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
35 struct 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
43 static atomic_t *prof_buffer;
44 static unsigned long prof_len;
45 static unsigned short int prof_shift;
46
47 int prof_on __read_mostly;
48 EXPORT_SYMBOL_GPL(prof_on);
49
50 static cpumask_var_t prof_cpu_mask;
51 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
52 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
53 static DEFINE_PER_CPU(int, cpu_profile_flip);
54 static DEFINE_MUTEX(profile_flip_mutex);
55 #endif /* CONFIG_SMP */
56
profile_setup(char * str)57 int profile_setup(char *str)
58 {
59 static const char schedstr[] = "schedule";
60 static const char sleepstr[] = "sleep";
61 static const char kvmstr[] = "kvm";
62 int par;
63
64 if (!strncmp(str, sleepstr, strlen(sleepstr))) {
65 #ifdef CONFIG_SCHEDSTATS
66 force_schedstat_enabled();
67 prof_on = SLEEP_PROFILING;
68 if (str[strlen(sleepstr)] == ',')
69 str += strlen(sleepstr) + 1;
70 if (get_option(&str, &par))
71 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
72 pr_info("kernel sleep profiling enabled (shift: %u)\n",
73 prof_shift);
74 #else
75 pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
76 #endif /* CONFIG_SCHEDSTATS */
77 } else if (!strncmp(str, schedstr, strlen(schedstr))) {
78 prof_on = SCHED_PROFILING;
79 if (str[strlen(schedstr)] == ',')
80 str += strlen(schedstr) + 1;
81 if (get_option(&str, &par))
82 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
83 pr_info("kernel schedule profiling enabled (shift: %u)\n",
84 prof_shift);
85 } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
86 prof_on = KVM_PROFILING;
87 if (str[strlen(kvmstr)] == ',')
88 str += strlen(kvmstr) + 1;
89 if (get_option(&str, &par))
90 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
91 pr_info("kernel KVM profiling enabled (shift: %u)\n",
92 prof_shift);
93 } else if (get_option(&str, &par)) {
94 prof_shift = clamp(par, 0, BITS_PER_LONG - 1);
95 prof_on = CPU_PROFILING;
96 pr_info("kernel profiling enabled (shift: %u)\n",
97 prof_shift);
98 }
99 return 1;
100 }
101 __setup("profile=", profile_setup);
102
103
profile_init(void)104 int __ref profile_init(void)
105 {
106 int buffer_bytes;
107 if (!prof_on)
108 return 0;
109
110 /* only text is profiled */
111 prof_len = (_etext - _stext) >> prof_shift;
112 buffer_bytes = prof_len*sizeof(atomic_t);
113
114 if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
115 return -ENOMEM;
116
117 cpumask_copy(prof_cpu_mask, cpu_possible_mask);
118
119 prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
120 if (prof_buffer)
121 return 0;
122
123 prof_buffer = alloc_pages_exact(buffer_bytes,
124 GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
125 if (prof_buffer)
126 return 0;
127
128 prof_buffer = vzalloc(buffer_bytes);
129 if (prof_buffer)
130 return 0;
131
132 free_cpumask_var(prof_cpu_mask);
133 return -ENOMEM;
134 }
135
136 /* Profile event notifications */
137
138 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
139 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
140 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
141
profile_task_exit(struct task_struct * task)142 void profile_task_exit(struct task_struct *task)
143 {
144 blocking_notifier_call_chain(&task_exit_notifier, 0, task);
145 }
146
profile_handoff_task(struct task_struct * task)147 int profile_handoff_task(struct task_struct *task)
148 {
149 int ret;
150 ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
151 return (ret == NOTIFY_OK) ? 1 : 0;
152 }
153
profile_munmap(unsigned long addr)154 void profile_munmap(unsigned long addr)
155 {
156 blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
157 }
158
task_handoff_register(struct notifier_block * n)159 int task_handoff_register(struct notifier_block *n)
160 {
161 return atomic_notifier_chain_register(&task_free_notifier, n);
162 }
163 EXPORT_SYMBOL_GPL(task_handoff_register);
164
task_handoff_unregister(struct notifier_block * n)165 int task_handoff_unregister(struct notifier_block *n)
166 {
167 return atomic_notifier_chain_unregister(&task_free_notifier, n);
168 }
169 EXPORT_SYMBOL_GPL(task_handoff_unregister);
170
profile_event_register(enum profile_type type,struct notifier_block * n)171 int profile_event_register(enum profile_type type, struct notifier_block *n)
172 {
173 int err = -EINVAL;
174
175 switch (type) {
176 case PROFILE_TASK_EXIT:
177 err = blocking_notifier_chain_register(
178 &task_exit_notifier, n);
179 break;
180 case PROFILE_MUNMAP:
181 err = blocking_notifier_chain_register(
