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 #include <sys/mman.h>
  28
  29 /* This is deprecated on glibc but is still used by FreeBSD */
  30 #if !defined(MAP_ANONYMOUS) && defined(MAP_ANON)
  31 # define MAP_ANONYMOUS MAP_ANON
  32 #endif
  33
  34 #include <pulse/xmalloc.h>
  35
  36 #include <pulsecore/core-util.h>
  37 #include <pulsecore/aupdate.h>
  38 #include <pulsecore/atomic.h>
  39 #include <pulsecore/once.h>
  40 #include <pulsecore/mutex.h>
  41
  42 #include "memtrap.h"
  43
  44 struct pa_memtrap {
  45     void *start;
  46     size_t size;
  47     pa_atomic_t bad;
  48     pa_memtrap *next[2], *prev[2];
  49 };
  50
  51 static pa_memtrap *memtraps[2] = { NULL, NULL };
  52 static pa_aupdate *aupdate;
  53 static pa_static_mutex mutex = PA_STATIC_MUTEX_INIT; /* only required to serialize access to the write side */
  54
  55 static void allocate_aupdate(void) {
  56     PA_ONCE_BEGIN {
  57         aupdate = pa_aupdate_new();
  58     } PA_ONCE_END;
  59 }
  60
  61 pa_bool_t pa_memtrap_is_good(pa_memtrap *m) {
  62     pa_assert(m);
  63
  64     return !pa_atomic_load(&m->bad);
  65 }
  66
  67 static void sigsafe_error(const char *s) {
  68     (void) write(STDERR_FILENO, s, strlen(s));
  69 }
  70
  71 static void signal_handler(int sig, siginfo_t* si, void *data) {
  72     unsigned j;
  73     pa_memtrap *m;
  74     void *r;
  75
  76     j = pa_aupdate_read_begin(aupdate);
  77
  78     for (m = memtraps[j]; m; m = m->next[j])
  79         if (si->si_addr >= m->start &&
  80             (uint8_t*) si->si_addr < (uint8_t*) m->start + m->size)
  81             break;
  82
  83     if (!m)
  84         goto fail;
  85
  86     pa_atomic_store(&m->bad, 1);
  87
  88     /* Remap anonymous memory into the bad segment */
  89     if ((r = mmap(m->start, m->size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_FIXED|MAP_PRIVATE, -1, 0)) == MAP_FAILED) {
  90         sigsafe_error("mmap() failed.\n");
  91         goto fail;
  92     }
  93
  94     pa_assert(r == m->start);
  95
  96     pa_aupdate_read_end(aupdate);
  97     return;
  98
  99 fail:
 100     pa_aupdate_read_end(aupdate);
 101
 102     sigsafe_error("Failed to handle SIGBUS.\n");
 103     abort();
 104 }
 105
 106 static void memtrap_link(pa_memtrap *m, unsigned j) {
 107     pa_assert(m);
 108
 109     m->prev[j] = NULL;
 110
 111     if ((m->next[j] = memtraps[j]))
 112         m->next[j]->prev[j] = m;
 113
 114     memtraps[j] = m;
 115 }
 116
 117 static void memtrap_unlink(pa_memtrap *m, unsigned j) {
 118     pa_assert(m);
 119
 120     if (m->next[j])
 121         m->next[j]->prev[j] = m->prev[j];
 122
 123     if (m->prev[j])
 124         m->prev[j]->next[j] = m->next[j];
 125     else
 126         memtraps[j] = m->next[j];
 127 }
 128
 129 pa_memtrap* pa_memtrap_add(const void *start, size_t size) {
 130     pa_memtrap *m = NULL;
 131     unsigned j;
 132     pa_mutex *mx;
 133
 134     pa_assert(start);
 135     pa_assert(size > 0);
 136
 137     start = PA_PAGE_ALIGN_PTR(start);
 138     size = PA_PAGE_ALIGN(size);
 139
 140     m = pa_xnew(pa_memtrap, 1);
 141     m->start = (void*) start;
 142     m->size = size;
 143     pa_atomic_store(&m->bad, 0);
 144
 145     allocate_aupdate();
 146
 147     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 148     pa_mutex_lock(mx);
 149
 150     j = pa_aupdate_write_begin(aupdate);
 151     memtrap_link(m, j);
 152     j = pa_aupdate_write_swap(aupdate);
 153     memtrap_link(m, j);
 154     pa_aupdate_write_end(aupdate);
 155
 156     pa_mutex_unlock(mx);
 157
 158     return m;
 159 }
 160
 161 void pa_memtrap_remove(pa_memtrap *m) {
 162     unsigned j;
 163     pa_mutex *mx;
 164
 165     pa_assert(m);
 166
 167     allocate_aupdate();
 168
 169     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 170     pa_mutex_lock(mx);
 171
 172     j = pa_aupdate_write_begin(aupdate);
 173     memtrap_unlink(m, j);
 174     j = pa_aupdate_write_swap(aupdate);
 175     memtrap_unlink(m, j);
 176     pa_aupdate_write_end(aupdate);
 177
 178     pa_mutex_unlock(mx);
 179
 180     pa_xfree(m);
 181 }
 182
 183 pa_memtrap *pa_memtrap_update(pa_memtrap *m, const void *start, size_t size) {
 184     unsigned j;
 185     pa_mutex *mx;
 186
 187     pa_assert(m);
 188
 189     pa_assert(start);
 190     pa_assert(size > 0);
 191
 192     start = PA_PAGE_ALIGN_PTR(start);
 193     size = PA_PAGE_ALIGN(size);
 194
 195     allocate_aupdate();
 196
 197     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 198     pa_mutex_lock(mx);
 199
 200     j = pa_aupdate_write_begin(aupdate);
 201
 202     if (m->start == start && m->size == size)
 203         goto unlock;
 204
 205     memtrap_unlink(m, j);
 206     pa_aupdate_write_swap(aupdate);
 207
 208     m->start = (void*) start;
 209     m->size = size;
 210     pa_atomic_store(&m->bad, 0);
 211
 212     pa_assert_se(pa_aupdate_write_swap(aupdate) == j);
 213     memtrap_link(m, j);
 214
 215 unlock:
 216     pa_aupdate_write_end(aupdate);
 217
 218     pa_mutex_unlock(mx);
 219
 220     return m;
 221 }
 222
 223 void pa_memtrap_install(void) {
 224     struct sigaction sa;
 225
 226     allocate_aupdate();
 227
 228     memset(&sa, 0, sizeof(sa));
 229     sa.sa_sigaction = signal_handler;
 230     sa.sa_flags = SA_RESTART|SA_SIGINFO;
 231
 232     pa_assert_se(sigaction(SIGBUS, &sa, NULL) == 0);
 233 }