Commit ea701f11 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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ftrace: Add selftest to test function trace recursion protection



Add selftests to test the function tracing recursion protection actually
does work. It also tests if a ftrace_ops states it will perform its own
protection. Although, even if the ftrace_ops states it will protect itself,
the ftrace infrastructure may still provide protection if the arch does
not support all features or another ftrace_ops is registered.
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 47239c4d
......@@ -220,6 +220,10 @@ extern void ftrace_stub(unsigned long a0, unsigned long a1,
*/
#define register_ftrace_function(ops) ({ 0; })
#define unregister_ftrace_function(ops) ({ 0; })
static inline int ftrace_nr_registered_ops(void)
{
return 0;
}
static inline void clear_ftrace_function(void) { }
static inline void ftrace_kill(void) { }
static inline void ftrace_stop(void) { }
......@@ -275,6 +279,8 @@ extern void unregister_ftrace_function_probe_all(char *glob);
extern int ftrace_text_reserved(void *start, void *end);
extern int ftrace_nr_registered_ops(void);
/*
* The dyn_ftrace record's flags field is split into two parts.
* the first part which is '0-FTRACE_REF_MAX' is a counter of
......
......@@ -111,6 +111,27 @@ static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip);
#define ftrace_ops_list_func ((ftrace_func_t)ftrace_ops_no_ops)
#endif
/**
* ftrace_nr_registered_ops - return number of ops registered
*
* Returns the number of ftrace_ops registered and tracing functions
*/
int ftrace_nr_registered_ops(void)
{
struct ftrace_ops *ops;
int cnt = 0;
mutex_lock(&ftrace_lock);
for (ops = ftrace_ops_list;
ops != &ftrace_list_end; ops = ops->next)
cnt++;
mutex_unlock(&ftrace_lock);
return cnt;
}
/*
* Traverse the ftrace_global_list, invoking all entries. The reason that we
* can use rcu_dereference_raw() is that elements removed from this list
......
......@@ -406,8 +406,141 @@ int trace_selftest_startup_dynamic_tracing(struct tracer *trace,
return ret;
}
static int trace_selftest_recursion_cnt;
static void trace_selftest_test_recursion_func(unsigned long ip,
unsigned long pip,
struct ftrace_ops *op,
struct pt_regs *pt_regs)
{
/*
* This function is registered without the recursion safe flag.
* The ftrace infrastructure should provide the recursion
* protection. If not, this will crash the kernel!
*/
trace_selftest_recursion_cnt++;
DYN_FTRACE_TEST_NAME();
}
static void trace_selftest_test_recursion_safe_func(unsigned long ip,
unsigned long pip,
struct ftrace_ops *op,
struct pt_regs *pt_regs)
{
/*
* We said we would provide our own recursion. By calling
* this function again, we should recurse back into this function
* and count again. But this only happens if the arch supports
* all of ftrace features and nothing else is using the function
* tracing utility.
*/
if (trace_selftest_recursion_cnt++)
return;
DYN_FTRACE_TEST_NAME();
}
static struct ftrace_ops test_rec_probe = {
.func = trace_selftest_test_recursion_func,
};
static struct ftrace_ops test_recsafe_probe = {
.func = trace_selftest_test_recursion_safe_func,
.flags = FTRACE_OPS_FL_RECURSION_SAFE,
};
static int
trace_selftest_function_recursion(void)
{
int save_ftrace_enabled = ftrace_enabled;
int save_tracer_enabled = tracer_enabled;
char *func_name;
int len;
int ret;
int cnt;
/* The previous test PASSED */
pr_cont("PASSED\n");
pr_info("Testing ftrace recursion: ");
/* enable tracing, and record the filter function */
ftrace_enabled = 1;
tracer_enabled = 1;
/* Handle PPC64 '.' name */
func_name = "*" __stringify(DYN_FTRACE_TEST_NAME);
len = strlen(func_name);
ret = ftrace_set_filter(&test_rec_probe, func_name, len, 1);
if (ret) {
pr_cont("*Could not set filter* ");
goto out;
}
ret = register_ftrace_function(&test_rec_probe);
if (ret) {
pr_cont("*could not register callback* ");
goto out;
}
DYN_FTRACE_TEST_NAME();
unregister_ftrace_function(&test_rec_probe);
ret = -1;
if (trace_selftest_recursion_cnt != 1) {
pr_cont("*callback not called once (%d)* ",
trace_selftest_recursion_cnt);
goto out;
}
trace_selftest_recursion_cnt = 1;
pr_cont("PASSED\n");
pr_info("Testing ftrace recursion safe: ");
ret = ftrace_set_filter(&test_recsafe_probe, func_name, len, 1);
if (ret) {
pr_cont("*Could not set filter* ");
goto out;
}
ret = register_ftrace_function(&test_recsafe_probe);
if (ret) {
pr_cont("*could not register callback* ");
goto out;
}
DYN_FTRACE_TEST_NAME();
unregister_ftrace_function(&test_recsafe_probe);
/*
* If arch supports all ftrace features, and no other task
* was on the list, we should be fine.
*/
if (!ftrace_nr_registered_ops() && !FTRACE_FORCE_LIST_FUNC)
cnt = 2; /* Should have recursed */
else
cnt = 1;
ret = -1;
if (trace_selftest_recursion_cnt != cnt) {
pr_cont("*callback not called expected %d times (%d)* ",
cnt, trace_selftest_recursion_cnt);
goto out;
}
ret = 0;
out:
ftrace_enabled = save_ftrace_enabled;
tracer_enabled = save_tracer_enabled;
return ret;
}
#else
# define trace_selftest_startup_dynamic_tracing(trace, tr, func) ({ 0; })
# define trace_selftest_function_recursion() ({ 0; })
#endif /* CONFIG_DYNAMIC_FTRACE */
/*
......@@ -455,7 +588,10 @@ trace_selftest_startup_function(struct tracer *trace, struct trace_array *tr)
ret = trace_selftest_startup_dynamic_tracing(trace, tr,
DYN_FTRACE_TEST_NAME);
if (ret)
goto out;
ret = trace_selftest_function_recursion();
out:
ftrace_enabled = save_ftrace_enabled;
tracer_enabled = save_tracer_enabled;
......
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