glibc/sysdeps/posix/profil.c

/* Low-level statistical profiling support function.  Mostly POSIX.1 version.
Copyright (C) 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <sys/time.h>

#ifndef SIGPROF

#include_next <profil.c>

#else

static u_short *samples;
static size_t nsamples;
static size_t pc_offset;
static u_int pc_scale;

static inline void
profil_count (void *pc)
{
  size_t i = (pc - pc_offset - (void *) 0) / 2;

  if (sizeof (unsigned long long int) > sizeof (size_t))
    i = (unsigned long long int) i * pc_scale / 65536;
  else
    i = i / 65536 * pc_scale + i % 65536 * pc_scale / 65536;

  if (i < nsamples)
    ++samples[i];
}

/* Get the machine-dependent definition of `profil_counter', the signal
   handler for SIGPROF.  It calls `profil_count' (above) with the PC of the
   interrupted code.  */
#include "profil-counter.h"

/* Enable statistical profiling, writing samples of the PC into at most
   SIZE bytes of SAMPLE_BUFFER; every processor clock tick while profiling
   is enabled, the system examines the user PC and increments
   SAMPLE_BUFFER[((PC - OFFSET) / 2) * SCALE / 65536].  If SCALE is zero,
   disable profiling.  Returns zero on success, -1 on error.  */

int
profil (u_short *sample_buffer, size_t size, size_t offset, u_int scale)
{
  static struct sigaction act, oact;
  static struct itimerval timer, otimer;

  if (sample_buffer == NULL)
    {
      /* Disable profiling.  */
      if (samples == NULL)
	/* Wasn't turned on.  */
	return 0;

      if (setitimer (ITIMER_PROF, &otimer, NULL) < 0)
	return -1;
      samples = NULL;
      return sigaction (SIGPROF, &oact, NULL);
    }

  samples = sample_buffer;
  nsamples = size / sizeof *samples;
  pc_offset = offset;
  pc_scale = scale;

  act.sa_handler = (sighandler_t) &profil_counter;
  act.sa_flags = SA_RESTART;
  sigfillset (&act.sa_mask);
  if (sigaction (SIGPROF, &act, &oact) < 0)
    return -1;

  timer.it_value.tv_sec = 0;
  timer.it_value.tv_usec = 1;
  timer.it_interval = timer.it_value;
  return setitimer (ITIMER_PROF, &timer, &otimer);
}

#endif