[libcxx-commits] [PATCH] D96560: libunwind: Don't attempt to authenticate a null return address.

[Peter Collingbourne via Phabricator via libcxx-commits]

pcc created this revision.
pcc added reviewers: rprichard, danielkiss.
Herald added a project: libunwind.
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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.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D96560

Files:
  libunwind/src/DwarfInstructions.hpp


Index: libunwind/src/DwarfInstructions.hpp
===================================================================
--- libunwind/src/DwarfInstructions.hpp
+++ libunwind/src/DwarfInstructions.hpp
@@ -213,7 +213,8 @@
       // 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


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