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)