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[BOLT][AArch64] Fix symbolization of unoptimized TLS access (#134332)

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TLS relocations may not have a valid BOLT symbol associated with them.
While symbolizing the operand, we were checking for the symbol value,
and since there was no symbol the check resulted in a crash.

Handle TLS case while performing operand symbolization on AArch64.
This commit is contained in:
Maksim Panchenko 2025-04-04 11:42:21 -07:00 committed by GitHub
parent e2092a430a
commit e4cbb7780b
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GPG Key ID: B5690EEEBB952194
3 changed files with 36 additions and 14 deletions
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7
bolt/lib/Rewrite/RewriteInstance.cpp
View File

@ -2827,9 +2827,10 @@ void RewriteInstance::handleRelocation(const SectionRef &RelocatedSection,
if (SymbolAddress == 0)
ReferencedSymbol = BC->registerNameAtAddress(SymbolName, 0, 0, 0);
LLVM_DEBUG(dbgs() << "BOLT-DEBUG: forcing relocation against symbol "
<< ReferencedSymbol->getName() << " with addend "
<< Addend << '\n');
LLVM_DEBUG(
dbgs() << "BOLT-DEBUG: forcing relocation against symbol "
<< (ReferencedSymbol ? ReferencedSymbol->getName() : "<none>")
<< " with addend " << Addend << '\n');
} else if (ReferencedBF) {
ReferencedSymbol = ReferencedBF->getSymbol();
uint64_t RefFunctionOffset = 0;

35
bolt/lib/Target/AArch64/AArch64MCSymbolizer.cpp
View File

@ -119,26 +119,39 @@ AArch64MCSymbolizer::adjustRelocation(const Relocation &Rel,
// The ADRP+LDR sequence was converted into ADRP+ADD. We are looking at the
// second instruction and have to use the relocation type for ADD.
AdjustedRel.Type = ELF::R_AARCH64_ADD_ABS_LO12_NC;
} else {
// For instructions that reference GOT, ignore the referenced symbol and
// use value at the relocation site. FixRelaxationPass will look at
// instruction pairs and will perform necessary adjustments.
return AdjustedRel;
}
// ADRP is a special case since the linker can leave the instruction opcode
// intact and modify only the operand. We are doing our best to detect when
// such conversion has happened without looking at the next instruction.
//
// If we detect that a page referenced by the ADRP cannot belong to GOT, and
// that it matches the symbol from the relocation, then we can be certain
// that the linker converted the GOT reference into the local one. Otherwise,
// we leave the disambiguation resolution to FixRelaxationPass.
//
// Note that ADRP relaxation described above cannot happen for TLS relocation.
// Since TLS relocations may not even have a valid symbol (not supported by
// BOLT), we explicitly exclude them from the check.
if (BC.MIB->isADRP(Inst) && Rel.Addend == 0 && !Relocation::isTLS(Rel.Type)) {
ErrorOr<uint64_t> SymbolValue = BC.getSymbolValue(*Rel.Symbol);
assert(SymbolValue && "Symbol value should be set");
const uint64_t SymbolPageAddr = *SymbolValue & ~0xfffULL;
// Check if defined symbol and GOT are on the same page. If they are not,
// disambiguate the operand.
if (BC.MIB->isADRP(Inst) && Rel.Addend == 0 &&
SymbolPageAddr == Rel.Value &&
if (SymbolPageAddr == Rel.Value &&
!isPageAddressValidForGOT(SymbolPageAddr)) {
AdjustedRel.Type = ELF::R_AARCH64_ADR_PREL_PG_HI21;
} else {
AdjustedRel.Symbol = BC.registerNameAtAddress("__BOLT_got_zero", 0, 0, 0);
AdjustedRel.Addend = Rel.Value;
return AdjustedRel;
}
}
// For instructions that reference GOT, ignore the referenced symbol and
// use value at the relocation site. FixRelaxationPass will look at
// instruction pairs and will perform necessary adjustments.
AdjustedRel.Symbol = BC.registerNameAtAddress("__BOLT_got_zero", 0, 0, 0);
AdjustedRel.Addend = Rel.Value;
return AdjustedRel;
}

8
bolt/test/AArch64/tls.c
View File

@ -34,3 +34,11 @@ int main() {
// RUN: -target aarch64-linux -fuse-ld=lld \
// RUN: -nostdlib
// RUN: llvm-bolt %t_pie.exe -o %t.bolt
// RUN: %clang %cflags -fPIC -shared %s -o %t.so -Wl,-q -fuse-ld=lld
// RUN: llvm-objdump -d -r --disassemble-symbols=main %t.so | FileCheck %s
// RUN: llvm-bolt %t.so -o %t.bolt.so
// Verify that unoptimized TLS access was generated for shared object.
// CHECK: adrp x0
// CHECK-NEXT: R_AARCH64_TLSDESC_ADR_PAGE21 tbssstruct