print rudimentary stack traceback after panic

SVN=123524

diff --git a/src/runtime/runtime.c b/src/runtime/runtime.c
index ee6f75f09c2bc2a65abc1502d01d478ea9aadad8..73ae1972e2cbe5d479099858f57e53751998abf8 100644 (file)
--- a/src/runtime/runtime.c
+++ b/src/runtime/runtime.c
@@ -102,11 +102,61 @@ sys_printpc(void *p)
 void
 sys_panicl(int32 lno)
 {
+       uint8 *pc;
+       uint8 *sp;
+       uint8 *retpc;
+       int32 spoff;
+       static int8 spmark[] = "\xa7\xf1\xd9\x2a\x82\xc8\xd8\xfe";
+       int8* spp;
+       int32 counter;
+       int32 i;
+
        prints("\npanic on line ");
        sys_printint(lno);
        prints(" ");
        sys_printpc(&lno);
        prints("\n");
+       sp = (uint8*)&lno;
+       pc = (uint8*)sys_panicl;
+       counter = 0;
+       while((pc = ((uint8**)sp)[-1]) > (uint8*)0x1000) {
+               for(i = 0; i < 3; i++){
+                       prints("\tint32[");
+                       sys_printint(i);
+                       prints("]=");
+                       sys_printint(((uint32*)sp)[i]);
+                       prints("\tint64*[");
+                       sys_printint(i);
+                       prints("]=");
+                       sys_printpointer(((void**)sp)[i]);
+                       prints("\n");
+               }
+               prints("0x");
+               sys_printpointer(pc);
+               prints(" ");
+               /* next word down on stack is PC */
+               retpc = pc;
+               /* find SP offset by stepping back through instructions to SP offset marker */
+               while(pc > (uint8*)0x1000+11) {
+                       for(spp = spmark; *spp != '\0' && *pc++ == (uint8)*spp++; )
+                               ;
+                       if(*spp == '\0'){
+                               spoff = *pc++;
+                               spoff += *pc++ << 8;
+                               spoff += *pc++ << 16;
+                               prints((int8*)pc);
+                               prints("+");
+                               sys_printint(pc-retpc);
+                               prints("?zi\n");
+                               sp += spoff + 8;
+                               break;
+                       }
+               }
+               if(counter++ > 100){
+                       prints("stack trace terminated\n");
+                       break;
+               }
+       }
        *(int32*)0 = 0;
 }