[libunwind] cddc53e - libunwind: Don't attempt to authenticate a null return address.

[Peter Collingbourne via cfe-commits]

Author: Peter Collingbourne
Date: 2021-02-16T11:18:02-08:00
New Revision: cddc53ef088b68586094c9841a76b41bee3994a4

URL: https://github.com/llvm/llvm-project/commit/cddc53ef088b68586094c9841a76b41bee3994a4
DIFF: https://github.com/llvm/llvm-project/commit/cddc53ef088b68586094c9841a76b41bee3994a4.diff

LOG: libunwind: Don't attempt to authenticate a null return address.

Null return addresses can appear at the bottom of the stack (i.e. the
frame corresponding to the entry point). Authenticating these addresses
will set the error code in the address, which will lead to a segfault
in the sigreturn trampoline detection code. Fix this problem by not
authenticating null addresses.

Differential Revision: https://reviews.llvm.org/D96560

Added: 
    

Modified: 
    libunwind/src/DwarfInstructions.hpp

Removed: 
    


################################################################################
diff  --git a/libunwind/src/DwarfInstructions.hpp b/libunwind/src/DwarfInstructions.hpp
index c39cabe1f783..bd13d1623153 100644
--- a/libunwind/src/DwarfInstructions.hpp
+++ b/libunwind/src/DwarfInstructions.hpp
@@ -213,7 +213,8 @@ int DwarfInstructions<A, R>::stepWithDwarf(A &addressSpace, pint_t pc,
       // restored. autia1716 is used instead of autia as autia1716 assembles
       // to a NOP on pre-v8.3a architectures.
       if ((R::getArch() == REGISTERS_ARM64) &&
-          prolog.savedRegisters[UNW_ARM64_RA_SIGN_STATE].value) {
+          prolog.savedRegisters[UNW_ARM64_RA_SIGN_STATE].value &&
+          returnAddress != 0) {
 #if !defined(_LIBUNWIND_IS_NATIVE_ONLY)
         return UNW_ECROSSRASIGNING;
 #else