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[ELF2] - Implemented rel[a].plt sections 

.rela.plt contains list of elements in the PLT, which are liable to the relocation during the dynamic linking.

Differential Revision: http://reviews.llvm.org/D13569

llvm-svn: 249816
This commit is contained in:
George Rimar 2015-10-09 09:58:08 +00:00
parent c4cb3b10dc
commit b352b9ce69
6 changed files with 55 additions and 29 deletions
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24
lld/ELF/OutputSections.cpp
View File

@ -48,6 +48,10 @@ template <> RelocationSection<ELF32BE> *Out<ELF32BE>::RelaDyn = nullptr;
template <> RelocationSection<ELF32LE> *Out<ELF32LE>::RelaDyn = nullptr;
template <> RelocationSection<ELF64BE> *Out<ELF64BE>::RelaDyn = nullptr;
template <> RelocationSection<ELF64LE> *Out<ELF64LE>::RelaDyn = nullptr;
template <> RelocationSection<ELF32BE> *Out<ELF32BE>::RelaPlt = nullptr;
template <> RelocationSection<ELF32LE> *Out<ELF32LE>::RelaPlt = nullptr;
template <> RelocationSection<ELF64BE> *Out<ELF64BE>::RelaPlt = nullptr;
template <> RelocationSection<ELF64LE> *Out<ELF64LE>::RelaPlt = nullptr;
template <> StringTableSection<false> *Out<ELF32BE>::DynStrTab = nullptr;
template <> StringTableSection<false> *Out<ELF32LE>::DynStrTab = nullptr;
template <> StringTableSection<true> *Out<ELF64BE>::DynStrTab = nullptr;
@ -139,10 +143,9 @@ void PltSection<ELFT>::finalize() {
}
template <class ELFT>
RelocationSection<ELFT>::RelocationSection(bool IsRela)
: OutputSectionBase<ELFT::Is64Bits>(IsRela ? ".rela.dyn" : ".rel.dyn",
IsRela ? llvm::ELF::SHT_RELA
: llvm::ELF::SHT_REL,
RelocationSection<ELFT>::RelocationSection(StringRef Name, bool IsRela)
: OutputSectionBase<ELFT::Is64Bits>(Name, IsRela ? llvm::ELF::SHT_RELA
: llvm::ELF::SHT_REL,
llvm::ELF::SHF_ALLOC),
IsRela(IsRela) {
this->Header.sh_entsize = IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel);
@ -300,6 +303,13 @@ template <class ELFT> void DynamicSection<ELFT>::finalize() {
++NumEntries; // DT_RELASZ / DT_RELSZ
++NumEntries; // DT_RELAENT / DT_RELENT
}
if (Out<ELFT>::RelaPlt->hasRelocs()) {
++NumEntries; // DT_JMPREL
++NumEntries; // DT_PLTRELSZ
++NumEntries; // DT_PLTGOT
++NumEntries; // DT_PLTREL
}
++NumEntries; // DT_SYMTAB
++NumEntries; // DT_SYMENT
++NumEntries; // DT_STRTAB
@ -367,6 +377,12 @@ template <class ELFT> void DynamicSection<ELFT>::writeTo(uint8_t *Buf) {
WriteVal(IsRela ? DT_RELAENT : DT_RELENT,
IsRela ? sizeof(Elf_Rela) : sizeof(Elf_Rel));
}
if (Out<ELFT>::RelaPlt->hasRelocs()) {
WritePtr(DT_JMPREL, Out<ELFT>::RelaPlt->getVA());
WriteVal(DT_PLTRELSZ, Out<ELFT>::RelaPlt->getSize());
WritePtr(DT_PLTGOT, Out<ELFT>::Got->getVA());
WriteVal(DT_PLTREL, Out<ELFT>::RelaPlt->isRela() ? DT_RELA : DT_REL);
}
WritePtr(DT_SYMTAB, Out<ELFT>::DynSymTab->getVA());
WritePtr(DT_SYMENT, sizeof(Elf_Sym));

