// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2008-2014 Mathieu Desnoyers
*/
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/types.h>
#include <linux/jhash.h>
#include <linux/list.h>
#include <linux/rcupdate.h>
#include <linux/tracepoint.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/sched/task.h>
#include <linux/static_key.h>
enum tp_func_state {
TP_FUNC_0,
TP_FUNC_1,
TP_FUNC_2,
TP_FUNC_N,
};
extern tracepoint_ptr_t __start___tracepoints_ptrs[];
extern tracepoint_ptr_t __stop___tracepoints_ptrs[];
DEFINE_SRCU(tracepoint_srcu);
EXPORT_SYMBOL_GPL(tracepoint_srcu);
enum tp_transition_sync {
TP_TRANSITION_SYNC_1_0_1,
TP_TRANSITION_SYNC_N_2_1,
_NR_TP_TRANSITION_SYNC,
};
struct tp_transition_snapshot {
unsigned long rcu;
unsigned long srcu;
bool ongoing;
};
/* Protected by tracepoints_mutex */
static struct tp_transition_snapshot tp_transition_snapshot[_NR_TP_TRANSITION_SYNC];
static void tp_rcu_get_state(enum tp_transition_sync sync)
{
struct tp_transition_snapshot *snapshot = &tp_transition_snapshot[sync];
/* Keep the latest get_state snapshot. */
snapshot->rcu = get_state_synchronize_rcu();
snapshot->srcu = start_poll_synchronize_srcu(&tracepoint_srcu);
snapshot->ongoing = true;
}
static void tp_rcu_cond_sync(enum tp_transition_sync sync)
{
struct tp_transition_snapshot *snapshot = &tp_transition_snapshot[sync];
if (!snapshot->ongoing)
return;
cond_synchronize_rcu(snapshot->rcu);
if (!poll_state_synchronize_srcu(&tracepoint_srcu, snapshot->srcu))
synchronize_srcu(&tracepoint_srcu);
snapshot->ongoing = false;
}
/* Set to 1 to enable tracepoint debug output */
static const int tracepoint_debug;
#ifdef CONFIG_MODULES
/*
* Tracepoint module list mutex protects the local module list.
*/
static DEFINE_MUTEX(tracepoint_module_list_mutex);
/* Local list of struct tp_module */
static LIST_HEAD(tracepoint_module_list);
#endif /* CONFIG_MODULES */
/*
* tracepoints_mutex protects the builtin and module tracepoints.
* tracepoints_mutex nests inside tracepoint_module_list_mutex.
*/
static DEFINE_MUTEX(tracepoints_mutex);
static struct rcu_head *early_probes;
static bool ok_to_free_tracepoints;
/*
* Note about RCU :
* It is used to delay the free of multiple probes array until a quiescent
* state is reached.
*/
struct tp_probes {
struct rcu_head rcu;
struct tracepoint_func probes[];
};
/* Called in removal of a func but failed to allocate a new tp_funcs */
static void tp_stub_func(void)
{
return;
}
static inline void *allocate_probes(int count)
{
struct tp_probes *p = kmalloc(struct_size(p, probes, count),
GFP_KERNEL);
return p == NULL ? NULL : p->probes;
}
static void srcu_free_old_probes(struct rcu_head *head)
{
kfree(container_of(head, struct tp_probes, rcu));
}
static void rcu_free_old_probes(struct rcu_head *head)
{
call_srcu(&tracepoint_srcu, head, srcu_free_old_probes);
}
static __init int release_early_probes(void)
{
struct rcu_head *tmp;
ok_to_free_tracepoints = true;
while (early_probes) {
tmp = early_probes;
early_probes = tmp->next;
call_rcu(tmp, rcu_free_old_probes);
}
return 0;
}
/* SRCU is initialized at core_initcall */
postcore_initcall(release_early_probes);
static inline void release_probes(struct tracepoint_func *old)
{
if (old) {
struct tp_probes *tp_probes = container_of(old,
struct tp_probes, probes[0]);
/*
* We can't free probes if SRCU is not initialized yet.
* Postpone the freeing till after SRCU is initialized.
*/
if (unlikely(!ok_to_free_tracepoints)) {
tp_probes->rcu.next = early_probes;
early_probes = &tp_probes->rcu;
return;
}
/*
* Tracepoint probes are protected by both sched RCU and SRCU,
* by calling the SRCU callback in the sched RCU callback we
* cover both cases. So let us chain the SRCU and sched RCU
* callbacks to wait for both grace periods.
