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ELF: Add support for R_AARCH64_PATCHINST relocation type.
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: ARM-software/abi-aa#340 Reviewers: smithp35, davemgreen, MaskRay Reviewed By: MaskRay, davemgreen, smithp35 Pull Request: llvm#133534
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‎lld/ELF/Arch/AArch64.cpp

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -154,6 +154,12 @@ RelExpr AArch64::getRelExpr(RelType type, const Symbol &s,
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case R_AARCH64_MOVW_UABS_G2_NC:
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case R_AARCH64_MOVW_UABS_G3:
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return R_ABS;
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case R_AARCH64_PATCHINST:
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if (!isAbsolute(s))
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Err(ctx) << getErrorLoc(ctx, loc)
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<< "R_AARCH64_PATCHINST relocation against non-absolute symbol "
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<< &s;
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return R_ABS;
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case R_AARCH64_AUTH_ABS64:
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return RE_AARCH64_AUTH;
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case R_AARCH64_TLSDESC_ADR_PAGE21:
@@ -506,6 +512,12 @@ void AArch64::relocate(uint8_t *loc, const Relocation &rel,
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checkIntUInt(ctx, loc, val, 32, rel);
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write32(ctx, loc, val);
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break;
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case R_AARCH64_PATCHINST:
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if (!rel.sym->isUndefined()) {
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checkUInt(ctx, loc, val, 32, rel);
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write32le(loc, val);
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}
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break;
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case R_AARCH64_PLT32:
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case R_AARCH64_GOTPCREL32:
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checkInt(ctx, loc, val, 32, rel);

‎lld/ELF/Relocations.cpp

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -176,7 +176,7 @@ static RelType getMipsPairType(RelType type, bool isLocal) {
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// True if non-preemptable symbol always has the same value regardless of where
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// the DSO is loaded.
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static bool isAbsolute(const Symbol &sym) {
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bool elf::isAbsolute(const Symbol &sym) {
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if (sym.isUndefined())
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return true;
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if (const auto *dr = dyn_cast<Defined>(&sym))

‎lld/ELF/Relocations.h

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

‎lld/test/ELF/aarch64-patchinst.s

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

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