debug/pcprofile.c

   1 /* Profile PC and write result to FIFO.
   2    Copyright (C) 1999-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <stdint.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24
  25 /* Nonzero if we are actually doing something.  */
  26 static int active;
  27
  28 /* The file descriptor of the FIFO.  */
  29 static int fd;
  30
  31
  32 static void
  33 __attribute__ ((constructor))
  34 install (void)
  35 {
  36   /* See whether the environment variable `PCPROFILE_OUTPUT' is defined.
  37      If yes, it should name a FIFO.  We open it and mark ourself as active.  */
  38   const char *outfile = getenv ("PCPROFILE_OUTPUT");
  39
  40   if (outfile != NULL && *outfile != '\0')
  41     {
  42       fd = open (outfile, O_RDWR | O_CREAT, 0666);
  43
  44       if (fd != -1)
  45         {
  46           uint32_t word;
  47
  48           active = 1;
  49
  50           /* Write a magic word which tells the reader about the byte
  51              order and the size of the following entries.  */
  52           word = 0xdeb00000 | sizeof (void *);
  53           if (TEMP_FAILURE_RETRY (write (fd, &word, 4)) != 4)
  54             {
  55               /* If even this fails we shouldn't try further.  */
  56               close (fd);
  57               fd = -1;
  58               active = 0;
  59             }
  60         }
  61     }
  62 }
  63
  64
  65 static void
  66 __attribute__ ((destructor))
  67 uninstall (void)
  68 {
  69   if (active)
  70     close (fd);
  71 }
  72
  73
  74 void
  75 __cyg_profile_func_enter (void *this_fn, void *call_site)
  76 {
  77   void *buf[2];
  78
  79   if (! active)
  80     return;
  81
  82   /* Now write out the current position and that of the caller.  We do
  83      this now, and don't cache the because we want real-time output.  */
  84   buf[0] = this_fn;
  85   buf[1] = call_site;
  86
  87   write (fd, buf, sizeof buf);
  88 }
  89 /* We don't handle entry and exit differently here.  */
  90 strong_alias (__cyg_profile_func_enter, __cyg_profile_func_exit)