code.delx.au - pulseaudio/blob - 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     m->next[j] = memtraps[j];
 111     memtraps[j] = m;
 112 }
 113
 114 static void memtrap_unlink(pa_memtrap *m, unsigned j) {
 115     pa_assert(m);
 116
 117     if (m->next[j])
 118         m->next[j]->prev[j] = m->prev[j];
 119
 120     if (m->prev[j])
 121         m->prev[j]->next[j] = m->next[j];
 122     else
 123         memtraps[j] = m->next[j];
 124 }
 125
 126 pa_memtrap* pa_memtrap_add(const void *start, size_t size) {
 127     pa_memtrap *m = NULL;
 128     unsigned j;
 129     pa_mutex *mx;
 130
 131     pa_assert(start);
 132     pa_assert(size > 0);
 133
 134     start = PA_PAGE_ALIGN_PTR(start);
 135     size = PA_PAGE_ALIGN(size);
 136
 137     m = pa_xnew(pa_memtrap, 1);
 138     m->start = (void*) start;
 139     m->size = size;
 140     pa_atomic_store(&m->bad, 0);
 141
 142     allocate_aupdate();
 143
 144     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 145     pa_mutex_lock(mx);
 146
 147     j = pa_aupdate_write_begin(aupdate);
 148     memtrap_link(m, j);
 149     j = pa_aupdate_write_swap(aupdate);
 150     memtrap_link(m, j);
 151     pa_aupdate_write_end(aupdate);
 152
 153     pa_mutex_unlock(mx);
 154
 155     return m;
 156 }
 157
 158 void pa_memtrap_remove(pa_memtrap *m) {
 159     unsigned j;
 160     pa_mutex *mx;
 161
 162     pa_assert(m);
 163
 164     allocate_aupdate();
 165
 166     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 167     pa_mutex_lock(mx);
 168
 169     j = pa_aupdate_write_begin(aupdate);
 170     memtrap_unlink(m, j);
 171     j = pa_aupdate_write_swap(aupdate);
 172     memtrap_unlink(m, j);
 173     pa_aupdate_write_end(aupdate);
 174
 175     pa_mutex_unlock(mx);
 176
 177     pa_xfree(m);
 178 }
 179
 180 pa_memtrap *pa_memtrap_update(pa_memtrap *m, const void *start, size_t size) {
 181     unsigned j;
 182     pa_mutex *mx;
 183
 184     pa_assert(m);
 185
 186     pa_assert(start);
 187     pa_assert(size > 0);
 188
 189     start = PA_PAGE_ALIGN_PTR(start);
 190     size = PA_PAGE_ALIGN(size);
 191
 192     allocate_aupdate();
 193
 194     mx = pa_static_mutex_get(&mutex, FALSE, TRUE);
 195     pa_mutex_lock(mx);
 196
 197     j = pa_aupdate_write_begin(aupdate);
 198
 199     if (m->start == start && m->size == size)
 200         goto unlock;
 201
 202     memtrap_unlink(m, j);
 203     j = pa_aupdate_write_swap(aupdate);
 204
 205     m->start = (void*) start;
 206     m->size = size;
 207     pa_atomic_store(&m->bad, 0);
 208
 209     j = pa_aupdate_write_swap(aupdate);
 210     memtrap_link(m, j);
 211
 212 unlock:
 213     pa_aupdate_write_end(aupdate);
 214
 215     pa_mutex_unlock(mx);
 216
 217     return m;
 218 }
 219
 220 void pa_memtrap_install(void) {
 221     struct sigaction sa;
 222
 223     allocate_aupdate();
 224
 225     memset(&sa, 0, sizeof(sa));
 226     sa.sa_sigaction = signal_handler;
 227     sa.sa_flags = SA_RESTART|SA_SIGINFO;
 228
 229     pa_assert_se(sigaction(SIGBUS, &sa, NULL) == 0);
 230 }