182 &munmap_notifier, n);
183 break;
184 }
185
186 return err;
187 }
188 EXPORT_SYMBOL_GPL(profile_event_register);
189
profile_event_unregister(enum profile_type type,struct notifier_block * n)190 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
191 {
192 int err = -EINVAL;
193
194 switch (type) {
195 case PROFILE_TASK_EXIT:
196 err = blocking_notifier_chain_unregister(
197 &task_exit_notifier, n);
198 break;
199 case PROFILE_MUNMAP:
200 err = blocking_notifier_chain_unregister(
201 &munmap_notifier, n);
202 break;
203 }
204
205 return err;
206 }
207 EXPORT_SYMBOL_GPL(profile_event_unregister);
208
209 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
210 /*
211 * Each cpu has a pair of open-addressed hashtables for pending
212 * profile hits. read_profile() IPI's all cpus to request them
213 * to flip buffers and flushes their contents to prof_buffer itself.
214 * Flip requests are serialized by the profile_flip_mutex. The sole
215 * use of having a second hashtable is for avoiding cacheline
216 * contention that would otherwise happen during flushes of pending
217 * profile hits required for the accuracy of reported profile hits
218 * and so resurrect the interrupt livelock issue.
219 *
220 * The open-addressed hashtables are indexed by profile buffer slot
221 * and hold the number of pending hits to that profile buffer slot on
222 * a cpu in an entry. When the hashtable overflows, all pending hits
223 * are accounted to their corresponding profile buffer slots with
224 * atomic_add() and the hashtable emptied. As numerous pending hits
225 * may be accounted to a profile buffer slot in a hashtable entry,
226 * this amortizes a number of atomic profile buffer increments likely
227 * to be far larger than the number of entries in the hashtable,
228 * particularly given that the number of distinct profile buffer
229 * positions to which hits are accounted during short intervals (e.g.
230 * several seconds) is usually very small. Exclusion from buffer
231 * flipping is provided by interrupt disablement (note that for
232 * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
233 * process context).
234 * The hash function is meant to be lightweight as opposed to strong,
235 * and was vaguely inspired by ppc64 firmware-supported inverted
236 * pagetable hash functions, but uses a full hashtable full of finite
237 * collision chains, not just pairs of them.
238 *
239 * -- nyc
240 */
__profile_flip_buffers(void * unused)241 static void __profile_flip_buffers(void *unused)
242 {
243 int cpu = smp_processor_id();
244
245 per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
246 }
247
profile_flip_buffers(void)248 static void profile_flip_buffers(void)
249 {
250 int i, j, cpu;
251
252 mutex_lock(&profile_flip_mutex);
253 j = per_cpu(cpu_profile_flip, get_cpu());
254 put_cpu();
255 on_each_cpu(__profile_flip_buffers, NULL, 1);
256 for_each_online_cpu(cpu) {
257 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
258 for (i = 0; i < NR_PROFILE_HIT; ++i) {
259 if (!hits[i].hits) {
260 if (hits[i].pc)
261 hits[i].pc = 0;
262 continue;
263 }
264 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
265 hits[i].hits = hits[i].pc = 0;
266 }
267 }
268 mutex_unlock(&profile_flip_mutex);
269 }
270
profile_discard_flip_buffers(void)271 static void profile_discard_flip_buffers(void)
272 {
273 int i, cpu;
274
275 mutex_lock(&profile_flip_mutex);
276 i = per_cpu(cpu_profile_flip, get_cpu());
277 put_cpu();
278 on_each_cpu(__profile_flip_buffers, NULL, 1);
279 for_each_online_cpu(cpu) {
280 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
281 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
282 }
283 mutex_unlock(&profile_flip_mutex);
284 }
285
do_profile_hits(int type,void * __pc,unsigned int nr_hits)286 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
287 {
288 unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
289 int i, j, cpu;
290 struct profile_hit *hits;
291
292 pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
293 i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
294 secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
295 cpu = get_cpu();
296 hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
297 if (!hits) {
298 put_cpu();
299 return;
300 }
301 /*
302 * We buffer the global profiler buffer into a per-CPU
303 * queue and thus reduce the number of global (and possibly
304 * NUMA-alien) accesses. The write-queue is self-coalescing:
305 */
306 local_irq_save(flags);
307 do {
308 for (j = 0; j < PROFILE_GRPSZ; ++j) {
309 if (hits[i + j].pc == pc) {
