uclibc-ng/libc/sysdeps/linux/common/pcprofile.c

/* Profile PC and write result to FIFO.
   Copyright (C) 1999, 2000 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1999.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#define _GNU_SOURCE
#include <features.h>
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>

/* Nonzero if we are actually doing something.  */
static int active;

/* The file descriptor of the FIFO.  */
static int fd;


static void __attribute__ ((constructor))
install (void)
{
    /* See whether the environment variable `PCPROFILE_OUTPUT' is defined.
       If yes, it should name a FIFO.  We open it and mark ourself as active.  */
    const char *outfile = getenv ("PCPROFILE_OUTPUT");

    if (outfile != NULL && *outfile != '\0')
    {
	fd = open (outfile, O_RDWR | O_CREAT, 0666);

	if (fd != -1)
	{
	    uint32_t word;

	    active = 1;

	    /* Write a magic word which tells the reader about the byte
	       order and the size of the following entries.  */
	    word = 0xdeb00000 | sizeof (void *);
	    if (TEMP_FAILURE_RETRY (write (fd, &word, 4)) != 4)
	    {
		/* If even this fails we shouldn't try further.  */
		close (fd);
		fd = -1;
		active = 0;
	    }
	}
    }
}


static void __attribute__ ((destructor))
uninstall (void)
{
    if (active)
	close (fd);
}


void __cyg_profile_func_enter (void *this_fn, void *call_site)
{
    void *buf[2];

    if (! active)
	return;

    /* Now write out the current position and that of the caller.  We do
       this now, and don't cache the because we want real-time output.  */
    buf[0] = this_fn;
    buf[1] = call_site;

    write (fd, buf, sizeof buf);
}
/* We don't handle entry and exit differently here.  */
strong_alias (__cyg_profile_func_enter, __cyg_profile_func_exit)