This is an archive of the discontinued LLVM Phabricator instance.

Differential D136655

[BOLT] Add mold-style PLT support
ClosedPublic

Authored by maksfb on Oct 24 2022, 6:35 PM.

Details

Reviewers
yota9
Amir
ayermolo
rafauler
yavtuk
treapster
Commits
rG20204db50389: [BOLT] Add mold-style PLT support
Summary

mold linker creates symbols for PLT entries and that caught BOLT by
surprise. Add the support for marked PLT entries.

Fixes: #58498

Diff Detail

Event Timeline

maksfb created this revision.Oct 24 2022, 6:35 PM
Herald added a project: Restricted Project. · View Herald TranscriptOct 24 2022, 6:35 PM
maksfb requested review of this revision.Oct 24 2022, 6:35 PM
Herald added a project: Restricted Project. · View Herald TranscriptOct 24 2022, 6:35 PM
Herald added a subscriber: llvm-commits. · View Herald Transcript
Harbormaster completed remote builds in B194078: Diff 470349.Oct 24 2022, 6:42 PM
yota9 accepted this revision.Oct 24 2022, 10:03 PM

LGTM thanks!

bolt/test/X86/plt-mold.test
6

May I ask why it is "printf$plt and not printf@PLT? Is there a typo?

This revision is now accepted and ready to land.Oct 24 2022, 10:03 PM
maksfb added inline comments.Oct 24 2022, 10:22 PM
bolt/test/X86/plt-mold.test
6

That’s the symbol mold creates at the moment. It also has local visibility.

yota9 added inline comments.Oct 24 2022, 11:30 PM
bolt/test/X86/plt-mold.test
6

Oh, it is part of the symbol name, interesting. I was thinking about the addend we add with @PLT. Thanks

Closed by commit rG20204db50389: [BOLT] Add mold-style PLT support (authored by maksfb). · Explain WhyOct 25 2022, 11:04 AM
This revision was automatically updated to reflect the committed changes.
maksfb added a commit: rG20204db50389: [BOLT] Add mold-style PLT support.

Revision Contents

PathSize
bolt/
lib/
Rewrite/
25 lines
test/
X86/
Inputs/
399 lines
6 lines

Diff 470349

bolt/lib/Rewrite/RewriteInstance.cpp

Show First 20 Lines • Show All 1,271 Lines • ▼ Show 20 Linesvoid RewriteInstance::createPLTBinaryFunction(uint64_t TargetAddress,
} }
const Relocation *Rel = BC->getDynamicRelocationAt(TargetAddress); const Relocation *Rel = BC->getDynamicRelocationAt(TargetAddress);
if (!Rel || !Rel->Symbol) if (!Rel || !Rel->Symbol)
return; return;
ErrorOr<BinarySection &> Section = BC->getSectionForAddress(EntryAddress); ErrorOr<BinarySection &> Section = BC->getSectionForAddress(EntryAddress);
assert(Section && "cannot get section for address"); assert(Section && "cannot get section for address");
BF = BC->createBinaryFunction(Rel->Symbol->getName().str() + "@PLT", *Section, if (!BF)
EntryAddress, 0, EntrySize, BF = BC->createBinaryFunction(Rel->Symbol->getName().str() + "@PLT",
*Section, EntryAddress, 0, EntrySize,
Section->getAlignment()); Section->getAlignment());
else
BF->addAlternativeName(Rel->Symbol->getName().str() + "@PLT");
setPLTSymbol(BF, Rel->Symbol->getName()); setPLTSymbol(BF, Rel->Symbol->getName());
} }
void RewriteInstance::disassemblePLTSectionAArch64(BinarySection &Section) { void RewriteInstance::disassemblePLTSectionAArch64(BinarySection &Section) {
const uint64_t SectionAddress = Section.getAddress(); const uint64_t SectionAddress = Section.getAddress();
const uint64_t SectionSize = Section.getSize(); const uint64_t SectionSize = Section.getSize();
StringRef PLTContents = Section.getContents(); StringRef PLTContents = Section.getContents();
ArrayRef<uint8_t> PLTData( ArrayRef<uint8_t> PLTData(
▲ Show 20 Lines • Show All 115 Lines • ▼ Show 20 Linesvoid RewriteInstance::disassemblePLT() {
}; };
for (BinarySection &Section : BC->allocatableSections()) { for (BinarySection &Section : BC->allocatableSections()) {
const PLTSectionInfo *PLTSI = getPLTSectionInfo(Section.getName()); const PLTSectionInfo *PLTSI = getPLTSectionInfo(Section.getName());
if (!PLTSI) if (!PLTSI)
continue; continue;
analyzeOnePLTSection(Section, PLTSI->EntrySize); analyzeOnePLTSection(Section, PLTSI->EntrySize);
BinaryFunction *PltBF;
auto BFIter = BC->getBinaryFunctions().find(Section.getAddress());
if (BFIter != BC->getBinaryFunctions().end()) {
PltBF = &BFIter->second;
} else {
// If we did not register any function at the start of the section, // If we did not register any function at the start of the section,
// then it must be a general PLT entry. Add a function at the location. // then it must be a general PLT entry. Add a function at the location.
if (BC->getBinaryFunctions().find(Section.getAddress()) == PltBF = BC->createBinaryFunction(
BC->getBinaryFunctions().end()) {
BinaryFunction *BF = BC->createBinaryFunction(
"__BOLT_PSEUDO_" + Section.getName().str(), Section, "__BOLT_PSEUDO_" + Section.getName().str(), Section,
Section.getAddress(), 0, PLTSI->EntrySize, Section.getAlignment()); Section.getAddress(), 0, PLTSI->EntrySize, Section.getAlignment());
BF->setPseudo(true);
} }
PltBF->setPseudo(true);
} }
} }
void RewriteInstance::adjustFunctionBoundaries() { void RewriteInstance::adjustFunctionBoundaries() {
for (auto BFI = BC->getBinaryFunctions().begin(), for (auto BFI = BC->getBinaryFunctions().begin(),
BFE = BC->getBinaryFunctions().end(); BFE = BC->getBinaryFunctions().end();
BFI != BFE; ++BFI) { BFI != BFE; ++BFI) {
BinaryFunction &Function = BFI->second; BinaryFunction &Function = BFI->second;
▲ Show 20 Lines • Show All 4,177 Lines • Show Last 20 Lines

