1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/kernel/profile.c
4 * Simple profiling. Manages a direct-mapped profile hit count buffer,
5 * with configurable resolution, support for restricting the cpus on
6 * which profiling is done, and switching between cpu time and
7 * schedule() calls via kernel command line parameters passed at boot.
8 *
9 * Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
10 * Red Hat, July 2004
11 * Consolidation of architecture support code for profiling,
12 * Nadia Yvette Chambers, Oracle, July 2004
13 * Amortized hit count accounting via per-cpu open-addressed hashtables
14 * to resolve timer interrupt livelocks, Nadia Yvette Chambers,
15 * Oracle, 2004
16 */
17
18#include <linux/export.h>
19#include <linux/profile.h>
20#include <linux/memblock.h>
21#include <linux/notifier.h>
22#include <linux/mm.h>
23#include <linux/cpumask.h>
24#include <linux/cpu.h>
25#include <linux/highmem.h>
26#include <linux/mutex.h>
27#include <linux/slab.h>
28#include <linux/vmalloc.h>
29#include <linux/sched/stat.h>
30
31#include <asm/sections.h>
32#include <asm/irq_regs.h>
33#include <asm/ptrace.h>
34
35struct profile_hit {
36 u32 pc, hits;
37};
38#define PROFILE_GRPSHIFT 3
39#define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT)
40#define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit))
41#define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ)
42
43static atomic_t *prof_buffer;
44static unsigned long prof_len;
45static unsigned short int prof_shift;
46
47int prof_on __read_mostly;
48EXPORT_SYMBOL_GPL(prof_on);
49
50static cpumask_var_t prof_cpu_mask;
51#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
52static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
53static DEFINE_PER_CPU(int, cpu_profile_flip);
54static DEFINE_MUTEX(profile_flip_mutex);
55#endif /* CONFIG_SMP */
56
57int profile_setup(char *str)
58{
59 static const char schedstr[] = "schedule";
60 static const char sleepstr[] = "sleep";
61 static const char kvmstr[] = "kvm";
62 const char *select = NULL;
63 int par;
64
65 if (!strncmp(str, sleepstr, strlen(sleepstr))) {
66#ifdef CONFIG_SCHEDSTATS
67 force_schedstat_enabled();
68 prof_on = SLEEP_PROFILING;
69 select = sleepstr;
70#else
71 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
72#endif /* CONFIG_SCHEDSTATS */
73 } else if (!strncmp(str, schedstr, strlen(schedstr))) {
74 prof_on = SCHED_PROFILING;
75 select = schedstr;
76 } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
77 prof_on = KVM_PROFILING;
78 select = kvmstr;
79 } else if (get_option(str: &str, pint: &par)) {
80 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
81 prof_on = CPU_PROFILING;
82 pr_info("kernel profiling enabled (shift: %u)\n",
83 prof_shift);
84 }
85
86 if (select) {
87 if (str[strlen(select)] == ',')
88 str += strlen(select) + 1;
89 if (get_option(str: &str, pint: &par))
90 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
91 pr_info("kernel %s profiling enabled (shift: %u)\n",
92 select, prof_shift);
93 }
94
95 return 1;
96}
97__setup("profile=", profile_setup);
98
99
100int __ref profile_init(void)
101{
102 int buffer_bytes;
103 if (!prof_on)
104 return 0;
105
106 /* only text is profiled */
107 prof_len = (_etext - _stext) >> prof_shift;
108
109 if (!prof_len) {
110 pr_warn("profiling shift: %u too large\n", prof_shift);
111 prof_on = 0;
112 return -EINVAL;
113 }
114
115 buffer_bytes = prof_len*sizeof(atomic_t);
116
117 if (!alloc_cpumask_var(mask: &prof_cpu_mask, GFP_KERNEL))
118 return -ENOMEM;
119
120 cpumask_copy(dstp: prof_cpu_mask, cpu_possible_mask);
121
122 prof_buffer = kzalloc(size: buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
123 if (prof_buffer)
124 return 0;
125
126 prof_buffer = alloc_pages_exact(size: buffer_bytes,
127 GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
128 if (prof_buffer)
129 return 0;
130
131 prof_buffer = vzalloc(size: buffer_bytes);
132 if (prof_buffer)
133 return 0;
134
135 free_cpumask_var(mask: prof_cpu_mask);
136 return -ENOMEM;
137}
138
139#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
140/*
141 * Each cpu has a pair of open-addressed hashtables for pending
142 * profile hits. read_profile() IPI's all cpus to request them
143 * to flip buffers and flushes their contents to prof_buffer itself.
