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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
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 <linux/sched/task_stack.h>
15
16#include "internal.h"
17
18struct callchain_cpus_entries {
19 struct rcu_head rcu_head;
20 struct perf_callchain_entry *cpu_entries[0];
21};
22
23int sysctl_perf_event_max_stack __read_mostly = PERF_MAX_STACK_DEPTH;
24int sysctl_perf_event_max_contexts_per_stack __read_mostly = PERF_MAX_CONTEXTS_PER_STACK;
25
26static inline size_t perf_callchain_entry__sizeof(void)
27{
28 return (sizeof(struct perf_callchain_entry) +
29 sizeof(__u64) * (sysctl_perf_event_max_stack +
30 sysctl_perf_event_max_contexts_per_stack));
31}
32
33static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
34static atomic_t nr_callchain_events;
35static DEFINE_MUTEX(callchain_mutex);
36static struct callchain_cpus_entries *callchain_cpus_entries;
37
38
39__weak void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
40 struct pt_regs *regs)
41{
42}
43
44__weak void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
45 struct pt_regs *regs)
46{
47}
48
49static void release_callchain_buffers_rcu(struct rcu_head *head)
50{
51 struct callchain_cpus_entries *entries;
52 int cpu;
53
54 entries = container_of(head, struct callchain_cpus_entries, rcu_head);
55
56 for_each_possible_cpu(cpu)
57 kfree(entries->cpu_entries[cpu]);
58
59 kfree(entries);
60}
61
62static void release_callchain_buffers(void)
63{
64 struct callchain_cpus_entries *entries;
65
66 entries = callchain_cpus_entries;
67 RCU_INIT_POINTER(callchain_cpus_entries, NULL);
68 call_rcu(&entries->rcu_head, release_callchain_buffers_rcu);
69}
70
71static int alloc_callchain_buffers(void)
72{
73 int cpu;
74 int size;
75 struct callchain_cpus_entries *entries;
76
77 /*
78 * We can't use the percpu allocation API for data that can be
79 * accessed from NMI. Use a temporary manual per cpu allocation
80 * until that gets sorted out.
81 */
82 size = offsetof(struct callchain_cpus_entries, cpu_entries[nr_cpu_ids]);
83
84 entries = kzalloc(size, GFP_KERNEL);
85 if (!entries)
86 return -ENOMEM;
87
88 size = perf_callchain_entry__sizeof() * PERF_NR_CONTEXTS;
89
90 for_each_possible_cpu(cpu) {
91 entries->cpu_entries[cpu] = kmalloc_node(size, GFP_KERNEL,
92 cpu_to_node(cpu));
93 if (!entries->cpu_entries[cpu])
94 goto fail;
95 }
96
97 rcu_assign_pointer(callchain_cpus_entries, entries);
98
99 return 0;
100
101fail:
102 for_each_possible_cpu(cpu)
103 kfree(entries->cpu_entries[cpu]);
104 kfree(entries);
105
106 return -ENOMEM;
107}
108
109int get_callchain_buffers(int event_max_stack)
110{
111 int err = 0;
112 int count;
113
114 mutex_lock(&callchain_mutex);
115
116 count = atomic_inc_return(&nr_callchain_events);
117 if (WARN_ON_ONCE(count < 1)) {
118 err = -EINVAL;
119 goto exit;
120 }
121
122 /*
123 * If requesting per event more than the global cap,
124 * return a different error to help userspace figure
125 * this out.
126 *
127 * And also do it here so that we have &callchain_mutex held.
128 */
129 if (event_max_stack > sysctl_perf_event_max_stack) {
130 err = -EOVERFLOW;
131 goto exit;
132 }
133
134 if (count == 1)
135 err = alloc_callchain_buffers();
136exit:
137 if (err)
138 atomic_dec(&nr_callchain_events);
139
140 mutex_unlock(&callchain_mutex);
141
142 return err;
143}
144
145void put_callchain_buffers(void)
146{
147 if (atomic_dec_and_mutex_lock(&nr_callchain_events, &callchain_mutex)) {
148 release_callchain_buffers();
149 mutex_unlock(&callchain_mutex);
150 }
151}
152
153static struct perf_callchain_entry *get_callchain_entry(int *rctx)
154{
155 int cpu;
156 struct callchain_cpus_entries *entries;
157
158 *rctx = get_recursion_context(this_cpu_ptr(callchain_recursion));
159 if (*rctx == -1)
160 return NULL;
161
162 entries = rcu_dereference(callchain_cpus_entries);
163 if (!entries)
164 return NULL;
165
166 cpu = smp_processor_id();
167
168 return (((void *)entries->cpu_entries[cpu]) +
169 (*rctx * perf_callchain_entry__sizeof()));
170}
171
172static void
173put_callchain_entry(int rctx)
174{
175 put_recursion_context(this_cpu_ptr(callchain_recursion), rctx);
176}
177
178struct perf_callchain_entry *
179get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
180 u32 max_stack, bool crosstask, bool add_mark)
181{
182 struct perf_callchain_entry *entry;
183 struct perf_callchain_entry_ctx ctx;
184 int rctx;
185
186 entry = get_callchain_entry(&rctx);
187 if (rctx == -1)
188 return NULL;
189
190 if (!entry)
191 goto exit_put;
192
193 ctx.entry = entry;
194 ctx.max_stack = max_stack;
195 ctx.nr = entry->nr = init_nr;
196 ctx.contexts = 0;
197 ctx.contexts_maxed = false;
198
199 if (kernel && !user_mode(regs)) {
200 if (add_mark)
201 perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL);
202 perf_callchain_kernel(&ctx, regs);
203 }
204
205 if (user) {
206 if (!user_mode(regs)) {
207 if (current->mm)
208 regs = task_pt_regs(current);
209 else
210 regs = NULL;
211 }
212
213 if (regs) {
214 mm_segment_t fs;
215
216 if (crosstask)
217 goto exit_put;
218
219 if (add_mark)
220 perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);
221
222 fs = get_fs();
223 set_fs(USER_DS);
224 perf_callchain_user(&ctx, regs);
225 set_fs(fs);
226 }
227 }
228
229exit_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 */
239int 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}