310 hits[i + j].hits += nr_hits;
311 goto out;
312 } else if (!hits[i + j].hits) {
313 hits[i + j].pc = pc;
314 hits[i + j].hits = nr_hits;
315 goto out;
316 }
317 }
318 i = (i + secondary) & (NR_PROFILE_HIT - 1);
319 } while (i != primary);
320
321 /*
322 * Add the current hit(s) and flush the write-queue out
323 * to the global buffer:
324 */
325 atomic_add(nr_hits, &prof_buffer[pc]);
326 for (i = 0; i < NR_PROFILE_HIT; ++i) {
327 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
328 hits[i].pc = hits[i].hits = 0;
329 }
330 out:
331 local_irq_restore(flags);
332 put_cpu();
333 }
334
profile_dead_cpu(unsigned int cpu)335 static int profile_dead_cpu(unsigned int cpu)
336 {
337 struct page *page;
338 int i;
339
340 if (cpumask_available(prof_cpu_mask))
341 cpumask_clear_cpu(cpu, prof_cpu_mask);
342
343 for (i = 0; i < 2; i++) {
344 if (per_cpu(cpu_profile_hits, cpu)[i]) {
345 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
346 per_cpu(cpu_profile_hits, cpu)[i] = NULL;
347 __free_page(page);
348 }
349 }
350 return 0;
351 }
352
profile_prepare_cpu(unsigned int cpu)353 static int profile_prepare_cpu(unsigned int cpu)
354 {
355 int i, node = cpu_to_mem(cpu);
356 struct page *page;
357
358 per_cpu(cpu_profile_flip, cpu) = 0;
359
360 for (i = 0; i < 2; i++) {
361 if (per_cpu(cpu_profile_hits, cpu)[i])
362 continue;
363
364 page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
365 if (!page) {
366 profile_dead_cpu(cpu);
367 return -ENOMEM;
368 }
369 per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);
370
371 }
372 return 0;
373 }
374
profile_online_cpu(unsigned int cpu)375 static int profile_online_cpu(unsigned int cpu)
376 {
377 if (cpumask_available(prof_cpu_mask))
378 cpumask_set_cpu(cpu, prof_cpu_mask);
379
380 return 0;
381 }
382
383 #else /* !CONFIG_SMP */
384 #define profile_flip_buffers() do { } while (0)
385 #define profile_discard_flip_buffers() do { } while (0)
386
do_profile_hits(int type,void * __pc,unsigned int nr_hits)387 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
388 {
389 unsigned long pc;
390 pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
391 atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
392 }
393 #endif /* !CONFIG_SMP */
394
profile_hits(int type,void * __pc,unsigned int nr_hits)395 void profile_hits(int type, void *__pc, unsigned int nr_hits)
396 {
397 if (prof_on != type || !prof_buffer)
398 return;
399 do_profile_hits(type, __pc, nr_hits);
400 }
401 EXPORT_SYMBOL_GPL(profile_hits);
402
profile_tick(int type)403 void profile_tick(int type)
404 {
405 struct pt_regs *regs = get_irq_regs();
406
407 if (!user_mode(regs) && cpumask_available(prof_cpu_mask) &&
408 cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
409 profile_hit(type, (void *)profile_pc(regs));
410 }
411
412 #ifdef CONFIG_PROC_FS
413 #include <linux/proc_fs.h>
414 #include <linux/seq_file.h>
415 #include <linux/uaccess.h>
416
prof_cpu_mask_proc_show(struct seq_file * m,void * v)417 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
418 {
419 seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
420 return 0;
421 }
422
prof_cpu_mask_proc_open(struct inode * inode,struct file * file)423 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
424 {
425 return single_open(file, prof_cpu_mask_proc_show, NULL);
426 }
427
prof_cpu_mask_proc_write(struct file * file,const char __user * buffer,size_t count,loff_t * pos)428 static ssize_t prof_cpu_mask_proc_write(struct file *file,
429 const char __user *buffer, size_t count, loff_t *pos)
430 {
431 cpumask_var_t new_value;
432 int err;
433
434 if (!zalloc_cpumask_var(&new_value, GFP_KERNEL))
435 return -ENOMEM;
436
437 err = cpumask_parse_user(buffer, count, new_value);
438 if (!err) {
439 cpumask_copy(prof_cpu_mask, new_value);
440 err = count;
441 }
442 free_cpumask_var(new_value);
443 return err;
444 }
445
446 static const struct proc_ops prof_cpu_mask_proc_ops = {
447 .proc_open = prof_cpu_mask_proc_open,
448 .proc_read = seq_read,
449 .proc_lseek = seq_lseek,
450 .proc_release = single_release,
451 .proc_write = prof_cpu_mask_proc_write,
452 };
453
create_prof_cpu_mask(void)454 void create_prof_cpu_mask(void)
455 {
456 /* create /proc/irq/prof_cpu_mask */
457 proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_ops);
458 }
459
460 /*
461 * This function accesses profiling information. The returned data is
462 * binary: the sampling step and the actual contents of the profile
463 * buffer. Use of the program readprofile is recommended in order to
464 * get meaningful info out of these data.
