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 "backtrace.h"
  10
  11 #include "runtime.h"
  12 #include "array.h"
  13
  14 /* This is set to non-zero when calling backtrace_full.  This is used
  15    to avoid getting hanging on a recursive lock in dl_iterate_phdr on
  16    older versions of glibc when a SIGPROF signal arrives while
  17    collecting a backtrace.  */
  18
  19 uint32 runtime_in_callers;
  20
  21 /* Argument passed to callback function.  */
  22
  23 struct callers_data
  24 {
  25   Location *locbuf;
  26   int skip;
  27   int index;
  28   int max;
  29 };
  30
  31 /* Callback function for backtrace_full.  Just collect the locations.
  32    Return zero to continue, non-zero to stop.  */
  33
  34 static int
  35 callback (void *data, uintptr_t pc, const char *filename, int lineno,
  36           const char *function)
  37 {
  38   struct callers_data *arg = (struct callers_data *) data;
  39   Location *loc;
  40
  41   /* Skip split stack functions.  */
  42   if (function != NULL)
  43     {
  44       const char *p;
  45
  46       p = function;
  47       if (__builtin_strncmp (p, "___", 3) == 0)
  48         ++p;
  49       if (__builtin_strncmp (p, "__morestack_", 12) == 0)
  50         return 0;
  51     }
  52   else if (filename != NULL)
  53     {
  54       const char *p;
  55
  56       p = strrchr (filename, '/');
  57       if (p == NULL)
  58         p = filename;
  59       if (__builtin_strncmp (p, "/morestack.S", 12) == 0)
  60         return 0;
  61     }
  62
  63   /* Skip thunks and recover functions.  There is no equivalent to
  64      these functions in the gc toolchain, so returning them here means
  65      significantly different results for runtime.Caller(N).  */
  66   if (function != NULL)
  67     {
  68       const char *p;
  69
  70       p = __builtin_strchr (function, '.');
  71       if (p != NULL && __builtin_strncmp (p + 1, "$thunk", 6) == 0)
  72         return 0;
  73       p = __builtin_strrchr (function, '$');
  74       if (p != NULL && __builtin_strcmp(p, "$recover") == 0)
  75         return 0;
  76     }
  77
  78   if (arg->skip > 0)
  79     {
  80       --arg->skip;
  81       return 0;
  82     }
  83
  84   loc = &arg->locbuf[arg->index];
  85   loc->pc = pc;
  86
  87   /* The libbacktrace library says that these strings might disappear,
  88      but with the current implementation they won't.  We can't easily
  89      allocate memory here, so for now assume that we can save a
  90      pointer to the strings.  */
  91   loc->filename = runtime_gostringnocopy ((const byte *) filename);
  92   loc->function = runtime_gostringnocopy ((const byte *) function);
  93
  94   loc->lineno = lineno;
  95   ++arg->index;
  96
  97   /* There is no point to tracing past certain runtime functions.
  98      Stopping the backtrace here can avoid problems on systems that
  99      don't provide proper unwind information for makecontext, such as
 100      Solaris (http://gcc.gnu.org/PR52583 comment #21).  */
 101   if (function != NULL)
 102     {
 103       if (__builtin_strcmp (function, "makecontext") == 0)
 104         return 1;
 105       if (filename != NULL)
 106         {
 107           const char *p;
 108
 109           p = strrchr (filename, '/');
 110           if (p == NULL)
 111             p = filename;
 112           if (__builtin_strcmp (p, "/proc.c") == 0)
 113             {
 114               if (__builtin_strcmp (function, "kickoff") == 0
 115                   || __builtin_strcmp (function, "runtime_mstart") == 0
 116                   || __builtin_strcmp (function, "runtime_main") == 0)
 117                 return 1;
 118             }
 119         }
 120     }
 121
 122   return arg->index >= arg->max;
 123 }
 124
 125 /* Error callback.  */
 126
 127 static void
 128 error_callback (void *data __attribute__ ((unused)),
 129                 const char *msg, int errnum)
 130 {
 131   if (errnum != 0)
 132     runtime_printf ("%s errno %d\n", msg, errnum);
 133   runtime_throw (msg);
 134 }
 135
 136 /* Gather caller PC's.  */
 137
 138 int32
 139 runtime_callers (int32 skip, Location *locbuf, int32 m)
 140 {
 141   struct callers_data data;
 142
 143   data.locbuf = locbuf;
 144   data.skip = skip + 1;
 145   data.index = 0;
 146   data.max = m;
 147   runtime_xadd (&runtime_in_callers, 1);
 148   backtrace_full (__go_get_backtrace_state (), 0, callback, error_callback,
 149                   &data);
 150   runtime_xadd (&runtime_in_callers, -1);
 151   return data.index;
 152 }
 153
 154 int Callers (int, struct __go_open_array)
 155   __asm__ (GOSYM_PREFIX "runtime.Callers");
 156
 157 int
 158 Callers (int skip, struct __go_open_array pc)
 159 {
 160   Location *locbuf;
 161   int ret;
 162   int i;
 163
 164   locbuf = (Location *) runtime_mal (pc.__count * sizeof (Location));
 165
 166   /* In the Go 1 release runtime.Callers has an off-by-one error,
 167      which we can not correct because it would break backward
 168      compatibility.  Normally we would add 1 to SKIP here, but we
 169      don't so that we are compatible.  */
 170   ret = runtime_callers (skip, locbuf, pc.__count);
 171
 172   for (i = 0; i < ret; i++)
 173     ((uintptr *) pc.__values)[i] = locbuf[i].pc;
 174
 175   return ret;
 176 }