Borislav Petkov | 9251f90 | 2011-10-16 17:15:04 +0200 | [diff] [blame] | 1 | /* |
| 2 | * Performance events callchain code, extracted from core.c: |
| 3 | * |
| 4 | * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de> |
| 5 | * Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar |
| 6 | * Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> |
| 7 | * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com> |
| 8 | * |
| 9 | * For licensing details see kernel-base/COPYING |
| 10 | */ |
| 11 | |
| 12 | #include <linux/perf_event.h> |
| 13 | #include <linux/slab.h> |
| 14 | #include "internal.h" |
| 15 | |
| 16 | struct callchain_cpus_entries { |
| 17 | struct rcu_head rcu_head; |
| 18 | struct perf_callchain_entry *cpu_entries[0]; |
| 19 | }; |
| 20 | |
| 21 | static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]); |
| 22 | static atomic_t nr_callchain_events; |
| 23 | static DEFINE_MUTEX(callchain_mutex); |
| 24 | static struct callchain_cpus_entries *callchain_cpus_entries; |
| 25 | |
| 26 | |
| 27 | __weak void perf_callchain_kernel(struct perf_callchain_entry *entry, |
| 28 | struct pt_regs *regs) |
| 29 | { |
| 30 | } |
| 31 | |
| 32 | __weak void perf_callchain_user(struct perf_callchain_entry *entry, |
| 33 | struct pt_regs *regs) |
| 34 | { |
| 35 | } |
| 36 | |
| 37 | static void release_callchain_buffers_rcu(struct rcu_head *head) |
| 38 | { |
| 39 | struct callchain_cpus_entries *entries; |
| 40 | int cpu; |
| 41 | |
| 42 | entries = container_of(head, struct callchain_cpus_entries, rcu_head); |
| 43 | |
| 44 | for_each_possible_cpu(cpu) |
| 45 | kfree(entries->cpu_entries[cpu]); |
| 46 | |
| 47 | kfree(entries); |
| 48 | } |
| 49 | |
| 50 | static void release_callchain_buffers(void) |
| 51 | { |
| 52 | struct callchain_cpus_entries *entries; |
| 53 | |
| 54 | entries = callchain_cpus_entries; |
| 55 | rcu_assign_pointer(callchain_cpus_entries, NULL); |
| 56 | call_rcu(&entries->rcu_head, release_callchain_buffers_rcu); |
| 57 | } |
| 58 | |
| 59 | static int alloc_callchain_buffers(void) |
| 60 | { |
| 61 | int cpu; |
| 62 | int size; |
| 63 | struct callchain_cpus_entries *entries; |
| 64 | |
| 65 | /* |
| 66 | * We can't use the percpu allocation API for data that can be |
| 67 | * accessed from NMI. Use a temporary manual per cpu allocation |
| 68 | * until that gets sorted out. |
| 69 | */ |
| 70 | size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]); |
| 71 | |
| 72 | entries = kzalloc(size, GFP_KERNEL); |
| 73 | if (!entries) |
| 74 | return -ENOMEM; |
| 75 | |
| 76 | size = sizeof(struct perf_callchain_entry) * PERF_NR_CONTEXTS; |
| 77 | |
| 78 | for_each_possible_cpu(cpu) { |
| 79 | entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL, |
| 80 | cpu_to_node(cpu)); |
| 81 | if (!entries->cpu_entries[cpu]) |
| 82 | goto fail; |
| 83 | } |
| 84 | |
| 85 | rcu_assign_pointer(callchain_cpus_entries, entries); |
| 86 | |
| 87 | return 0; |
| 88 | |
| 89 | fail: |
| 90 | for_each_possible_cpu(cpu) |
| 91 | kfree(entries->cpu_entries[cpu]); |
| 92 | kfree(entries); |
| 93 | |
| 94 | return -ENOMEM; |
| 95 | } |
| 96 | |
| 97 | int get_callchain_buffers(void) |
| 98 | { |
| 99 | int err = 0; |
| 100 | int count; |
| 101 | |
| 102 | mutex_lock(&callchain_mutex); |
| 103 | |
| 104 | count = atomic_inc_return(&nr_callchain_events); |
| 105 | if (WARN_ON_ONCE(count < 1)) { |
| 106 | err = -EINVAL; |
| 107 | goto exit; |
| 108 | } |
| 109 | |
| 110 | if (count > 1) { |
| 111 | /* If the allocation failed, give up */ |
| 112 | if (!callchain_cpus_entries) |
| 113 | err = -ENOMEM; |
| 114 | goto exit; |
| 115 | } |
| 116 | |
| 117 | err = alloc_callchain_buffers(); |
Borislav Petkov | 9251f90 | 2011-10-16 17:15:04 +0200 | [diff] [blame] | 118 | exit: |
| 119 | mutex_unlock(&callchain_mutex); |
| 120 | |
| 121 | return err; |
| 122 | } |
| 123 | |
| 124 | void put_callchain_buffers(void) |
| 125 | { |
| 126 | if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) { |
| 127 | release_callchain_buffers(); |
| 128 | mutex_unlock(&callchain_mutex); |
| 129 | } |
| 130 | } |
| 131 | |
| 132 | static struct perf_callchain_entry *get_callchain_entry(int *rctx) |
| 133 | { |
| 134 | int cpu; |
| 135 | struct callchain_cpus_entries *entries; |
| 136 | |
| 137 | *rctx = get_recursion_context(__get_cpu_var(callchain_recursion)); |
| 138 | if (*rctx == -1) |
| 139 | return NULL; |
| 140 | |
| 141 | entries = rcu_dereference(callchain_cpus_entries); |
| 142 | if (!entries) |
| 143 | return NULL; |
| 144 | |
| 145 | cpu = smp_processor_id(); |
| 146 | |
| 147 | return &entries->cpu_entries[cpu][*rctx]; |
| 148 | } |
| 149 | |
| 150 | static void |
| 151 | put_callchain_entry(int rctx) |
| 152 | { |
| 153 | put_recursion_context(__get_cpu_var(callchain_recursion), rctx); |
| 154 | } |
| 155 | |
| 156 | struct perf_callchain_entry *perf_callchain(struct pt_regs *regs) |
| 157 | { |
| 158 | int rctx; |
| 159 | struct perf_callchain_entry *entry; |
| 160 | |
| 161 | |
| 162 | entry = get_callchain_entry(&rctx); |
| 163 | if (rctx == -1) |
| 164 | return NULL; |
| 165 | |
| 166 | if (!entry) |
| 167 | goto exit_put; |
| 168 | |
| 169 | entry->nr = 0; |
| 170 | |
| 171 | if (!user_mode(regs)) { |
| 172 | perf_callchain_store(entry, PERF_CONTEXT_KERNEL); |
| 173 | perf_callchain_kernel(entry, regs); |
| 174 | if (current->mm) |
| 175 | regs = task_pt_regs(current); |
| 176 | else |
| 177 | regs = NULL; |
| 178 | } |
| 179 | |
| 180 | if (regs) { |
| 181 | perf_callchain_store(entry, PERF_CONTEXT_USER); |
| 182 | perf_callchain_user(entry, regs); |
| 183 | } |
| 184 | |
| 185 | exit_put: |
| 186 | put_callchain_entry(rctx); |
| 187 | |
| 188 | return entry; |
| 189 | } |