libgo/runtime/go-callers.c

   1 /* go-callers.c -- get callers for Go.
   2
   3    Copyright 2012 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 #include "config.h"
   8
   9 #include "unwind.h"
  10
  11 #include "runtime.h"
  12
  13 /* Argument passed to backtrace function.  */
  14
  15 struct callers_data
  16 {
  17   int skip;
  18   uintptr *pcbuf;
  19   int index;
  20   int max;
  21 };
  22
  23 static _Unwind_Reason_Code
  24 backtrace (struct _Unwind_Context *context, void *varg)
  25 {
  26   struct callers_data *arg = (struct callers_data *) varg;
  27   uintptr pc;
  28   int ip_before_insn = 0;
  29
  30 #ifdef HAVE_GETIPINFO
  31   pc = _Unwind_GetIPInfo (context, &ip_before_insn);
  32 #else
  33   pc = _Unwind_GetIP (context);
  34 #endif
  35
  36   /* FIXME: If PC is in the __morestack routine, we should ignore
  37      it.  */
  38
  39   if (arg->skip > 0)
  40     --arg->skip;
  41   else if (arg->index >= arg->max)
  42     return _URC_END_OF_STACK;
  43   else
  44     {
  45       /* Here PC will be the return address.  We actually want the
  46          address of the call instruction, so back up one byte and
  47          count on the lookup routines handling that correctly.  */
  48       if (!ip_before_insn)
  49         --pc;
  50       arg->pcbuf[arg->index] = pc;
  51       ++arg->index;
  52     }
  53   return _URC_NO_REASON;
  54 }
  55
  56 int32
  57 runtime_callers (int32 skip, uintptr *pcbuf, int32 m)
  58 {
  59   struct callers_data arg;
  60
  61   arg.skip = skip + 1;
  62   arg.pcbuf = pcbuf;
  63   arg.index = 0;
  64   arg.max = m;
  65   _Unwind_Backtrace (backtrace, &arg);
  66   return arg.index;
  67 }
  68
  69 int Callers (int, struct __go_open_array)
  70   __asm__ ("runtime.Callers");
  71
  72 int
  73 Callers (int skip, struct __go_open_array pc)
  74 {
  75   /* In the Go 1 release runtime.Callers has an off-by-one error,
  76      which we can not correct because it would break backward
  77      compatibility.  Adjust SKIP here to be compatible.  */
  78   return runtime_callers (skip - 1, (uintptr *) pc.__values, pc.__count);
  79 }