144 * Flip requests are serialized by the profile_flip_mutex. The sole
145 * use of having a second hashtable is for avoiding cacheline
146 * contention that would otherwise happen during flushes of pending
147 * profile hits required for the accuracy of reported profile hits
148 * and so resurrect the interrupt livelock issue.
149 *
150 * The open-addressed hashtables are indexed by profile buffer slot
151 * and hold the number of pending hits to that profile buffer slot on
152 * a cpu in an entry. When the hashtable overflows, all pending hits
153 * are accounted to their corresponding profile buffer slots with
154 * atomic_add() and the hashtable emptied. As numerous pending hits
155 * may be accounted to a profile buffer slot in a hashtable entry,
156 * this amortizes a number of atomic profile buffer increments likely
157 * to be far larger than the number of entries in the hashtable,
158 * particularly given that the number of distinct profile buffer
159 * positions to which hits are accounted during short intervals (e.g.
160 * several seconds) is usually very small. Exclusion from buffer
161 * flipping is provided by interrupt disablement (note that for
162 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
163 * process context).
164 * The hash function is meant to be lightweight as opposed to strong,
165 * and was vaguely inspired by ppc64 firmware-supported inverted
166 * pagetable hash functions, but uses a full hashtable full of finite
167 * collision chains, not just pairs of them.
168 *
169 * -- nyc
170 */
171static void __profile_flip_buffers(void *unused)
172{
173 int cpu = smp_processor_id();
174
175 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
176}
177
178static void profile_flip_buffers(void)
179{
180 int i, j, cpu;
181
182 mutex_lock(&profile_flip_mutex);
183 j = per_cpu(cpu_profile_flip, get_cpu());
184 put_cpu();
185 on_each_cpu(func: __profile_flip_buffers, NULL, wait: 1);
186 for_each_online_cpu(cpu) {
187 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
188 for (i = 0; i < NR_PROFILE_HIT; ++i) {
189 if (!hits[i].hits) {
190 if (hits[i].pc)
191 hits[i].pc = 0;
192 continue;
193 }
194 atomic_add(i: hits[i].hits, v: &prof_buffer[hits[i].pc]);
195 hits[i].hits = hits[i].pc = 0;
196 }
197 }
198 mutex_unlock(lock: &profile_flip_mutex);
199}
200
201static void profile_discard_flip_buffers(void)
202{
203 int i, cpu;
204
205 mutex_lock(&profile_flip_mutex);
206 i = per_cpu(cpu_profile_flip, get_cpu());
207 put_cpu();
208 on_each_cpu(func: __profile_flip_buffers, NULL, wait: 1);
209 for_each_online_cpu(cpu) {
210 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
211 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
212 }
213 mutex_unlock(lock: &profile_flip_mutex);
214}
215
216static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
217{
218 unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
219 int i, j, cpu;
220 struct profile_hit *hits;
221
222 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
223 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
224 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
225 cpu = get_cpu();
226 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
227 if (!hits) {
228 put_cpu();
229 return;
230 }
231 /*
232 * We buffer the global profiler buffer into a per-CPU
233 * queue and thus reduce the number of global (and possibly
234 * NUMA-alien) accesses. The write-queue is self-coalescing:
235 */
236 local_irq_save(flags);
237 do {
238 for (j = 0; j < PROFILE_GRPSZ; ++j) {
239 if (hits[i + j].pc == pc) {
240 hits[i + j].hits += nr_hits;
241 goto out;
242 } else if (!hits[i + j].hits) {
243 hits[i + j].pc = pc;
244 hits[i + j].hits = nr_hits;
245 goto out;
246 }
247 }
248 i = (i + secondary) & (NR_PROFILE_HIT - 1);
249 } while (i != primary);
250
251 /*
252 * Add the current hit(s) and flush the write-queue out
