[BOLT] Fix order of R_*_IRELATIVE in .rela.plt #106515
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linsinan1995
requested review from
aaupov,
maksfb,
rafaelauler,
ayermolo and
dcci
as code owners
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@llvm/pr-subscribers-bolt Author: sinan (linsinan1995) ChangesGNU ld might place R_*_IRELATIVE in .rela.plt, and have a layout like Relocation section '.rela.plt' ... Right now this layout in BOLTed binary will be So that the reloc_index is incorrect and then the dynamic linker fails to resolve the address in .got.plt R_IRELATIVE entries all come after JUMP_SLOT entries. This patch will change the allocatable rela patching order to keep this layout if we find R_IRELATIVE is in .rela.plt section. Full diff: https://github.com/llvm/llvm-project/pull/106515.diff 5 Files Affected:
diff --git a/bolt/include/bolt/Core/Relocation.h b/bolt/include/bolt/Core/Relocation.h
index 933f62a31f8fd7..d925f87f762b30 100644
--- a/bolt/include/bolt/Core/Relocation.h
+++ b/bolt/include/bolt/Core/Relocation.h
@@ -117,6 +117,9 @@ struct Relocation {
/// Return code for a RELATIVE relocation
static uint64_t getRelative();
+ /// Return code for a IRELATIVE relocation
+ static uint64_t getIRelative();
+
/// Return true if this relocation is PC-relative. Return false otherwise.
bool isPCRelative() const { return isPCRelative(Type); }
diff --git a/bolt/lib/Core/Relocation.cpp b/bolt/lib/Core/Relocation.cpp
index 4e888a5b147aca..7caf0446dfe34b 100644
--- a/bolt/lib/Core/Relocation.cpp
+++ b/bolt/lib/Core/Relocation.cpp
@@ -1009,6 +1009,19 @@ uint64_t Relocation::getRelative() {
}
}
+uint64_t Relocation::getIRelative() {
+ switch (Arch) {
+ default:
+ llvm_unreachable("Unsupported architecture");
+ case Triple::aarch64:
+ return ELF::R_AARCH64_IRELATIVE;
+ case Triple::riscv64:
+ llvm_unreachable("not implemented");
+ case Triple::x86_64:
+ return ELF::R_X86_64_IRELATIVE;
+ }
+}
+
size_t Relocation::emit(MCStreamer *Streamer) const {
const size_t Size = getSizeForType(Type);
const auto *Value = createExpr(Streamer);
diff --git a/bolt/lib/Rewrite/RewriteInstance.cpp b/bolt/lib/Rewrite/RewriteInstance.cpp
index adacb50dc167c8..71c92d616c6915 100644
--- a/bolt/lib/Rewrite/RewriteInstance.cpp
+++ b/bolt/lib/Rewrite/RewriteInstance.cpp
@@ -5185,12 +5185,15 @@ RewriteInstance::patchELFAllocatableRelaSections(ELFObjectFile<ELFT> *File) {
DynamicRelativeRelocationsCount = 0;
+ const bool HasIRelativeInPLT =
+ IsJmpRelocation.contains(Relocation::getIRelative());
+
auto writeRela = [&OS](const Elf_Rela *RelA, uint64_t &Offset) {
OS.pwrite(reinterpret_cast<const char *>(RelA), sizeof(*RelA), Offset);
Offset += sizeof(*RelA);
};
- auto writeRelocations = [&](bool PatchRelative) {
+ auto writeRelocations = [&](bool PatchRelative, bool PatchIRelativeInPLT) {
for (BinarySection &Section : BC->allocatableSections()) {
const uint64_t SectionInputAddress = Section.getAddress();
uint64_t SectionAddress = Section.getOutputAddress();
@@ -5199,9 +5202,14 @@ RewriteInstance::patchELFAllocatableRelaSections(ELFObjectFile<ELFT> *File) {
for (const Relocation &Rel : Section.dynamicRelocations()) {
const bool IsRelative = Rel.isRelative();
+ const bool IsIRelativeInPLT = HasIRelativeInPLT && Rel.isIRelative();
+
if (PatchRelative != IsRelative)
continue;
+ if (PatchIRelativeInPLT != IsIRelativeInPLT)
+ continue;
+
if (IsRelative)
++DynamicRelativeRelocationsCount;
@@ -5249,8 +5257,13 @@ RewriteInstance::patchELFAllocatableRelaSections(ELFObjectFile<ELFT> *File) {
// The dynamic linker expects all R_*_RELATIVE relocations in RELA
// to be emitted first.
