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kernel/tracepoint.c
14.9 KB
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// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* Copyright (C) 2008-2014 Mathieu Desnoyers |
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*/ #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> |
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#include <linux/sched/signal.h> |
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#include <linux/sched/task.h> |
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#include <linux/static_key.h> |
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extern tracepoint_ptr_t __start___tracepoints_ptrs[]; extern tracepoint_ptr_t __stop___tracepoints_ptrs[]; |
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DEFINE_SRCU(tracepoint_srcu); EXPORT_SYMBOL_GPL(tracepoint_srcu); |
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/* Set to 1 to enable tracepoint debug output */ static const int tracepoint_debug; |
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#ifdef CONFIG_MODULES |
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/* |
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* Tracepoint module list mutex protects the local module list. |
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*/ |
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static DEFINE_MUTEX(tracepoint_module_list_mutex); |
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/* Local list of struct tp_module */ |
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static LIST_HEAD(tracepoint_module_list); #endif /* CONFIG_MODULES */ |
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/* |
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* tracepoints_mutex protects the builtin and module tracepoints. * tracepoints_mutex nests inside tracepoint_module_list_mutex. |
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*/ |
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static DEFINE_MUTEX(tracepoints_mutex); |
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static struct rcu_head *early_probes; static bool ok_to_free_tracepoints; |
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/* * Note about RCU : |
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* It is used to delay the free of multiple probes array until a quiescent |
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* state is reached. |
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*/ |
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struct tp_probes { |
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struct rcu_head rcu; |
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struct tracepoint_func probes[0]; |
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}; |
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static inline void *allocate_probes(int count) |
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{ |
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struct tp_probes *p = kmalloc(struct_size(p, probes, count), GFP_KERNEL); |
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return p == NULL ? NULL : p->probes; |
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} |
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static void srcu_free_old_probes(struct rcu_head *head) |
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{ |
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kfree(container_of(head, struct tp_probes, rcu)); |
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} |
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static void rcu_free_old_probes(struct rcu_head *head) { call_srcu(&tracepoint_srcu, head, srcu_free_old_probes); } |
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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; |
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call_rcu(tmp, rcu_free_old_probes); |
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} return 0; } /* SRCU is initialized at core_initcall */ postcore_initcall(release_early_probes); |
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static inline void release_probes(struct tracepoint_func *old) |
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{ if (old) { struct tp_probes *tp_probes = container_of(old, struct tp_probes, probes[0]); |
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/* * 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; } |
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/* * 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. */ |
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call_rcu(&tp_probes->rcu, rcu_free_old_probes); |
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} |
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} |
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static void debug_print_probes(struct tracepoint_func *funcs) |
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{ int i; |
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if (!tracepoint_debug || !funcs) |
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return; |
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for (i = 0; funcs[i].func; i++) printk(KERN_DEBUG "Probe %d : %p ", i, funcs[i].func); |
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} |
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static struct tracepoint_func * func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func, int prio) |
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{ |
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struct tracepoint_func *old, *new; |
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int nr_probes = 0; int pos = -1; |
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if (WARN_ON(!tp_func->func)) |
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return ERR_PTR(-EINVAL); |
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|
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debug_print_probes(*funcs); old = *funcs; |
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if (old) { /* (N -> N+1), (N != 0, 1) probes */ |
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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; |
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if (old[nr_probes].func == tp_func->func && old[nr_probes].data == tp_func->data) |
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return ERR_PTR(-EEXIST); |
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} |
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} /* + 2 : one for new probe, one for NULL func */ |
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new = allocate_probes(nr_probes + 2); |
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if (new == NULL) return ERR_PTR(-ENOMEM); |
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if (old) { 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; |
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new[nr_probes + 1].func = NULL; |
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*funcs = new; debug_print_probes(*funcs); |
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return old; } |
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static void *func_remove(struct tracepoint_func **funcs, struct tracepoint_func *tp_func) |
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{ int nr_probes = 0, nr_del = 0, i; |
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struct tracepoint_func *old, *new; |
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old = *funcs; |
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if (!old) |
