Merge pull request #10988 from bulbazord/20240723-signal-handler

[Support] Don't re-raise signals sent from kernel (llvm#145759)

Author: bulbazord

llvm/lib/Support/Unix/Signals.inc

@@ -80,6 +80,10 @@
 #endif
 #endif
 
+#if defined(__linux__)
+#include <sys/syscall.h>
+#endif
+
 using namespace llvm;
 
 static void SignalHandler(int Sig, siginfo_t *Info, void *);
@@ -411,10 +415,21 @@ static void SignalHandler(int Sig, siginfo_t *Info, void *) {
     raise(Sig);
 #endif
 
-  // Signal sent from another process, do not assume that continuing the
-  // execution would re-raise it.
-  if (Info->si_pid != getpid())
+#if defined(__linux__)
+  // Re-raising a signal via `raise` loses the original siginfo. Recent
+  // versions of linux (>= 3.9) support processes sending a signal to itself
+  // with arbitrary signal information using a syscall. If this syscall is
+  // unsupported, errno will be set to EPERM and `raise` will be used instead.
+  int retval =
+      syscall(SYS_rt_tgsigqueueinfo, getpid(), syscall(SYS_gettid), Sig, Info);
+  if (retval != 0 && errno == EPERM)
     raise(Sig);
+#else
+  // Signal sent from another userspace process, do not assume that continuing
+  // the execution would re-raise it.
+  if (Info->si_pid != getpid() && Info->si_pid != 0)
+    raise(Sig);
+#endif
 }
 
 static void InfoSignalHandler(int Sig) {