bolt/test/X86/Inputs/plt-mold.yaml

  • This file was added.
--- !ELF
FileHeader:
Class: ELFCLASS64
Data: ELFDATA2LSB
Type: ET_DYN
Machine: EM_X86_64
Entry: 0x13D0
ProgramHeaders:
- Type: PT_PHDR
Flags: [ PF_R ]
VAddr: 0x40
Align: 0x8
- Type: PT_INTERP
Flags: [ PF_R ]
FirstSec: .interp
LastSec: .interp
VAddr: 0x270
- Type: PT_LOAD
Flags: [ PF_R ]
FirstSec: .interp
LastSec: .rodata.str
Align: 0x1000
- Type: PT_LOAD
Flags: [ PF_X, PF_R ]
FirstSec: .plt
LastSec: .text
VAddr: 0x13A0
Align: 0x1000
- Type: PT_LOAD
Flags: [ PF_W, PF_R ]
FirstSec: .dynamic
LastSec: .relro_padding
VAddr: 0x23F8
Align: 0x1000
- Type: PT_LOAD
Flags: [ PF_W, PF_R ]
FirstSec: .got.plt
LastSec: .got.plt
VAddr: 0x3550
Align: 0x1000
- Type: PT_DYNAMIC
Flags: [ PF_W, PF_R ]
FirstSec: .dynamic
LastSec: .dynamic
VAddr: 0x23F8
Align: 0x8
- Type: PT_GNU_EH_FRAME
Flags: [ PF_R ]
FirstSec: .eh_frame_hdr
LastSec: .eh_frame_hdr
VAddr: 0x37C
Align: 0x4
- Type: PT_GNU_STACK
Flags: [ PF_W, PF_R ]
- Type: PT_GNU_RELRO
Flags: [ PF_R ]
FirstSec: .dynamic
LastSec: .relro_padding
VAddr: 0x23F8
Sections:
- Name: .interp
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC ]
Address: 0x270
AddressAlign: 0x1
Content: 2F6C696236342F6C642D6C696E75782D7838362D36342E736F2E3200
- Name: .gnu.hash
Type: SHT_GNU_HASH
Flags: [ SHF_ALLOC ]
Address: 0x290
Link: .dynsym
AddressAlign: 0x8
Header:
SymNdx: 0x2
Shift2: 0x1A
BloomFilter: [ 0x0 ]
HashBuckets: [ 0x0 ]
HashValues: [ ]
- Name: .dynsym
Type: SHT_DYNSYM
Flags: [ SHF_ALLOC ]
Address: 0x2B0
Link: .dynstr
AddressAlign: 0x8
- Name: .dynstr
Type: SHT_STRTAB
Flags: [ SHF_ALLOC ]
Address: 0x2E0
AddressAlign: 0x1
- Name: .gnu.version
Type: SHT_GNU_versym
Flags: [ SHF_ALLOC ]
Address: 0x2FE
Link: .dynsym
AddressAlign: 0x2
Entries: [ 0, 2 ]
- Name: .gnu.version_r
Type: SHT_GNU_verneed
Flags: [ SHF_ALLOC ]
Address: 0x308
Link: .dynstr
AddressAlign: 0x8
Dependencies:
- Version: 1
File: libc.so.6
Entries:
- Name: GLIBC_2.2.5
Hash: 157882997
Flags: 0
Other: 2
- Name: .rela.plt
Type: SHT_RELA
Flags: [ SHF_ALLOC, SHF_INFO_LINK ]
Address: 0x328
Link: .dynsym
AddressAlign: 0x8
Info: .got.plt
Relocations:
- Offset: 0x3568
Symbol: printf
Type: R_X86_64_JUMP_SLOT
- Name: .eh_frame
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC ]
Address: 0x340
AddressAlign: 0x8
Content: 1400000000000000017A5200017810011B0C0708900100001C0000001C000000701000002500000000410E108602430D06600C070800000000000000
- Name: .eh_frame_hdr
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC ]
Address: 0x37C
AddressAlign: 0x4
Content: 011B033BC0FFFFFF0100000054100000DCFFFFFF
- Name: .rodata.str
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC ]
Address: 0x390
AddressAlign: 0x1
Content: 48656C6C6F20776F726C64210A00
- Name: .plt
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
Address: 0x13A0
AddressAlign: 0x10
