[dfsan] Clean TLS after signal callbacks

[stephan.yichao.zhao]

Summary

Similar to https://reviews.llvm.org/D95642, this diff fixes signal.

[morehouse]

compiler-rt/lib/dfsan/dfsan_custom.cpp

956

Side question: how does this trampoline get inserted?

962–975

Can remove some casting like this.

971

Don't we need to check that ret == SignalHandler before changing it?

compiler-rt/test/dfsan/custom.cpp

866

Shouldn't this return SIG_DFL?

[stephan.yichao.zhao]

updated

compiler-rt/lib/dfsan/dfsan_custom.cpp

956

It is by this.

For normal function pointer arguments, we can use it like

dfsan_label ret_l;
handler_trampoline(handler, signo, 0, &ret_l);

pthread_create does so.

In this case, we have SignalHandler shared with sigaction to do the similar work. So I ignored it.
The reason that sigaction must define its own SignalHandler and SigAction is because our code knows only how to create trampoline to top-level function pointers.

971

Yes. Thank you. Also changed test cases.

compiler-rt/test/dfsan/custom.cpp

866

updated. will be adding similar test cases for test_sigaction later.

[morehouse]

compiler-rt/lib/dfsan/dfsan_custom.cpp

970

Nit: The != SIG_ERR check is now unnecessary.

[stephan.yichao.zhao]

addressed comments

compiler-rt/lib/dfsan/dfsan_custom.cpp

int __dfsw_sigaction(int signum, const struct sigaction *act,
   if (oldact) {
     dfsan_set_label(0, oldact, sizeof(struct sigaction));
   }
   *ret_label = 0;
   return ret;
 }
 
 SANITIZER_INTERFACE_ATTRIBUTE
+sighandler_t __dfsw_signal(int signum,
+                           void *(*handler_trampoline)(void *, int, dfsan_label,
+                                                       dfsan_label *),
+                           sighandler_t handler, dfsan_label signum_label,
+                           dfsan_label handler_label, dfsan_label *ret_label) {
+  CHECK_LT(signum, kMaxSignals);
+  SignalSpinLocker lock;
+  uptr old_cb = atomic_load(&sigactions[signum], memory_order_relaxed);
+  if (handler != SIG_IGN && handler != SIG_DFL) {
+    atomic_store(&sigactions[signum], (uptr)handler, memory_order_relaxed);
+    handler = &SignalHandler;
+  }
+
+  sighandler_t ret = signal(signum, handler);
+
+  if (ret == SignalHandler)
+    ret = (sighandler_t)old_cb;
+
+  *ret_label = 0;
+  return ret;
+}
+
+SANITIZER_INTERFACE_ATTRIBUTE
 int __dfsw_sigaltstack(const stack_t *ss, stack_t *old_ss, dfsan_label ss_label,
                        dfsan_label old_ss_label, dfsan_label *ret_label) {
   int ret = sigaltstack(ss, old_ss);
   if (ret != -1 && old_ss)
     dfsan_set_label(0, old_ss, sizeof(*old_ss));
   *ret_label = 0;
   return ret;
 }

compiler-rt/lib/dfsan/done_abilist.txt

 fun:dl_iterate_phdr=custom
 
 fun:getpwuid_r=custom
 fun:poll=custom
 fun:sched_getaffinity=custom
 fun:select=custom
 fun:sigemptyset=custom
 fun:sigaction=custom
+fun:signal=custom
 fun:gettimeofday=custom
 
 # sprintf-like
 fun:sprintf=custom
 fun:snprintf=custom
 
 # TODO: custom
 fun:asprintf=discard

compiler-rt/test/dfsan/custom.cpp

void test_sigaction() {
   assert(0 == sigaction(SIGUSR1, &newact_with_sighandler, &oldact));
   assert(oldact.sa_sigaction == SignalAction);
 
   // Restore sigaction to the orginal setting, check the last one is SignalHandler
   assert(0 == sigaction(SIGUSR1, &origin_act, &oldact));
   assert(oldact.sa_handler == SignalHandler);
 }
 
+void test_signal() {
+  // Set signal to be SignalHandler, save the previous one into
+  // old_signal_handler.
+  sighandler_t old_signal_handler = signal(SIGHUP, SignalHandler);
+  ASSERT_ZERO_LABEL(old_signal_handler);
+
+  // Set SIG_IGN or SIG_DFL, and check the previous one is expected.
+  assert(SignalHandler == signal(SIGHUP, SIG_DFL));
+  assert(SIG_DFL == signal(SIGHUP, SIG_IGN));
+
+  // Restore signal to old_signal_handler.
+  assert(SIG_IGN == signal(SIGHUP, old_signal_handler));
+}
+
 void test_sigaltstack() {
   stack_t old_altstack = {};
   dfsan_set_label(j_label, &old_altstack, sizeof(old_altstack));
   int ret = sigaltstack(NULL, &old_altstack);
   assert(ret == 0);
   ASSERT_ZERO_LABEL(ret);
   ASSERT_READ_ZERO_LABEL(&old_altstack, sizeof(old_altstack));
 }
#endif
   test_pthread_create();
   test_pthread_join();
   test_read();
   test_recvmmsg();
   test_recvmsg();
   test_sched_getaffinity();
   test_select();
   test_sigaction();
+  test_signal();
   test_sigaltstack();
   test_sigemptyset();
   test_snprintf();
   test_socketpair();
   test_sprintf();
   test_stat();
   test_strcasecmp();
   test_strchr();