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[cherry-pick] [ELF] --emit-relocs: adjust offsets of .rel[a].eh_frame relocations #134

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Merged
merged 2 commits into from
May 5, 2022
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[cherry-pick] [ELF] --emit-relocs: adjust offsets of .rel[a].eh_frame relocations #134

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9ec2566
[ELF][test] Refactor some .eh_frame tests
MaskRay Mar 28, 2022
61da316
[ELF] --emit-relocs: adjust offsets of .rel[a].eh_frame relocations
MaskRay Mar 29, 2022
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25 changes: 21 additions & 4 deletions lld/ELF/InputSection.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -165,11 +165,19 @@ uint64_t SectionBase::getOffset(uint64_t offset) const {
case Regular:
case Synthetic:
return cast<InputSection>(this)->outSecOff + offset;
case EHFrame:
// The file crtbeginT.o has relocations pointing to the start of an empty
// .eh_frame that is known to be the first in the link. It does that to
// identify the start of the output .eh_frame.
case EHFrame: {
// Two code paths may reach here. First, clang_rt.crtbegin.o and GCC
// crtbeginT.o may reference the start of an empty .eh_frame to identify the
// start of the output .eh_frame. Just return offset.
//
// Second, InputSection::copyRelocations on .eh_frame. Some pieces may be
// discarded due to GC/ICF. We should compute the output section offset.
const EhInputSection *es = cast<EhInputSection>(this);
if (!es->rawData.empty())
if (InputSection *isec = es->getParent())
return isec->outSecOff + es->getParentOffset(offset);
return offset;
}
case Merge:
const MergeInputSection *ms = cast<MergeInputSection>(this);
if (InputSection *isec = ms->getParent())
Expand Down Expand Up @@ -1351,6 +1359,15 @@ void EhInputSection::split(ArrayRef<RelTy> rels) {
getObjMsg(d.data() - rawData.data()));
}

// Return the offset in an output section for a given input offset.
uint64_t EhInputSection::getParentOffset(uint64_t offset) const {
const EhSectionPiece &piece = partition_point(
pieces, [=](EhSectionPiece p) { return p.inputOff <= offset; })[-1];
if (piece.outputOff == -1) // invalid piece
return offset - piece.inputOff;
return piece.outputOff + (offset - piece.inputOff);
}

static size_t findNull(StringRef s, size_t entSize) {
for (unsigned i = 0, n = s.size(); i != n; i += entSize) {
const char *b = s.begin() + i;
Expand Down
1 change: 1 addition & 0 deletions lld/ELF/InputSection.h
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Expand Up @@ -328,6 +328,7 @@ class EhInputSection : public InputSectionBase {
SmallVector<EhSectionPiece, 0> pieces;

SyntheticSection *getParent() const;
uint64_t getParentOffset(uint64_t offset) const;
};

// This is a section that is added directly to an output section
Expand Down
2 changes: 1 addition & 1 deletion lld/test/ELF/eh-frame-begin-end.s
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Expand Up @@ -10,7 +10,7 @@
// CHECK-NEXT: Flags [
// CHECK-NEXT: SHF_ALLOC
// CHECK-NEXT: ]
// CHECK-NEXT: Address: 0x200120
// CHECK-NEXT: Address:
// CHECK-NEXT: Offset: 0x120
// CHECK-NEXT: Size: 4

Expand Down
87 changes: 35 additions & 52 deletions lld/test/ELF/eh-frame-merge.s
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@@ -1,12 +1,39 @@
// REQUIRES: x86
// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
// RUN: ld.lld --hash-style=sysv %t.o %t.o -o %t -shared
// RUN: llvm-readobj -S --section-data %t | FileCheck %s
# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
# RUN: ld.lld %t.o %t.o -shared --emit-relocs -o %t.so
# RUN: llvm-readelf -S -r %t.so | FileCheck %s --check-prefixes=CHECK,RELOC
# RUN: llvm-dwarfdump --eh-frame %t.so | FileCheck %s --check-prefix=EH

