| // 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> |
| |
| extern tracepoint_ptr_t __start___tracepoints_ptrs[]; |
| extern tracepoint_ptr_t __stop___tracepoints_ptrs[]; |
| |
| DEFINE_SRCU(tracepoint_srcu); |
| EXPORT_SYMBOL_GPL(tracepoint_srcu); |
| |
| /* 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[0]; |
| }; |
| |
| /* 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 nr_probes = 0; |
| int stub_funcs = 0; |
| int pos = -1; |
| |
| 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 (nr_probes = 0; old[nr_probes].func; nr_probes++) { |
| /* Insert before probes of lower priority */ |
| if (pos < 0 && old[nr_probes].prio < prio) |
| pos = nr_probes; |
| if (old[nr_probes].func == tp_func->func && |
| old[nr_probes].data == tp_func->data) |
| return ERR_PTR(-EEXIST); |
| if (old[nr_probes].func == tp_stub_func) |
| stub_funcs++; |
| } |
| } |
| /* + 2 : one for new probe, one for NULL func - stub functions */ |
| new = allocate_probes(nr_probes + 2 - stub_funcs); |
| if (new == NULL) |
| return ERR_PTR(-ENOMEM); |
| if (old) { |
| if (stub_funcs) { |
| /* Need to copy one at a time to remove stubs */ |
| int probes = 0; |
| |
| pos = -1; |
| for (nr_probes = 0; old[nr_probes].func; nr_probes++) { |
| if (old[nr_probes].func == tp_stub_func) |
| continue; |
| if (pos < 0 && old[nr_probes].prio < prio) |
| pos = probes++; |
| new[probes++] = old[nr_probes]; |
| } |
| nr_probes = probes; |
| if (pos < 0) |
| pos = probes; |
| else |
| nr_probes--; /* Account for insertion */ |
| |
| } else if (pos < 0) { |
| pos = nr_probes; |
| memcpy(new, old, nr_probes * sizeof(struct tracepoint_func)); |
| } else { |
| /* Copy higher priority probes ahead of the new probe */ |
| memcpy(new, old, pos * sizeof(struct tracepoint_func)); |
| /* Copy the rest after it. */ |
| memcpy(new + pos + 1, old + pos, |
| (nr_probes - pos) * sizeof(struct tracepoint_func)); |
| } |
| } else |
| pos = 0; |
| new[pos] = *tp_func; |
| new[nr_probes + 1].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) { |
| old[i].func = tp_stub_func; |
| /* Set the prio to the next event. */ |
| if (old[i + 1].func) |
| old[i].prio = |
| old[i + 1].prio; |
| else |
| old[i].prio = -1; |
| } |
| *funcs = old; |
| } |
| } |
| debug_print_probes(*funcs); |
| return old; |
| } |
| |
| /* |
| * Add the probe function to a tracepoint. |
| */ |
| static int tracepoint_add_func(struct tracepoint *tp, |
| struct tracepoint_func *func, int prio) |
| { |
| 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(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(). |
| */ |
| rcu_assign_pointer(tp->funcs, tp_funcs); |
| if (!static_key_enabled(&tp->key)) |
| static_key_slow_inc(&tp->key); |
| 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; |
| |
| if (!tp_funcs) { |
| /* Removed last function */ |
| if (tp->unregfunc && static_key_enabled(&tp->key)) |
| tp->unregfunc(); |
| |
| if (static_key_enabled(&tp->key)) |
| static_key_slow_dec(&tp->key); |
| } |
| rcu_assign_pointer(tp->funcs, tp_funcs); |
| release_probes(old); |
| return 0; |
| } |
| |
| /** |
| * 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); |
| 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)); |
| } |
| |
| static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list); |
| |
| /** |
| * register_tracepoint_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_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; |
| int ret = 0; |
| |
| 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, and unsigned GPL modules are fine. |
| */ |
| if (trace_module_has_bad_taint(mod)) |
| return 0; |
| mutex_lock(&tracepoint_module_list_mutex); |
| tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL); |
| if (!tp_mod) { |
| ret = -ENOMEM; |
| goto end; |
| } |
| tp_mod->mod = mod; |
| list_add_tail(&tp_mod->list, &tracepoint_module_list); |
| blocking_notifier_call_chain(&tracepoint_notify_list, |
| MODULE_STATE_COMING, tp_mod); |
| end: |
| mutex_unlock(&tracepoint_module_list_mutex); |
| return ret; |
| } |
| |
| 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 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); |
| #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_tsk_thread_flag(t, TIF_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_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); |
| } |
| read_unlock(&tasklist_lock); |
| } |
| } |
| #endif |