/* * Performance events callchain code, extracted from core.c: * * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de> * Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar * Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra * Copyright � 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com> * * For licensing details see kernel-base/COPYING */ #include <linux/perf_event.h> #include <linux/slab.h> #include "internal.h" struct callchain_cpus_entries { struct rcu_head rcu_head; struct perf_callchain_entry *cpu_entries[0]; }; int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH; int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK; static inline size_t perf_callchain_entry__sizeof(void) { return (sizeof(struct perf_callchain_entry) + sizeof(__u64) * (sysctl_perf_event_max_stack + sysctl_perf_event_max_contexts_per_stack)); } static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]); static atomic_t nr_callchain_events; static DEFINE_MUTEX(callchain_mutex); static struct callchain_cpus_entries *callchain_cpus_entries; __weak void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs) { } __weak void perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs) { } static void release_callchain_buffers_rcu(struct rcu_head *head) { struct callchain_cpus_entries *entries; int cpu; entries = container_of(head, struct callchain_cpus_entries, rcu_head); for_each_possible_cpu(cpu) kfree(entries->cpu_entries[cpu]); kfree(entries); } static void release_callchain_buffers(void) { struct callchain_cpus_entries *entries; entries = callchain_cpus_entries; RCU_INIT_POINTER(callchain_cpus_entries, NULL); call_rcu(&entries->rcu_head, release_callchain_buffers_rcu); } static int alloc_callchain_buffers(void) { int cpu; int size; struct callchain_cpus_entries *entries; /* * We can't use the percpu allocation API for data that can be * accessed from NMI. Use a temporary manual per cpu allocation * until that gets sorted out. */ size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]); entries = kzalloc(size, GFP_KERNEL); if (!entries) return -ENOMEM; size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS; for_each_possible_cpu(cpu) { entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL, cpu_to_node(cpu)); if (!entries->cpu_entries[cpu]) goto fail; } rcu_assign_pointer(callchain_cpus_entries, entries); return 0; fail: for_each_possible_cpu(cpu) kfree(entries->cpu_entries[cpu]); kfree(entries); return -ENOMEM; } int get_callchain_buffers(int event_max_stack) { int err = 0; int count; mutex_lock(&callchain_mutex); count = atomic_inc_return(&nr_callchain_events); if (WARN_ON_ONCE(count < 1)) { err = -EINVAL; goto exit; } if (count > 1) { /* If the allocation failed, give up */ if (!callchain_cpus_entries) err = -ENOMEM; /* * If requesting per event more than the global cap, * return a different error to help userspace figure * this out. * * And also do it here so that we have &callchain_mutex held. */ if (event_max_stack > sysctl_perf_event_max_stack) err = -EOVERFLOW; goto exit; } err = alloc_callchain_buffers(); exit: if (err) atomic_dec(&nr_callchain_events); mutex_unlock(&callchain_mutex); return err; } void put_callchain_buffers(void) { if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) { release_callchain_buffers(); mutex_unlock(&callchain_mutex); } } static struct perf_callchain_entry *get_callchain_entry(int *rctx) { int cpu; struct callchain_cpus_entries *entries; *rctx = get_recursion_context(this_cpu_ptr(callchain_recursion)); if (*rctx == -1) return NULL; entries = rcu_dereference(callchain_cpus_entries); if (!entries) return NULL; cpu = smp_processor_id(); return (((void *)entries->cpu_entries[cpu]) + (*rctx * perf_callchain_entry__sizeof())); } static void put_callchain_entry(int rctx) { put_recursion_context(this_cpu_ptr(callchain_recursion), rctx); } struct perf_callchain_entry * perf_callchain(struct perf_event *event, struct pt_regs *regs) { bool kernel = !event->attr.exclude_callchain_kernel; bool user = !event->attr.exclude_callchain_user; /* Disallow cross-task user callchains. */ bool crosstask = event->ctx->task && event->ctx->task != current; const u32 max_stack = event->attr.sample_max_stack; if (!kernel && !user) return NULL; return get_perf_callchain(regs, 0, kernel, user, max_stack, crosstask, true); } struct perf_callchain_entry * get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, u32 max_stack, bool crosstask, bool add_mark) { struct perf_callchain_entry *entry; struct perf_callchain_entry_ctx ctx; int rctx; entry = get_callchain_entry(&rctx); if (rctx == -1) return NULL; if (!entry) goto exit_put; ctx.entry = entry; ctx.max_stack = max_stack; ctx.nr = entry->nr = init_nr; ctx.contexts = 0; ctx.contexts_maxed = false; if (kernel && !user_mode(regs)) { if (add_mark) perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL); perf_callchain_kernel(&ctx, regs); } if (user) { if (!user_mode(regs)) { if (current->mm) regs = task_pt_regs(current); else regs = NULL; } if (regs) { if (crosstask) goto exit_put; if (add_mark) perf_callchain_store_context(&ctx, PERF_CONTEXT_USER); perf_callchain_user(&ctx, regs); } } exit_put: put_callchain_entry(rctx); return entry; } /* * Used for sysctl_perf_event_max_stack and * sysctl_perf_event_max_contexts_per_stack. */ int perf_event_max_stack_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { int *value = table->data; int new_value = *value, ret; struct ctl_table new_table = *table; new_table.data = &new_value; ret = proc_dointvec_minmax(&new_table, write, buffer, lenp, ppos); if (ret || !write) return ret; mutex_lock(&callchain_mutex); if (atomic_read(&nr_callchain_events)) ret = -EBUSY; else *value = new_value; mutex_unlock(&callchain_mutex); return ret; }