Content: F30F1EFA4153FF35AC210000FF25AE210000CCCCCCCCCCCCCCCCCCCCCCCCCCCCF30F1EFA41BB00000000FF2598210000
- Name: .text
Type: SHT_PROGBITS
Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
Address: 0x13D0
AddressAlign: 0x10
Content: 554889E54883EC10C745FC00000000488D3DAAEFFFFFB000E8D3FFFFFF31C04883C4105DC3
- Name: .dynamic
Type: SHT_DYNAMIC
Flags: [ SHF_WRITE, SHF_ALLOC ]
Address: 0x23F8
Link: .dynstr
AddressAlign: 0x8
Entries:
- Tag: DT_NEEDED
Value: 0x1
- Tag: DT_JMPREL
Value: 0x328
- Tag: DT_PLTRELSZ
Value: 0x18
- Tag: DT_PLTREL
Value: 0x7
- Tag: DT_PLTGOT
Value: 0x3550
- Tag: DT_SYMTAB
Value: 0x2B0
- Tag: DT_SYMENT
Value: 0x18
- Tag: DT_STRTAB
Value: 0x2E0
- Tag: DT_STRSZ
Value: 0x1E
- Tag: DT_VERSYM
Value: 0x2FE
- Tag: DT_VERNEED
Value: 0x308
- Tag: DT_VERNEEDNUM
Value: 0x1
- Tag: DT_GNU_HASH
Value: 0x290
- Tag: DT_FLAGS_1
Value: 0x8000000
- Tag: DT_DEBUG
Value: 0x0
- Tag: DT_NULL
Value: 0x0
- Tag: DT_NULL
Value: 0x0
- Tag: DT_NULL
Value: 0x0
- Tag: DT_NULL
Value: 0x0
- Tag: DT_NULL
Value: 0x0
- Tag: DT_NULL
Value: 0x0
- Name: .got
Type: SHT_PROGBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
Address: 0x2548
AddressAlign: 0x8
Content: '0000000000000000'
- Name: .relro_padding
Type: SHT_NOBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
Address: 0x2550
AddressAlign: 0x1
Size: 0xAB0
- Name: .got.plt
Type: SHT_PROGBITS
Flags: [ SHF_WRITE, SHF_ALLOC ]
Address: 0x3550
AddressAlign: 0x8
Content: F82300000000000000000000000000000000000000000000A013000000000000
- Name: .rela.text
Type: SHT_RELA
Flags: [ SHF_INFO_LINK ]
Link: .symtab
AddressAlign: 0x8
Info: .text
Relocations:
- Offset: 0x13E2
Symbol: .L.str
Type: R_X86_64_PC32
Addend: -4
- Offset: 0x13E9
Symbol: printf
Type: R_X86_64_PLT32
Addend: -4
- Type: SectionHeaderTable
Sections:
- Name: .interp
- Name: .gnu.hash
- Name: .dynsym
- Name: .dynstr
- Name: .gnu.version
- Name: .gnu.version_r
- Name: .rela.plt
- Name: .eh_frame
- Name: .eh_frame_hdr
- Name: .rodata.str
- Name: .plt
- Name: .text
- Name: .rela.text
- Name: .dynamic
- Name: .got
- Name: .relro_padding
- Name: .got.plt
- Name: .symtab
- Name: .strtab
- Name: .shstrtab
Symbols:
- Name: .interp
Type: STT_SECTION
Section: .interp
Value: 0x270
- Name: .gnu.hash
Type: STT_SECTION
Section: .gnu.hash
Value: 0x290
- Name: .dynsym
Type: STT_SECTION
Section: .dynsym
Value: 0x2B0
- Name: .dynstr
Type: STT_SECTION
Section: .dynstr
Value: 0x2E0
- Name: .gnu.version
Type: STT_SECTION
Section: .gnu.version
Value: 0x2FE
- Name: .gnu.version_r
Type: STT_SECTION
Section: .gnu.version_r
Value: 0x308
- Name: .rela.plt
Type: STT_SECTION
Section: .rela.plt
Value: 0x328
- Name: .eh_frame
Type: STT_SECTION
Section: .eh_frame
Value: 0x340
- Name: .eh_frame_hdr
Type: STT_SECTION
Section: .eh_frame_hdr
Value: 0x37C
- Name: .rodata.str
Type: STT_SECTION
