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ELF: Add support for R_AARCH64_PATCHINST relocation type.

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The R_AARCH64_PATCHINST relocation type is to support deactivation
symbols. For more information, see the RFC:
https://discourse.llvm.org/t/rfc-deactivation-symbols/85556

Part of the AArch64 psABI extension:
https://github.com/ARM-software/abi-aa/issues/340

Reviewers: smithp35, davemgreen, MaskRay

Reviewed By: MaskRay, davemgreen, smithp35

Pull Request: https://github.com/llvm/llvm-project/pull/133534
This commit is contained in:
Peter Collingbourne 2025-08-11 11:33:08 -07:00 committed by GitHub
parent a9227316bf
commit 53c41f19e3
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
4 changed files with 102 additions and 1 deletions
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12
lld/ELF/Arch/AArch64.cpp
View File

@ -154,6 +154,12 @@ RelExpr AArch64::getRelExpr(RelType type, const Symbol &s,
case R_AARCH64_MOVW_UABS_G2_NC:
case R_AARCH64_MOVW_UABS_G3:
return R_ABS;
case R_AARCH64_PATCHINST:
if (!isAbsolute(s))
Err(ctx) << getErrorLoc(ctx, loc)
<< "R_AARCH64_PATCHINST relocation against non-absolute symbol "
<< &s;
return R_ABS;
case R_AARCH64_AUTH_ABS64:
return RE_AARCH64_AUTH;
case R_AARCH64_TLSDESC_ADR_PAGE21:
@ -506,6 +512,12 @@ void AArch64::relocate(uint8_t *loc, const Relocation &rel,
checkIntUInt(ctx, loc, val, 32, rel);
write32(ctx, loc, val);
break;
case R_AARCH64_PATCHINST:
if (!rel.sym->isUndefined()) {
checkUInt(ctx, loc, val, 32, rel);
write32le(loc, val);
}
break;
case R_AARCH64_PLT32:
case R_AARCH64_GOTPCREL32:
checkInt(ctx, loc, val, 32, rel);

2
lld/ELF/Relocations.cpp
View File

@ -176,7 +176,7 @@ static RelType getMipsPairType(RelType type, bool isLocal) {
// True if non-preemptable symbol always has the same value regardless of where
// the DSO is loaded.
static bool isAbsolute(const Symbol &sym) {
bool elf::isAbsolute(const Symbol &sym) {
if (sym.isUndefined())
return true;
if (const auto *dr = dyn_cast<Defined>(&sym))

2
lld/ELF/Relocations.h
View File

@ -165,6 +165,8 @@ void addGotEntry(Ctx &ctx, Symbol &sym);
void hexagonTLSSymbolUpdate(Ctx &ctx);
bool hexagonNeedsTLSSymbol(ArrayRef<OutputSection *> outputSections);
bool isAbsolute(const Symbol &sym);
class ThunkSection;
class Thunk;
class InputSectionDescription;