*/
call_rcu(&tp_probes->rcu, rcu_free_old_probes);
}
}
static void debug_print_probes(struct tracepoint_func *funcs)
{
int i;
if (!tracepoint_debug || !funcs)
return;
for (i = 0; funcs[i].func; i++)
printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
}
static struct tracepoint_func *
func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
int prio)
{
struct tracepoint_func *old, *new;
int iter_probes; /* Iterate over old probe array. */
int nr_probes = 0; /* Counter for probes */
int pos = -1; /* Insertion position into new array */
if (WARN_ON(!tp_func->func))
return ERR_PTR(-EINVAL);
debug_print_probes(*funcs);
old = *funcs;
if (old) {
/* (N -> N+1), (N != 0, 1) probes */
for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
if (old[iter_probes].func == tp_stub_func)
continue; /* Skip stub functions. */
if (old[iter_probes].func == tp_func->func &&
old[iter_probes].data == tp_func->data)
return ERR_PTR(-EEXIST);
nr_probes++;
}
}
/* + 2 : one for new probe, one for NULL func */
new = allocate_probes(nr_probes + 2);
if (new == NULL)
return ERR_PTR(-ENOMEM);
if (old) {
nr_probes = 0;
for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
if (old[iter_probes].func == tp_stub_func)
continue;
/* Insert before probes of lower priority */
if (pos < 0 && old[iter_probes].prio < prio)
pos = nr_probes++;
new[nr_probes++] = old[iter_probes];
}
if (pos < 0)
pos = nr_probes++;
/* nr_probes now points to the end of the new array */
} else {
pos = 0;
nr_probes = 1; /* must point at end of array */
}
new[pos] = *tp_func;
new[nr_probes].func = NULL;
*funcs = new;
debug_print_probes(*funcs);
return old;
}
static void *func_remove(struct tracepoint_func **funcs,
struct tracepoint_func *tp_func)
{
int nr_probes = 0, nr_del = 0, i;
struct tracepoint_func *old, *new;
old = *funcs;
if (!old)
return ERR_PTR(-ENOENT);
debug_print_probes(*funcs);
/* (N -> M), (N > 1, M >= 0) probes */
if (tp_func->func) {
for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
if ((old[nr_probes].func == tp_func->func &&
old[nr_probes].data == tp_func->data) ||
old[nr_probes].func == tp_stub_func)
nr_del++;
}
}
/*
* If probe is NULL, then nr_probes = nr_del = 0, and then the
* entire entry will be removed.
*/
if (nr_probes - nr_del == 0) {
/* N -> 0, (N > 1) */
*funcs = NULL;
debug_print_probes(*funcs);
return old;
} else {
int j = 0;
/* N -> M, (N > 1, M > 0) */
/* + 1 for NULL */
new = allocate_probes(nr_probes - nr_del + 1);
if (new) {
for (i = 0; old[i].func; i++) {
if ((old[i].func != tp_func->func ||
old[i].data != tp_func->data) &&
old[i].func != tp_stub_func)
new[j++] = old[i];
}
new[nr_probes - nr_del].func = NULL;
*funcs = new;
} else {
/*
* Failed to allocate, replace the old function
* with calls to tp_stub_func.
*/
for (i = 0; old[i].func; i++) {
if (old[i].func == tp_func->func &&
old[i].data == tp_func->data)
WRITE_ONCE(old[i].func, tp_stub_func);
}
*funcs = old;
}
}
debug_print_probes(*funcs);
return old;
}
/*
* Count the number of functions (enum tp_func_state) in a tp_funcs array.
*/
static enum tp_func_state nr_func_state(const struct tracepoint_func *tp_funcs)
{
if (!tp_funcs)
return TP_FUNC_0;
if (!tp_funcs[1].func)
return TP_FUNC_1;
if (!tp_funcs[2].func)
return TP_FUNC_2;
return TP_FUNC_N; /* 3 or more */
}
static void tracepoint_update_call(struct tracepoint *tp, struct tracepoint_func *tp_funcs)
{
void *func = tp->iterator;
/* Synthetic events do not have static call sites */
if (!tp->static_call_key)
return;
if (nr_func_state(tp_funcs) == TP_FUNC_1)
func = tp_funcs[0].func;
__static_call_update(tp->static_call_key, tp->static_call_tramp, func);
}
/*
* Add the probe function to a tracepoint.
