debug/pcprofile.c

   1 /* Profile PC and write result to FIFO.
   2    Copyright (C) 1999, 2000 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1999.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <stdint.h>
  23 #include <stdlib.h>
  24 #include <unistd.h>
  25 #include <libc-internal.h>
  26
  27 /* Nonzero if we are actually doing something.  */
  28 static int active;
  29
  30 /* The file descriptor of the FIFO.  */
  31 static int fd;
  32
  33
  34 static void
  35 __attribute__ ((constructor))
  36 install (void)
  37 {
  38   /* See whether the environment variable `PCPROFILE_OUTPUT' is defined.
  39      If yes, it should name a FIFO.  We open it and mark ourself as active.  */
  40   const char *outfile = getenv ("PCPROFILE_OUTPUT");
  41
  42   if (outfile != NULL && *outfile != '\0')
  43     {
  44       fd = open (outfile, O_RDWR | O_CREAT, 0666);
  45
  46       if (fd != -1)
  47         {
  48           uint32_t word;
  49
  50           active = 1;
  51
  52           /* Write a magic word which tells the reader about the byte
  53              order and the size of the following entries.  */
  54           word = 0xdeb00000 | sizeof (void *);
  55           if (TEMP_FAILURE_RETRY (write (fd, &word, 4)) != 4)
  56             {
  57               /* If even this fails we shouldn't try further.  */
  58               close (fd);
  59               fd = -1;
  60               active = 0;
  61             }
  62         }
  63     }
  64 }
  65
  66
  67 static void
  68 __attribute__ ((destructor))
  69 uninstall (void)
  70 {
  71   if (active)
  72     close (fd);
  73 }
  74
  75
  76 void
  77 __cyg_profile_func_enter (void *this_fn, void *call_site)
  78 {
  79   void *buf[2];
  80
  81   if (! active)
  82     return;
  83
  84   /* Now write out the current position and that of the caller.  We do
  85      this now, and don't cache the because we want real-time output.  */
  86   buf[0] = this_fn;
  87   buf[1] = call_site;
  88
  89   write (fd, buf, sizeof buf);
  90 }
  91 /* We don't handle entry and exit differently here.  */
  92 strong_alias (__cyg_profile_func_enter, __cyg_profile_func_exit)