static void dump_fault_addr(log_t* log, pid_t tid, int sig)
{
siginfo_t si;
memset(&si, 0, sizeof(si));
if (ptrace(PTRACE_GETSIGINFO, tid, 0, &si)){
_LOG(log, false, "cannot get siginfo: %s\n", strerror(errno));
} else if (signal_has_address(sig)) {
_LOG(log, false, "signal %d (%s), code %d (%s), fault addr %08x\n",
sig, get_signame(sig),
si.si_code, get_sigcode(sig, si.si_code),
(uintptr_t) si.si_addr);
} else {
_LOG(log, false, "signal %d (%s), code %d (%s), fault addr --------\n",
sig, get_signame(sig), si.si_code, get_sigcode(sig, si.si_code));
}
}
/*
* If this isn't clearly a null pointer dereference, dump the
* /proc/maps entries near the fault address.
*
* This only makes sense to do on the thread that crashed.
*/
static void show_nearby_maps(int tfd, int pid, mapinfo *map)
{
siginfo_t si;
memset(&si, 0, sizeof(si));
if (ptrace(PTRACE_GETSIGINFO, pid, 0, &si)) {
_LOG(tfd, false, "cannot get siginfo for %d: %s\n",
pid, strerror(errno));
return;
}
if (!signal_has_address(si.si_signo))
return;
uintptr_t addr = (uintptr_t) si.si_addr;
addr &= ~0xfff; /* round to 4K page boundary */
if (addr == 0) /* null-pointer deref */
return;
_LOG(tfd, false, "\nmemory map around addr %08x:\n", si.si_addr);
/*
* Search for a match, or for a hole where the match would be. The list
* is backward from the file content, so it starts at high addresses.
*/
bool found = false;
mapinfo *next = NULL;
mapinfo *prev = NULL;
while (map != NULL) {
if (addr >= map->start && addr < map->end) {
found = true;
next = map->next;
break;
} else if (addr >= map->end) {
/* map would be between "prev" and this entry */
next = map;
map = NULL;
break;
}
prev = map;
map = map->next;
}
/*
* Show "next" then "match" then "prev" so that the addresses appear in
* ascending order (like /proc/pid/maps).
*/
if (next != NULL) {
_LOG(tfd, false, "%08x-%08x %s\n", next->start, next->end, next->name);
} else {
_LOG(tfd, false, "(no map below)\n");
}
if (map != NULL) {
_LOG(tfd, false, "%08x-%08x %s\n", map->start, map->end, map->name);
} else {
_LOG(tfd, false, "(no map for address)\n");
}
if (prev != NULL) {
_LOG(tfd, false, "%08x-%08x %s\n", prev->start, prev->end, prev->name);
} else {
_LOG(tfd, false, "(no map above)\n");
}
}
