sysdeps/posix/profil.c

   1 /* Low-level statistical profiling support function.  Mostly POSIX.1 version.
   2    Copyright (C) 1996-2016 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
  26 #ifndef SIGPROF
  27
  28 #include <gmon/profil.c>
  29
  30 #else
  31
  32 static u_short *samples;
  33 static size_t nsamples;
  34 static size_t pc_offset;
  35 static u_int pc_scale;
  36
  37 static inline void
  38 profil_count (void *pc)
  39 {
  40   size_t i = (pc - pc_offset - (void *) 0) / 2;
  41
  42   if (sizeof (unsigned long long int) > sizeof (size_t))
  43     i = (unsigned long long int) i * pc_scale / 65536;
  44   else
  45     i = i / 65536 * pc_scale + i % 65536 * pc_scale / 65536;
  46
  47   if (i < nsamples)
  48     ++samples[i];
  49 }
  50
  51 /* Get the machine-dependent definition of `__profil_counter', the signal
  52    handler for SIGPROF.  It calls `profil_count' (above) with the PC of the
  53    interrupted code.  */
  54 #include "profil-counter.h"
  55
  56 /* Enable statistical profiling, writing samples of the PC into at most
  57    SIZE bytes of SAMPLE_BUFFER; every processor clock tick while profiling
  58    is enabled, the system examines the user PC and increments
  59    SAMPLE_BUFFER[((PC - OFFSET) / 2) * SCALE / 65536].  If SCALE is zero,
  60    disable profiling.  Returns zero on success, -1 on error.  */
  61
  62 int
  63 __profil (u_short *sample_buffer, size_t size, size_t offset, u_int scale)
  64 {
  65   struct sigaction act;
  66   struct itimerval timer;
  67 #if !IS_IN (rtld)
  68   static struct sigaction oact;
  69   static struct itimerval otimer;
  70 # define oact_ptr &oact
  71 # define otimer_ptr &otimer
  72
  73   if (sample_buffer == NULL)
  74     {
  75       /* Disable profiling.  */
  76       if (samples == NULL)
  77         /* Wasn't turned on.  */
  78         return 0;
  79
  80       if (__setitimer (ITIMER_PROF, &otimer, NULL) < 0)
  81         return -1;
  82       samples = NULL;
  83       return __sigaction (SIGPROF, &oact, NULL);
  84     }
  85
  86  if (samples)
  87     {
  88       /* Was already turned on.  Restore old timer and signal handler
  89          first.  */
  90       if (__setitimer (ITIMER_PROF, &otimer, NULL) < 0
  91           || __sigaction (SIGPROF, &oact, NULL) < 0)
  92         return -1;
  93     }
  94 #else
  95  /* In ld.so profiling should never be disabled once it runs.  */
  96  //assert (sample_buffer != NULL);
  97 # define oact_ptr NULL
  98 # define otimer_ptr NULL
  99 #endif
 100
 101   samples = sample_buffer;
 102   nsamples = size / sizeof *samples;
 103   pc_offset = offset;
 104   pc_scale = scale;
 105
 106   act.sa_handler = (sighandler_t) &__profil_counter;
 107   act.sa_flags = SA_RESTART;
 108   __sigfillset (&act.sa_mask);
 109   if (__sigaction (SIGPROF, &act, oact_ptr) < 0)
 110     return -1;
 111
 112   timer.it_value.tv_sec = 0;
 113   timer.it_value.tv_usec = 1000000 / __profile_frequency ();
 114   timer.it_interval = timer.it_value;
 115   return __setitimer (ITIMER_PROF, &timer, otimer_ptr);
 116 }
 117 weak_alias (__profil, profil)
 118
 119 #endif