*/
static int tracepoint_add_func(struct tracepoint *tp,
struct tracepoint_func *func, int prio,
bool warn)
{
struct tracepoint_func *old, *tp_funcs;
int ret;
if (tp->regfunc && !static_key_enabled(&tp->key)) {
ret = tp->regfunc();
if (ret < 0)
return ret;
}
tp_funcs = rcu_dereference_protected(tp->funcs,
lockdep_is_held(&tracepoints_mutex));
old = func_add(&tp_funcs, func, prio);
if (IS_ERR(old)) {
WARN_ON_ONCE(warn && PTR_ERR(old) != -ENOMEM);
return PTR_ERR(old);
}
/*
* rcu_assign_pointer has as smp_store_release() which makes sure
* that the new probe callbacks array is consistent before setting
* a pointer to it. This array is referenced by __DO_TRACE from
* include/linux/tracepoint.h using rcu_dereference_sched().
*/
switch (nr_func_state(tp_funcs)) {
case TP_FUNC_1: /* 0->1 */
/*
* Make sure new static func never uses old data after a
* 1->0->1 transition sequence.
*/
tp_rcu_cond_sync(TP_TRANSITION_SYNC_1_0_1);
/* Set static call to first function */
tracepoint_update_call(tp, tp_funcs);
/* Both iterator and static call handle NULL tp->funcs */
rcu_assign_pointer(tp->funcs, tp_funcs);
static_key_enable(&tp->key);
break;
case TP_FUNC_2: /* 1->2 */
/* Set iterator static call */
tracepoint_update_call(tp, tp_funcs);
/*
* Iterator callback installed before updating tp->funcs.
* Requires ordering between RCU assign/dereference and
* static call update/call.
*/
fallthrough;
case TP_FUNC_N: /* N->N+1 (N>1) */
rcu_assign_pointer(tp->funcs, tp_funcs);
/*
* Make sure static func never uses incorrect data after a
* N->...->2->1 (N>1) transition sequence.
*/
if (tp_funcs[0].data != old[0].data)
tp_rcu_get_state(TP_TRANSITION_SYNC_N_2_1);
break;
default:
WARN_ON_ONCE(1);
break;
}
release_probes(old);
return 0;
}
/*
* Remove a probe function from a tracepoint.
* Note: only waiting an RCU period after setting elem->call to the empty
* function insures that the original callback is not used anymore. This insured
* by preempt_disable around the call site.
*/
static int tracepoint_remove_func(struct tracepoint *tp,
struct tracepoint_func *func)
{
struct tracepoint_func *old, *tp_funcs;
tp_funcs = rcu_dereference_protected(tp->funcs,
lockdep_is_held(&tracepoints_mutex));
old = func_remove(&tp_funcs, func);
if (WARN_ON_ONCE(IS_ERR(old)))
return PTR_ERR(old);
if (tp_funcs == old)
/* Failed allocating new tp_funcs, replaced func with stub */
return 0;
switch (nr_func_state(tp_funcs)) {
case TP_FUNC_0: /* 1->0 */
/* Removed last function */
if (tp->unregfunc && static_key_enabled(&tp->key))
tp->unregfunc();
static_key_disable(&tp->key);
/* Set iterator static call */
tracepoint_update_call(tp, tp_funcs);
/* Both iterator and static call handle NULL tp->funcs */
rcu_assign_pointer(tp->funcs, NULL);
/*
* Make sure new static func never uses old data after a
* 1->0->1 transition sequence.
*/
tp_rcu_get_state(TP_TRANSITION_SYNC_1_0_1);
break;
case TP_FUNC_1: /* 2->1 */
rcu_assign_pointer(tp->funcs, tp_funcs);
/*
* Make sure static func never uses incorrect data after a
* N->...->2->1 (N>2) transition sequence. If the first
* element's data has changed, then force the synchronization
* to prevent current readers that have loaded the old data
* from calling the new function.
*/
if (tp_funcs[0].data != old[0].data)
tp_rcu_get_state(TP_TRANSITION_SYNC_N_2_1);
tp_rcu_cond_sync(TP_TRANSITION_SYNC_N_2_1);
/* Set static call to first function */
tracepoint_update_call(tp, tp_funcs);
break;
case TP_FUNC_2: /* N->N-1 (N>2) */
fallthrough;
case TP_FUNC_N:
rcu_assign_pointer(tp->funcs, tp_funcs);
/*
* Make sure static func never uses incorrect data after a
* N->...->2->1 (N>2) transition sequence.
*/
if (tp_funcs[0].data != old[0].data)
tp_rcu_get_state(TP_TRANSITION_SYNC_N_2_1);
break;
default:
WARN_ON_ONCE(1);
break;
}
release_probes(old);
return 0;
}
/**
* tracepoint_probe_register_prio_may_exist - Connect a probe to a tracepoint with priority
* @tp: tracepoint
* @probe: probe handler
* @data: tracepoint data
* @prio: priority of this function over other registered functions
*
* Same as tracepoint_probe_register_prio() except that it will not warn
* if the tracepoint is already registered.