Section: .rodata.str
Value: 0x390
- Name: .plt
Type: STT_SECTION
Section: .plt
Value: 0x13A0
- Name: .text
Type: STT_SECTION
Section: .text
Value: 0x13D0
- Name: .dynamic
Type: STT_SECTION
Section: .dynamic
Value: 0x23F8
- Name: .got
Type: STT_SECTION
Section: .got
Value: 0x2548
- Name: .relro_padding
Type: STT_SECTION
Section: .relro_padding
Value: 0x2550
- Name: .got.plt
Type: STT_SECTION
Section: .got.plt
Value: 0x3550
- Name: 'printf$plt'
Type: STT_FUNC
Section: .plt
Value: 0x13C0
- Name: hello.c
Type: STT_FILE
Index: SHN_ABS
- Name: .L.str
Type: STT_OBJECT
Section: .rodata.str
Value: 0x390
- Name: main
Type: STT_FUNC
Section: .text
Value: 0x13D0
Size: 0x25
- Name: __ehdr_start
Section: .interp
- Name: __init_array_start
Index: SHN_ABS
- Name: __init_array_end
Index: SHN_ABS
- Name: __fini_array_start
Index: SHN_ABS
- Name: __fini_array_end
Index: SHN_ABS
- Name: __preinit_array_start
Index: SHN_ABS
- Name: __preinit_array_end
Index: SHN_ABS
- Name: _DYNAMIC
Section: .dynamic
Value: 0x23F8
- Name: _GLOBAL_OFFSET_TABLE_
Section: .got.plt
Value: 0x3550
- Name: _PROCEDURE_LINKAGE_TABLE_
Section: .plt
Value: 0x13A0
- Name: __bss_start
Index: SHN_ABS
- Name: _end
Section: .got.plt
Value: 0x3570
- Name: _etext
Section: .text
Value: 0x13F5
- Name: _edata
Section: .got.plt
Value: 0x3570
- Name: __executable_start
Section: .interp
- Name: __rela_iplt_start
Index: SHN_ABS
- Name: __rela_iplt_end
Index: SHN_ABS
- Name: __GNU_EH_FRAME_HDR
Section: .eh_frame_hdr
Value: 0x37C
- Name: end
Section: .got.plt
Value: 0x3570
- Name: etext
Section: .text
Value: 0x13F5
- Name: edata
Section: .got.plt
Value: 0x3570
- Name: __dso_handle
Section: .interp
- Name: _TLS_MODULE_BASE_
Section: .interp
- Name: printf
Binding: STB_GLOBAL
DynamicSymbols:
- Name: printf
Type: STT_FUNC
Binding: STB_GLOBAL
...

bolt/test/X86/plt-mold.test

  • This file was added.
# RUN: yaml2obj %p/Inputs/plt-mold.yaml &> %t.exe
# RUN: llvm-bolt %t.exe --print-cfg --print-only=main.* -o %t.out | FileCheck %s
## Check that llvm-bolt correctly parses PLT created by mold linker.
## The only call instruction in main() should be a call to printf() in PLT.
CHECK: callq "printf$plt
yota9Unsubmitted
Not Done
ReplyInline Actions

May I ask why it is "printf$plt and not printf@PLT? Is there a typo?

yota9: May I ask why it is "printf$plt and not printf@PLT? Is there a typo?
maksfbAuthorUnsubmitted
Done
ReplyInline Actions

That’s the symbol mold creates at the moment. It also has local visibility.

maksfb: That’s the symbol mold creates at the moment. It also has local visibility.
yota9Unsubmitted
Not Done
ReplyInline Actions

Oh, it is part of the symbol name, interesting. I was thinking about the addend we add with @PLT. Thanks

yota9: Oh, it is part of the symbol name, interesting. I was thinking about the addend we add with…