253 * to the global buffer:
254 */
255 atomic_add(i: nr_hits, v: &prof_buffer[pc]);
256 for (i = 0; i < NR_PROFILE_HIT; ++i) {
257 atomic_add(i: hits[i].hits, v: &prof_buffer[hits[i].pc]);
258 hits[i].pc = hits[i].hits = 0;
259 }
260out:
261 local_irq_restore(flags);
262 put_cpu();
263}
264
265static int profile_dead_cpu(unsigned int cpu)
266{
267 struct page *page;
268 int i;
269
270 if (cpumask_available(mask: prof_cpu_mask))
271 cpumask_clear_cpu(cpu, dstp: prof_cpu_mask);
272
273 for (i = 0; i < 2; i++) {
274 if (per_cpu(cpu_profile_hits, cpu)[i]) {
275 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
276 per_cpu(cpu_profile_hits, cpu)[i] = NULL;
277 __free_page(page);
278 }
279 }
280 return 0;
281}
282
283static int profile_prepare_cpu(unsigned int cpu)
284{
285 int i, node = cpu_to_mem(cpu);
286 struct page *page;
287
288 per_cpu(cpu_profile_flip, cpu) = 0;
289
290 for (i = 0; i < 2; i++) {
291 if (per_cpu(cpu_profile_hits, cpu)[i])
292 continue;
293
294 page = __alloc_pages_node(nid: node, GFP_KERNEL | __GFP_ZERO, order: 0);
295 if (!page) {
296 profile_dead_cpu(cpu);
297 return -ENOMEM;
298 }
299 per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);
300
301 }
302 return 0;
303}
304
305static int profile_online_cpu(unsigned int cpu)
306{
307 if (cpumask_available(mask: prof_cpu_mask))
308 cpumask_set_cpu(cpu, dstp: prof_cpu_mask);
309
310 return 0;
311}
312
313#else /* !CONFIG_SMP */
314#define profile_flip_buffers() do { } while (0)
315#define profile_discard_flip_buffers() do { } while (0)
316
317static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
318{
319 unsigned long pc;
320 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
321 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
322}
323#endif /* !CONFIG_SMP */
324
325void profile_hits(int type, void *__pc, unsigned int nr_hits)
326{
327 if (prof_on != type || !prof_buffer)
328 return;
329 do_profile_hits(type, __pc, nr_hits);
330}
331EXPORT_SYMBOL_GPL(profile_hits);
332
333void profile_tick(int type)
334{
335 struct pt_regs *regs = get_irq_regs();
336
337 if (!user_mode(regs) && cpumask_available(mask: prof_cpu_mask) &&
338 cpumask_test_cpu(smp_processor_id(), cpumask: prof_cpu_mask))
339 profile_hit(type, ip: (void *)profile_pc(regs));
340}
341
342#ifdef CONFIG_PROC_FS
343#include <linux/proc_fs.h>
344#include <linux/seq_file.h>
345#include <linux/uaccess.h>
346
347static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
348{
349 seq_printf(m, fmt: "%*pb\n", cpumask_pr_args(prof_cpu_mask));
350 return 0;
351}
352
353static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
354{
355 return single_open(file, prof_cpu_mask_proc_show, NULL);
356}
357
358static ssize_t prof_cpu_mask_proc_write(struct file *file,
359 const char __user *buffer, size_t count, loff_t *pos)
360{
361 cpumask_var_t new_value;
362 int err;
363
364 if (!zalloc_cpumask_var(mask: &new_value, GFP_KERNEL))
365 return -ENOMEM;
366
367 err = cpumask_parse_user(buf: buffer, len: count, dstp: new_value);
368 if (!err) {
369 cpumask_copy(dstp: prof_cpu_mask, srcp: new_value);
370 err = count;
371 }
372 free_cpumask_var(mask: new_value);
373 return err;
374}
375
376static const struct proc_ops prof_cpu_mask_proc_ops = {
377 .proc_open = prof_cpu_mask_proc_open,
378 .proc_read = seq_read,
379 .proc_lseek = seq_lseek,
380 .proc_release = single_release,
381 .proc_write = prof_cpu_mask_proc_write,
382};
383
384void create_prof_cpu_mask(void)
385{
386 /* create /proc/irq/prof_cpu_mask */
387 proc_create(name: "irq/prof_cpu_mask", mode: 0600, NULL, proc_ops: &prof_cpu_mask_proc_ops);
388}
389
390/*
391 * This function accesses profiling information. The returned data is
392 * binary: the sampling step and the actual contents of the profile
393 * buffer. Use of the program readprofile is recommended in order to
394 * get meaningful info out of these data.