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return ERR_PTR(-ENOENT); |
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debug_print_probes(*funcs); |
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/* (N -> M), (N > 1, M >= 0) probes */ |
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if (tp_func->func) { |
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for (nr_probes = 0; old[nr_probes].func; nr_probes++) { |
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if (old[nr_probes].func == tp_func->func && old[nr_probes].data == tp_func->data) |
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nr_del++; } |
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} |
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/* * If probe is NULL, then nr_probes = nr_del = 0, and then the * entire entry will be removed. */ |
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if (nr_probes - nr_del == 0) { /* N -> 0, (N > 1) */ |
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*funcs = NULL; debug_print_probes(*funcs); |
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return old; } else { int j = 0; /* N -> M, (N > 1, M > 0) */ /* + 1 for NULL */ |
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new = allocate_probes(nr_probes - nr_del + 1); |
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if (new == NULL) return ERR_PTR(-ENOMEM); |
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for (i = 0; old[i].func; i++) |
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if (old[i].func != tp_func->func || old[i].data != tp_func->data) |
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new[j++] = old[i]; |
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new[nr_probes - nr_del].func = NULL; |
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*funcs = new; |
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} |
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debug_print_probes(*funcs); |
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return old; } /* |
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* Add the probe function to a tracepoint. |
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*/ |
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static int tracepoint_add_func(struct tracepoint *tp, |
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struct tracepoint_func *func, int prio) |
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{ |
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struct tracepoint_func *old, *tp_funcs; |
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int ret; |
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if (tp->regfunc && !static_key_enabled(&tp->key)) { ret = tp->regfunc(); if (ret < 0) return ret; } |
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tp_funcs = rcu_dereference_protected(tp->funcs, lockdep_is_held(&tracepoints_mutex)); |
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old = func_add(&tp_funcs, func, prio); |
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if (IS_ERR(old)) { |
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WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM); |
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return PTR_ERR(old); } |
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/* |
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* 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(). |
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*/ |
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rcu_assign_pointer(tp->funcs, tp_funcs); if (!static_key_enabled(&tp->key)) static_key_slow_inc(&tp->key); |
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release_probes(old); |
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return 0; |
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} /* |
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* Remove a probe function from a tracepoint. |
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* 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. */ |
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static int tracepoint_remove_func(struct tracepoint *tp, struct tracepoint_func *func) |
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{ |
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struct tracepoint_func *old, *tp_funcs; |
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tp_funcs = rcu_dereference_protected(tp->funcs, lockdep_is_held(&tracepoints_mutex)); |
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old = func_remove(&tp_funcs, func); if (IS_ERR(old)) { |
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WARN_ON_ONCE(PTR_ERR(old) != -ENOMEM); |
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return PTR_ERR(old); |
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} |
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if (!tp_funcs) { /* Removed last function */ if (tp->unregfunc && static_key_enabled(&tp->key)) tp->unregfunc(); |
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if (static_key_enabled(&tp->key)) static_key_slow_dec(&tp->key); |
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} |
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rcu_assign_pointer(tp->funcs, tp_funcs); |
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release_probes(old); |
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return 0; |
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} |
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/** |
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* tracepoint_probe_register_prio - Connect a probe to a tracepoint with priority |
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* @tp: tracepoint |
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* @probe: probe handler |
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* @data: tracepoint data |
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* @prio: priority of this function over other registered functions |
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* |
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* 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. |
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*/ |
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int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe, void *data, int prio) |
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{ |
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struct tracepoint_func tp_func; int ret; |
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mutex_lock(&tracepoints_mutex); |
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tp_func.func = probe; tp_func.data = data; |
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tp_func.prio = prio; ret = tracepoint_add_func(tp, &tp_func, prio); |
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mutex_unlock(&tracepoints_mutex); |
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return ret; |
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} |
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EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio); /** * tracepoint_probe_register - Connect a probe to a tracepoint * @tp: tracepoint * @probe: probe handler * @data: tracepoint data |
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* * 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); } |
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EXPORT_SYMBOL_GPL(tracepoint_probe_register); /** * tracepoint_probe_unregister - Disconnect a probe from a tracepoint |
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* @tp: tracepoint |
