ftrace: Add :mod: caching infrastructure to trace_array

This is the start of the infrastructure work to allow for tracing module
functions before it is loaded.

Currently the following command:

  # echo :mod:some-mod > set_ftrace_filter

will enable tracing of all functions within the module "some-mod" if it is
loaded. What we want, is if the module is not loaded, that line will be
saved. When the module is loaded, then the "some-mod" will have that line
executed on it, so that the functions within it starts being traced.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2017-06-23 15:26:26 -04:00
parent feaf1283d1
commit 673feb9d76
2 changed files with 148 additions and 6 deletions

View File

@ -1293,6 +1293,28 @@ static void ftrace_hash_clear(struct ftrace_hash *hash)
FTRACE_WARN_ON(hash->count);
}
static void free_ftrace_mod(struct ftrace_mod_load *ftrace_mod)
{
list_del(&ftrace_mod->list);
kfree(ftrace_mod->module);
kfree(ftrace_mod->func);
kfree(ftrace_mod);
}
static void clear_ftrace_mod_list(struct list_head *head)
{
struct ftrace_mod_load *p, *n;
/* stack tracer isn't supported yet */
if (!head)
return;
mutex_lock(&ftrace_lock);
list_for_each_entry_safe(p, n, head, list)
free_ftrace_mod(p);
mutex_unlock(&ftrace_lock);
}
static void free_ftrace_hash(struct ftrace_hash *hash)
{
if (!hash || hash == EMPTY_HASH)
@ -1346,6 +1368,35 @@ static struct ftrace_hash *alloc_ftrace_hash(int size_bits)
return hash;
}
static int ftrace_add_mod(struct trace_array *tr,
const char *func, const char *module,
int enable)
{
struct ftrace_mod_load *ftrace_mod;
struct list_head *mod_head = enable ? &tr->mod_trace : &tr->mod_notrace;
ftrace_mod = kzalloc(sizeof(*ftrace_mod), GFP_KERNEL);
if (!ftrace_mod)
return -ENOMEM;
ftrace_mod->func = kstrdup(func, GFP_KERNEL);
ftrace_mod->module = kstrdup(module, GFP_KERNEL);
ftrace_mod->enable = enable;
if (!ftrace_mod->func || !ftrace_mod->module)
goto out_free;
list_add(&ftrace_mod->list, mod_head);
return 0;
out_free:
free_ftrace_mod(ftrace_mod);
return -ENOMEM;
}
static struct ftrace_hash *
alloc_and_copy_ftrace_hash(int size_bits, struct ftrace_hash *hash)
{
@ -3457,6 +3508,8 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
{
struct ftrace_iterator *iter;
struct ftrace_hash *hash;
struct list_head *mod_head;
struct trace_array *tr = ops->private;
int ret = 0;
ftrace_ops_init(ops);
@ -3478,18 +3531,23 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
mutex_lock(&ops->func_hash->regex_lock);
if (flag & FTRACE_ITER_NOTRACE)
if (flag & FTRACE_ITER_NOTRACE) {
hash = ops->func_hash->notrace_hash;
else
mod_head = tr ? &tr->mod_trace : NULL;
} else {
hash = ops->func_hash->filter_hash;
mod_head = tr ? &tr->mod_notrace : NULL;
}
if (file->f_mode & FMODE_WRITE) {
const int size_bits = FTRACE_HASH_DEFAULT_BITS;
if (file->f_flags & O_TRUNC)
if (file->f_flags & O_TRUNC) {
iter->hash = alloc_ftrace_hash(size_bits);
else
clear_ftrace_mod_list(mod_head);
} else {
iter->hash = alloc_and_copy_ftrace_hash(size_bits, hash);
}
if (!iter->hash) {
trace_parser_put(&iter->parser);
@ -3761,6 +3819,68 @@ static int ftrace_hash_move_and_update_ops(struct ftrace_ops *ops,
return ret;
}
static bool module_exists(const char *module)
{
/* All modules have the symbol __this_module */
const char this_mod[] = "__this_module";
const int modname_size = MAX_PARAM_PREFIX_LEN + sizeof(this_mod) + 1;
char modname[modname_size + 1];
unsigned long val;
int n;
n = snprintf(modname, modname_size + 1, "%s:%s", module, this_mod);
if (n > modname_size)
return false;
val = module_kallsyms_lookup_name(modname);
return val != 0;
}
static int cache_mod(struct trace_array *tr,
const char *func, char *module, int enable)
{
struct ftrace_mod_load *ftrace_mod, *n;
struct list_head *head = enable ? &tr->mod_trace : &tr->mod_notrace;
int ret;
mutex_lock(&ftrace_lock);
/* We do not cache inverse filters */
if (func[0] == '!') {
func++;
ret = -EINVAL;
/* Look to remove this hash */
list_for_each_entry_safe(ftrace_mod, n, head, list) {
if (strcmp(ftrace_mod->module, module) != 0)
continue;
/* no func matches all */
if (!func || strcmp(func, "*") == 0 ||
(ftrace_mod->func &&
strcmp(ftrace_mod->func, func) == 0)) {
ret = 0;
free_ftrace_mod(ftrace_mod);
continue;
}
}
goto out;
}
ret = -EINVAL;
/* We only care about modules that have not been loaded yet */
if (module_exists(module))
goto out;
/* Save this string off, and execute it when the module is loaded */
ret = ftrace_add_mod(tr, func, module, enable);
out:
mutex_unlock(&ftrace_lock);
return ret;
}
/*
* We register the module command as a template to show others how
* to register the a command as well.
@ -3768,10 +3888,16 @@ static int ftrace_hash_move_and_update_ops(struct ftrace_ops *ops,
static int
ftrace_mod_callback(struct trace_array *tr, struct ftrace_hash *hash,
char *func, char *cmd, char *module, int enable)
char *func_orig, char *cmd, char *module, int enable)
{
char *func;
int ret;
/* match_records() modifies func, and we need the original */
func = kstrdup(func_orig, GFP_KERNEL);
if (!func)
return -ENOMEM;
/*
* cmd == 'mod' because we only registered this func
* for the 'mod' ftrace_func_command.
@ -3780,8 +3906,10 @@ ftrace_mod_callback(struct trace_array *tr, struct ftrace_hash *hash,
* parameter.
*/
ret = match_records(hash, func, strlen(func), module);
kfree(func);
if (!ret)
return -EINVAL;
return cache_mod(tr, func_orig, module, enable);
if (ret < 0)
return ret;
return 0;
@ -5570,6 +5698,8 @@ static void ftrace_update_trampoline(struct ftrace_ops *ops)
void ftrace_init_trace_array(struct trace_array *tr)
{
INIT_LIST_HEAD(&tr->func_probes);
INIT_LIST_HEAD(&tr->mod_trace);
INIT_LIST_HEAD(&tr->mod_notrace);
}
#else

View File

@ -263,7 +263,10 @@ struct trace_array {
struct ftrace_ops *ops;
struct trace_pid_list __rcu *function_pids;
#ifdef CONFIG_DYNAMIC_FTRACE
/* All of these are protected by the ftrace_lock */
struct list_head func_probes;
struct list_head mod_trace;
struct list_head mod_notrace;
#endif
/* function tracing enabled */
int function_enabled;
@ -761,6 +764,15 @@ enum print_line_t print_trace_line(struct trace_iterator *iter);
extern char trace_find_mark(unsigned long long duration);
struct ftrace_hash;
struct ftrace_mod_load {
struct list_head list;
char *func;
char *module;
int enable;
};
struct ftrace_hash {
unsigned long size_bits;
struct hlist_head *buckets;