Fix stack overflow handling with SuperPMI

src/coreclr/pal/src/exception/signal.cpp

@@ -641,34 +641,39 @@ static void sigsegv_handler(int code, siginfo_t *siginfo, void *context)
                 {
                     PROCAbort(SIGSEGV, siginfo);
                 }
+
+                // The current executable (shared library) doesn't have hardware exception handler installed or opted to not to 
+                // handle it. So this handler will invoke the previously installed handler at the end of this function.
             }
             else
             {
                 (void)!write(STDERR_FILENO, StackOverflowMessage, sizeof(StackOverflowMessage) - 1);
                 PROCAbort(SIGSEGV, siginfo);
             }
         }
-
-        // Now that we know the SIGSEGV didn't happen due to a stack overflow, execute the common
-        // hardware signal handler on the original stack.
-
-        if (GetCurrentPalThread() && IsRunningOnAlternateStack(context))
+        else
         {
-            if (SwitchStackAndExecuteHandler(code, siginfo, context, 0 /* sp */)) // sp == 0 indicates execution on the original stack
+            // Now that we know the SIGSEGV didn't happen due to a stack overflow, execute the common
+            // hardware signal handler on the original stack.
+
+            if (GetCurrentPalThread() && IsRunningOnAlternateStack(context))
             {
-                return;
+                if (SwitchStackAndExecuteHandler(code, siginfo, context, 0 /* sp */)) // sp == 0 indicates execution on the original stack
+                {
+                    return;
+                }
             }
-        }
-        else
-        {
-            // The code flow gets here when the signal handler is not running on an alternate stack or when it wasn't created
-            // by coreclr. In both cases, we execute the common_signal_handler directly.
-            // If thread isn't created by coreclr and has alternate signal stack GetCurrentPalThread() will return NULL too.
-            // But since in this case we don't handle hardware exceptions (IsSafeToHandleHardwareException returns false)
-            // we can call common_signal_handler on the alternate stack.
-            if (common_signal_handler(code, siginfo, context, 2, (size_t)0, (size_t)siginfo->si_addr))
+            else
             {
-                return;
+                // The code flow gets here when the signal handler is not running on an alternate stack or when it wasn't created
+                // by coreclr. In both cases, we execute the common_signal_handler directly.
+                // If thread isn't created by coreclr and has alternate signal stack GetCurrentPalThread() will return NULL too.
+                // But since in this case we don't handle hardware exceptions (IsSafeToHandleHardwareException returns false)
+                // we can call common_signal_handler on the alternate stack.
+                if (common_signal_handler(code, siginfo, context, 2, (size_t)0, (size_t)siginfo->si_addr))
+                {
+                    return;
+                }
             }
         }
     }