1  /* Low-level statistical profiling support function.  Mostly POSIX.1 version.
       2     Copyright (C) 1996-2023 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 <sys/types.h>
      20  #include <unistd.h>
      21  #include <errno.h>
      22  #include <signal.h>
      23  #include <sys/time.h>
      24  #include <stdint.h>
      25  #include <libc-internal.h>
      26  #include <sigsetops.h>
      27  
      28  #ifndef SIGPROF
      29  
      30  #include <gmon/profil.c>
      31  
      32  #else
      33  
      34  static u_short *samples;
      35  static size_t nsamples;
      36  static size_t pc_offset;
      37  static u_int pc_scale;
      38  
      39  static inline void
      40  profil_count (uintptr_t pc)
      41  {
      42    size_t i = (pc - pc_offset) / 2;
      43  
      44    if (sizeof (unsigned long long int) > sizeof (size_t))
      45      i = (unsigned long long int) i * pc_scale / 65536;
      46    else
      47      i = i / 65536 * pc_scale + i % 65536 * pc_scale / 65536;
      48  
      49    if (i < nsamples)
      50      ++samples[i];
      51  }
      52  
      53  /* Get the machine-dependent definition of `__profil_counter', the signal
      54     handler for SIGPROF.  It calls `profil_count' (above) with the PC of the
      55     interrupted code.  */
      56  #include "profil-counter.h"
      57  
      58  /* Enable statistical profiling, writing samples of the PC into at most
      59     SIZE bytes of SAMPLE_BUFFER; every processor clock tick while profiling
      60     is enabled, the system examines the user PC and increments
      61     SAMPLE_BUFFER[((PC - OFFSET) / 2) * SCALE / 65536].  If SCALE is zero,
      62     disable profiling.  Returns zero on success, -1 on error.  */
      63  
      64  int
      65  __profil (u_short *sample_buffer, size_t size, size_t offset, u_int scale)
      66  {
      67    struct sigaction act;
      68    struct itimerval timer;
      69  #if !IS_IN (rtld)
      70    static struct sigaction oact;
      71    static struct itimerval otimer;
      72  # define oact_ptr &oact
      73  # define otimer_ptr &otimer
      74  
      75    if (sample_buffer == NULL)
      76      {
      77        /* Disable profiling.  */
      78        if (samples == NULL)
      79  	/* Wasn't turned on.  */
      80  	return 0;
      81  
      82        if (__setitimer (ITIMER_PROF, &otimer, NULL) < 0)
      83  	return -1;
      84        samples = NULL;
      85        return __sigaction (SIGPROF, &oact, NULL);
      86      }
      87  
      88   if (samples)
      89      {
      90        /* Was already turned on.  Restore old timer and signal handler
      91  	 first.  */
      92        if (__setitimer (ITIMER_PROF, &otimer, NULL) < 0
      93  	  || __sigaction (SIGPROF, &oact, NULL) < 0)
      94  	return -1;
      95      }
      96  #else
      97   /* In ld.so profiling should never be disabled once it runs.  */
      98   //assert (sample_buffer != NULL);
      99  # define oact_ptr NULL
     100  # define otimer_ptr NULL
     101  #endif
     102  
     103    samples = sample_buffer;
     104    nsamples = size / sizeof *samples;
     105    pc_offset = offset;
     106    pc_scale = scale;
     107  
     108  #ifdef SA_SIGINFO
     109    act.sa_sigaction = __profil_counter;
     110    act.sa_flags = SA_SIGINFO;
     111  #else
     112    act.sa_handler = __profil_counter;
     113    act.sa_flags = 0;
     114  #endif
     115    act.sa_flags |= SA_RESTART;
     116    __sigfillset (&act.sa_mask);
     117    if (__sigaction (SIGPROF, &act, oact_ptr) < 0)
     118      return -1;
     119  
     120    timer.it_value.tv_sec = 0;
     121    timer.it_value.tv_usec = 1000000 / __profile_frequency ();
     122    timer.it_interval = timer.it_value;
     123    return __setitimer (ITIMER_PROF, &timer, otimer_ptr);
     124  }
     125  weak_alias (__profil, profil)
     126  
     127  #endif