if (!DynamicRelrAddress)
- writeRelocations(/* PatchRelative */ true);
- writeRelocations(/* PatchRelative */ false);
+ writeRelocations(/* PatchRelative */ true, /* PatchIRelativeInPLT */ false);
+ writeRelocations(/* PatchRelative */ false, /* PatchIRelativeInPLT */ false);
+
+ // Place R_*_IRELATIVE after all R_*_JUMP_SLOT relocations emitted if
+ // R_*_IRELATIVE is presented at .rela.plt
+ if (HasIRelativeInPLT)
+ writeRelocations(/* PatchRelative */ false, /* PatchIRelativeInPLT */ true);
auto fillNone = [&](uint64_t &Offset, uint64_t EndOffset) {
if (!Offset)
diff --git a/bolt/test/X86/Inputs/ifunc-ld.yaml b/bolt/test/X86/Inputs/ifunc-ld.yaml
new file mode 100644
index 00000000000000..18032397e107e8
--- /dev/null
+++ b/bolt/test/X86/Inputs/ifunc-ld.yaml
@@ -0,0 +1,424 @@
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ OSABI: ELFOSABI_GNU
+ Type: ET_EXEC
+ Machine: EM_X86_64
+ Entry: 0x401050
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+ VAddr: 0x400040
+ Align: 0x8
+ Offset: 0x40
+ - Type: PT_INTERP
+ Flags: [ PF_R ]
+ FirstSec: .interp
+ LastSec: .interp
+ VAddr: 0x400270
+ Offset: 0x270
+ - Type: PT_LOAD
+ Flags: [ PF_R ]
+ FirstSec: .interp
+ LastSec: .rela.plt
+ VAddr: 0x400000
+ Align: 0x1000
+ Offset: 0x0
+ - Type: PT_LOAD
+ Flags: [ PF_X, PF_R ]
+ FirstSec: .plt
+ LastSec: .text
+ VAddr: 0x401000
+ Align: 0x1000
+ Offset: 0x1000
+ - Type: PT_LOAD
+ Flags: [ PF_R ]
+ FirstSec: .rodata
+ LastSec: .eh_frame
+ VAddr: 0x402000
+ Align: 0x1000
+ Offset: 0x2000
+ - Type: PT_LOAD
+ Flags: [ PF_W, PF_R ]
+ FirstSec: .dynamic
+ LastSec: .got.plt
+ VAddr: 0x403EB8
+ Align: 0x1000
+ Offset: 0x2EB8
+ - Type: PT_DYNAMIC
+ Flags: [ PF_W, PF_R ]
+ FirstSec: .dynamic
+ LastSec: .dynamic
+ VAddr: 0x403EB8
+ Align: 0x8
+ Offset: 0x2EB8
+ - Type: PT_GNU_EH_FRAME
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+ FirstSec: .eh_frame_hdr
+ LastSec: .eh_frame_hdr
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+ Offset: 0x2004
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+ - Type: PT_GNU_RELRO
+ Flags: [ PF_R ]
+ FirstSec: .dynamic
+ LastSec: .got
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+Sections:
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+ Type: SHT_GNU_HASH
+ Flags: [ SHF_ALLOC ]
+ Address: 0x400290
+ Link: .dynsym
+ AddressAlign: 0x8
+ Header:
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+ Type: SHT_STRTAB
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+ AddressAlign: 0x1
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+ Type: SHT_RELA
+ Flags: [ SHF_ALLOC ]
+ Address: 0x400330
+ Link: .dynsym
+ AddressAlign: 0x8
+ Relocations:
+ - Offset: 0x403FF8
+ Symbol: memcpy
+ Type: R_X86_64_GLOB_DAT
+ - Name: .rela.plt
+ Type: SHT_RELA
+ Flags: [ SHF_ALLOC, SHF_INFO_LINK ]
+ Address: 0x400348
+ Link: .dynsym
+ AddressAlign: 0x8
+ Info: .got.plt
+ Relocations:
+ - Offset: 0x404018
+ Symbol: printf
+ Type: R_X86_64_JUMP_SLOT
+ - Offset: 0x404028
+ Symbol: rand
+ Type: R_X86_64_JUMP_SLOT
+ - Offset: 0x404030
+ Type: R_X86_64_IRELATIVE
+ Addend: 4198480