465 */
466 static ssize_t
read_profile(struct file * file,char __user * buf,size_t count,loff_t * ppos)467 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
468 {
469 unsigned long p = *ppos;
470 ssize_t read;
471 char *pnt;
472 unsigned long sample_step = 1UL << prof_shift;
473
474 profile_flip_buffers();
475 if (p >= (prof_len+1)*sizeof(unsigned int))
476 return 0;
477 if (count > (prof_len+1)*sizeof(unsigned int) - p)
478 count = (prof_len+1)*sizeof(unsigned int) - p;
479 read = 0;
480
481 while (p < sizeof(unsigned int) && count > 0) {
482 if (put_user(*((char *)(&sample_step)+p), buf))
483 return -EFAULT;
484 buf++; p++; count--; read++;
485 }
486 pnt = (char *)prof_buffer + p - sizeof(atomic_t);
487 if (copy_to_user(buf, (void *)pnt, count))
488 return -EFAULT;
489 read += count;
490 *ppos += read;
491 return read;
492 }
493
494 /*
495 * Writing to /proc/profile resets the counters
496 *
497 * Writing a 'profiling multiplier' value into it also re-sets the profiling
498 * interrupt frequency, on architectures that support this.
499 */
write_profile(struct file * file,const char __user * buf,size_t count,loff_t * ppos)500 static ssize_t write_profile(struct file *file, const char __user *buf,
501 size_t count, loff_t *ppos)
502 {
503 #ifdef CONFIG_SMP
504 extern int setup_profiling_timer(unsigned int multiplier);
505
506 if (count == sizeof(int)) {
507 unsigned int multiplier;
508
509 if (copy_from_user(&multiplier, buf, sizeof(int)))
510 return -EFAULT;
511
512 if (setup_profiling_timer(multiplier))
513 return -EINVAL;
514 }
515 #endif
516 profile_discard_flip_buffers();
517 memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
518 return count;
519 }
520
521 static const struct proc_ops profile_proc_ops = {
522 .proc_read = read_profile,
523 .proc_write = write_profile,
524 .proc_lseek = default_llseek,
525 };
526
create_proc_profile(void)527 int __ref create_proc_profile(void)
528 {
529 struct proc_dir_entry *entry;
530 #ifdef CONFIG_SMP
531 enum cpuhp_state online_state;
532 #endif
533
534 int err = 0;
535
536 if (!prof_on)
537 return 0;
538 #ifdef CONFIG_SMP
539 err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
540 profile_prepare_cpu, profile_dead_cpu);
541 if (err)
542 return err;
543
544 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
545 profile_online_cpu, NULL);
546 if (err < 0)
547 goto err_state_prep;
548 online_state = err;
549 err = 0;
550 #endif
551 entry = proc_create("profile", S_IWUSR | S_IRUGO,
552 NULL, &profile_proc_ops);
553 if (!entry)
554 goto err_state_onl;
555 proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
556
557 return err;
558 err_state_onl:
559 #ifdef CONFIG_SMP
560 cpuhp_remove_state(online_state);
561 err_state_prep:
562 cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
563 #endif
564 return err;
565 }
566 subsys_initcall(create_proc_profile);
567 #endif /* CONFIG_PROC_FS */
568
