HA: [lld] r249816 - [ELF2] - Implemented rel[a].plt sections
George Rimar via llvm-commits
llvm-commits at lists.llvm.org
Fri Oct 9 07:50:35 PDT 2015
Oh, that sad.
Just wanted to introduce another change. I noticed that symbol can be both in rela.dyn and rela.plt sections,
for example when we call a function from DSO and also take its address.
Current implemention of Writer<ELFT>::scanRelocs will not work correctly for that case (will exit early and put symbol only in rela.plt).
But anyways hope to return to that later when lld be ready for such changes.
________________________________________
От: Rafael Espíndola [rafael.espindola at gmail.com]
Отправлено: 9 октября 2015 г. 18:29
Кому: George Rimar
Копия: llvm-commits
Тема: Re: [lld] r249816 - [ELF2] - Implemented rel[a].plt sections
Sorry, I had to revert this.
See r249835 for the details.
Cheers,
Rafael
On 9 October 2015 at 05:58, George Rimar via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: grimar
> Date: Fri Oct 9 04:58:08 2015
> New Revision: 249816
>
> URL: http://llvm.org/viewvc/llvm-project?rev=249816&view=rev
> Log:
> [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
>
> Modified:
> lld/trunk/ELF/OutputSections.cpp
> lld/trunk/ELF/OutputSections.h
> lld/trunk/ELF/Writer.cpp
> lld/trunk/test/elf2/plt-i686.s
> lld/trunk/test/elf2/plt.s
> lld/trunk/test/elf2/relocation.s
>
> Modified: lld/trunk/ELF/OutputSections.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=249816&r1=249815&r2=249816&view=diff
> ==============================================================================
> --- lld/trunk/ELF/OutputSections.cpp (original)
> +++ lld/trunk/ELF/OutputSections.cpp Fri Oct 9 04:58:08 2015
> @@ -48,6 +48,10 @@ template <> RelocationSection<ELF32BE> *
> 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 DynamicSectio
> ++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 DynamicSectio
> 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));
>
> Modified: lld/trunk/ELF/OutputSections.h
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.h?rev=249816&r1=249815&r2=249816&view=diff
> ==============================================================================
> --- lld/trunk/ELF/OutputSections.h (original)
> +++ lld/trunk/ELF/OutputSections.h Fri Oct 9 04:58:08 2015
> @@ -171,7 +171,7 @@ class RelocationSection final : public O
> 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;
>
> Modified: lld/trunk/ELF/Writer.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=249816&r1=249815&r2=249816&view=diff
> ==============================================================================
> --- lld/trunk/ELF/Writer.cpp (original)
> +++ lld/trunk/ELF/Writer.cpp Fri Oct 9 04:58:08 2015
> @@ -134,8 +134,11 @@ template <class ELFT> static void doWrit
> 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>:
> 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);
>
> Modified: lld/trunk/test/elf2/plt-i686.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/plt-i686.s?rev=249816&r1=249815&r2=249816&view=diff
> ==============================================================================
> --- lld/trunk/test/elf2/plt-i686.s (original)
> +++ lld/trunk/test/elf2/plt-i686.s Fri Oct 9 04:58:08 2015
> @@ -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
>
>
> Modified: lld/trunk/test/elf2/plt.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/plt.s?rev=249816&r1=249815&r2=249816&view=diff
> ==============================================================================
> --- lld/trunk/test/elf2/plt.s (original)
> +++ lld/trunk/test/elf2/plt.s Fri Oct 9 04:58:08 2015
> @@ -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
>
>
> Modified: lld/trunk/test/elf2/relocation.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/relocation.s?rev=249816&r1=249815&r2=249816&view=diff
> ==============================================================================
> --- lld/trunk/test/elf2/relocation.s (original)
> +++ lld/trunk/test/elf2/relocation.s Fri Oct 9 04:58:08 2015
> @@ -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 at 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
>
>
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