+ - Offset: 0x404020
+ Type: R_X86_64_IRELATIVE
+ Addend: 4198496
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+ AddressAlign: 0x10
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+ - Name: .dynamic
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+ Flags: [ SHF_WRITE, SHF_ALLOC ]
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+ - Name: .rela.text
+ Type: SHT_RELA
+ Flags: [ SHF_INFO_LINK ]
+ Link: .symtab
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+ Info: .text
+ Relocations:
+ - Offset: 0x401063
+ Symbol: memcpy
+ Type: R_X86_64_REX_GOTPCRELX
+ Addend: -4
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+ Symbol: imemcpy
+ Type: R_X86_64_PLT32
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+ Type: R_X86_64_PLT32
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+ Type: SHT_RELA
+ Flags: [ SHF_INFO_LINK ]
+ Link: .symtab
+ AddressAlign: 0x8
+ Info: .eh_frame
+ Relocations:
+ - Offset: 0x402058
+ Symbol: .text
+ Type: R_X86_64_PC32
+ - Offset: 0x40206C
+ Symbol: .text
+ Type: R_X86_64_PC32
+ Addend: 16
+ - Offset: 0x402080
+ Symbol: .text
+ Type: R_X86_64_PC32
+ Addend: 32
+ - Offset: 0x4020A0
+ Symbol: .text
+ Type: R_X86_64_PC32
+ Addend: 128
+ - Type: SectionHeaderTable
+ Sections:
+ - Name: .interp
+ - Name: .gnu.hash
+ - Name: .dynsym
+ - Name: .dynstr
+ - Name: .rela.dyn
+ - Name: .rela.plt
+ - Name: .plt
+ - Name: .text
+ - Name: .rela.text
+ - Name: .rodata
+ - Name: .eh_frame_hdr
+ - Name: .eh_frame
+ - Name: .rela.eh_frame
+ - Name: .dynamic
+ - Name: .got
+ - Name: .got.plt
+ - Name: .comment
+ - Name: .symtab
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+ Value: 0x400310
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+ Value: 0x400348
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+ Section: .eh_frame
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+ Section: .got
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+ Type: STT_SECTION
+ Section: .got.plt
+ Value: 0x404000
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+ Type: STT_SECTION
+ Section: .comment
+ - Name: .L.str
+ Type: STT_OBJECT
+ Section: .rodata
+ Value: 0x402000
+ Size: 0x3
+ - Name: printf
+ Type: STT_FUNC
+ Binding: STB_GLOBAL
+ - Name: imemcpy
+ Type: STT_GNU_IFUNC
+ Section: .text
+ Binding: STB_GLOBAL
+ Value: 0x401060
+ Size: 0x8
+ - Name: memcpy
+ Type: STT_FUNC
+ Binding: STB_GLOBAL
+ - Name: rand
+ Type: STT_FUNC
+ Binding: STB_GLOBAL
+ - Name: __bss_start
+ Section: .got.plt
+ Binding: STB_GLOBAL
+ Value: 0x404038
+ - Name: main
+ Type: STT_FUNC
+ Section: .text
+ Binding: STB_GLOBAL
+ Value: 0x401070
+ Size: 0x57
+ - Name: _edata
+ Section: .got.plt
+ Binding: STB_GLOBAL
+ Value: 0x404038
+ - Name: _end
+ Section: .got.plt
+ Binding: STB_GLOBAL
+ Value: 0x404038
+ - Name: ifoo
+ Type: STT_GNU_IFUNC
+ Section: .text
+ Binding: STB_GLOBAL
+ Value: 0x401050
+ Size: 0x8
+DynamicSymbols:
+ - Name: printf
+ Type: STT_FUNC
+ Binding: STB_GLOBAL
+ - Name: memcpy
+ Type: STT_FUNC
+ Binding: STB_GLOBAL
+ - Name: rand
+ Type: STT_FUNC
+ Binding: STB_GLOBAL
+...
