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 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 int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH; 22 int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK; 23 24 static inline size_t perf_callchain_entry__sizeof(void) 25 { 26 return (sizeof(struct perf_callchain_entry) + 27 sizeof(__u64) * (sysctl_perf_event_max_stack + 28 sysctl_perf_event_max_contexts_per_stack)); 29 } 30 31 static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]); 32 static atomic_t nr_callchain_events; 33 static DEFINE_MUTEX(callchain_mutex); 34 static struct callchain_cpus_entries *callchain_cpus_entries; 35 36 37 __weak void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, 38 struct pt_regs *regs) 39 { 40 } 41 42 __weak void perf_callchain_user(struct perf_callchain_entry_ctx *entry, 43 struct pt_regs *regs) 44 { 45 } 46 47 static void release_callchain_buffers_rcu(struct rcu_head *head) 48 { 49 struct callchain_cpus_entries *entries; 50 int cpu; 51 52 entries = container_of(head, struct callchain_cpus_entries, rcu_head); 53 54 for_each_possible_cpu(cpu) 55 kfree(entries->cpu_entries[cpu]); 56 57 kfree(entries); 58 } 59 60 static void release_callchain_buffers(void) 61 { 62 struct callchain_cpus_entries *entries; 63 64 entries = callchain_cpus_entries; 65 RCU_INIT_POINTER(callchain_cpus_entries, NULL); 66 call_rcu(&entries->rcu_head, release_callchain_buffers_rcu); 67 } 68 69 static int alloc_callchain_buffers(void) 70 { 71 int cpu; 72 int size; 73 struct callchain_cpus_entries *entries; 74 75 /* 76 * We can't use the percpu allocation API for data that can be 77 * accessed from NMI. Use a temporary manual per cpu allocation 78 * until that gets sorted out. 79 */ 80 size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]); 81 82 entries = kzalloc(size, GFP_KERNEL); 83 if (!entries) 84 return -ENOMEM; 85 86 size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS; 87 88 for_each_possible_cpu(cpu) { 89 entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL, 90 cpu_to_node(cpu)); 91 if (!entries->cpu_entries[cpu]) 92 goto fail; 93 } 94 95 rcu_assign_pointer(callchain_cpus_entries, entries); 96 97 return 0; 98 99 fail: 100 for_each_possible_cpu(cpu) 101 kfree(entries->cpu_entries[cpu]); 102 kfree(entries); 103 104 return -ENOMEM; 105 } 106 107 int get_callchain_buffers(int event_max_stack) 108 { 109 int err = 0; 110 int count; 111 112 mutex_lock(&callchain_mutex); 113 114 count = atomic_inc_return(&nr_callchain_events); 115 if (WARN_ON_ONCE(count < 1)) { 116 err = -EINVAL; 117 goto exit; 118 } 119 120 if (count > 1) { 121 /* If the allocation failed, give up */ 122 if (!callchain_cpus_entries) 123 err = -ENOMEM; 124 /* 125 * If requesting per event more than the global cap, 126 * return a different error to help userspace figure 127 * this out. 128 * 129 * And also do it here so that we have &callchain_mutex held. 130 */ 131 if (event_max_stack > sysctl_perf_event_max_stack) 132 err = -EOVERFLOW; 133 goto exit; 134 } 135 136 err = alloc_callchain_buffers(); 137 exit: 138 if (err) 139 atomic_dec(&nr_callchain_events); 140 141 mutex_unlock(&callchain_mutex); 142 143 return err; 144 } 145 146 void put_callchain_buffers(void) 147 { 148 if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) { 149 release_callchain_buffers(); 150 mutex_unlock(&callchain_mutex); 151 } 152 } 153 154 static struct perf_callchain_entry *get_callchain_entry(int *rctx) 155 { 156 int cpu; 157 struct callchain_cpus_entries *entries; 158 159 *rctx = get_recursion_context(this_cpu_ptr(callchain_recursion)); 160 if (*rctx == -1) 161 return NULL; 162 163 entries = rcu_dereference(callchain_cpus_entries); 164 if (!entries) 165 return NULL; 166 167 cpu = smp_processor_id(); 168 169 return (((void *)entries->cpu_entries[cpu]) + 170 (*rctx * perf_callchain_entry__sizeof())); 171 } 172 173 static void 174 put_callchain_entry(int rctx) 175 { 176 put_recursion_context(this_cpu_ptr(callchain_recursion), rctx); 177 } 178 179 struct perf_callchain_entry * 180 perf_callchain(struct perf_event *event, struct pt_regs *regs) 181 { 182 bool kernel = !event->attr.exclude_callchain_kernel; 183 bool user = !event->attr.exclude_callchain_user; 184 /* Disallow cross-task user callchains. */ 185 bool crosstask = event->ctx->task && event->ctx->task != current; 186 const u32 max_stack = event->attr.sample_max_stack; 187 188 if (!kernel && !user) 189 return NULL; 190 191 return get_perf_callchain(regs, 0, kernel, user, max_stack, crosstask, true); 192 } 193 194 struct perf_callchain_entry * 195 get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user, 196 u32 max_stack, bool crosstask, bool add_mark) 197 { 198 struct perf_callchain_entry *entry; 199 struct perf_callchain_entry_ctx ctx; 200 int rctx; 201 202 entry = get_callchain_entry(&rctx); 203 if (rctx == -1) 204 return NULL; 205 206 if (!entry) 207 goto exit_put; 208 209 ctx.entry = entry; 210 ctx.max_stack = max_stack; 211 ctx.nr = entry->nr = init_nr; 212 ctx.contexts = 0; 213 ctx.contexts_maxed = false; 214 215 if (kernel && !user_mode(regs)) { 216 if (add_mark) 217 perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL); 218 perf_callchain_kernel(&ctx, regs); 219 } 220 221 if (user) { 222 if (!user_mode(regs)) { 223 if (current->mm) 224 regs = task_pt_regs(current); 225 else 226 regs = NULL; 227 } 228 229 if (regs) { 230 if (crosstask) 231 goto exit_put; 232 233 if (add_mark) 234 perf_callchain_store_context(&ctx, PERF_CONTEXT_USER); 235 perf_callchain_user(&ctx, regs); 236 } 237 } 238 239 exit_put: 240 put_callchain_entry(rctx); 241 242 return entry; 243 } 244 245 /* 246 * Used for sysctl_perf_event_max_stack and 247 * sysctl_perf_event_max_contexts_per_stack. 248 */ 249 int perf_event_max_stack_handler(struct ctl_table *table, int write, 250 void __user *buffer, size_t *lenp, loff_t *ppos) 251 { 252 int *value = table->data; 253 int new_value = *value, ret; 254 struct ctl_table new_table = *table; 255 256 new_table.data = &new_value; 257 ret = proc_dointvec_minmax(&new_table, write, buffer, lenp, ppos); 258 if (ret || !write) 259 return ret; 260 261 mutex_lock(&callchain_mutex); 262 if (atomic_read(&nr_callchain_events)) 263 ret = -EBUSY; 264 else 265 *value = new_value; 266 267 mutex_unlock(&callchain_mutex); 268 269 return ret; 270 } 271