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// Copyright 2009 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 "malloc.h"
static uintptr isclosureentry(uintptr);
void runtime·deferproc(void);
void runtime·newproc(void);
// This code is also used for the 386 tracebacks.
// Use uintptr for an appropriate word-sized integer.
// Generic traceback. Handles runtime stack prints (pcbuf == nil)
// as well as the runtime.Callers function (pcbuf != nil).
// A little clunky to merge the two but avoids duplicating
// the code and all its subtlety.
static int32
gentraceback(byte *pc0, byte *sp, G *g, int32 skip, uintptr *pcbuf, int32 m)
{
byte *p;
int32 i, n, iter, nascent;
uintptr pc, tracepc, *fp;
Stktop *stk;
Func *f;
pc = (uintptr)pc0;
// If the PC is zero, it's likely a nil function call.
// Start in the caller's frame.
if(pc == 0) {
pc = *(uintptr*)sp;
sp += sizeof(uintptr);
}
nascent = 0;
if(pc0 == g->sched.pc && sp == g->sched.sp && pc0 == (byte*)runtime·goexit) {
// Hasn't started yet. g->sched is set up for goexit
// but goroutine will start at g->entry.
nascent = 1;
pc = (uintptr)g->entry;
}
n = 0;
stk = (Stktop*)g->stackbase;
for(iter = 0; iter < 100 && n < m; iter++) { // iter avoids looping forever
if(pc == (uintptr)runtime·lessstack) {
// Hit top of stack segment. Unwind to next segment.
pc = (uintptr)stk->gobuf.pc;
sp = stk->gobuf.sp;
stk = (Stktop*)stk->stackbase;
continue;
}
if(pc <= 0x1000 || (f = runtime·findfunc(pc)) == nil) {
// Dangerous, but worthwhile: see if this is a closure:
// ADDQ $wwxxyyzz, SP; RET
// [48] 81 c4 zz yy xx ww c3
// The 0x48 byte is only on amd64.
p = (byte*)pc;
// We check p < p+8 to avoid wrapping and faulting if we lose track.
if(runtime·mheap.arena_start < p && p < p+8 && p+8 < runtime·mheap.arena_used && // pointer in allocated memory
(sizeof(uintptr) != 8 || *p++ == 0x48) && // skip 0x48 byte on amd64
p[0] == 0x81 && p[1] == 0xc4 && p[6] == 0xc3) {
sp += *(uint32*)(p+2);
pc = *(uintptr*)sp;
sp += sizeof(uintptr);
continue;
}
if(nascent && (pc = isclosureentry(pc)) != 0)
continue;
// Unknown pc; stop.
break;
}
// Found an actual function worth reporting.
if(skip > 0)
skip--;
else if(pcbuf != nil)
pcbuf[n++] = pc;
else {
// Print during crash.
// main+0xf /home/rsc/go/src/runtime/x.go:23
// main(0x1, 0x2, 0x3)
runtime·printf("%S", f->name);
if(pc > f->entry)
runtime·printf("+%p", (uintptr)(pc - f->entry));
tracepc = pc; // back up to CALL instruction for funcline.
if(n > 0 && pc > f->entry)
tracepc--;
runtime·printf(" %S:%d\n", f->src, runtime·funcline(f, tracepc));
runtime·printf("\t%S(", f->name);
fp = (uintptr*)sp;
if(f->frame < sizeof(uintptr))
fp++;
else
fp += f->frame/sizeof(uintptr);
for(i = 0; i < f->args; i++) {
if(i != 0)
runtime·prints(", ");
runtime·printhex(fp[i]);
if(i >= 4) {
runtime·prints(", ...");
break;
}
}
runtime·prints(")\n");
n++;
}
if(nascent) {
pc = (uintptr)g->sched.pc;
sp = g->sched.sp;
nascent = 0;
continue;
}
if(f->frame < sizeof(uintptr)) // assembly functions lie
sp += sizeof(uintptr);
else
sp += f->frame;
pc = *((uintptr*)sp - 1);
if(f->entry == (uintptr)runtime·deferproc || f->entry == (uintptr)runtime·newproc)
sp += 2*sizeof(uintptr);
}
return n;
}
void
runtime·traceback(byte *pc0, byte *sp, byte*, G *g)
{
gentraceback(pc0, sp, g, 0, nil, 100);
}
int32
runtime·callers(int32 skip, uintptr *pcbuf, int32 m)
{
byte *pc, *sp;
// our caller's pc, sp.
sp = (byte*)&skip;
pc = runtime·getcallerpc(&skip);
return gentraceback(pc, sp, g, skip, pcbuf, m);
}
static uintptr
isclosureentry(uintptr pc)
{
byte *p;
int32 i, siz;
p = (byte*)pc;
if(p < runtime·mheap.arena_start || p+32 > runtime·mheap.arena_used)
return 0;
// SUBQ $siz, SP
if((sizeof(uintptr) == 8 && *p++ != 0x48) || *p++ != 0x81 || *p++ != 0xec)
return 0;
siz = *(uint32*)p;
p += 4;
// MOVQ $q, SI
if((sizeof(uintptr) == 8 && *p++ != 0x48) || *p++ != 0xbe)
return 0;
p += sizeof(uintptr);
// MOVQ SP, DI
if((sizeof(uintptr) == 8 && *p++ != 0x48) || *p++ != 0x89 || *p++ != 0xe7)
return 0;
// CLD on 32-bit
if(sizeof(uintptr) == 4 && *p++ != 0xfc)
return 0;
if(siz <= 4*sizeof(uintptr)) {
// MOVSQ...
for(i=0; i<siz; i+=sizeof(uintptr))
if((sizeof(uintptr) == 8 && *p++ != 0x48) || *p++ != 0xa5)
return 0;
} else {
// MOVQ $(siz/8), CX [32-bit immediate siz/8]
if((sizeof(uintptr) == 8 && *p++ != 0x48) || *p++ != 0xc7 || *p++ != 0xc1)
return 0;
p += 4;
// REP MOVSQ
if(*p++ != 0xf3 || (sizeof(uintptr) == 8 && *p++ != 0x48) || *p++ != 0xa5)
return 0;
}
// CALL fn
if(*p == 0xe8) {
p++;
return (uintptr)p+4 + *(int32*)p;
}
// MOVQ $fn, CX; CALL *CX
if(sizeof(uintptr) != 8 || *p++ != 0x48 || *p++ != 0xb9)
return 0;
pc = *(uintptr*)p;
p += 8;
if(*p++ != 0xff || *p != 0xd1)
return 0;
return pc;
}
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