/*
* Copyright (c) 2013 Luca Clementi <luca.clementi@gmail.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "defs.h"
#include <limits.h>
#include <libunwind-ptrace.h>
#ifdef _LARGEFILE64_SOURCE
# ifdef HAVE_FOPEN64
# define fopen_for_input fopen64
# else
# define fopen_for_input fopen
# endif
#else
# define fopen_for_input fopen
#endif
#define DPRINTF(F, A, ...) if (debug_flag) error_msg("[unwind(" A ")] " F, __VA_ARGS__)
/*
* Кeep a sorted array of cache entries,
* so that we can binary search through it.
*/
struct mmap_cache_t {
/**
* example entry:
* 7fabbb09b000-7fabbb09f000 r-xp 00179000 fc:00 1180246 /lib/libc-2.11.1.so
*
* start_addr is 0x7fabbb09b000
* end_addr is 0x7fabbb09f000
* mmap_offset is 0x179000
* binary_filename is "/lib/libc-2.11.1.so"
*/
unsigned long start_addr;
unsigned long end_addr;
unsigned long mmap_offset;
char *binary_filename;
};
/*
* Type used in stacktrace walker
*/
typedef void (*call_action_fn)(void *data,
const char *binary_filename,
const char *symbol_name,
unw_word_t function_offset,
unsigned long true_offset);
typedef void (*error_action_fn)(void *data,
const char *error,
unsigned long true_offset);
/*
* Type used in stacktrace capturing
*/
struct call_t {
struct call_t* next;
char *output_line;
};
struct queue_t {
struct call_t *tail;
struct call_t *head;
};
static void queue_print(struct queue_t *queue);
static void delete_mmap_cache(struct tcb *tcp, const char *caller);
static unw_addr_space_t libunwind_as;
static unsigned int mmap_cache_generation;
void
unwind_init(void)
{
libunwind_as = unw_create_addr_space(&_UPT_accessors, 0);
if (!libunwind_as)
error_msg_and_die("failed to create address space for stack tracing");
unw_set_caching_policy(libunwind_as, UNW_CACHE_GLOBAL);
}
void
unwind_tcb_init(struct tcb *tcp)
{
if (tcp->libunwind_ui)
return;
tcp->libunwind_ui = _UPT_create(tcp->pid);
if (!tcp->libunwind_ui)
die_out_of_memory();
tcp->queue = xmalloc(sizeof(*tcp->queue));
tcp->queue->head = NULL;
tcp->queue->tail = NULL;
}
void
unwind_tcb_fin(struct tcb *tcp)
{
queue_print(tcp->queue);
free(tcp->queue);
tcp->queue = NULL;
delete_mmap_cache(tcp, __FUNCTION__);
_UPT_destroy(tcp->libunwind_ui);
tcp->libunwind_ui = NULL;
}
/*
* caching of /proc/ID/maps for each process to speed up stack tracing
*
* The cache must be refreshed after syscalls that affect memory mappings,
* e.g. mmap, mprotect, munmap, execve.
