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TOMOYO Linux Cross Reference
Linux/kernel/events/callchain.c

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  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(void)
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                 goto exit;
125         }
126 
127         err = alloc_callchain_buffers();
128 exit:
129         if (err)
130                 atomic_dec(&nr_callchain_events);
131 
132         mutex_unlock(&callchain_mutex);
133 
134         return err;
135 }
136 
137 void put_callchain_buffers(void)
138 {
139         if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) {
140                 release_callchain_buffers();
141                 mutex_unlock(&callchain_mutex);
142         }
143 }
144 
145 static struct perf_callchain_entry *get_callchain_entry(int *rctx)
146 {
147         int cpu;
148         struct callchain_cpus_entries *entries;
149 
150         *rctx = get_recursion_context(this_cpu_ptr(callchain_recursion));
151         if (*rctx == -1)
152                 return NULL;
153 
154         entries = rcu_dereference(callchain_cpus_entries);
155         if (!entries)
156                 return NULL;
157 
158         cpu = smp_processor_id();
159 
160         return (((void *)entries->cpu_entries[cpu]) +
161                 (*rctx * perf_callchain_entry__sizeof()));
162 }
163 
164 static void
165 put_callchain_entry(int rctx)
166 {
167         put_recursion_context(this_cpu_ptr(callchain_recursion), rctx);
168 }
169 
170 struct perf_callchain_entry *
171 perf_callchain(struct perf_event *event, struct pt_regs *regs)
172 {
173         bool kernel = !event->attr.exclude_callchain_kernel;
174         bool user   = !event->attr.exclude_callchain_user;
175         /* Disallow cross-task user callchains. */
176         bool crosstask = event->ctx->task && event->ctx->task != current;
177 
178         if (!kernel && !user)
179                 return NULL;
180 
181         return get_perf_callchain(regs, 0, kernel, user, sysctl_perf_event_max_stack, crosstask, true);
182 }
183 
184 struct perf_callchain_entry *
185 get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
186                    u32 max_stack, bool crosstask, bool add_mark)
187 {
188         struct perf_callchain_entry *entry;
189         struct perf_callchain_entry_ctx ctx;
190         int rctx;
191 
192         entry = get_callchain_entry(&rctx);
193         if (rctx == -1)
194                 return NULL;
195 
196         if (!entry)
197                 goto exit_put;
198 
199         ctx.entry     = entry;
200         ctx.max_stack = max_stack;
201         ctx.nr        = entry->nr = init_nr;
202         ctx.contexts       = 0;
203         ctx.contexts_maxed = false;
204 
205         if (kernel && !user_mode(regs)) {
206                 if (add_mark)
207                         perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL);
208                 perf_callchain_kernel(&ctx, regs);
209         }
210 
211         if (user) {
212                 if (!user_mode(regs)) {
213                         if  (current->mm)
214                                 regs = task_pt_regs(current);
215                         else
216                                 regs = NULL;
217                 }
218 
219                 if (regs) {
220                         if (crosstask)
221                                 goto exit_put;
222 
223                         if (add_mark)
224                                 perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
225                         perf_callchain_user(&ctx, regs);
226                 }
227         }
228 
229 exit_put:
230         put_callchain_entry(rctx);
231 
232         return entry;
233 }
234 
235 /*
236  * Used for sysctl_perf_event_max_stack and
237  * sysctl_perf_event_max_contexts_per_stack.
238  */
239 int perf_event_max_stack_handler(struct ctl_table *table, int write,
240                                  void __user *buffer, size_t *lenp, loff_t *ppos)
241 {
242         int *value = table->data;
243         int new_value = *value, ret;
244         struct ctl_table new_table = *table;
245 
246         new_table.data = &new_value;
247         ret = proc_dointvec_minmax(&new_table, write, buffer, lenp, ppos);
248         if (ret || !write)
249                 return ret;
250 
251         mutex_lock(&callchain_mutex);
252         if (atomic_read(&nr_callchain_events))
253                 ret = -EBUSY;
254         else
255                 *value = new_value;
256 
257         mutex_unlock(&callchain_mutex);
258 
259         return ret;
260 }
261 

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