/// Also show that the merging happens when going via a -r link.
// RUN: ld.lld -r %t.o %t.o -o %t.r.o
// RUN: ld.lld --hash-style=sysv %t.r.o -o %t2 -shared
// RUN: llvm-readobj -S --section-data %t2 | FileCheck %s
## Also show that the merging happens when going via a -r link.
# RUN: ld.lld -r %t.o %t.o -o %t.ro
# RUN: ld.lld %t.ro -o %t2.so -shared
# RUN: llvm-readelf -S -r %t2.so | FileCheck %s

# CHECK: Name Type Address Off Size ES Flg Lk Inf Al
# CHECK: .eh_frame PROGBITS [[#%x,]] [[#%x,]] 000064 00 A 0 0 8
# CHECK: foo PROGBITS {{0*}}[[#%x,FOO:]] [[#%x,]] 000002 00 AX 0 0 1
# CHECK-NEXT: bar PROGBITS {{0*}}[[#%x,FOO+2]] [[#%x,]] 000002 00 AX 0 0 1

# RELOC: Offset Info Type Symbol's Value Symbol's Name + Addend
# RELOC-NEXT: {{0*}}[[#%x,OFF:]] [[#%x,]] R_X86_64_PC32 [[#%x,]] foo + 0
# RELOC-NEXT: {{0*}}[[#%x,OFF+24]] [[#%x,]] R_X86_64_PC32 [[#%x,]] bar + 0
# RELOC-NEXT: {{0*}}[[#OFF+48]] [[#%x,]] R_X86_64_PC32 [[#%x,]] foo + 1
# RELOC-NEXT: {{0*}}[[#%x,OFF-24]] [[#%x,]] R_X86_64_NONE 0{{$}}

# EH: Format: DWARF32
# EH: 00000018 00000014 0000001c FDE cie=00000000 pc={{0*}}[[#%x,FOO:]]...
# EH-SAME: {{0*}}[[#%x,FOO+1]]
# EH-COUNT-7: DW_CFA_nop:
# EH-EMPTY:
# EH: 00000030 00000014 00000034 FDE cie=00000000 pc={{0*}}[[#%x,FOO+2]]...{{0*}}[[#%x,FOO+4]]
# EH-COUNT-7: DW_CFA_nop:
# EH-EMPTY:
# EH: 00000048 00000014 0000004c FDE cie=00000000 pc={{0*}}[[#%x,FOO+1]]...{{0*}}[[#%x,FOO+2]]
# EH-COUNT-7: DW_CFA_nop:
# EH-EMPTY:
# EH-NEXT: 0x[[#%x,]]: CFA=RSP+8: RIP=[CFA-8]
# EH-EMPTY:
# EH-NEXT: 00000060 ZERO terminator

.section foo,"ax",@progbits
.cfi_startproc
Expand All @@ -18,47 +45,3 @@
nop
nop
.cfi_endproc

// FIXME: We could really use a .eh_frame parser.
// The intention is to show that:
// * There is only one copy of the CIE
// * There are two copies of the first FDE
// * There is only one copy of the second FDE

// CHECK: Name: .eh_frame
// CHECK-NEXT: Type: SHT_PROGBITS
// CHECK-NEXT: Flags [
// CHECK-NEXT: SHF_ALLOC
// CHECK-NEXT: ]
// CHECK-NEXT: Address:
// CHECK-NEXT: Offset:
// CHECK-NEXT: Size: 100
// CHECK-NEXT: Link: 0
// CHECK-NEXT: Info: 0
// CHECK-NEXT: AddressAlignment: 8
// CHECK-NEXT: EntrySize: 0
// CHECK-NEXT: SectionData (
// CHECK-NEXT: 0000: 14000000 00000000 017A5200 01781001 |
// CHECK-NEXT: 0010: 1B0C0708 90010000 14000000 1C000000 |
// CHECK-NEXT: 0020: 44100000 01000000 00000000 00000000 |
// CHECK-NEXT: 0030: 14000000 34000000 2E100000 02000000 |
// CHECK-NEXT: 0040: 00000000 00000000 14000000 4C000000 |
// CHECK-NEXT: 0050: 15100000 01000000 00000000 00000000 |
// CHECK-NEXT: 0060: 00000000
// CHECK-NEXT: )