*/
int tracepoint_probe_register_prio_may_exist(struct tracepoint *tp, void *probe,
void *data, int prio)
{
struct tracepoint_func tp_func;
int ret;
mutex_lock(&tracepoints_mutex);
tp_func.func = probe;
tp_func.data = data;
tp_func.prio = prio;
ret = tracepoint_add_func(tp, &tp_func, prio, false);
mutex_unlock(&tracepoints_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio_may_exist);
/**
* tracepoint_probe_register_prio - Connect a probe to a tracepoint with priority
* @tp: tracepoint
* @probe: probe handler
* @data: tracepoint data
* @prio: priority of this function over other registered functions
*
* Returns 0 if ok, error value on error.
* Note: if @tp is within a module, the caller is responsible for
* unregistering the probe before the module is gone. This can be
* performed either with a tracepoint module going notifier, or from
* within module exit functions.
*/
int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
void *data, int prio)
{
struct tracepoint_func tp_func;
int ret;
mutex_lock(&tracepoints_mutex);
tp_func.func = probe;
tp_func.data = data;
tp_func.prio = prio;
ret = tracepoint_add_func(tp, &tp_func, prio, true);
mutex_unlock(&tracepoints_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio);
/**
* tracepoint_probe_register - Connect a probe to a tracepoint
* @tp: tracepoint
* @probe: probe handler
* @data: tracepoint data
*
* Returns 0 if ok, error value on error.
* Note: if @tp is within a module, the caller is responsible for
* unregistering the probe before the module is gone. This can be
* performed either with a tracepoint module going notifier, or from
* within module exit functions.
*/
int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
{
return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
}
EXPORT_SYMBOL_GPL(tracepoint_probe_register);
/**
* tracepoint_probe_unregister - Disconnect a probe from a tracepoint
* @tp: tracepoint
* @probe: probe function pointer
* @data: tracepoint data
*
* Returns 0 if ok, error value on error.
*/
int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
{
struct tracepoint_func tp_func;
int ret;
mutex_lock(&tracepoints_mutex);
tp_func.func = probe;
tp_func.data = data;
ret = tracepoint_remove_func(tp, &tp_func);
mutex_unlock(&tracepoints_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
static void for_each_tracepoint_range(
tracepoint_ptr_t *begin, tracepoint_ptr_t *end,
void (*fct)(struct tracepoint *tp, void *priv),
void *priv)
{
tracepoint_ptr_t *iter;
if (!begin)
return;
for (iter = begin; iter < end; iter++)
fct(tracepoint_ptr_deref(iter), priv);
}
#ifdef CONFIG_MODULES
bool trace_module_has_bad_taint(struct module *mod)
{
return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
(1 << TAINT_UNSIGNED_MODULE) | (1 << TAINT_TEST) |
(1 << TAINT_LIVEPATCH));
}
static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
/**
* register_tracepoint_module_notifier - register tracepoint coming/going notifier
* @nb: notifier block
*
* Notifiers registered with this function are called on module
* coming/going with the tracepoint_module_list_mutex held.
* The notifier block callback should expect a "struct tp_module" data
* pointer.
*/
int register_tracepoint_module_notifier(struct notifier_block *nb)
{
struct tp_module *tp_mod;
int ret;
mutex_lock(&tracepoint_module_list_mutex);
ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
if (ret)
goto end;
list_for_each_entry(tp_mod, &tracepoint_module_list, list)
(void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
end:
mutex_unlock(&tracepoint_module_list_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
/**
* unregister_tracepoint_module_notifier - unregister tracepoint coming/going notifier
* @nb: notifier block
*
* The notifier block callback should expect a "struct tp_module" data
* pointer.
*/
int unregister_tracepoint_module_notifier(struct notifier_block *nb)
{
struct tp_module *tp_mod;
int ret;
mutex_lock(&tracepoint_module_list_mutex);
ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
if (ret)
goto end;
list_for_each_entry(tp_mod, &tracepoint_module_list, list)
(void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
end:
mutex_unlock(&tracepoint_module_list_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
/*
* Ensure the tracer unregistered the module's probes before the module
* teardown is performed. Prevents leaks of probe and data pointers.
*/
static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv)
{
WARN_ON_ONCE(tp->funcs);
}
static int tracepoint_module_coming(struct module *mod)
{
struct tp_module *tp_mod;
if (!mod->num_tracepoints)
return 0;
/*
* We skip modules that taint the kernel, especially those with different
* module headers (for forced load), to make sure we don't cause a crash.
* Staging, out-of-tree, unsigned GPL, and test modules are fine.
