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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <stdint.h>
  24 #include <stdlib.h>
  25 #include <unistd.h>
  26 #include <libc-internal.h>
  27
  28 /* Nonzero if we are actually doing something.  */
  29 static int active;
  30
  31 /* The file descriptor of the FIFO.  */
  32 static int fd;
  33
  34
  35 static void
  36 __attribute__ ((constructor))
  37 install (void)
  38 {
  39   /* See whether the environment variable `PCPROFILE_OUTPUT' is defined.
  40      If yes, it should name a FIFO.  We open it and mark ourself as active.  */
  41   const char *outfile = getenv ("PCPROFILE_OUTPUT");
  42
  43   if (outfile != NULL && *outfile != '\0')
  44     {
  45       fd = open (outfile, O_RDWR | O_CREAT, 0666);
  46
  47       if (fd != -1)
  48         {
  49           uint32_t word;
  50
  51           active = 1;
  52
  53           /* Write a magic word which tells the reader about the byte
  54              order and the size of the following entries.  */
  55           word = 0xdeb00000 | sizeof (void *);
  56           if (TEMP_FAILURE_RETRY (write (fd, &word, 4)) != 4)
  57             {
  58               /* If even this fails we shouldn't try further.  */
  59               close (fd);
  60               fd = -1;
  61               active = 0;
  62             }
  63         }
  64     }
  65 }
  66
  67
  68 static void
  69 __attribute__ ((destructor))
  70 uninstall (void)
  71 {
  72   if (active)
  73     close (fd);
  74 }
  75
  76
  77 void
  78 __cyg_profile_func_enter (void *this_fn, void *call_site)
  79 {
  80   void *buf[2];
  81
  82   if (! active)
  83     return;
  84
  85   /* Now write out the current position and that of the caller.  We do
  86      this now, and don't cache the because we want real-time output.  */
  87   buf[0] = this_fn;
  88   buf[1] = call_site;
  89
  90   write (fd, buf, sizeof buf);
  91 }
  92 /* We don't handle entry and exit differently here.  */
  93 strong_alias (__cyg_profile_func_enter, __cyg_profile_func_exit)