*/
static void
build_mmap_cache(struct tcb* tcp)
{
FILE *fp;
struct mmap_cache_t *cache_head;
/* start with a small dynamically-allocated array and then expand it */
size_t cur_array_size = 10;
char filename[sizeof("/proc/4294967296/maps")];
char buffer[PATH_MAX + 80];
unw_flush_cache(libunwind_as, 0, 0);
sprintf(filename, "/proc/%u/maps", tcp->pid);
fp = fopen_for_input(filename, "r");
if (!fp) {
perror_msg("fopen: %s", filename);
return;
}
cache_head = xcalloc(cur_array_size, sizeof(*cache_head));
while (fgets(buffer, sizeof(buffer), fp) != NULL) {
struct mmap_cache_t *entry;
unsigned long start_addr, end_addr, mmap_offset;
char exec_bit;
char binary_path[PATH_MAX];
if (sscanf(buffer, "%lx-%lx %*c%*c%c%*c %lx %*x:%*x %*d %[^\n]",
&start_addr, &end_addr, &exec_bit,
&mmap_offset, binary_path) != 5)
continue;
/* ignore mappings that have no PROT_EXEC bit set */
if (exec_bit != 'x')
continue;
if (end_addr < start_addr) {
error_msg("%s: unrecognized file format", filename);
break;
}
/*
* sanity check to make sure that we're storing
* non-overlapping regions in ascending order
*/
if (tcp->mmap_cache_size > 0) {
entry = &cache_head[tcp->mmap_cache_size - 1];
if (entry->start_addr == start_addr &&
entry->end_addr == end_addr) {
/* duplicate entry, e.g. [vsyscall] */
continue;
}
if (start_addr <= entry->start_addr ||
start_addr < entry->end_addr) {
error_msg("%s: overlapping memory region",
filename);
continue;
}
}
if (tcp->mmap_cache_size >= cur_array_size) {
cur_array_size *= 2;
cache_head = xreallocarray(cache_head, cur_array_size,
sizeof(*cache_head));
}
entry = &cache_head[tcp->mmap_cache_size];
entry->start_addr = start_addr;
entry->end_addr = end_addr;
entry->mmap_offset = mmap_offset;
entry->binary_filename = xstrdup(binary_path);
tcp->mmap_cache_size++;
}
fclose(fp);
tcp->mmap_cache = cache_head;
tcp->mmap_cache_generation = mmap_cache_generation;
DPRINTF("tgen=%u, ggen=%u, tcp=%p, cache=%p",
"cache-build",
tcp->mmap_cache_generation,
mmap_cache_generation,
tcp, tcp->mmap_cache);
}
/* deleting the cache */
static void
delete_mmap_cache(struct tcb *tcp, const char *caller)
{
unsigned int i;
DPRINTF("tgen=%u, ggen=%u, tcp=%p, cache=%p, caller=%s",
"cache-delete",
tcp->mmap_cache_generation,
mmap_cache_generation,
tcp, tcp->mmap_cache, caller);
for (i = 0; i < tcp->mmap_cache_size; i++) {
free(tcp->mmap_cache[i].binary_filename);
tcp->mmap_cache[i].binary_filename = NULL;
}
free(tcp->mmap_cache);
tcp->mmap_cache = NULL;
tcp->mmap_cache_size = 0;
}
static bool
rebuild_cache_if_invalid(struct tcb *tcp, const char *caller)
{
if ((tcp->mmap_cache_generation != mmap_cache_generation)
&& tcp->mmap_cache)
delete_mmap_cache(tcp, caller);
if (!tcp->mmap_cache)
build_mmap_cache(tcp);
if (!tcp->mmap_cache || !tcp->mmap_cache_size)
return false;
else
return true;
}
void
unwind_cache_invalidate(struct tcb* tcp)
{
#if SUPPORTED_PERSONALITIES > 1
if (tcp->currpers != DEFAULT_PERSONALITY) {
/* disable strack trace */
return;
}
#endif
mmap_cache_generation++;
DPRINTF("tgen=%u, ggen=%u, tcp=%p, cache=%p", "increment",
tcp->mmap_cache_generation,
mmap_cache_generation,
tcp,
tcp->mmap_cache);
}
static void
