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[libunwind][PAuthLR] Remove PC offset when using FEAT_PAuthLR #164224

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Merged
merged 4 commits into from
Oct 29, 2025
Merged

[libunwind][PAuthLR] Remove PC offset when using FEAT_PAuthLR #164224

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87a7351
[libunwind][PAuthLR] Remove PC offset when using FEAT_PAuthLR
Stylie777 Oct 20, 2025
b46d555
Still set results->ptrAuthDiversifier
Stylie777 Oct 21, 2025
d18b658
Reintroduce comment
Stylie777 Oct 27, 2025
ce85b8b
Merge branch 'main' into remove_libunwind_pauthlr_offset
Stylie777 Oct 28, 2025
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10 changes: 4 additions & 6 deletions libunwind/src/DwarfParser.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -842,12 +842,10 @@ bool CFI_Parser<A>::parseFDEInstructions(A &addressSpace,
results->savedRegisters[UNW_AARCH64_RA_SIGN_STATE].value ^ 0x3;
results->setRegisterValue(UNW_AARCH64_RA_SIGN_STATE, value,
initialState);
// When calculating the value of the PC, it is assumed that the CFI
// instruction is placed before the signing instruction, however it is
// placed after. Because of this, we need to take into account the CFI
// instruction is one instruction call later than expected, and reduce
// the PC value by 4 bytes to compensate.
results->ptrAuthDiversifier = fdeInfo.pcStart + codeOffset - 0x4;
// When using Feat_PAuthLR, the PC value needs to be captured so that
// during unwinding, the correct PC value is used for re-authentication.
// It is assumed that the CFI is placed before the signing instruction.
results->ptrAuthDiversifier = fdeInfo.pcStart + codeOffset;
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@MaskRay MaskRay Oct 22, 2025

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Can you edit this comment instead of entirely discarding it?

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@Stylie777 Stylie777 Oct 27, 2025

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Done

_LIBUNWIND_TRACE_DWARF(
"DW_CFA_AARCH64_negate_ra_state_with_pc(pc=0x%" PRIx64 ")\n",
static_cast<uint64_t>(results->ptrAuthDiversifier));
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