Author: Simon Tatham Date: 2022-06-27T09:36:21+01:00 New Revision: 43c84e463426ca35fe9fc2d38063d75fed944f23
URL: https://github.com/llvm/llvm-project/commit/43c84e463426ca35fe9fc2d38063d75fed944f23 DIFF: https://github.com/llvm/llvm-project/commit/43c84e463426ca35fe9fc2d38063d75fed944f23.diff LOG: [libunwind,EHABI,ARM] Fix get/set of RA_AUTH_CODE. According to EHABI32 ยง8.5.2, the PAC for the return address of a function described in an exception table is supposed to be addressed in the _Unwind_VRS_{Get,Set} API by setting regclass=_UVRSC_PSEUDO and regno=0. (The space of 'regno' values is independent for each regclass, and for _UVRSC_PSEUDO, there is only one valid regno so far.) That is indeed what libunwind's _Unwind_VRS_{Get,Set} functions expect to receive. But at two call sites, the wrong values are passed in: regno is being set to UNW_ARM_RA_AUTH_CODE (0x8F) instead of 0, and in one case, regclass is _UVRSC_CORE instead of _UVRSC_PSEUDO. As a result, those calls to _Unwind_VRS_{Get,Set} return _UVRSR_FAILED, which their callers ignore. So if you compile in the AUTG instruction that actually validates the PAC, it will try to validate what's effectively an uninitialised register as an authentication code, and trigger a CPU fault even on correct exception unwinding. Reviewed By: danielkiss Differential Revision: https://reviews.llvm.org/D128522 Added: Modified: libunwind/src/Unwind-EHABI.cpp Removed: ################################################################################ diff --git a/libunwind/src/Unwind-EHABI.cpp b/libunwind/src/Unwind-EHABI.cpp index 6ac09adfb8fe..f203887567b6 100644 --- a/libunwind/src/Unwind-EHABI.cpp +++ b/libunwind/src/Unwind-EHABI.cpp @@ -432,8 +432,7 @@ _Unwind_VRS_Interpret(_Unwind_Context *context, const uint32_t *data, uint32_t sp; uint32_t pac; _Unwind_VRS_Get(context, _UVRSC_CORE, UNW_ARM_SP, _UVRSD_UINT32, &sp); - _Unwind_VRS_Get(context, _UVRSC_PSEUDO, UNW_ARM_RA_AUTH_CODE, - _UVRSD_UINT32, &pac); + _Unwind_VRS_Get(context, _UVRSC_PSEUDO, 0, _UVRSD_UINT32, &pac); __asm__ __volatile__("autg %0, %1, %2" : : "r"(pac), "r"(lr), "r"(sp) :); } #else @@ -1138,8 +1137,7 @@ _Unwind_VRS_Pop(_Unwind_Context *context, _Unwind_VRS_RegClass regclass, } uint32_t pac = *sp++; _Unwind_VRS_Set(context, _UVRSC_CORE, UNW_ARM_SP, _UVRSD_UINT32, &sp); - return _Unwind_VRS_Set(context, _UVRSC_CORE, UNW_ARM_RA_AUTH_CODE, - _UVRSD_UINT32, &pac); + return _Unwind_VRS_Set(context, _UVRSC_PSEUDO, 0, _UVRSD_UINT32, &pac); } } _LIBUNWIND_ABORT("unsupported register class"); _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
