[libunwind] [libunwind] fix unwinding from signal handler (PR #92291)

[Azat Khuzhin via cfe-commits]

https://github.com/azat created https://github.com/llvm/llvm-project/pull/92291

In case of this is frame of signal handler, the IP should be incremented, because the IP saved in the signal handler points to first non-executed instruction, while FDE/CIE expects IP to be after the first non-executed instruction.

Refs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26208

>From 5e3635c1852ac280f06f9e54793d4181d2845b64 Mon Sep 17 00:00:00 2001
From: Azat Khuzhin <a3at.mail at gmail.com>
Date: Wed, 15 May 2024 08:17:22 +0200
Subject: [PATCH] [libunwind] fix unwinding from signal handler

In case of this is frame of signal handler, the IP should be
incremented, because the IP saved in the signal handler points to first
non-executed instruction, while FDE/CIE expects IP to be after the
first non-executed instruction.

Refs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=26208
---
 libunwind/src/DwarfInstructions.hpp | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libunwind/src/DwarfInstructions.hpp b/libunwind/src/DwarfInstructions.hpp
index bd9ece60ee588..5ea535be4b974 100644
--- a/libunwind/src/DwarfInstructions.hpp
+++ b/libunwind/src/DwarfInstructions.hpp
@@ -365,7 +365,12 @@ int DwarfInstructions<A, R>::stepWithDwarf(A &addressSpace, pint_t pc,
 
       // Return address is address after call site instruction, so setting IP to
       // that does simulates a return.
-      newRegisters.setIP(returnAddress);
+      //
+      // In case of this is frame of signal handler, the IP should be
+      // incremented, because the IP saved in the signal handler points to
+      // first non-executed instruction, while FDE/CIE expects IP to be after
+      // the first non-executed instruction.
+      newRegisters.setIP(returnAddress + cieInfo.isSignalFrame);
 
       // Simulate the step by replacing the register set with the new ones.
       registers = newRegisters;