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     size_t ret PA_GCC_UNUSED;
  73     ret = write(STDERR_FILENO, s, strlen(s));
  74 }
  75
  76 static void signal_handler(int sig, siginfo_t* si, void *data) {
  77     unsigned j;
  78     pa_memtrap *m;
  79     void *r;
  80
  81     j = pa_aupdate_read_begin(aupdate);
  82
  83     for (m = memtraps[j]; m; m = m->next[j])
  84         if (si->si_addr >= m->start &&
  85             (uint8_t*) si->si_addr < (uint8_t*) m->start + m->size)
  86             break;
  87
  88     if (!m)
  89         goto fail;
  90
  91     pa_atomic_store(&m->bad, 1);
  92
  93     /* Remap anonymous memory into the bad segment */
  94     if ((r = mmap(m->start, m->size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_FIXED|MAP_PRIVATE, -1, 0)) == MAP_FAILED) {
  95         sigsafe_error("mmap() failed.\n");
  96         goto fail;
  97     }
  98
  99     pa_assert(r == m->start);
 100
 101     pa_aupdate_read_end(aupdate);
 102     return;
 103
 104 fail:
 105     pa_aupdate_read_end(aupdate);
 106
 107     sigsafe_error("Failed to handle SIGBUS.\n");
 108     abort();
 109 }
 110 #endif
 111
 112 static void memtrap_link(pa_memtrap *m, unsigned j) {
 113     pa_assert(m);
 114
 115     m->prev[j] = NULL;
 116
 117     if ((m->next[j] = memtraps[j]))
 118         m->next[j]->prev[j] = m;
 119
 120     memtraps[j] = m;
 121 }
 122
 123 static void memtrap_unlink(pa_memtrap *m, unsigned j) {
 124     pa_assert(m);
 125
 126     if (m->next[j])
 127         m->next[j]->prev[j] = m->prev[j];
 128
 129     if (m->prev[j])
 130         m->prev[j]->next[j] = m->next[j];
 131     else
 132         memtraps[j] = m->next[j];
 133 }
 134
 135 pa_memtrap* pa_memtrap_add(const void *start, size_t size) {
 136     pa_memtrap *m = NULL;
 137     unsigned j;
 138     pa_mutex *mx;
 139
 140     pa_assert(start);
 141     pa_assert(size > 0);
 142
 143     start = PA_PAGE_ALIGN_PTR(start);
 144     size = PA_PAGE_ALIGN(size);
 145
 146     m = pa_xnew(pa_memtrap, 1);
 147     m->start = (void*) start;
 148     m->size = size;
 149     pa_atomic_store(&m->bad, 0);
 150
 151     allocate_aupdate();
 152
 153     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 154     pa_mutex_lock(mx);
 155
 156     j = pa_aupdate_write_begin(aupdate);
 157     memtrap_link(m, j);
 158     j = pa_aupdate_write_swap(aupdate);
 159     memtrap_link(m, j);
 160     pa_aupdate_write_end(aupdate);
 161
 162     pa_mutex_unlock(mx);
 163
 164     return m;
 165 }
 166
 167 void pa_memtrap_remove(pa_memtrap *m) {
 168     unsigned j;
 169     pa_mutex *mx;
 170
 171     pa_assert(m);
 172
 173     allocate_aupdate();
 174
 175     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 176     pa_mutex_lock(mx);
 177
 178     j = pa_aupdate_write_begin(aupdate);
 179     memtrap_unlink(m, j);
 180     j = pa_aupdate_write_swap(aupdate);
 181     memtrap_unlink(m, j);
 182     pa_aupdate_write_end(aupdate);
 183
 184     pa_mutex_unlock(mx);
 185
 186     pa_xfree(m);
 187 }
 188
 189 pa_memtrap *pa_memtrap_update(pa_memtrap *m, const void *start, size_t size) {
 190     unsigned j;
 191     pa_mutex *mx;
 192
 193     pa_assert(m);
 194
 195     pa_assert(start);
 196     pa_assert(size > 0);
 197
 198     start = PA_PAGE_ALIGN_PTR(start);
 199     size = PA_PAGE_ALIGN(size);
 200
 201     allocate_aupdate();
 202
 203     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 204     pa_mutex_lock(mx);
 205
 206     j = pa_aupdate_write_begin(aupdate);
 207
 208     if (m->start == start && m->size == size)
 209         goto unlock;
 210
 211     memtrap_unlink(m, j);
 212     pa_aupdate_write_swap(aupdate);
 213
 214     m->start = (void*) start;
 215     m->size = size;
 216     pa_atomic_store(&m->bad, 0);
 217
 218     pa_assert_se(pa_aupdate_write_swap(aupdate) == j);
 219     memtrap_link(m, j);
 220
 221 unlock:
 222     pa_aupdate_write_end(aupdate);
 223
 224     pa_mutex_unlock(mx);
 225
 226     return m;
 227 }
 228
 229 void pa_memtrap_install(void) {
 230 #ifdef HAVE_SIGACTION
 231     struct sigaction sa;
 232
 233     allocate_aupdate();
 234
 235     memset(&sa, 0, sizeof(sa));
 236     sa.sa_sigaction = signal_handler;
 237     sa.sa_flags = SA_RESTART|SA_SIGINFO;
 238
 239     pa_assert_se(sigaction(SIGBUS, &sa, NULL) == 0);
 240 #endif
 241 }