*/
if (trace_module_has_bad_taint(mod))
return 0;
tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
if (!tp_mod)
return -ENOMEM;
tp_mod->mod = mod;
mutex_lock(&tracepoint_module_list_mutex);
list_add_tail(&tp_mod->list, &tracepoint_module_list);
blocking_notifier_call_chain(&tracepoint_notify_list,
MODULE_STATE_COMING, tp_mod);
mutex_unlock(&tracepoint_module_list_mutex);
return 0;
}
static void tracepoint_module_going(struct module *mod)
{
struct tp_module *tp_mod;
if (!mod->num_tracepoints)
return;
mutex_lock(&tracepoint_module_list_mutex);
list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
if (tp_mod->mod == mod) {
blocking_notifier_call_chain(&tracepoint_notify_list,
MODULE_STATE_GOING, tp_mod);
list_del(&tp_mod->list);
kfree(tp_mod);
/*
* Called the going notifier before checking for
* quiescence.
*/
for_each_tracepoint_range(mod->tracepoints_ptrs,
mod->tracepoints_ptrs + mod->num_tracepoints,
tp_module_going_check_quiescent, NULL);
break;
}
}
/*
* In the case of modules that were tainted at "coming", we'll simply
* walk through the list without finding it. We cannot use the "tainted"
* flag on "going", in case a module taints the kernel only after being
* loaded.
*/
mutex_unlock(&tracepoint_module_list_mutex);
}
static int tracepoint_module_notify(struct notifier_block *self,
unsigned long val, void *data)
{
struct module *mod = data;
int ret = 0;
switch (val) {
case MODULE_STATE_COMING:
ret = tracepoint_module_coming(mod);
break;
case MODULE_STATE_LIVE:
break;
case MODULE_STATE_GOING:
tracepoint_module_going(mod);
break;
case MODULE_STATE_UNFORMED:
break;
}
return notifier_from_errno(ret);
}
static struct notifier_block tracepoint_module_nb = {
.notifier_call = tracepoint_module_notify,
.priority = 0,
};
static __init int init_tracepoints(void)
{
int ret;
ret = register_module_notifier(&tracepoint_module_nb);
if (ret)
pr_warn("Failed to register tracepoint module enter notifier\n");
return ret;
}
__initcall(init_tracepoints);
/**
* for_each_tracepoint_in_module - iteration on all tracepoints in a module
* @mod: module
* @fct: callback
* @priv: private data
*/
void for_each_tracepoint_in_module(struct module *mod,
void (*fct)(struct tracepoint *tp,
struct module *mod, void *priv),
void *priv)
{
tracepoint_ptr_t *begin, *end, *iter;
lockdep_assert_held(&tracepoint_module_list_mutex);
if (!mod)
return;
begin = mod->tracepoints_ptrs;
end = mod->tracepoints_ptrs + mod->num_tracepoints;
for (iter = begin; iter < end; iter++)
fct(tracepoint_ptr_deref(iter), mod, priv);
}
/**
* for_each_module_tracepoint - iteration on all tracepoints in all modules
* @fct: callback
* @priv: private data
*/
void for_each_module_tracepoint(void (*fct)(struct tracepoint *tp,
struct module *mod, void *priv),
void *priv)
{
struct tp_module *tp_mod;
mutex_lock(&tracepoint_module_list_mutex);
list_for_each_entry(tp_mod, &tracepoint_module_list, list)
for_each_tracepoint_in_module(tp_mod->mod, fct, priv);
mutex_unlock(&tracepoint_module_list_mutex);
}
#endif /* CONFIG_MODULES */
/**
* for_each_kernel_tracepoint - iteration on all kernel tracepoints
* @fct: callback
* @priv: private data
*/
void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
void *priv)
{
for_each_tracepoint_range(__start___tracepoints_ptrs,
__stop___tracepoints_ptrs, fct, priv);
}
EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
static int sys_tracepoint_refcount;
int syscall_regfunc(void)
{
struct task_struct *p, *t;
if (!sys_tracepoint_refcount) {
read_lock(&tasklist_lock);
for_each_process_thread(p, t) {
set_task_syscall_work(t, SYSCALL_TRACEPOINT);
}
read_unlock(&tasklist_lock);
}
sys_tracepoint_refcount++;
return 0;
}
void syscall_unregfunc(void)
{
struct task_struct *p, *t;
sys_tracepoint_refcount--;
if (!sys_tracepoint_refcount) {
read_lock(&tasklist_lock);
for_each_process_thread(p, t) {
clear_task_syscall_work(t, SYSCALL_TRACEPOINT);
}
read_unlock(&tasklist_lock);
}
}
#endif
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