395 */
396static ssize_t
397read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
398{
399 unsigned long p = *ppos;
400 ssize_t read;
401 char *pnt;
402 unsigned long sample_step = 1UL << prof_shift;
403
404 profile_flip_buffers();
405 if (p >= (prof_len+1)*sizeof(unsigned int))
406 return 0;
407 if (count > (prof_len+1)*sizeof(unsigned int) - p)
408 count = (prof_len+1)*sizeof(unsigned int) - p;
409 read = 0;
410
411 while (p < sizeof(unsigned int) && count > 0) {
412 if (put_user(*((char *)(&sample_step)+p), buf))
413 return -EFAULT;
414 buf++; p++; count--; read++;
415 }
416 pnt = (char *)prof_buffer + p - sizeof(atomic_t);
417 if (copy_to_user(to: buf, from: (void *)pnt, n: count))
418 return -EFAULT;
419 read += count;
420 *ppos += read;
421 return read;
422}
423
424/* default is to not implement this call */
425int __weak setup_profiling_timer(unsigned mult)
426{
427 return -EINVAL;
428}
429
430/*
431 * Writing to /proc/profile resets the counters
432 *
433 * Writing a 'profiling multiplier' value into it also re-sets the profiling
434 * interrupt frequency, on architectures that support this.
435 */
436static ssize_t write_profile(struct file *file, const char __user *buf,
437 size_t count, loff_t *ppos)
438{
439#ifdef CONFIG_SMP
440 if (count == sizeof(int)) {
441 unsigned int multiplier;
442
443 if (copy_from_user(to: &multiplier, from: buf, n: sizeof(int)))
444 return -EFAULT;
445
446 if (setup_profiling_timer(multiplier))
447 return -EINVAL;
448 }
449#endif
450 profile_discard_flip_buffers();
451 memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
452 return count;
453}
454
455static const struct proc_ops profile_proc_ops = {
456 .proc_read = read_profile,
457 .proc_write = write_profile,
458 .proc_lseek = default_llseek,
459};
460
461int __ref create_proc_profile(void)
462{
463 struct proc_dir_entry *entry;
464#ifdef CONFIG_SMP
465 enum cpuhp_state online_state;
466#endif
467
468 int err = 0;
469
470 if (!prof_on)
471 return 0;
472#ifdef CONFIG_SMP
473 err = cpuhp_setup_state(state: CPUHP_PROFILE_PREPARE, name: "PROFILE_PREPARE",
474 startup: profile_prepare_cpu, teardown: profile_dead_cpu);
475 if (err)
476 return err;
477
478 err = cpuhp_setup_state(state: CPUHP_AP_ONLINE_DYN, name: "AP_PROFILE_ONLINE",
479 startup: profile_online_cpu, NULL);
480 if (err < 0)
481 goto err_state_prep;
482 online_state = err;
483 err = 0;
484#endif
485 entry = proc_create(name: "profile", S_IWUSR | S_IRUGO,
486 NULL, proc_ops: &profile_proc_ops);
487 if (!entry)
488 goto err_state_onl;
489 proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
490
491 return err;
492err_state_onl:
493#ifdef CONFIG_SMP
494 cpuhp_remove_state(state: online_state);
495err_state_prep:
496 cpuhp_remove_state(state: CPUHP_PROFILE_PREPARE);
497#endif
498 return err;
499}
500subsys_initcall(create_proc_profile);
501#endif /* CONFIG_PROC_FS */
502

source code of linux/kernel/profile.c