[ubsan] warn inside the sigaction interceptor if static linking is suspected, and continue instead of crashing on null deref

[kcc]

Summary

[ubsan] warn inside the sigaction interceptor if static linking is suspected, and continue instead of crashing on null deref

compiler-rt/lib/sanitizer_common/sanitizer_signal_interceptors.inc

 #endif
 
 #ifndef SIGNAL_INTERCEPTOR_SIGNAL_IMPL
 #define SIGNAL_INTERCEPTOR_SIGNAL_IMPL(func, signum, handler) \
   { return REAL(func)(signum, handler); }
 #endif
 
 #ifndef SIGNAL_INTERCEPTOR_SIGACTION_IMPL
-#define SIGNAL_INTERCEPTOR_SIGACTION_IMPL(signum, act, oldact) \
-  { return REAL(sigaction_symname)(signum, act, oldact); }
+#  define SIGNAL_INTERCEPTOR_SIGACTION_IMPL(signum, act, oldact)              \
+    {                                                                         \
+      if (!REAL(sigaction_symname)) {                                         \
+        Printf(                                                               \
+            "Warning: REAL(sigaction_symname) == nullptr. This may happen "   \
+            "if you link with ubsan statically. Sigaction will not work.\n"); \
+        return -1;                                                            \
+      }                                                                       \
+      return REAL(sigaction_symname)(signum, act, oldact);                    \
+    }
 #endif
 
 #if SANITIZER_INTERCEPT_BSD_SIGNAL
 INTERCEPTOR(uptr, bsd_signal, int signum, uptr handler) {
   if (GetHandleSignalMode(signum) == kHandleSignalExclusive) return 0;
   SIGNAL_INTERCEPTOR_SIGNAL_IMPL(bsd_signal, signum, handler);
 }
 #define INIT_BSD_SIGNAL COMMON_INTERCEPT_FUNCTION(bsd_signal)

 #endif  // SANITIZER_INTERCEPT_SIGNAL_AND_SIGACTION
 
 static void InitializeSignalInterceptors() {
   static bool was_called_once;
   CHECK(!was_called_once);
   was_called_once = true;
 
   INIT_BSD_SIGNAL;
   INIT_SIGNAL;
   INIT_SIGACTION;
 }

compiler-rt/test/ubsan/TestCases/Misc/Linux/static-link.cpp

+// REQUIRES: ubsan-standalone
+// REQUIRES: arch=x86_64
+// RUN: %clangxx -fsanitize=bool -static  %s -o %t && UBSAN_OPTIONS=handle_segv=0:handle_sigbus=0:handle_sigfpe=0 %run %t 2>&1 | FileCheck %s
+#include <signal.h>
+#include <stdio.h>
+
+int main() {
+  struct sigaction old_action;
+  sigaction(SIGINT, nullptr, &old_action);
+  // CHECK: Warning: REAL(sigaction_symname) == nullptr.
+  printf("PASS\n");
+  // CHECK: PASS
+}