sysdeps/posix/profil.c

   1 /* Low-level statistical profiling support function.  Mostly POSIX.1 version.
   2    Copyright (C) 1996-2018 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    <http://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 <libc-internal.h>
  25 #include <sigsetops.h>
  26
  27 #ifndef SIGPROF
  28
  29 #include <gmon/profil.c>
  30
  31 #else
  32
  33 static u_short *samples;
  34 static size_t nsamples;
  35 static size_t pc_offset;
  36 static u_int pc_scale;
  37
  38 static inline void
  39 profil_count (void *pc)
  40 {
  41   size_t i = (pc - pc_offset - (void *) 0) / 2;
  42
  43   if (sizeof (unsigned long long int) > sizeof (size_t))
  44     i = (unsigned long long int) i * pc_scale / 65536;
  45   else
  46     i = i / 65536 * pc_scale + i % 65536 * pc_scale / 65536;
  47
  48   if (i < nsamples)
  49     ++samples[i];
  50 }
  51
  52 /* Get the machine-dependent definition of `__profil_counter', the signal
  53    handler for SIGPROF.  It calls `profil_count' (above) with the PC of the
  54    interrupted code.  */
  55 #include "profil-counter.h"
  56
  57 /* Enable statistical profiling, writing samples of the PC into at most
  58    SIZE bytes of SAMPLE_BUFFER; every processor clock tick while profiling
  59    is enabled, the system examines the user PC and increments
  60    SAMPLE_BUFFER[((PC - OFFSET) / 2) * SCALE / 65536].  If SCALE is zero,
  61    disable profiling.  Returns zero on success, -1 on error.  */
  62
  63 int
  64 __profil (u_short *sample_buffer, size_t size, size_t offset, u_int scale)
  65 {
  66   struct sigaction act;
  67   struct itimerval timer;
  68 #if !IS_IN (rtld)
  69   static struct sigaction oact;
  70   static struct itimerval otimer;
  71 # define oact_ptr &oact
  72 # define otimer_ptr &otimer
  73
  74   if (sample_buffer == NULL)
  75     {
  76       /* Disable profiling.  */
  77       if (samples == NULL)
  78         /* Wasn't turned on.  */
  79         return 0;
  80
  81       if (__setitimer (ITIMER_PROF, &otimer, NULL) < 0)
  82         return -1;
  83       samples = NULL;
  84       return __sigaction (SIGPROF, &oact, NULL);
  85     }
  86
  87  if (samples)
  88     {
  89       /* Was already turned on.  Restore old timer and signal handler
  90          first.  */
  91       if (__setitimer (ITIMER_PROF, &otimer, NULL) < 0
  92           || __sigaction (SIGPROF, &oact, NULL) < 0)
  93         return -1;
  94     }
  95 #else
  96  /* In ld.so profiling should never be disabled once it runs.  */
  97  //assert (sample_buffer != NULL);
  98 # define oact_ptr NULL
  99 # define otimer_ptr NULL
 100 #endif
 101
 102   samples = sample_buffer;
 103   nsamples = size / sizeof *samples;
 104   pc_offset = offset;
 105   pc_scale = scale;
 106
 107   act.sa_handler = (sighandler_t) &__profil_counter;
 108   act.sa_flags = SA_RESTART;
 109   __sigfillset (&act.sa_mask);
 110   if (__sigaction (SIGPROF, &act, oact_ptr) < 0)
 111     return -1;
 112
 113   timer.it_value.tv_sec = 0;
 114   timer.it_value.tv_usec = 1000000 / __profile_frequency ();
 115   timer.it_interval = timer.it_value;
 116   return __setitimer (ITIMER_PROF, &timer, otimer_ptr);
 117 }
 118 weak_alias (__profil, profil)
 119
 120 #endif