From 00b18e9f1578b1f40278dfaed4388374bba497fb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-Andr=C3=A9=20Santoni?= <jean.andre.santoni@gmail.com>
Date: Thu, 21 May 2026 10:14:41 +0200
Subject: [PATCH] Backup and restore signal stack

---
 Common/ExceptionHandlerSetup.cpp | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/Common/ExceptionHandlerSetup.cpp b/Common/ExceptionHandlerSetup.cpp
index f1b9778885..8b1a1a5e0e 100644
--- a/Common/ExceptionHandlerSetup.cpp
+++ b/Common/ExceptionHandlerSetup.cpp
@@ -222,6 +222,8 @@ void UninstallExceptionHandler() {
 
 static struct sigaction old_sa_segv;
 static struct sigaction old_sa_bus;
+static stack_t old_signal_stack{};
+static bool old_signal_stack_valid = false;
 
 static void sigsegv_handler(int sig, siginfo_t* info, void* raw_context) {
 	if (sig != SIGSEGV && sig != SIGBUS) {
@@ -298,6 +300,9 @@ void InstallExceptionHandler(BadAccessHandler badAccessHandler) {
 	g_badAccessHandler = badAccessHandler;
 
 	stack_t signal_stack{};
+	if (sigaltstack(nullptr, &old_signal_stack) == 0) {
+		old_signal_stack_valid = true;
+	}
 	altStack = malloc(altStackSize);
 #ifdef __FreeBSD__
 	signal_stack.ss_sp = (char*)altStack;
@@ -324,10 +329,11 @@ void UninstallExceptionHandler() {
 	if (!g_badAccessHandler) {
 		return;
 	}
-	stack_t signal_stack{};
-	signal_stack.ss_flags = SS_DISABLE;
-	if (0 != sigaltstack(&signal_stack, nullptr)) {
-		ERROR_LOG(Log::System, "Could not remove signal altstack");
+	if (old_signal_stack_valid) {
+		if (0 != sigaltstack(&old_signal_stack, nullptr)) {
+			ERROR_LOG(Log::System, "Could not restore previous signal altstack");
+		}
+		old_signal_stack_valid = false;
 	}
 	if (altStack) {
 		free(altStack);