// CHECK: Name: foo
// CHECK-NEXT: Type: SHT_PROGBITS
// CHECK-NEXT: Flags [
// CHECK-NEXT: SHF_ALLOC
// CHECK-NEXT: SHF_EXECINSTR
// CHECK-NEXT: ]
// CHECK-NEXT: Address: 0x125C

// CHECK: Name: bar
// CHECK-NEXT: Type: SHT_PROGBITS
// CHECK-NEXT: Flags [
// CHECK-NEXT: SHF_ALLOC
// CHECK-NEXT: SHF_EXECINSTR
// CHECK-NEXT: ]
// CHECK-NEXT: Address: 0x125E
13 changes: 6 additions & 7 deletions lld/test/ELF/ehframe-relocation.s
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
// RUN: echo '.cfi_startproc; .cfi_endproc' | llvm-mc -filetype=obj -triple=x86_64 - -o %t2.o
// RUN: ld.lld %t.o %t2.o -o %t
// RUN: llvm-readobj -S %t | FileCheck %s
// RUN: llvm-objdump -d %t | FileCheck --check-prefix=DISASM %s
// RUN: llvm-objdump -d --print-imm-hex %t | FileCheck --check-prefix=DISASM %s

// CHECK: Name: .eh_frame
// CHECK-NEXT: Type: SHT_PROGBITS
Expand All @@ -15,18 +15,17 @@
// CHECK-NEXT: Size: 52
// CHECK-NOT: .eh_frame

// 0x200120 = 2097440
// 0x200120 + 5 = 2097445
// DISASM: Disassembly of section .text:
// DISASM-EMPTY:
// DISASM-NEXT: <_start>:
// DISASM-NEXT: 201154: {{.*}} movq 2097440, %rax
// DISASM-NEXT: 20115c: {{.*}} movq 2097445, %rax
// DISASM-NEXT: movq 0x200120, %rax
// DISASM-NEXT: leaq {{.*}}(%rip), %rax # {{.*}} <__EH_FRAME_LIST__>

.section .eh_frame,"a",@unwind
__EH_FRAME_LIST__:

.section .text
.globl _start
_start:
movq .eh_frame, %rax
movq .eh_frame + 5, %rax
movq .eh_frame, %rax # addend=0
leaq __EH_FRAME_LIST__(%rip), %rax # addend=-4, used by libclang_rt.crtbegin.o
4 changes: 2 additions & 2 deletions lld/test/ELF/mips64-eh-abs-reloc.s
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Expand Up @@ -2,13 +2,13 @@
# Having an R_MIPS_64 relocation in eh_frame would previously crash LLD
# RUN: llvm-mc -filetype=obj -triple=mips64-unknown-freebsd %s -o %t.o
# RUN: llvm-readobj -r %t.o | FileCheck %s -check-prefix OBJ
# RUN: ld.lld --eh-frame-hdr -shared -z notext -o %t.so %t.o
# RUN: ld.lld --eh-frame-hdr -shared -z notext -o %t.so %t.o --no-check-dynamic-relocations
# RUN: llvm-readobj -r %t.so | FileCheck %s -check-prefix PIC-RELOCS

# Linking this as a PIE executable would also previously crash
# RUN: llvm-mc -filetype=obj -triple=mips64-unknown-freebsd %S/Inputs/archive2.s -o %t-foo.o
# -pie needs -z notext because of the R_MIPS_64 relocation
# RUN: ld.lld --eh-frame-hdr -Bdynamic -pie -z notext -o %t-pie-dynamic.exe %t.o %t-foo.o
# RUN: ld.lld --eh-frame-hdr -Bdynamic -pie -z notext -o %t-pie-dynamic.exe %t.o %t-foo.o --no-check-dynamic-relocations
# RUN: llvm-readobj -r %t-pie-dynamic.exe | FileCheck %s -check-prefix PIC-RELOCS


Expand Down