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