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