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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Performance events callchain code, extracted from core.c:
4 *
5 * Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
6 * Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
7 * Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra
8 * Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
9 */
10
11#include <linux/perf_event.h>
12#include <linux/slab.h>
13#include <linux/sched/task_stack.h>
14
15#include "internal.h"
16
17struct callchain_cpus_entries {
18 struct rcu_head rcu_head;
19 struct perf_callchain_entry *cpu_entries[0];
20};
21
22int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH;
23int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK;
24
25static inline size_t perf_callchain_entry__sizeof(void)
26{
27 return (sizeof(struct perf_callchain_entry) +
28 sizeof(__u64) * (sysctl_perf_event_max_stack +
29 sysctl_perf_event_max_contexts_per_stack));
30}
31
32static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
33static atomic_t nr_callchain_events;
34static DEFINE_MUTEX(callchain_mutex);
35static struct callchain_cpus_entries *callchain_cpus_entries;
36
37
38__weak void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
39 struct pt_regs *regs)
40{
41}
42
43__weak void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
44 struct pt_regs *regs)
45{
46}
47
48static void release_callchain_buffers_rcu(struct rcu_head *head)
49{
50 struct callchain_cpus_entries *entries;
51 int cpu;
52
53 entries = container_of(head, struct callchain_cpus_entries, rcu_head);
54
55 for_each_possible_cpu(cpu)
56 kfree(entries->cpu_entries[cpu]);
57
58 kfree(entries);
59}
60
61static void release_callchain_buffers(void)
62{
63 struct callchain_cpus_entries *entries;
64
65 entries = callchain_cpus_entries;
66 RCU_INIT_POINTER(callchain_cpus_entries, NULL);
67 call_rcu(&entries->rcu_head, release_callchain_buffers_rcu);
68}
69
70static int alloc_callchain_buffers(void)
71{
72 int cpu;
73 int size;
74 struct callchain_cpus_entries *entries;
75
76 /*
77 * We can't use the percpu allocation API for data that can be
78 * accessed from NMI. Use a temporary manual per cpu allocation
79 * until that gets sorted out.
80 */
81 size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]);
82
83 entries = kzalloc(size, GFP_KERNEL);
84 if (!entries)
85 return -ENOMEM;
86
87 size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS;
88
89 for_each_possible_cpu(cpu) {
90 entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL,
91 cpu_to_node(cpu));
92 if (!entries->cpu_entries[cpu])
93 goto fail;
94 }
95
96 rcu_assign_pointer(callchain_cpus_entries, entries);
97
98 return 0;
99
100fail:
101 for_each_possible_cpu(cpu)
102 kfree(entries->cpu_entries[cpu]);
103 kfree(entries);
104
105 return -ENOMEM;
106}
107
108int get_callchain_buffers(int event_max_stack)
109{
110 int err = 0;
111 int count;
112
113 mutex_lock(&callchain_mutex);
114
115 count = atomic_inc_return(&nr_callchain_events);
116 if (WARN_ON_ONCE(count < 1)) {
117 err = -EINVAL;
118 goto exit;
119 }
120
121 /*
122 * If requesting per event more than the global cap,
123 * return a different error to help userspace figure
124 * this out.
125 *
126 * And also do it here so that we have &callchain_mutex held.
127 */
128 if (event_max_stack > sysctl_perf_event_max_stack) {
129 err = -EOVERFLOW;
130 goto exit;
131 }
132
133 if (count == 1)
134 err = alloc_callchain_buffers();
135exit:
136 if (err)
137 atomic_dec(&nr_callchain_events);
138
139 mutex_unlock(&callchain_mutex);
140
141 return err;
142}
143
144void put_callchain_buffers(void)
145{
146 if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) {
147 release_callchain_buffers();
148 mutex_unlock(&callchain_mutex);
149 }
150}
151
152static struct perf_callchain_entry *get_callchain_entry(int *rctx)
153{
154 int cpu;
155 struct callchain_cpus_entries *entries;
156
157 *rctx = get_recursion_context(this_cpu_ptr(callchain_recursion));
158 if (*rctx == -1)
159 return NULL;
160
161 entries = rcu_dereference(callchain_cpus_entries);
162 if (!entries)
163 return NULL;
164
165 cpu = smp_processor_id();
166
167 return (((void *)entries->cpu_entries[cpu]) +
168 (*rctx * perf_callchain_entry__sizeof()));
169}
170
171static void
172put_callchain_entry(int rctx)
173{
174 put_recursion_context(this_cpu_ptr(callchain_recursion), rctx);
175}
176
177struct perf_callchain_entry *
178get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
179 u32 max_stack, bool crosstask, bool add_mark)
180{
181 struct perf_callchain_entry *entry;
182 struct perf_callchain_entry_ctx ctx;
183 int rctx;
184
185 entry = get_callchain_entry(&rctx);
186 if (rctx == -1)
187 return NULL;
188
189 if (!entry)
190 goto exit_put;
191
192 ctx.entry = entry;
193 ctx.max_stack = max_stack;
194 ctx.nr = entry->nr = init_nr;
195 ctx.contexts = 0;
196 ctx.contexts_maxed = false;
197
198 if (kernel && !user_mode(regs)) {
199 if (add_mark)
200 perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL);
201 perf_callchain_kernel(&ctx, regs);
202 }
203
204 if (user) {
205 if (!user_mode(regs)) {
206 if (current->mm)
207 regs = task_pt_regs(current);
208 else
209 regs = NULL;
210 }
211
212 if (regs) {
213 mm_segment_t fs;
214
215 if (crosstask)
216 goto exit_put;
217
218 if (add_mark)
219 perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
220
221 fs = get_fs();
222 set_fs(USER_DS);
223 perf_callchain_user(&ctx, regs);
224 set_fs(fs);
225 }
226 }
227
228exit_put:
229 put_callchain_entry(rctx);
230
231 return entry;
232}
233
234/*
235 * Used for sysctl_perf_event_max_stack and
236 * sysctl_perf_event_max_contexts_per_stack.
237 */
238int perf_event_max_stack_handler(struct ctl_table *table, int write,
239 void __user *buffer, size_t *lenp, loff_t *ppos)
240{
241 int *value = table->data;
242 int new_value = *value, ret;
243 struct ctl_table new_table = *table;
244
245 new_table.data = &new_value;
246 ret = proc_dointvec_minmax(&new_table, write, buffer, lenp, ppos);
247 if (ret || !write)
248 return ret;
249
250 mutex_lock(&callchain_mutex);
251 if (atomic_read(&nr_callchain_events))
252 ret = -EBUSY;
253 else
254 *value = new_value;
255
256 mutex_unlock(&callchain_mutex);
257
258 return ret;
259}
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
16struct callchain_cpus_entries {
17 struct rcu_head rcu_head;
18 struct perf_callchain_entry *cpu_entries[0];
19};
20
21static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
22static atomic_t nr_callchain_events;
23static DEFINE_MUTEX(callchain_mutex);
24static 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
37static 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
50static 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
59static 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
89fail:
90 for_each_possible_cpu(cpu)
91 kfree(entries->cpu_entries[cpu]);
92 kfree(entries);
93
94 return -ENOMEM;
95}
96
97int 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();
118exit:
119 mutex_unlock(&callchain_mutex);
120
121 return err;
122}
123
124void 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
132static 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
150static void
151put_callchain_entry(int rctx)
152{
153 put_recursion_context(__get_cpu_var(callchain_recursion), rctx);
154}
155
156struct 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
185exit_put:
186 put_callchain_entry(rctx);
187
188 return entry;
189}