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![Steven Rostedt (VMware)](/assets/img/avatar_default.png)
Restructure the code a bit to make it simpler, fix some formatting problems and add READ_ONCE/WRITE_ONCE to make sure there's no compiler load/store tearing to the variables that can be accessed across CPUs. Started with Mathieu Desnoyers's patch: Link: https://lore.kernel.org/lkml/20210203175741.20665-1-mathieu.desnoyers@efficios.com/ And will keep his signature, but I will take the responsibility of this being correct, and keep the authorship. Link: https://lkml.kernel.org/r/20210204143004.61126582@gandalf.local.home Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
646 lines
16 KiB
C
646 lines
16 KiB
C
// 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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*/
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/types.h>
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#include <linux/jhash.h>
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#include <linux/list.h>
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#include <linux/rcupdate.h>
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#include <linux/tracepoint.h>
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#include <linux/err.h>
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#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[];
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extern tracepoint_ptr_t __stop___tracepoints_ptrs[];
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DEFINE_SRCU(tracepoint_srcu);
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EXPORT_SYMBOL_GPL(tracepoint_srcu);
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/* Set to 1 to enable tracepoint debug output */
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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);
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#endif /* CONFIG_MODULES */
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/*
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* tracepoints_mutex protects the builtin and module tracepoints.
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* 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;
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static bool ok_to_free_tracepoints;
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/*
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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[];
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};
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/* Called in removal of a func but failed to allocate a new tp_funcs */
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static void tp_stub_func(void)
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{
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return;
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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),
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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)
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{
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call_srcu(&tracepoint_srcu, head, srcu_free_old_probes);
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}
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static __init int release_early_probes(void)
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{
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struct rcu_head *tmp;
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ok_to_free_tracepoints = true;
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while (early_probes) {
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tmp = early_probes;
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early_probes = tmp->next;
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call_rcu(tmp, rcu_free_old_probes);
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}
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return 0;
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}
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/* SRCU is initialized at core_initcall */
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postcore_initcall(release_early_probes);
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static inline void release_probes(struct tracepoint_func *old)
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{
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if (old) {
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struct tp_probes *tp_probes = container_of(old,
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struct tp_probes, probes[0]);
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/*
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* We can't free probes if SRCU is not initialized yet.
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* Postpone the freeing till after SRCU is initialized.
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*/
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if (unlikely(!ok_to_free_tracepoints)) {
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tp_probes->rcu.next = early_probes;
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early_probes = &tp_probes->rcu;
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return;
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}
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/*
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* Tracepoint probes are protected by both sched RCU and SRCU,
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* by calling the SRCU callback in the sched RCU callback we
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* cover both cases. So let us chain the SRCU and sched RCU
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* callbacks to wait for both grace periods.
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*/
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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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{
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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++)
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printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
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}
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static struct tracepoint_func *
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func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
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int prio)
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{
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struct tracepoint_func *old, *new;
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int iter_probes; /* Iterate over old probe array. */
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int nr_probes = 0; /* Counter for probes */
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int pos = -1; /* Insertion position into new array */
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if (WARN_ON(!tp_func->func))
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return ERR_PTR(-EINVAL);
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debug_print_probes(*funcs);
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old = *funcs;
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if (old) {
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/* (N -> N+1), (N != 0, 1) probes */
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for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
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if (old[iter_probes].func == tp_stub_func)
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continue; /* Skip stub functions. */
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if (old[iter_probes].func == tp_func->func &&
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old[iter_probes].data == tp_func->data)
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return ERR_PTR(-EEXIST);
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nr_probes++;
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}
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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)
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return ERR_PTR(-ENOMEM);
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if (old) {
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nr_probes = 0;
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for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
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if (old[iter_probes].func == tp_stub_func)
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continue;
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/* Insert before probes of lower priority */
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if (pos < 0 && old[iter_probes].prio < prio)
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pos = nr_probes++;
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new[nr_probes++] = old[iter_probes];
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}
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if (pos < 0)
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pos = nr_probes++;
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/* nr_probes now points to the end of the new array */
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} else {
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pos = 0;
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nr_probes = 1; /* must point at end of array */
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}
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new[pos] = *tp_func;
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new[nr_probes].func = NULL;
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*funcs = new;
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debug_print_probes(*funcs);
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return old;
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}
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static void *func_remove(struct tracepoint_func **funcs,
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struct tracepoint_func *tp_func)
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{
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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 &&
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old[nr_probes].data == tp_func->data) ||
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old[nr_probes].func == tp_stub_func)
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nr_del++;
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}
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}
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/*
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* If probe is NULL, then nr_probes = nr_del = 0, and then the
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* entire entry will be removed.
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*/
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if (nr_probes - nr_del == 0) {
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/* N -> 0, (N > 1) */
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*funcs = NULL;
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debug_print_probes(*funcs);
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return old;
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} else {
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int j = 0;
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/* N -> M, (N > 1, M > 0) */
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/* + 1 for NULL */
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new = allocate_probes(nr_probes - nr_del + 1);
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if (new) {
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for (i = 0; old[i].func; i++) {
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if ((old[i].func != tp_func->func ||
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old[i].data != tp_func->data) &&
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old[i].func != tp_stub_func)
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new[j++] = old[i];
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}
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new[nr_probes - nr_del].func = NULL;
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*funcs = new;
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} else {
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/*
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* Failed to allocate, replace the old function
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* with calls to tp_stub_func.
