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
  41 #include "memtrap.h"
  42
  43 struct pa_memtrap {
  44     void *start;
  45     size_t size;
  46     pa_atomic_t bad;
  47     pa_memtrap *next[2], *prev[2];
  48 };
  49
  50 static pa_memtrap *memtraps[2] = { NULL, NULL };
  51 static pa_aupdate *aupdate;
  52
  53 static void allocate_aupdate(void) {
  54     PA_ONCE_BEGIN {
  55         aupdate = pa_aupdate_new();
  56     } PA_ONCE_END;
  57 }
  58
  59 pa_bool_t pa_memtrap_is_good(pa_memtrap *m) {
  60     pa_assert(m);
  61
  62     return !pa_atomic_load(&m->bad);
  63 }
  64
  65 static void sigsafe_error(const char *s) {
  66     write(STDERR_FILENO, s, strlen(s));
  67 }
  68
  69 static void signal_handler(int sig, siginfo_t* si, void *data) {
  70     unsigned j;
  71     pa_memtrap *m;
  72     void *r;
  73
  74     j = pa_aupdate_read_begin(aupdate);
  75
  76     for (m = memtraps[j]; m; m = m->next[j])
  77         if (si->si_addr >= m->start &&
  78             (uint8_t*) si->si_addr < (uint8_t*) m->start + m->size)
  79             break;
  80
  81     if (!m)
  82         goto fail;
  83
  84     pa_atomic_store(&m->bad, 1);
  85
  86     /* Remap anonymous memory into the bad segment */
  87     if ((r = mmap(m->start, m->size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_FIXED|MAP_PRIVATE, -1, 0)) == MAP_FAILED) {
  88         sigsafe_error("mmap() failed.\n");
  89         goto fail;
  90     }
  91
  92     pa_assert(r == m->start);
  93
  94     pa_aupdate_read_end(aupdate);
  95     return;
  96
  97 fail:
  98     pa_aupdate_read_end(aupdate);
  99
 100     sigsafe_error("Failed to handle SIGBUS.\n");
 101     abort();
 102 }
 103
 104 static void memtrap_link(pa_memtrap *m, unsigned j) {
 105     pa_assert(m);
 106
 107     m->prev[j] = NULL;
 108     m->next[j] = memtraps[j];
 109     memtraps[j] = m;
 110 }
 111
 112 static void memtrap_unlink(pa_memtrap *m, unsigned j) {
 113     pa_assert(m);
 114
 115     if (m->next[j])
 116         m->next[j]->prev[j] = m->prev[j];
 117
 118     if (m->prev[j])
 119         m->prev[j]->next[j] = m->next[j];
 120     else
 121         memtraps[j] = m->next[j];
 122 }
 123
 124 pa_memtrap* pa_memtrap_add(const void *start, size_t size) {
 125     pa_memtrap *m = NULL;
 126     unsigned j;
 127
 128     pa_assert(start);
 129     pa_assert(size > 0);
 130
 131     start = PA_PAGE_ALIGN_PTR(start);
 132     size = PA_PAGE_ALIGN(size);
 133
 134     m = pa_xnew(pa_memtrap, 1);
 135     m->start = (void*) start;
 136     m->size = size;
 137     pa_atomic_store(&m->bad, 0);
 138
 139     allocate_aupdate();
 140
 141     j = pa_aupdate_write_begin(aupdate);
 142     memtrap_link(m, j);
 143     j = pa_aupdate_write_swap(aupdate);
 144     memtrap_link(m, j);
 145     pa_aupdate_write_end(aupdate);
 146
 147     return m;
 148 }
 149
 150 void pa_memtrap_remove(pa_memtrap *m) {
 151     unsigned j;
 152
 153     pa_assert(m);
 154
 155     allocate_aupdate();
 156
 157     j = pa_aupdate_write_begin(aupdate);
 158     memtrap_unlink(m, j);
 159     j = pa_aupdate_write_swap(aupdate);
 160     memtrap_unlink(m, j);
 161     pa_aupdate_write_end(aupdate);
 162
 163     pa_xfree(m);
 164 }
 165
 166 pa_memtrap *pa_memtrap_update(pa_memtrap *m, const void *start, size_t size) {
 167     unsigned j;
 168
 169     pa_assert(m);
 170
 171     pa_assert(start);
 172     pa_assert(size > 0);
 173
 174     start = PA_PAGE_ALIGN_PTR(start);
 175     size = PA_PAGE_ALIGN(size);
 176
 177     allocate_aupdate();
 178
 179     j = pa_aupdate_write_begin(aupdate);
 180
 181     if (m->start == start && m->size == size)
 182         goto unlock;
 183
 184     memtrap_unlink(m, j);
 185     j = pa_aupdate_write_swap(aupdate);
 186
 187     m->start = (void*) start;
 188     m->size = size;
 189     pa_atomic_store(&m->bad, 0);
 190
 191     j = pa_aupdate_write_swap(aupdate);
 192     memtrap_link(m, j);
 193
 194 unlock:
 195     pa_aupdate_write_end(aupdate);
 196
 197     return m;
 198 }
 199
 200 void pa_memtrap_install(void) {
 201     struct sigaction sa;
 202
 203     allocate_aupdate();
 204
 205     memset(&sa, 0, sizeof(sa));
 206     sa.sa_sigaction = signal_handler;
 207     sa.sa_flags = SA_RESTART|SA_SIGINFO;
 208
 209     pa_assert_se(sigaction(SIGBUS, &sa, NULL) == 0);
 210 }