diff --git a/bolt/test/X86/ifunc-ld.test b/bolt/test/X86/ifunc-ld.test
new file mode 100644
index 00000000000000..64cbd6d758fed7
--- /dev/null
+++ b/bolt/test/X86/ifunc-ld.test
@@ -0,0 +1,13 @@
+// This test checks R_X86_64_IRELATIVE in .rela.plt can be properly
+// placed after R_X86_64_JUMP_SLOT entries by BOLT
+
+RUN: yaml2obj %p/Inputs/ifunc-ld.yaml &> %t.exe
+RUN: llvm-bolt %t.exe -o %t.bolt
+RUN: llvm-readelf -aW %t.bolt | FileCheck %s
+
+# CHECK: Relocation section '.rela.plt'
+# CHECK-NEXT: Offset
+# CHECK-NEXT: R_X86_64_JUMP_SLOT
+# CHECK-NEXT: R_X86_64_JUMP_SLOT
+# CHECK-NEXT: R_X86_64_IRELATIVE
+# CHECK-NEXT: R_X86_64_IRELATIVE
|
|
The testcase is generated from bolt/test/runtime/iplt.c with gnu-ld with commands |
GNU ld might place R_*_IRELATIVE in .rela.plt, and have a layout like Relocation section '.rela.plt' ... Offset Type cc9040 R_X86_64_JUMP_SLOT cc9048 R_X86_64_JUMP_SLOT cc9060 R_X86_64_JUMP_SLOT cc9050 R_X86_64_IRELATIVE R_*_IRELATIVE entries all come after JUMP_SLOT entries. This patch will change the allocatable rela patching order to keep this layout if we find R_*_IRELATIVE is in .rela.plt section.
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Reproduce from a real-world case.
The order of jump_slop entries are messed up with R_X86_64_IRELATIVE. So when dl_fixup tries to resolve _ZNSt12out_of_rangeC1E@PLT, then it will find This issue depends on the Arch and linker you use, and I only found it happened with X86 & gnu-ld so far. |
maksfb
reviewed
Sep 16, 2024
| @@ -899,7 +899,7 @@ bool Relocation::isIRelative(uint64_t Type) { | |||
| case Triple::aarch64: | |||
| return Type == ELF::R_AARCH64_IRELATIVE; | |||
| case Triple::riscv64: | |||
| llvm_unreachable("not implemented"); | |||
| return Type == ELF::R_RISCV_IRELATIVE; | |||
There was a problem hiding this comment.
Can we replace the whole function body with return Type == getIRelative();?
There was a problem hiding this comment.
Can we replace the whole function body with
return Type == getIRelative();?
Some extensions may introduce new variants（R_AARCH64_AUTH_[I]RELATIVE）, but currently, BOLT has no plans to support them, so I think we can make this chang. Do you have any suggestions?
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GNU ld might place R_*_IRELATIVE in .rela.plt, and have a layout like
Relocation section '.rela.plt' ...
Offset Type
cc9040 R_X86_64_JUMP_SLOT
cc9048 R_X86_64_JUMP_SLOT
cc9060 R_X86_64_JUMP_SLOT
cc9050 R_X86_64_IRELATIVE
Right now this layout in BOLTed binary will be
Relocation section '.rela.plt' ...
Offset Type
cc9040 R_X86_64_JUMP_SLOT
cc9048 R_X86_64_JUMP_SLOT
cc9050 R_X86_64_IRELATIVE
cc9060 R_X86_64_JUMP_SLOT
So that the reloc_index is incorrect and then the dynamic linker fails to resolve the address in .got.plt
R_IRELATIVE entries all come after JUMP_SLOT entries. This patch will change the allocatable rela patching order to keep this layout if we find R_IRELATIVE is in .rela.plt section.