get_symbol_name(unw_cursor_t *cursor, char **name,
size_t *size, unw_word_t *offset)
{
for (;;) {
int rc = unw_get_proc_name(cursor, *name, *size, offset);
if (rc == 0)
break;
if (rc != -UNW_ENOMEM) {
**name = '\0';
*offset = 0;
break;
}
*name = xreallocarray(*name, 2, *size);
*size *= 2;
}
}
static int
print_stack_frame(struct tcb *tcp,
call_action_fn call_action,
error_action_fn error_action,
void *data,
unw_cursor_t *cursor,
char **symbol_name,
size_t *symbol_name_size)
{
unw_word_t ip;
int lower = 0;
int upper = (int) tcp->mmap_cache_size - 1;
if (unw_get_reg(cursor, UNW_REG_IP, &ip) < 0) {
perror_msg("Can't walk the stack of process %d", tcp->pid);
return -1;
}
while (lower <= upper) {
struct mmap_cache_t *cur_mmap_cache;
int mid = (upper + lower) / 2;
cur_mmap_cache = &tcp->mmap_cache[mid];
if (ip >= cur_mmap_cache->start_addr &&
ip < cur_mmap_cache->end_addr) {
unsigned long true_offset;
unw_word_t function_offset;
get_symbol_name(cursor, symbol_name, symbol_name_size,
&function_offset);
true_offset = ip - cur_mmap_cache->start_addr +
cur_mmap_cache->mmap_offset;
call_action(data,
cur_mmap_cache->binary_filename,
*symbol_name,
function_offset,
true_offset);
return 0;
}
else if (ip < cur_mmap_cache->start_addr)
upper = mid - 1;
else
lower = mid + 1;
}
/*
* there is a bug in libunwind >= 1.0
* after a set_tid_address syscall
* unw_get_reg returns IP == 0
*/
if(ip)
error_action(data, "unexpected_backtracing_error", ip);
return -1;
}
/*
* walking the stack
*/
static void
stacktrace_walk(struct tcb *tcp,
call_action_fn call_action,
error_action_fn error_action,
void *data)
{
char *symbol_name;
size_t symbol_name_size = 40;
unw_cursor_t cursor;
int stack_depth;
if (!tcp->mmap_cache)
error_msg_and_die("bug: mmap_cache is NULL");
if (tcp->mmap_cache_size == 0)
error_msg_and_die("bug: mmap_cache is empty");
symbol_name = xmalloc(symbol_name_size);
if (unw_init_remote(&cursor, libunwind_as, tcp->libunwind_ui) < 0)
perror_msg_and_die("Can't initiate libunwind");
for (stack_depth = 0; stack_depth < 256; ++stack_depth) {
if (print_stack_frame(tcp, call_action, error_action, data,
&cursor, &symbol_name, &symbol_name_size) < 0)
break;
if (unw_step(&cursor) <= 0)
break;
}
if (stack_depth >= 256)
error_action(data, "too many stack frames", 0);
free(symbol_name);
}
/*
* printing an entry in stack to stream or buffer
*/
/*
* we want to keep the format used by backtrace_symbols from the glibc
*
* ./a.out() [0x40063d]
* ./a.out() [0x4006bb]
* ./a.out() [0x4006c6]
* /lib64/libc.so.6(__libc_start_main+0xed) [0x7fa2f8a5976d]
* ./a.out() [0x400569]
*/
#define STACK_ENTRY_SYMBOL_FMT \
" > %s(%s+0x%lx) [0x%lx]\n", \
binary_filename, \
symbol_name, \
(unsigned long) function_offset, \
true_offset
#define STACK_ENTRY_NOSYMBOL_FMT \
" > %s() [0x%lx]\n", \
binary_filename, true_offset
#define STACK_ENTRY_BUG_FMT \
" > BUG IN %s\n"
#define STACK_ENTRY_ERROR_WITH_OFFSET_FMT \
" > %s [0x%lx]\n", error, true_offset
#define STACK_ENTRY_ERROR_FMT \
" > %s\n", error
static void
print_call_cb(void *dummy,
const char *binary_filename,
const char *symbol_name,
unw_word_t function_offset,
unsigned long true_offset)
{