3
lld/ELF/OutputSections.h
View File

@ -171,7 +171,7 @@ class RelocationSection final : public OutputSectionBase<ELFT::Is64Bits> {
typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
public:
RelocationSection(bool IsRela);
RelocationSection(StringRef Name, bool IsRela);
void addReloc(const DynamicReloc<ELFT> &Reloc) { Relocs.push_back(Reloc); }
void finalize() override;
void writeTo(uint8_t *Buf) override;
@ -289,6 +289,7 @@ template <class ELFT> struct Out {
static OutputSection<ELFT> *Bss;
static PltSection<ELFT> *Plt;
static RelocationSection<ELFT> *RelaDyn;
static RelocationSection<ELFT> *RelaPlt;
static StringTableSection<ELFT::Is64Bits> *DynStrTab;
static StringTableSection<ELFT::Is64Bits> *StrTab;
static SymbolTableSection<ELFT> *DynSymTab;

19
lld/ELF/Writer.cpp
View File

@ -134,8 +134,11 @@ template <class ELFT> static void doWriteResult(SymbolTable *Symtab) {
Out<ELFT>::DynSymTab = &DynSymTab;
HashTableSection<ELFT> HashTab;
Out<ELFT>::HashTab = &HashTab;
RelocationSection<ELFT> RelaDyn(Symtab->shouldUseRela());
bool IsRela = Symtab->shouldUseRela();
RelocationSection<ELFT> RelaDyn(IsRela ? ".rela.dyn" : ".rel.dyn", IsRela);
Out<ELFT>::RelaDyn = &RelaDyn;
RelocationSection<ELFT> RelaPlt(IsRela ? ".rela.plt" : ".rel.plt", IsRela);
Out<ELFT>::RelaPlt = &RelaPlt;
DynamicSection<ELFT> Dynamic(*Symtab);
Out<ELFT>::Dynamic = &Dynamic;
@ -233,11 +236,15 @@ void Writer<ELFT>::scanRelocs(
Out<ELFT>::Got->addEntry(Body);
}
}
if (canBePreempted(Body)) {
bool CanBePreempted = canBePreempted(Body);
if (CanBePreempted)
Body->setUsedInDynamicReloc();
Out<ELFT>::RelaDyn->addReloc({C, RI});
} else if (Config->Shared && !Target->isRelRelative(Type)) {
Out<ELFT>::RelaDyn->addReloc({C, RI});
if (CanBePreempted || (Config->Shared && !Target->isRelRelative(Type))) {
if (Body && Body->isInPlt())
Out<ELFT>::RelaPlt->addReloc({C, RI});
else
Out<ELFT>::RelaDyn->addReloc({C, RI});
}
}
}
@ -466,6 +473,8 @@ template <class ELFT> void Writer<ELFT>::createSections() {
OutputSections.push_back(Out<ELFT>::DynStrTab);
if (Out<ELFT>::RelaDyn->hasRelocs())
OutputSections.push_back(Out<ELFT>::RelaDyn);
if (Out<ELFT>::RelaPlt->hasRelocs())
OutputSections.push_back(Out<ELFT>::RelaPlt);
}
if (!Out<ELFT>::Got->empty())
OutputSections.push_back(Out<ELFT>::Got);

