code review 9226043: runtime: fix crash in badsignal()

src/pkg/runtime/os_freebsd.c

 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 #include "runtime.h"
 #include "defs_GOOS_GOARCH.h"
 #include "os_GOOS.h"
 #include "signal_unix.h"
 #include "stack.h"
 
@@ skipping 234 matching lines @@
         runtime·write(2, badcallback, sizeof badcallback - 1);
 }
 
 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
 void
 runtime·badsignal(int32 sig)
 {
+        int32 len;
+
         if (sig == SIGPROF) {
                 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));
+                // Can't call findnull() because it will split stack.
+                for(len = 0; runtime·sigtab[sig].name[len]; len++) {}
+                runtime·write(2, runtime·sigtab[sig].name, len);
         }
         runtime·write(2, "\n", 1);
         runtime·exit(1);
 }
 
 extern void runtime·sigtramp(void);
 
 typedef struct sigaction {
         union {
                 void    (*__sa_handler)(int32);
@@ skipping 39 matching lines @@
 {
         StackT st;
 
         st.ss_sp = (void*)p;
         st.ss_size = n;
         st.ss_flags = 0;
         if(p == nil)
                 st.ss_flags = SS_DISABLE;
         runtime·sigaltstack(&st, nil);
 }