src/pulsecore/memtrap.c

   1 /***
   2   This file is part of PulseAudio.
   3
   4   Copyright 2009 Lennart Poettering
   5
   6   PulseAudio is free software; you can redistribute it and/or modify
   7   it under the terms of the GNU Lesser General Public License as
   8   published by the Free Software Foundation; either version 2.1 of the
   9   License, or (at your option) any later version.
  10
  11   PulseAudio is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public
  17   License along with PulseAudio; if not, write to the Free Software
  18   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
  19   USA.
  20 ***/
  21
  22 #ifdef HAVE_CONFIG_H
  23 #include <config.h>
  24 #endif
  25
  26 #include <signal.h>
  27
  28 #ifdef HAVE_SYS_MMAN_H
  29 #include <sys/mman.h>
  30 #endif
  31
  32 /* This is deprecated on glibc but is still used by FreeBSD */
  33 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
  34 # define MAP_ANONYMOUS MAP_ANON
  35 #endif
  36
  37 #include <pulse/xmalloc.h>
  38
  39 #include <pulsecore/core-util.h>
  40 #include <pulsecore/aupdate.h>
  41 #include <pulsecore/atomic.h>
  42 #include <pulsecore/once.h>
  43 #include <pulsecore/mutex.h>
  44
  45 #include "memtrap.h"
  46
  47 struct pa_memtrap {
  48     void *start;
  49     size_t size;
  50     pa_atomic_t bad;
  51     pa_memtrap *next[2], *prev[2];
  52 };
  53
  54 static pa_memtrap *memtraps[2] = { NULL, NULL };
  55 static pa_aupdate *aupdate;
  56 static pa_static_mutex mutex = PA_STATIC_MUTEX_INIT; /* only required to serialize access to the write side */
  57
  58 static void allocate_aupdate(void) {
  59     PA_ONCE_BEGIN {
  60         aupdate = pa_aupdate_new();
  61     } PA_ONCE_END;
  62 }
  63
  64 pa_bool_t pa_memtrap_is_good(pa_memtrap *m) {
  65     pa_assert(m);
  66
  67     return !pa_atomic_load(&m->bad);
  68 }
  69
  70 #ifdef HAVE_SIGACTION
  71 static void sigsafe_error(const char *s) {
  72     (void) write(STDERR_FILENO, s, strlen(s));
  73 }
  74
  75 static void signal_handler(int sig, siginfo_t* si, void *data) {
  76     unsigned j;
  77     pa_memtrap *m;
  78     void *r;
  79
  80     j = pa_aupdate_read_begin(aupdate);
  81
  82     for (m = memtraps[j]; m; m = m->next[j])
  83         if (si->si_addr >= m->start &&
  84             (uint8_t*) si->si_addr < (uint8_t*) m->start + m->size)
  85             break;
  86
  87     if (!m)
  88         goto fail;
  89
  90     pa_atomic_store(&m->bad, 1);
  91
  92     /* Remap anonymous memory into the bad segment */
  93     if ((r = mmap(m->start, m->size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_FIXED|MAP_PRIVATE, -1, 0)) == MAP_FAILED) {
  94         sigsafe_error("mmap() failed.\n");
  95         goto fail;
  96     }
  97
  98     pa_assert(r == m->start);
  99
 100     pa_aupdate_read_end(aupdate);
 101     return;
 102
 103 fail:
 104     pa_aupdate_read_end(aupdate);
 105
 106     sigsafe_error("Failed to handle SIGBUS.\n");
 107     abort();
 108 }
 109 #endif
 110
 111 static void memtrap_link(pa_memtrap *m, unsigned j) {
 112     pa_assert(m);
 113
 114     m->prev[j] = NULL;
 115
 116     if ((m->next[j] = memtraps[j]))
 117         m->next[j]->prev[j] = m;
 118
 119     memtraps[j] = m;
 120 }
 121
 122 static void memtrap_unlink(pa_memtrap *m, unsigned j) {
 123     pa_assert(m);
 124
 125     if (m->next[j])
 126         m->next[j]->prev[j] = m->prev[j];
 127
 128     if (m->prev[j])
 129         m->prev[j]->next[j] = m->next[j];
 130     else
 131         memtraps[j] = m->next[j];
 132 }
 133
 134 pa_memtrap* pa_memtrap_add(const void *start, size_t size) {
 135     pa_memtrap *m = NULL;
 136     unsigned j;
 137     pa_mutex *mx;
 138
 139     pa_assert(start);
 140     pa_assert(size > 0);
 141
 142     start = PA_PAGE_ALIGN_PTR(start);
 143     size = PA_PAGE_ALIGN(size);
 144
 145     m = pa_xnew(pa_memtrap, 1);
 146     m->start = (void*) start;
 147     m->size = size;
 148     pa_atomic_store(&m->bad, 0);
 149
 150     allocate_aupdate();
 151
 152     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 153     pa_mutex_lock(mx);
 154
 155     j = pa_aupdate_write_begin(aupdate);
 156     memtrap_link(m, j);
 157     j = pa_aupdate_write_swap(aupdate);
 158     memtrap_link(m, j);
 159     pa_aupdate_write_end(aupdate);
 160
 161     pa_mutex_unlock(mx);
 162
 163     return m;
 164 }
 165
 166 void pa_memtrap_remove(pa_memtrap *m) {
 167     unsigned j;
 168     pa_mutex *mx;
 169
 170     pa_assert(m);
 171
 172     allocate_aupdate();
 173
 174     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 175     pa_mutex_lock(mx);
 176
 177     j = pa_aupdate_write_begin(aupdate);
 178     memtrap_unlink(m, j);
 179     j = pa_aupdate_write_swap(aupdate);
 180     memtrap_unlink(m, j);
 181     pa_aupdate_write_end(aupdate);
 182
 183     pa_mutex_unlock(mx);
 184
 185     pa_xfree(m);
 186 }
 187
 188 pa_memtrap *pa_memtrap_update(pa_memtrap *m, const void *start, size_t size) {
 189     unsigned j;
 190     pa_mutex *mx;
 191
 192     pa_assert(m);
 193
 194     pa_assert(start);
 195     pa_assert(size > 0);
 196
 197     start = PA_PAGE_ALIGN_PTR(start);
 198     size = PA_PAGE_ALIGN(size);
 199
 200     allocate_aupdate();
 201
 202     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 203     pa_mutex_lock(mx);
 204
 205     j = pa_aupdate_write_begin(aupdate);
 206
 207     if (m->start == start && m->size == size)
 208         goto unlock;
 209
 210     memtrap_unlink(m, j);
 211     pa_aupdate_write_swap(aupdate);
 212
 213     m->start = (void*) start;
 214     m->size = size;
 215     pa_atomic_store(&m->bad, 0);
 216
 217     pa_assert_se(pa_aupdate_write_swap(aupdate) == j);
 218     memtrap_link(m, j);
 219
 220 unlock:
 221     pa_aupdate_write_end(aupdate);
 222
 223     pa_mutex_unlock(mx);
 224
 225     return m;
 226 }
 227
 228 void pa_memtrap_install(void) {
 229 #ifdef HAVE_SIGACTION
 230     struct sigaction sa;
 231
 232     allocate_aupdate();
 233
 234     memset(&sa, 0, sizeof(sa));
 235     sa.sa_sigaction = signal_handler;
 236     sa.sa_flags = SA_RESTART|SA_SIGINFO;
 237
 238     pa_assert_se(sigaction(SIGBUS, &sa, NULL) == 0);
 239 #endif
 240 }