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*/
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for (i = 0; old[i].func; i++) {
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if (old[i].func == tp_func->func &&
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old[i].data == tp_func->data)
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WRITE_ONCE(old[i].func, tp_stub_func);
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}
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*funcs = old;
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}
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}
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debug_print_probes(*funcs);
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return old;
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}
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static void tracepoint_update_call(struct tracepoint *tp, struct tracepoint_func *tp_funcs, bool sync)
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{
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void *func = tp->iterator;
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/* Synthetic events do not have static call sites */
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if (!tp->static_call_key)
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return;
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if (!tp_funcs[1].func) {
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func = tp_funcs[0].func;
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/*
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* If going from the iterator back to a single caller,
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* we need to synchronize with __DO_TRACE to make sure
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* that the data passed to the callback is the one that
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* belongs to that callback.
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*/
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if (sync)
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tracepoint_synchronize_unregister();
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}
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__static_call_update(tp->static_call_key, tp->static_call_tramp, func);
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}
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/*
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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)) {
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ret = tp->regfunc();
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if (ret < 0)
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return ret;
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}
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tp_funcs = rcu_dereference_protected(tp->funcs,
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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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/*
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* rcu_assign_pointer has as smp_store_release() which makes sure
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* that the new probe callbacks array is consistent before setting
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* a pointer to it. This array is referenced by __DO_TRACE from
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* include/linux/tracepoint.h using rcu_dereference_sched().
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*/
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rcu_assign_pointer(tp->funcs, tp_funcs);
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tracepoint_update_call(tp, tp_funcs, false);
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static_key_enable(&tp->key);
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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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* Remove a probe function from a tracepoint.
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* Note: only waiting an RCU period after setting elem->call to the empty
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* function insures that the original callback is not used anymore. This insured
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* by preempt_disable around the call site.
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*/
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static int tracepoint_remove_func(struct tracepoint *tp,
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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,
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lockdep_is_held(&tracepoints_mutex));
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old = func_remove(&tp_funcs, func);
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if (WARN_ON_ONCE(IS_ERR(old)))
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return PTR_ERR(old);
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if (tp_funcs == old)
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/* Failed allocating new tp_funcs, replaced func with stub */
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return 0;
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if (!tp_funcs) {
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/* Removed last function */
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if (tp->unregfunc && static_key_enabled(&tp->key))
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tp->unregfunc();
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static_key_disable(&tp->key);
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rcu_assign_pointer(tp->funcs, tp_funcs);
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} else {
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rcu_assign_pointer(tp->funcs, tp_funcs);
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tracepoint_update_call(tp, tp_funcs,
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tp_funcs[0].func != old[0].func);
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}
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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.
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* Note: if @tp is within a module, the caller is responsible for
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* unregistering the probe before the module is gone. This can be
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* performed either with a tracepoint module going notifier, or from
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* within module exit functions.
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*/
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int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
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void *data, int prio)
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{
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struct tracepoint_func tp_func;
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int ret;
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mutex_lock(&tracepoints_mutex);
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tp_func.func = probe;
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tp_func.data = data;
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tp_func.prio = prio;
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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);
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/**
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* tracepoint_probe_register - Connect a probe to a tracepoint
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* @tp: tracepoint
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* @probe: probe handler
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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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* Note: if @tp is within a module, the caller is responsible for
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* unregistering the probe before the module is gone. This can be
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* performed either with a tracepoint module going notifier, or from
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* within module exit functions.
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*/
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int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
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{
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return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
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}
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EXPORT_SYMBOL_GPL(tracepoint_probe_register);
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/**
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* 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;
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int ret;
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mutex_lock(&tracepoints_mutex);
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tp_func.func = probe;
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tp_func.data = data;
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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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}
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EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
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static void for_each_tracepoint_range(
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tracepoint_ptr_t *begin, tracepoint_ptr_t *end,
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void (*fct)(struct tracepoint *tp, void *priv),
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void *priv)
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{
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tracepoint_ptr_t *iter;
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if (!begin)
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return;
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for (iter = begin; iter < end; iter++)
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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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{
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return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
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(1 << TAINT_UNSIGNED_MODULE));
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}
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static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
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/**
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* register_tracepoint_notifier - register tracepoint coming/going notifier
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* @nb: notifier block
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*
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* Notifiers registered with this function are called on module
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* coming/going with the tracepoint_module_list_mutex held.
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* The notifier block callback should expect a "struct tp_module" data
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* pointer.
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*/
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int register_tracepoint_module_notifier(struct notifier_block *nb)
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{
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struct tp_module *tp_mod;
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int ret;
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mutex_lock(&tracepoint_module_list_mutex);
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ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
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if (ret)
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goto end;
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list_for_each_entry(tp_mod, &tracepoint_module_list, list)
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(void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
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end:
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mutex_unlock(&tracepoint_module_list_mutex);
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return ret;
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}
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EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
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/**
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* unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
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* @nb: notifier block
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*
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* The notifier block callback should expect a "struct tp_module" data
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* pointer.
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*/
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int unregister_tracepoint_module_notifier(struct notifier_block *nb)
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{
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struct tp_module *tp_mod;
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int ret;
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mutex_lock(&tracepoint_module_list_mutex);
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ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
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if (ret)
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goto end;
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list_for_each_entry(tp_mod, &tracepoint_module_list, list)
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(void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
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end:
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mutex_unlock(&tracepoint_module_list_mutex);
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return ret;
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}
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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 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);
|
|
#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
|