gcc/libgo/runtime/go-callers.c

/* go-callers.c -- get callers for Go.

   Copyright 2012 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 "config.h"

#include "backtrace.h"

#include "runtime.h"
#include "array.h"

/* This is set to non-zero when calling backtrace_full.  This is used
   to avoid getting hanging on a recursive lock in dl_iterate_phdr on
   older versions of glibc when a SIGPROF signal arrives while
   collecting a backtrace.  */

uint32 runtime_in_callers;

/* Argument passed to callback function.  */

struct callers_data
{
  Location *locbuf;
  int skip;
  int index;
  int max;
};

/* Callback function for backtrace_full.  Just collect the locations.
   Return zero to continue, non-zero to stop.  */

static int
callback (void *data, uintptr_t pc, const char *filename, int lineno,
	  const char *function)
{
  struct callers_data *arg = (struct callers_data *) data;
  Location *loc;

  /* Skip split stack functions.  */
  if (function != NULL)
    {
      const char *p;

      p = function;
      if (__builtin_strncmp (p, "___", 3) == 0)
	++p;
      if (__builtin_strncmp (p, "__morestack_", 12) == 0)
	return 0;
    }
  else if (filename != NULL)
    {
      const char *p;

      p = strrchr (filename, '/');
      if (p == NULL)
	p = filename;
      if (__builtin_strncmp (p, "/morestack.S", 12) == 0)
	return 0;
    }

  /* Skip thunks and recover functions.  There is no equivalent to
     these functions in the gc toolchain, so returning them here means
     significantly different results for runtime.Caller(N).  */
  if (function != NULL)
    {
      const char *p;

      p = __builtin_strchr (function, '.');
      if (p != NULL && __builtin_strncmp (p + 1, "$thunk", 6) == 0)
	return 0;
      p = __builtin_strrchr (function, '$');
      if (p != NULL && __builtin_strcmp(p, "$recover") == 0)
	return 0;
    }

  if (arg->skip > 0)
    {
      --arg->skip;
      return 0;
    }

  loc = &arg->locbuf[arg->index];
  loc->pc = pc;

  /* The libbacktrace library says that these strings might disappear,
     but with the current implementation they won't.  We can't easily
     allocate memory here, so for now assume that we can save a
     pointer to the strings.  */
  loc->filename = runtime_gostringnocopy ((const byte *) filename);
  loc->function = runtime_gostringnocopy ((const byte *) function);

  loc->lineno = lineno;
  ++arg->index;

  /* There is no point to tracing past certain runtime functions.
     Stopping the backtrace here can avoid problems on systems that
     don't provide proper unwind information for makecontext, such as
     Solaris (http://gcc.gnu.org/PR52583 comment #21).  */
  if (function != NULL)
    {
      if (__builtin_strcmp (function, "makecontext") == 0)
	return 1;
      if (filename != NULL)
	{
	  const char *p;

	  p = strrchr (filename, '/');
	  if (p == NULL)
	    p = filename;
	  if (__builtin_strcmp (p, "/proc.c") == 0)
	    {
	      if (__builtin_strcmp (function, "kickoff") == 0
		  || __builtin_strcmp (function, "runtime_mstart") == 0
		  || __builtin_strcmp (function, "runtime_main") == 0)
		return 1;
	    }
	}
    }

  return arg->index >= arg->max;
}

/* Error callback.  */

static void
error_callback (void *data __attribute__ ((unused)),
		const char *msg, int errnum)
{
  if (errnum != 0)
    runtime_printf ("%s errno %d\n", msg, errnum);
  runtime_throw (msg);
}

/* Gather caller PC's.  */

int32
runtime_callers (int32 skip, Location *locbuf, int32 m)
{
  struct callers_data data;

  data.locbuf = locbuf;
  data.skip = skip + 1;
  data.index = 0;
  data.max = m;
  runtime_xadd (&runtime_in_callers, 1);
  backtrace_full (__go_get_backtrace_state (), 0, callback, error_callback,
		  &data);
  runtime_xadd (&runtime_in_callers, -1);
  return data.index;
}

int Callers (int, struct __go_open_array)
  __asm__ (GOSYM_PREFIX "runtime.Callers");

int
Callers (int skip, struct __go_open_array pc)
{
  Location *locbuf;
  int ret;
  int i;

  locbuf = (Location *) runtime_mal (pc.__count * sizeof (Location));

  /* In the Go 1 release runtime.Callers has an off-by-one error,
     which we can not correct because it would break backward
     compatibility.  Normally we would add 1 to SKIP here, but we
     don't so that we are compatible.  */
  ret = runtime_callers (skip, locbuf, pc.__count);

  for (i = 0; i < ret; i++)
    ((uintptr *) pc.__values)[i] = locbuf[i].pc;

  return ret;
}