if (symbol_name && (symbol_name[0] != '\0'))
tprintf(STACK_ENTRY_SYMBOL_FMT);
else if (binary_filename)
tprintf(STACK_ENTRY_NOSYMBOL_FMT);
else
tprintf(STACK_ENTRY_BUG_FMT, __FUNCTION__);
line_ended();
}
static void
print_error_cb(void *dummy,
const char *error,
unsigned long true_offset)
{
if (true_offset)
tprintf(STACK_ENTRY_ERROR_WITH_OFFSET_FMT);
else
tprintf(STACK_ENTRY_ERROR_FMT);
line_ended();
}
static char *
sprint_call_or_error(const char *binary_filename,
const char *symbol_name,
unw_word_t function_offset,
unsigned long true_offset,
const char *error)
{
char *output_line = NULL;
int n;
if (symbol_name)
n = asprintf(&output_line, STACK_ENTRY_SYMBOL_FMT);
else if (binary_filename)
n = asprintf(&output_line, STACK_ENTRY_NOSYMBOL_FMT);
else if (error)
n = true_offset
? asprintf(&output_line, STACK_ENTRY_ERROR_WITH_OFFSET_FMT)
: asprintf(&output_line, STACK_ENTRY_ERROR_FMT);
else
n = asprintf(&output_line, STACK_ENTRY_BUG_FMT, __FUNCTION__);
if (n < 0)
error_msg_and_die("error in asprintf");
return output_line;
}
/*
* queue manipulators
*/
static void
queue_put(struct queue_t *queue,
const char *binary_filename,
const char *symbol_name,
unw_word_t function_offset,
unsigned long true_offset,
const char *error)
{
struct call_t *call;
call = xmalloc(sizeof(*call));
call->output_line = sprint_call_or_error(binary_filename,
symbol_name,
function_offset,
true_offset,
error);
call->next = NULL;
if (!queue->head) {
queue->head = call;
queue->tail = call;
} else {
queue->tail->next = call;
queue->tail = call;
}
}
static void
queue_put_call(void *queue,
const char *binary_filename,
const char *symbol_name,
unw_word_t function_offset,
unsigned long true_offset)
{
queue_put(queue,
binary_filename,
symbol_name,
function_offset,
true_offset,
NULL);
}
static void
queue_put_error(void *queue,
const char *error,
unsigned long ip)
{
queue_put(queue, NULL, NULL, 0, ip, error);
}
static void
queue_print(struct queue_t *queue)
{
struct call_t *call, *tmp;
queue->tail = NULL;
call = queue->head;
queue->head = NULL;
while (call) {
tmp = call;
call = call->next;
tprints(tmp->output_line);
line_ended();
free(tmp->output_line);
tmp->output_line = NULL;
tmp->next = NULL;
free(tmp);
}
}
/*
* printing stack
*/
void
unwind_print_stacktrace(struct tcb* tcp)
{
#if SUPPORTED_PERSONALITIES > 1
if (tcp->currpers != DEFAULT_PERSONALITY) {
/* disable strack trace */
return;
}
#endif
if (tcp->queue->head) {
DPRINTF("tcp=%p, queue=%p", "queueprint", tcp, tcp->queue->head);
queue_print(tcp->queue);
}
else if (rebuild_cache_if_invalid(tcp, __FUNCTION__)) {
DPRINTF("tcp=%p, queue=%p", "stackprint", tcp, tcp->queue->head);
stacktrace_walk(tcp, print_call_cb, print_error_cb, NULL);
}
}
/*
* capturing stack
*/
void
unwind_capture_stacktrace(struct tcb *tcp)
{
#if SUPPORTED_PERSONALITIES > 1
if (tcp->currpers != DEFAULT_PERSONALITY) {
/* disable strack trace */
return;
}
#endif
if (tcp->queue->head)
error_msg_and_die("bug: unprinted entries in queue");
if (rebuild_cache_if_invalid(tcp, __FUNCTION__)) {
stacktrace_walk(tcp, queue_put_call, queue_put_error,
tcp->queue);
DPRINTF("tcp=%p, queue=%p", "captured", tcp, tcp->queue->head);
}
}