commit 6f97c2bc00
6 changed files with 47 additions and 17 deletions
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2
lld/ELF/InputSection.cpp
View File

@ -57,7 +57,7 @@ void InputSection<ELFT>::relocate(
// resolved so we don't allocate a SymbolBody.
const Elf_Shdr *SymTab = File.getSymbolTable();
if (SymIndex < SymTab->sh_info) {
uintX_t SymVA = getLocalRelTarget(File, RI);
uintX_t SymVA = getLocalRelTarget(File, RI, Type);
relocateOne(Buf, BufEnd, RI, Type, BaseAddr, SymVA);
continue;
}

22
lld/ELF/OutputSections.cpp
View File

@ -126,7 +126,7 @@ template <class ELFT> void RelocationSection<ELFT>::writeTo(uint8_t *Buf) {
if (Body)
Addend += getSymVA<ELFT>(cast<ELFSymbolBody<ELFT>>(*Body));
else
Addend += getLocalRelTarget(File, RI);
Addend += getLocalRelTarget(File, RI, Type);
}
P->setSymbolAndType(0, Target->getRelativeReloc(), IsMips64EL);
}
@ -424,15 +424,19 @@ typename ELFFile<ELFT>::uintX_t lld::elf2::getSymVA(const SymbolBody &S) {
template <class ELFT>
typename ELFFile<ELFT>::uintX_t
lld::elf2::getLocalRelTarget(const ObjectFile<ELFT> &File,
const typename ELFFile<ELFT>::Elf_Rel &RI) {
const typename ELFFile<ELFT>::Elf_Rel &RI,
uint32_t Type) {
// PPC64 has a special relocation representing the TOC base pointer
// that does not have a corresponding symbol.
if (Config->EMachine == EM_PPC64 && Type == R_PPC64_TOC)
return getPPC64TocBase();
typedef typename ELFFile<ELFT>::Elf_Sym Elf_Sym;
const Elf_Sym *Sym =
File.getObj().getRelocationSymbol(&RI, File.getSymbolTable());
// For certain special relocations, such as R_PPC64_TOC, there's no
// corresponding symbol. Just return 0 in that case.
if (!Sym)
return 0;
error("Unsupported relocation without symbol");
// According to the ELF spec reference to a local symbol from outside
// the group are not allowed. Unfortunately .eh_frame breaks that rule
@ -743,19 +747,19 @@ template ELFFile<ELF64BE>::uintX_t getSymVA<ELF64BE>(const SymbolBody &);
template ELFFile<ELF32LE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF32LE> &,
const ELFFile<ELF32LE>::Elf_Rel &);
const ELFFile<ELF32LE>::Elf_Rel &, uint32_t);
template ELFFile<ELF32BE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF32BE> &,
const ELFFile<ELF32BE>::Elf_Rel &);
const ELFFile<ELF32BE>::Elf_Rel &, uint32_t);
template ELFFile<ELF64LE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF64LE> &,
const ELFFile<ELF64LE>::Elf_Rel &);
const ELFFile<ELF64LE>::Elf_Rel &, uint32_t);
template ELFFile<ELF64BE>::uintX_t
getLocalRelTarget(const ObjectFile<ELF64BE> &,
const ELFFile<ELF64BE>::Elf_Rel &);
const ELFFile<ELF64BE>::Elf_Rel &, uint32_t);
template bool includeInSymtab<ELF32LE>(const SymbolBody &);
template bool includeInSymtab<ELF32BE>(const SymbolBody &);

3
lld/ELF/OutputSections.h
View File

@ -38,7 +38,8 @@ typename llvm::object::ELFFile<ELFT>::uintX_t getSymVA(const SymbolBody &S);
template <class ELFT>
typename llvm::object::ELFFile<ELFT>::uintX_t
getLocalRelTarget(const ObjectFile<ELFT> &File,
const typename llvm::object::ELFFile<ELFT>::Elf_Rel &Sym);
const typename llvm::object::ELFFile<ELFT>::Elf_Rel &Sym,
uint32_t Type);
bool canBePreempted(const SymbolBody *Body, bool NeedsGot);
template <class ELFT> bool includeInSymtab(const SymbolBody &B);

8
lld/ELF/Target.cpp
View File

@ -345,7 +345,7 @@ PPC64TargetInfo::PPC64TargetInfo() {
VAStart = 0x10000000;
}
static uint64_t getPPC64TocBase() {
uint64_t getPPC64TocBase() {
// The TOC consists of sections .got, .toc, .tocbss, .plt in that
// order. The TOC starts where the first of these sections starts.
@ -426,11 +426,6 @@ void PPC64TargetInfo::relocateOne(uint8_t *Buf, uint8_t *BufEnd,
uint64_t P = BaseAddr + Rel.r_offset;
uint64_t TB = getPPC64TocBase();
if (Type == R_PPC64_TOC) {
write64be(L, TB);
return;
}
// For a TOC-relative relocation, adjust the addend and proceed in terms of
// the corresponding ADDR16 relocation type.
switch (Type) {
@ -536,6 +531,7 @@ void PPC64TargetInfo::relocateOne(uint8_t *Buf, uint8_t *BufEnd,
write64be(L, SA - P);
break;
case R_PPC64_ADDR64:
case R_PPC64_TOC:
write64be(L, SA);
break;
default:

2
lld/ELF/Target.h
View File

@ -58,6 +58,8 @@ protected:
unsigned PltEntrySize = 8;
};
uint64_t getPPC64TocBase();
extern std::unique_ptr<TargetInfo> Target;
TargetInfo *createTarget();
}

27
lld/test/elf2/ppc64-shared-rel-toc.s Normal file
View File

@ -0,0 +1,27 @@
// RUN: llvm-mc -filetype=obj -triple=powerpc64-unknown-linux %s -o %t.o
// RUN: ld.lld2 -shared %t.o -o %t.so
// RUN: llvm-readobj -t -r -dyn-symbols %t.so | FileCheck %s
// REQUIRES: ppc
// When we create the TOC reference in the shared library, make sure that the
// R_PPC64_RELATIVE relocation uses the correct (non-zero) offset.
.globl foo
.align 2
.type foo,@function
.section .opd,"aw",@progbits
foo: # @foo
.align 3
.quad .Lfunc_begin0
.quad .TOC.@tocbase
.quad 0
.text
.Lfunc_begin0:
blr
// CHECK: 0x20090 R_PPC64_RELATIVE - 0x10000
// CHECK: 0x20098 R_PPC64_RELATIVE - 0x8000
// CHECK: Name: foo (20)
// CHECK-NEXT: Value: 0x20090