87
lld/test/ELF/aarch64-patchinst.s Normal file
View File

@ -0,0 +1,87 @@
# RUN: rm -rf %t && split-file %s %t
# RUN: llvm-mc -filetype=obj -triple=aarch64 %t/use.s -o %t/use-le.o
# RUN: llvm-mc -filetype=obj -triple=aarch64 %t/def.s -o %t/def-le.o
# RUN: llvm-mc -filetype=obj -triple=aarch64 %t/rel.s -o %t/rel-le.o
## Deactivation symbol used without being defined: instruction emitted as usual.
# RUN: ld.lld -o %t/undef-le %t/use-le.o --emit-relocs
# RUN: llvm-objdump -r %t/undef-le | FileCheck --check-prefix=RELOC %s
# RUN: llvm-objdump -d %t/undef-le | FileCheck --check-prefix=UNDEF %s
# RUN: ld.lld -pie -o %t/undef-le %t/use-le.o --emit-relocs
# RUN: llvm-objdump -r %t/undef-le | FileCheck --check-prefix=RELOC %s
# RUN: llvm-objdump -d %t/undef-le | FileCheck --check-prefix=UNDEF %s
## Deactivation symbol defined: instructions overwritten with NOPs.
# RUN: ld.lld -o %t/def-le %t/use-le.o %t/def-le.o --emit-relocs
# RUN: llvm-objdump -r %t/def-le | FileCheck --check-prefix=RELOC %s
# RUN: llvm-objdump -d %t/def-le | FileCheck --check-prefix=DEF %s
# RUN: ld.lld -pie -o %t/def-le %t/use-le.o %t/def-le.o --emit-relocs
# RUN: llvm-objdump -r %t/def-le | FileCheck --check-prefix=RELOC %s
# RUN: llvm-objdump -d %t/def-le | FileCheck --check-prefix=DEF %s
## Relocation pointing to a non-SHN_UNDEF non-SHN_ABS symbol is an error.
# RUN: not ld.lld -o %t/rel-le %t/use-le.o %t/rel-le.o 2>&1 | FileCheck --check-prefix=ERROR %s
# RUN: not ld.lld -pie -o %t/rel-le %t/use-le.o %t/rel-le.o 2>&1 | FileCheck --check-prefix=ERROR %s
## Behavior unchanged by endianness: relocation always written as little endian.
# RUN: llvm-mc -filetype=obj -triple=aarch64_be %t/use.s -o %t/use-be.o
# RUN: llvm-mc -filetype=obj -triple=aarch64_be %t/def.s -o %t/def-be.o
# RUN: llvm-mc -filetype=obj -triple=aarch64_be %t/rel.s -o %t/rel-be.o
# RUN: ld.lld -o %t/undef-be %t/use-be.o --emit-relocs
# RUN: llvm-objdump -r %t/undef-be | FileCheck --check-prefix=RELOC %s
# RUN: llvm-objdump -d %t/undef-be | FileCheck --check-prefix=UNDEF %s
# RUN: ld.lld -pie -o %t/undef-be %t/use-be.o --emit-relocs
# RUN: llvm-objdump -r %t/undef-be | FileCheck --check-prefix=RELOC %s
# RUN: llvm-objdump -d %t/undef-be | FileCheck --check-prefix=UNDEF %s
# RUN: ld.lld -o %t/def-be %t/use-be.o %t/def-be.o --emit-relocs
# RUN: llvm-objdump -r %t/def-be | FileCheck --check-prefix=RELOC %s
# RUN: llvm-objdump -d %t/def-be | FileCheck --check-prefix=DEF %s
# RUN: ld.lld -pie -o %t/def-be %t/use-be.o %t/def-be.o --emit-relocs
# RUN: llvm-objdump -r %t/def-be | FileCheck --check-prefix=RELOC %s
# RUN: llvm-objdump -d %t/def-be | FileCheck --check-prefix=DEF %s
# RUN: not ld.lld -o %t/rel-be %t/use-be.o %t/rel-be.o 2>&1 | FileCheck --check-prefix=ERROR %s
# RUN: not ld.lld -pie -o %t/rel-be %t/use-be.o %t/rel-be.o 2>&1 | FileCheck --check-prefix=ERROR %s
# RELOC: R_AARCH64_JUMP26
# RELOC-NEXT: R_AARCH64_PATCHINST ds
# RELOC-NEXT: R_AARCH64_PATCHINST ds
# RELOC-NEXT: R_AARCH64_PATCHINST ds0+0xd503201f
#--- use.s
.weak ds
.weak ds0
# This instruction has a single relocation: the DS relocation.
# UNDEF: add x0, x1, x2
# DEF: nop
# ERROR: R_AARCH64_PATCHINST relocation against non-absolute symbol ds
.reloc ., R_AARCH64_PATCHINST, ds
add x0, x1, x2
# This instruction has two relocations: the DS relocation and the JUMP26 to f1.
# Make sure that the DS relocation takes precedence.
.reloc ., R_AARCH64_PATCHINST, ds
# UNDEF: b {{.*}} <f1>
# DEF: nop
# ERROR: R_AARCH64_PATCHINST relocation against non-absolute symbol ds
b f1
# Alternative representation: instruction opcode stored in addend.
# UNDEF: add x3, x4, x5
# DEF: nop
# ERROR: R_AARCH64_PATCHINST relocation against non-absolute symbol ds0
.reloc ., R_AARCH64_PATCHINST, ds0 + 0xd503201f
add x3, x4, x5
.section .text.f1,"ax",@progbits
f1:
ret
#--- def.s
.globl ds
ds = 0xd503201f
.globl ds0
ds0 = 0
#--- rel.s
.globl ds
ds:
.globl ds0
ds0: