/**
Access the pages of this process through /proc/self/task/<tid>/mem
in order to safely print the contents of a memory address range.
@param addr The address at the start of the memory region.
@param max_len The length of the memory region.
@return Zero on success.
*/
static int safe_print_str(const char *addr, int max_len)
{
int fd;
pid_t tid;
off_t offset;
ssize_t nbytes= 0;
size_t total, count;
char buf[256];
tid= (pid_t) syscall(SYS_gettid);
sprintf(buf, "/proc/self/task/%d/mem", tid);
if ((fd= open(buf, O_RDONLY)) < 0)
return -1;
/* Ensure that off_t can hold a pointer. */
compile_time_assert(sizeof(off_t) >= sizeof(intptr));
total= max_len;
offset= (intptr) addr;
/* Read up to the maximum number of bytes. */
while (total)
{
count= min(sizeof(buf), total);
if ((nbytes= pread(fd, buf, count, offset)) < 0)
{
/* Just in case... */
if (errno == EINTR)
continue;
else
break;
}
/* Advance offset into memory. */
total-= nbytes;
offset+= nbytes;
addr+= nbytes;
/* Output the printable characters. */
print_buffer(buf, nbytes);
/* Break if less than requested... */
if ((count - nbytes))
break;
}
/* Output a new line if something was printed. */
if (total != (size_t) max_len)
my_safe_printf_stderr("%s", "\n");
if (nbytes == -1)
my_safe_printf_stderr("Can't read from address %p\n", addr);
close(fd);
return 0;
}
void my_safe_print_str(const char* val, int max_len)
{
char *heap_end;
#ifdef __linux__
if (!safe_print_str(val, max_len))
return;
#endif
heap_end= (char*) sbrk(0);
if (!PTR_SANE(val))
{
my_safe_printf_stderr("%s", "is an invalid pointer\n");
return;
}
for (; max_len && PTR_SANE(val) && *val; --max_len)
my_write_stderr((val++), 1);
my_safe_printf_stderr("%s", "\n");
}
int my_safe_print_str(const char* val, int max_len)
{
char *heap_end;
#ifdef __linux__
// Try and make use of /proc filesystem to safely print memory contents.
if (!safe_print_str(val, max_len))
return 0;
#endif
heap_end= (char*) sbrk(0);
if (!PTR_SANE(val))
{
my_safe_printf_stderr("%s", "is an invalid pointer");
return 1;
}
for (; max_len && PTR_SANE(val) && *val; --max_len)
my_write_stderr((val++), 1);
my_safe_printf_stderr("%s", "\n");
return 0;
}
/**
* Handler for fatal signals
*
* Fatal events (seg.fault, bus error etc.) will trigger
* this signal handler. The handler will try to dump relevant
* debugging information to stderr and dump a core image.
*
* Signal handlers can only use a set of 'safe' system calls
* and library functions. A list of safe calls in POSIX systems
* are available at:
* http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html
* For MS Windows, guidelines are available at:
* http://msdn.microsoft.com/en-us/library/xdkz3x12(v=vs.71).aspx
*
* @param sig Signal number
*/
extern "C" sig_handler handle_fatal_signal(int sig)
{
if (segfaulted)
{
my_safe_printf_stderr("Fatal " SIGNAL_FMT " while backtracing\n", sig);
_exit(1); /* Quit without running destructors */
}
segfaulted = 1;
#ifdef __WIN__
SYSTEMTIME utc_time;
GetSystemTime(&utc_time);
const long hrs= utc_time.wHour;
const long mins= utc_time.wMinute;
const long secs= utc_time.wSecond;
#else
/* Using time() instead of my_time() to avoid looping */
const time_t curr_time= time(NULL);
/* Calculate time of day */
const long tmins = curr_time / 60;
const long thrs = tmins / 60;
const long hrs = thrs % 24;
const long mins = tmins % 60;
const long secs = curr_time % 60;
#endif
char hrs_buf[3]= "00";
char mins_buf[3]= "00";
char secs_buf[3]= "00";
my_safe_itoa(10, hrs, &hrs_buf[2]);
my_safe_itoa(10, mins, &mins_buf[2]);
my_safe_itoa(10, secs, &secs_buf[2]);
my_safe_printf_stderr("%s:%s:%s UTC - mysqld got " SIGNAL_FMT " ;\n",
hrs_buf, mins_buf, secs_buf, sig);
my_safe_printf_stderr("%s",
"This could be because you hit a bug. It is also possible that this binary\n"
"or one of the libraries it was linked against is corrupt, improperly built,\n"
"or misconfigured. This error can also be caused by malfunctioning hardware.\n");
my_safe_printf_stderr("%s",
"We will try our best to scrape up some info that will hopefully help\n"
"diagnose the problem, but since we have already crashed, \n"
"something is definitely wrong and this may fail.\n\n");
my_safe_printf_stderr("key_buffer_size=%lu\n",
(ulong) dflt_key_cache->key_cache_mem_size);
my_safe_printf_stderr("read_buffer_size=%ld\n",
(long) global_system_variables.read_buff_size);
my_safe_printf_stderr("max_used_connections=%lu\n",
(ulong) max_used_connections);
my_safe_printf_stderr("max_threads=%u\n",
(uint) thread_scheduler.max_threads);
my_safe_printf_stderr("thread_count=%u\n", (uint) thread_count);
my_safe_printf_stderr("connection_count=%u\n", (uint) connection_count);
my_safe_printf_stderr("It is possible that mysqld could use up to \n"
"key_buffer_size + "
"(read_buffer_size + sort_buffer_size)*max_threads = "
"%lu K bytes of memory\n",
((ulong) dflt_key_cache->key_cache_mem_size +
(global_system_variables.read_buff_size +
global_system_variables.sortbuff_size) *
thread_scheduler.max_threads +
max_connections * sizeof(THD)) / 1024);
my_safe_printf_stderr("%s",
"Hope that's ok; if not, decrease some variables in the equation.\n\n");
#if defined(HAVE_LINUXTHREADS)
#define UNSAFE_DEFAULT_LINUX_THREADS 200
if (sizeof(char*) == 4 && thread_count > UNSAFE_DEFAULT_LINUX_THREADS)
{
my_safe_printf_stderr(
"You seem to be running 32-bit Linux and have "
"%d concurrent connections.\n"
"If you have not changed STACK_SIZE in LinuxThreads "
"and built the binary \n"
"yourself, LinuxThreads is quite likely to steal "
"a part of the global heap for\n"
"the thread stack. Please read "
"http://dev.mysql.com/doc/mysql/en/linux-installation.html\n\n"
thread_count);
}
#endif /* HAVE_LINUXTHREADS */
#ifdef HAVE_STACKTRACE
THD *thd=current_thd;
if (!(test_flags & TEST_NO_STACKTRACE))
{
my_safe_printf_stderr("Thread pointer: 0x%p\n", thd);
my_safe_printf_stderr("%s",
"Attempting backtrace. You can use the following "
"information to find out\n"
"where mysqld died. If you see no messages after this, something went\n"
"terribly wrong...\n");
my_print_stacktrace(thd ? (uchar*) thd->thread_stack : NULL,
my_thread_stack_size);
}
if (thd)
{
const char *kreason= "UNKNOWN";
switch (thd->killed) {
case THD::NOT_KILLED:
kreason= "NOT_KILLED";
break;
case THD::KILL_BAD_DATA:
kreason= "KILL_BAD_DATA";
break;
case THD::KILL_CONNECTION:
kreason= "KILL_CONNECTION";
break;
case THD::KILL_QUERY:
kreason= "KILL_QUERY";
break;
case THD::KILLED_NO_VALUE:
kreason= "KILLED_NO_VALUE";
break;
}
my_safe_printf_stderr("%s", "\n"
"Trying to get some variables.\n"
"Some pointers may be invalid and cause the dump to abort.\n");
my_safe_printf_stderr("Query (%p): ", thd->query());
my_safe_print_str(thd->query(), min(1024U, thd->query_length()));
my_safe_printf_stderr("Connection ID (thread ID): %lu\n",
(ulong) thd->thread_id);
my_safe_printf_stderr("Status: %s\n\n", kreason);
}
my_safe_printf_stderr("%s",
"The manual page at "
"http://dev.mysql.com/doc/mysql/en/crashing.html contains\n"
"information that should help you find out what is causing the crash.\n");
#endif /* HAVE_STACKTRACE */
#ifdef HAVE_INITGROUPS
if (calling_initgroups)
{
my_safe_printf_stderr("%s", "\n"
"This crash occured while the server was calling initgroups(). This is\n"
"often due to the use of a mysqld that is statically linked against \n"
"glibc and configured to use LDAP in /etc/nsswitch.conf.\n"
"You will need to either upgrade to a version of glibc that does not\n"
"have this problem (2.3.4 or later when used with nscd),\n"
"disable LDAP in your nsswitch.conf, or use a "
"mysqld that is not statically linked.\n");
}
#endif
#ifdef HAVE_NPTL
if (thd_lib_detected == THD_LIB_LT && !ld_assume_kernel_is_set)
{
my_safe_printf_stderr("%s",
"You are running a statically-linked LinuxThreads binary on an NPTL\n"
"system. This can result in crashes on some distributions due to "
"LT/NPTL conflicts.\n"
"You should either build a dynamically-linked binary, "
"or force LinuxThreads\n"
"to be used with the LD_ASSUME_KERNEL environment variable.\n"
"Please consult the documentation for your distribution "
"on how to do that.\n");
}
#endif
if (locked_in_memory)
{
my_safe_printf_stderr("%s", "\n"
"The \"--memlock\" argument, which was enabled, "
"uses system calls that are\n"
"unreliable and unstable on some operating systems and "
"operating-system versions (notably, some versions of Linux).\n"
"This crash could be due to use of those buggy OS calls.\n"
"You should consider whether you really need the "
"\"--memlock\" parameter and/or consult the OS distributer about "
"\"mlockall\" bugs.\n");
}
#ifdef HAVE_WRITE_CORE
if (test_flags & TEST_CORE_ON_SIGNAL)
{
my_safe_printf_stderr("%s", "Writing a core file\n");
my_write_core(sig);
}
#endif
#ifndef __WIN__
/*
Quit, without running destructors (etc.)
On Windows, do not terminate, but pass control to exception filter.
*/
_exit(1); // Using _exit(), since exit() is not async signal safe
#endif
}