14
lld/test/elf2/plt-i686.s
View File

@ -20,9 +20,9 @@
// CHECK-NEXT: AddressAlignment: 16
// CHECK: Relocations [
// CHECK-NEXT: Section ({{.*}}) .rel.dyn {
// CHECK-NEXT: 0x13050 R_386_GLOB_DAT bar 0x0
// CHECK-NEXT: 0x13054 R_386_GLOB_DAT zed 0x0
// CHECK-NEXT: Section ({{.*}}) .rel.plt {
// CHECK-NEXT: 0x13058 R_386_GLOB_DAT bar 0x0
// CHECK-NEXT: 0x1305C R_386_GLOB_DAT zed 0x0
// CHECK-NEXT: }
// CHECK-NEXT: ]
@ -38,15 +38,15 @@
// DISASM-NEXT: 12005: e9 06 00 00 00 jmp 6
// DISASM-NEXT: 1200a: e9 09 00 00 00 jmp 9
// 0x13050 = 77904
// 0x13054 = 77908
// 0x13058 = 77912
// 0x1305C = 77916
// DISASM: Disassembly of section .plt:
// DISASM-NEXT: .plt:
// DISASM-NEXT: 12010: ff 25 {{.*}} jmpl *77904
// DISASM-NEXT: 12010: ff 25 {{.*}} jmpl *77912
// DISASM-NEXT: 12016: 90 nop
// DISASM-NEXT: 12017: 90 nop
// DISASM-NEXT: 12018: ff 25 {{.*}} jmpl *77908
// DISASM-NEXT: 12018: ff 25 {{.*}} jmpl *77916
// DISASM-NEXT: 1201e: 90 nop
// DISASM-NEXT: 1201f: 90 nop

16
lld/test/elf2/plt.s
View File

@ -20,10 +20,10 @@
// CHECK-NEXT: AddressAlignment: 16
// CHECK: Relocations [
// CHECK-NEXT: Section ({{.*}}) .rela.dyn {
// CHECK-NEXT: 0x30A0 R_X86_64_GLOB_DAT bar 0x0
// CHECK-NEXT: 0x30A8 R_X86_64_GLOB_DAT zed 0x0
// CHECK-NEXT: 0x30B0 R_X86_64_GLOB_DAT _start 0x0
// CHECK-NEXT: Section ({{.*}}) .rela.plt {
// CHECK-NEXT: 0x30B0 R_X86_64_GLOB_DAT bar 0x0
// CHECK-NEXT: 0x30B8 R_X86_64_GLOB_DAT zed 0x0
// CHECK-NEXT: 0x30C0 R_X86_64_GLOB_DAT _start 0x0
// CHECK-NEXT: }
// CHECK-NEXT: ]
@ -39,15 +39,15 @@
// DISASM-NEXT: 2005: e9 {{.*}} jmp 22
// DISASM-NEXT: 200a: e9 {{.*}} jmp 25
// 0x130A0 - 0x12026 = 4218
// 0x130A8 - 0x1202e = 4218
// 0x30B0 - 0x2026 = 4234
// 0x30B8 - 0x202e = 4234
// DISASM: Disassembly of section .plt:
// DISASM-NEXT: .plt:
// DISASM-NEXT: 2020: ff 25 {{.*}} jmpq *4218(%rip)
// DISASM-NEXT: 2020: ff 25 {{.*}} jmpq *4234(%rip)
// DISASM-NEXT: 2026: 90 nop
// DISASM-NEXT: 2027: 90 nop
// DISASM-NEXT: 2028: ff 25 {{.*}} jmpq *4218(%rip)
// DISASM-NEXT: 2028: ff 25 {{.*}} jmpq *4234(%rip)
// DISASM-NEXT: 202e: 90 nop
// DISASM-NEXT: 202f: 90 nop

8
lld/test/elf2/relocation.s
View File

@ -22,7 +22,7 @@
// SEC-NEXT: SHF_ALLOC
// SEC-NEXT: SHF_WRITE
// SEC-NEXT: ]
// SEC-NEXT: Address: 0x130A0
// SEC-NEXT: Address: 0x130E0
// SEC-NEXT: Offset:
// SEC-NEXT: Size: 16
// SEC-NEXT: Link: 0
@ -93,7 +93,7 @@ R_X86_64_64:
R_X86_64_GOTPCREL:
.long zed@gotpcrel
// 0x130A8 - 0x11008 = 8352
// 8352 = 0x80200000 in little endian
// 0x130E8 - 0x11008 = 8416
// 8416 = 0xE0200000 in little endian
// CHECK: Contents of section .R_X86_64_GOTPCREL
// CHECK-NEXT: 11008 a0200000
// CHECK-NEXT: 11008 e0200000