Revert "[compiler-rt] Don't reset non-default user handler if allow_user_segv_handler is true."

[vitalybuka]

Summary

On Android we still need to reset preinstalled handlers and allow use handlers later.

This reverts commit r304039.

lib/sanitizer_common/sanitizer_posix_libcdep.cc

void UnsetAlternateSignalStack() {
   altstack.ss_flags = SS_DISABLE;
   altstack.ss_size = kAltStackSize;  // Some sane value required on Darwin.
   CHECK_EQ(0, sigaltstack(&altstack, &oldstack));
   UnmapOrDie(oldstack.ss_sp, oldstack.ss_size);
 }
 
 static void MaybeInstallSigaction(int signum,
                                   SignalHandlerType handler) {
-  switch (GetHandleSignalMode(signum)) {
-    case kHandleSignalNo:
-      return;
-    case kHandleSignalYes: {
-      struct sigaction sigact;
-      internal_memset(&sigact, 0, sizeof(sigact));
-      CHECK_EQ(0, internal_sigaction(signum, nullptr, &sigact));
-      if (sigact.sa_flags & SA_SIGINFO) {
-        if (sigact.sa_sigaction) return;
-      } else {
-        if (sigact.sa_handler != SIG_DFL && sigact.sa_handler != SIG_IGN &&
-            sigact.sa_handler != SIG_ERR)
-          return;
-      }
-      break;
-    }
-    case kHandleSignalExclusive:
-      break;
-  }
+  if (GetHandleSignalMode(signum) == kHandleSignalNo) return;
 
   struct sigaction sigact;
   internal_memset(&sigact, 0, sizeof(sigact));
   sigact.sa_sigaction = (sa_sigaction_t)handler;
   // Do not block the signal from being received in that signal's handler.
   // Clients are responsible for handling this correctly.
   sigact.sa_flags = SA_SIGINFO | SA_NODEFER;
   if (common_flags()->use_sigaltstack) sigact.sa_flags |= SA_ONSTACK;

test/asan/TestCases/Linux/preinstalled_signal.cc

 // clang-format off
 // RUN: %clangxx -std=c++11 %s -o %t
 // RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=1 not %run %t 2>&1 | FileCheck %s
 // RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=2 not %run %t 2>&1 | FileCheck %s
 
 // RUN: %clangxx -std=c++11 -DTEST_INSTALL_SIG_HANDLER %s -o %t
-// RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=1 not %run %t 2>&1 | FileCheck --check-prefix=CHECK-HANDLER %s
+// RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=0 not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-HANDLER
+// RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=1 not %run %t 2>&1 | FileCheck %s
 // RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=2 not %run %t 2>&1 | FileCheck %s
 
 // RUN: %clangxx -std=c++11 -DTEST_INSTALL_SIG_ACTION %s -o %t
-// RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=1 not %run %t 2>&1 | FileCheck --check-prefix=CHECK-ACTION %s
+// RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=0 not %run %t 2>&1 | FileCheck %s --check-prefix=CHECK-ACTION
+// RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=1 not %run %t 2>&1 | FileCheck %s
 // RUN: env LD_PRELOAD=%shared_libasan %env_asan_opts=handle_segv=2 not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: asan-dynamic-runtime
 
 // This way of setting LD_PRELOAD does not work with Android test runner.
 // REQUIRES: not-android
 // clang-format on
 

 #if defined(__x86_64__)
     act->flags |= 0x04000000;
     act->restorer = &restorer;
 #endif
   }
   return syscall(__NR_rt_sigaction, sig, act, oact, NSIG / 8);
 }
 
-struct KernelSigaction sigact = {};
+struct KernelSigaction pre_asan = {};
 
 static void Init() {
-  int res = InternalSigaction(SIGSEGV, nullptr, &sigact);
+  int res = InternalSigaction(SIGSEGV, nullptr, &pre_asan);
   assert(res >= 0);
-  assert(sigact.handler == SIG_DFL || sigact.handler == SIG_IGN);
+  assert(pre_asan.handler == SIG_DFL || pre_asan.handler == SIG_IGN);
 #if defined(TEST_INSTALL_SIG_HANDLER)
-  sigact = {};
-  sigact.handler = &SigHandler;
-  res = InternalSigaction(SIGSEGV, &sigact, nullptr);
+  pre_asan = {};
+  pre_asan.handler = &SigHandler;
+  res = InternalSigaction(SIGSEGV, &pre_asan, nullptr);
   assert(res >= 0);
 #elif defined(TEST_INSTALL_SIG_ACTION)
-  sigact = {};
-  sigact.flags = SA_SIGINFO | SA_NODEFER;
-  sigact.handler = (__sighandler_t)&SigAction;
-  res = InternalSigaction(SIGSEGV, &sigact, nullptr);
+  pre_asan = {};
+  pre_asan.flags = SA_SIGINFO | SA_NODEFER;
+  pre_asan.handler = (__sighandler_t)&SigAction;
+  res = InternalSigaction(SIGSEGV, &pre_asan, nullptr);
   assert(res >= 0);
 #endif
 }
 
 __attribute__((section(".preinit_array"), used))
 void (*__local_test_preinit)(void) = Init;
 
-bool ShouldAsanInstallHandlers() {
+bool ExpectUserHandler() {
 #if defined(TEST_INSTALL_SIG_HANDLER) || defined(TEST_INSTALL_SIG_ACTION)
-  return !strcmp(getenv("ASAN_OPTIONS"), "handle_segv=2");
+  return !strcmp(getenv("ASAN_OPTIONS"), "handle_segv=0");
 #endif
-  return true;
+  return false;
 }
 
 int main(int argc, char *argv[]) {
-  KernelSigaction sigact_asan = {};
-  InternalSigaction(SIGSEGV, nullptr, &sigact_asan);
+  KernelSigaction post_asan = {};
+  InternalSigaction(SIGSEGV, nullptr, &post_asan);
 
-  assert(sigact_asan.handler != SIG_DFL);
-  assert(sigact_asan.handler != SIG_IGN);
-  assert(ShouldAsanInstallHandlers() ==
-         (sigact_asan.handler != sigact.handler));
+  assert(post_asan.handler != SIG_DFL);
+  assert(post_asan.handler != SIG_IGN);
+  assert(ExpectUserHandler() ==
+         (post_asan.handler == pre_asan.handler));
 
   raise(SIGSEGV);
   printf("%s\n", handler);
   return 1;
 }
 
 // CHECK-NOT: TestSig
 // CHECK: ASAN:DEADLYSIGNAL
 
 // CHECK-HANDLER-NOT: ASAN:DEADLYSIGNAL
 // CHECK-HANDLER: TestSigHandler
 
 // CHECK-ACTION-NOT: ASAN:DEADLYSIGNAL
 // CHECK-ACTION: TestSigAction