[compiler-rt] [sanitizer] Add cloak_sanitizer_signal_handlers runtime option (PR #162746)

[Thurston Dang via llvm-commits]

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@@ -56,19 +63,53 @@ INTERCEPTOR(uptr, bsd_signal, int signum, uptr handler) {
 INTERCEPTOR(uptr, signal, int signum, uptr handler) {
   SIGNAL_INTERCEPTOR_ENTER();
   if (GetHandleSignalMode(signum) == kHandleSignalExclusive)
+    // The user can neither view nor change the signal handler, regardless of
+    // the cloak_sanitizer_signal_handlers setting. This differs from
+    // sigaction().
     return (uptr) nullptr;
+  uptr ret;
   SIGNAL_INTERCEPTOR_SIGNAL_IMPL(signal, signum, handler);
+
+  if (signum >= 0 && signum < MaxSignals &&
+      signal_handler_is_from_sanitizer[signum] && ret != sig_err) {
+    // If the user sets a signal handler, it is never cloaked, even if they
+    // reuse a sanitizer's signal handler.
+    signal_handler_is_from_sanitizer[signum] = false;
+
+    ret = sig_dfl;
+  }
+
+  return ret;
 }
 #define INIT_SIGNAL COMMON_INTERCEPT_FUNCTION(signal)
 
 INTERCEPTOR(int, sigaction_symname, int signum,
             const __sanitizer_sigaction *act, __sanitizer_sigaction *oldact) {
   SIGNAL_INTERCEPTOR_ENTER();
+
   if (GetHandleSignalMode(signum) == kHandleSignalExclusive) {
     if (!oldact) return 0;
     act = nullptr;
+    // If cloak_sanitizer_signal_handlers=true, the user can neither view nor
+    // change the signal handle.
+    // If false, the user can view but not change the signal handler. This
+    // differs from signal().
   }
+  int ret;
   SIGNAL_INTERCEPTOR_SIGACTION_IMPL(signum, act, oldact);
+
+  if (signum >= 0 && signum < MaxSignals &&
+      signal_handler_is_from_sanitizer[signum] && ret == 0) {
+    if (act)
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thurstond wrote:

Done: https://github.com/llvm/llvm-project/pull/162746/commits/65468343534015455b18f7db64885511bbfb109b

https://github.com/llvm/llvm-project/pull/162746