runtime: expand error for signal received on non-Go thread.

We call runtime.findnull dynamically to avoid exceeding the
static nosplit stack limit check.  (Thanks minux!)

Fixes #4048.

R=rsc, minux.ma, ality
CC=golang-dev
https://golang.org/cl/7232066

src/pkg/runtime/thread_darwin.c

@@ -497,7 +497,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
-static int8 badsignal[] = "runtime: signal received on thread not created by Go.\n";
+static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
 #pragma textflag 7
@@ -508,5 +508,11 @@ runtime·badsignal(int32 sig)
 		return;  // Ignore SIGPROFs intended for a non-Go thread.
 	}
 	runtime·write(2, badsignal, sizeof badsignal - 1);
+	if (0 <= sig && sig < NSIG) {
+		// Call runtime·findnull dynamically to circumvent static stack size check.
+		static int32 (*findnull)(byte*) = runtime·findnull;
+		runtime·write(2, runtime·sigtab[sig].name, findnull((byte*)runtime·sigtab[sig].name));
+	}
+	runtime·write(2, "\n", 1);
 	runtime·exit(1);
 }

src/pkg/runtime/thread_freebsd.c

@@ -206,7 +206,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
-static int8 badsignal[] = "runtime: signal received on thread not created by Go.\n";
+static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
 #pragma textflag 7
@@ -217,5 +217,11 @@ runtime·badsignal(int32 sig)
 		return;  // Ignore SIGPROFs intended for a non-Go thread.
 	}
 	runtime·write(2, badsignal, sizeof badsignal - 1);
+	if (0 <= sig && sig < NSIG) {
+		// Call runtime·findnull dynamically to circumvent static stack size check.
+		static int32 (*findnull)(byte*) = runtime·findnull;
+		runtime·write(2, runtime·sigtab[sig].name, findnull((byte*)runtime·sigtab[sig].name));
+	}
+	runtime·write(2, "\n", 1);
 	runtime·exit(1);
 }

src/pkg/runtime/thread_linux.c

@@ -256,7 +256,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
-static int8 badsignal[] = "runtime: signal received on thread not created by Go.\n";
+static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
 #pragma textflag 7
@@ -267,5 +267,11 @@ runtime·badsignal(int32 sig)
 		return;  // Ignore SIGPROFs intended for a non-Go thread.
 	}
 	runtime·write(2, badsignal, sizeof badsignal - 1);
+	if (0 <= sig && sig < NSIG) {
+		// Call runtime·findnull dynamically to circumvent static stack size check.
+		static int32 (*findnull)(byte*) = runtime·findnull;
+		runtime·write(2, runtime·sigtab[sig].name, findnull((byte*)runtime·sigtab[sig].name));
+	}
+	runtime·write(2, "\n", 1);
 	runtime·exit(1);
 }

src/pkg/runtime/thread_netbsd.c

@@ -252,7 +252,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
-static int8 badsignal[] = "runtime: signal received on thread not created by Go.\n";
+static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
 #pragma textflag 7
@@ -263,5 +263,11 @@ runtime·badsignal(int32 sig)
 		return;  // Ignore SIGPROFs intended for a non-Go thread.
 	}
 	runtime·write(2, badsignal, sizeof badsignal - 1);
+	if (0 <= sig && sig < NSIG) {
+		// Call runtime·findnull dynamically to circumvent static stack size check.
+		static int32 (*findnull)(byte*) = runtime·findnull;
+		runtime·write(2, runtime·sigtab[sig].name, findnull((byte*)runtime·sigtab[sig].name));
+	}
+	runtime·write(2, "\n", 1);
 	runtime·exit(1);
 }

src/pkg/runtime/thread_openbsd.c

@@ -229,7 +229,7 @@ runtime·badcallback(void)
 	runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
-static int8 badsignal[] = "runtime: signal received on thread not created by Go.\n";
+static int8 badsignal[] = "runtime: signal received on thread not created by Go: ";
 
 // This runs on a foreign stack, without an m or a g.  No stack split.
 #pragma textflag 7
@@ -240,5 +240,11 @@ runtime·badsignal(int32 sig)
 		return;  // Ignore SIGPROFs intended for a non-Go thread.
 	}
 	runtime·write(2, badsignal, sizeof badsignal - 1);
+	if (0 <= sig && sig < NSIG) {
+		// Call runtime·findnull dynamically to circumvent static stack size check.
+		static int32 (*findnull)(byte*) = runtime·findnull;
+		runtime·write(2, runtime·sigtab[sig].name, findnull((byte*)runtime·sigtab[sig].name));
+	}
+	runtime·write(2, "\n", 1);
 	runtime·exit(1);
 }