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* @probe: probe function pointer |
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* @data: tracepoint data |
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* |
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* Returns 0 if ok, error value on error. |
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*/ |
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int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data) |
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{ |
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struct tracepoint_func tp_func; int ret; |
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mutex_lock(&tracepoints_mutex); |
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tp_func.func = probe; tp_func.data = data; ret = tracepoint_remove_func(tp, &tp_func); |
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mutex_unlock(&tracepoints_mutex); |
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return ret; |
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} EXPORT_SYMBOL_GPL(tracepoint_probe_unregister); |
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static void for_each_tracepoint_range( tracepoint_ptr_t *begin, tracepoint_ptr_t *end, |
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void (*fct)(struct tracepoint *tp, void *priv), void *priv) { |
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tracepoint_ptr_t *iter; |
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if (!begin) return; |
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for (iter = begin; iter < end; iter++) fct(tracepoint_ptr_deref(iter), priv); |
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} |
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#ifdef CONFIG_MODULES |
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bool trace_module_has_bad_taint(struct module *mod) { |
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return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) | (1 << TAINT_UNSIGNED_MODULE)); |
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} |
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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. */ |
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static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv) |
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{ |
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WARN_ON_ONCE(tp->funcs); |
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} |
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static int tracepoint_module_coming(struct module *mod) { |
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struct tp_module *tp_mod; |
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int ret = 0; |
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if (!mod->num_tracepoints) return 0; |
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/* |
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* 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. |
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* Staging, out-of-tree, and unsigned GPL modules are fine. |
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*/ |
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if (trace_module_has_bad_taint(mod)) |
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return 0; |
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mutex_lock(&tracepoint_module_list_mutex); |
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tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL); if (!tp_mod) { ret = -ENOMEM; goto end; } |
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tp_mod->mod = mod; |
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list_add_tail(&tp_mod->list, &tracepoint_module_list); |
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blocking_notifier_call_chain(&tracepoint_notify_list, MODULE_STATE_COMING, tp_mod); |
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446 |
end: |
de7b29739
|
447 |
mutex_unlock(&tracepoint_module_list_mutex); |
b75ef8b44
|
448 449 |
return ret; } |
de7b29739
|
450 |
static void tracepoint_module_going(struct module *mod) |
b75ef8b44
|
451 |
{ |
de7b29739
|
452 |
struct tp_module *tp_mod; |
b75ef8b44
|
453 |
|
7dec935a3
|
454 |
if (!mod->num_tracepoints) |
de7b29739
|
455 |
return; |
7dec935a3
|
456 |
|
de7b29739
|
457 458 |
mutex_lock(&tracepoint_module_list_mutex); list_for_each_entry(tp_mod, &tracepoint_module_list, list) { |
eb7d035c5
|
459 |
if (tp_mod->mod == mod) { |
de7b29739
|
460 461 462 463 464 465 466 467 |
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. */ |
46e0c9be2
|
468 469 470 |
for_each_tracepoint_range(mod->tracepoints_ptrs, mod->tracepoints_ptrs + mod->num_tracepoints, tp_module_going_check_quiescent, NULL); |
b75ef8b44
|
471 472 473 474 475 476 477 478 479 |
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. */ |
de7b29739
|
480 |
mutex_unlock(&tracepoint_module_list_mutex); |
b75ef8b44
|
481 |
} |
227a83756
|
482 |
|
de7b29739
|
483 484 |
static int tracepoint_module_notify(struct notifier_block *self, unsigned long val, void *data) |
32f857427
|
485 486 |
{ struct module *mod = data; |
b75ef8b44
|
487 |
int ret = 0; |
32f857427
|
488 489 490 |
switch (val) { case MODULE_STATE_COMING: |
b75ef8b44
|
491 492 493 494 |
ret = tracepoint_module_coming(mod); break; case MODULE_STATE_LIVE: break; |
32f857427
|
495 |
case MODULE_STATE_GOING: |
de7b29739
|
496 497 498 |
tracepoint_module_going(mod); break; case MODULE_STATE_UNFORMED: |
32f857427
|
499 500 |
break; } |
b75ef8b44
|
501 |
return ret; |
32f857427
|
502 |
} |
de7b29739
|
503 |
static struct notifier_block tracepoint_module_nb = { |
32f857427
|
504 505 506 |
.notifier_call = tracepoint_module_notify, .priority = 0, }; |
de7b29739
|
507 |
static __init int init_tracepoints(void) |
32f857427
|
508 |
{ |
de7b29739
|
509 510 511 |
int ret; ret = register_module_notifier(&tracepoint_module_nb); |
eb7d035c5
|
512 |
if (ret) |
a395d6a7e
|
513 514 |
pr_warn("Failed to register tracepoint module enter notifier "); |
eb7d035c5
|
515 |
|
de7b29739
|
516 |
return ret; |
32f857427
|
517 518 |
} __initcall(init_tracepoints); |
227a83756
|
519 |
#endif /* CONFIG_MODULES */ |
a871bd33a
|
520 |
|
de7b29739
|
521 522 523 524 525 526 527 528 529 530 531 532 |
/** * 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); |
3d27d8cb3
|
533 |
#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS |
60d970c25
|
534 |
|
974198758
|
535 |
/* NB: reg/unreg are called while guarded with the tracepoints_mutex */ |
a871bd33a
|
536 |
static int sys_tracepoint_refcount; |
8cf868aff
|
537 |
int syscall_regfunc(void) |
a871bd33a
|
538 |
{ |
8063e41d2
|
539 |
struct task_struct *p, *t; |
a871bd33a
|
540 |
|
a871bd33a
|
541 |
if (!sys_tracepoint_refcount) { |
8063e41d2
|
542 543 |
read_lock(&tasklist_lock); for_each_process_thread(p, t) { |
ea73c79e3
|
544 |
set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); |
8063e41d2
|
545 546 |
} read_unlock(&tasklist_lock); |
a871bd33a
|
547 548 |
} sys_tracepoint_refcount++; |
8cf868aff
|
549 550 |
return 0; |
a871bd33a
|
551 552 553 554 |
} void syscall_unregfunc(void) { |
8063e41d2
|
555 |
struct task_struct *p, *t; |
a871bd33a
|
556 |
|
a871bd33a
|
557 558 |
sys_tracepoint_refcount--; if (!sys_tracepoint_refcount) { |
8063e41d2
|
559 560 |
read_lock(&tasklist_lock); for_each_process_thread(p, t) { |
667000011
|
561 |
clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT); |
8063e41d2
|
562 563 |
} read_unlock(&tasklist_lock); |
a871bd33a
|
564 |
} |
a871bd33a
|
565 |
} |
60d970c25
|
566 |
#endif |