sysdeps/posix/profil.c

   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