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 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, &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, &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
profile_init(void)100 int __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(&prof_cpu_mask, GFP_KERNEL))
118 return -ENOMEM;
119
120 cpumask_copy(prof_cpu_mask, cpu_possible_mask);
121
122 prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
123 if (prof_buffer)
124 return 0;
125
126 prof_buffer = alloc_pages_exact(buffer_bytes,
127 GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
128 if (prof_buffer)
129 return 0;
130
131 prof_buffer = vzalloc(buffer_bytes);
132 if (prof_buffer)
133 return 0;
134
135 free_cpumask_var(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 */
__profile_flip_buffers(void * unused)171 static 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
profile_flip_buffers(void)178 static 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(__profile_flip_buffers, NULL, 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(hits[i].hits, &prof_buffer[hits[i].pc]);
195 hits[i].hits = hits[i].pc = 0;
196 }
197 }
198 mutex_unlock(&profile_flip_mutex);
199 }
200
profile_discard_flip_buffers(void)201 static 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(__profile_flip_buffers, NULL, 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(&profile_flip_mutex);
214 }
215
do_profile_hits(int type,void * __pc,unsigned int nr_hits)216 static 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(nr_hits, &prof_buffer[pc]);
256 for (i = 0; i < NR_PROFILE_HIT; ++i) {
257 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
258 hits[i].pc = hits[i].hits = 0;
259 }
260 out:
261 local_irq_restore(flags);
262 put_cpu();
263 }
264
profile_dead_cpu(unsigned int cpu)265 static int profile_dead_cpu(unsigned int cpu)
266 {
267 struct page *page;
268 int i;
269
270 if (cpumask_available(prof_cpu_mask))
271 cpumask_clear_cpu(cpu, 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
profile_prepare_cpu(unsigned int cpu)283 static 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(node, GFP_KERNEL | __GFP_ZERO, 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
profile_online_cpu(unsigned int cpu)305 static int profile_online_cpu(unsigned int cpu)
306 {
307 if (cpumask_available(prof_cpu_mask))
308 cpumask_set_cpu(cpu, 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
do_profile_hits(int type,void * __pc,unsigned int nr_hits)317 static 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
profile_hits(int type,void * __pc,unsigned int nr_hits)325 void 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 }
331 EXPORT_SYMBOL_GPL(profile_hits);
332
profile_tick(int type)333 void profile_tick(int type)
334 {
335 struct pt_regs *regs = get_irq_regs();
336
337 if (!user_mode(regs) && cpumask_available(prof_cpu_mask) &&
338 cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
339 profile_hit(type, (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
347 /*
348 * This function accesses profiling information. The returned data is
349 * binary: the sampling step and the actual contents of the profile
350 * buffer. Use of the program readprofile is recommended in order to
351 * get meaningful info out of these data.
352 */
353 static ssize_t
read_profile(struct file * file,char __user * buf,size_t count,loff_t * ppos)354 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
355 {
356 unsigned long p = *ppos;
357 ssize_t read;
358 char *pnt;
359 unsigned long sample_step = 1UL << prof_shift;
360
361 profile_flip_buffers();
362 if (p >= (prof_len+1)*sizeof(unsigned int))
363 return 0;
364 if (count > (prof_len+1)*sizeof(unsigned int) - p)
365 count = (prof_len+1)*sizeof(unsigned int) - p;
366 read = 0;
367
368 while (p < sizeof(unsigned int) && count > 0) {
369 if (put_user(*((char *)(&sample_step)+p), buf))
370 return -EFAULT;
371 buf++; p++; count--; read++;
372 }
373 pnt = (char *)prof_buffer + p - sizeof(atomic_t);
374 if (copy_to_user(buf, (void *)pnt, count))
375 return -EFAULT;
376 read += count;
377 *ppos += read;
378 return read;
379 }
380
381 /* default is to not implement this call */
setup_profiling_timer(unsigned mult)382 int __weak setup_profiling_timer(unsigned mult)
383 {
384 return -EINVAL;
385 }
386
387 /*
388 * Writing to /proc/profile resets the counters
389 *
390 * Writing a 'profiling multiplier' value into it also re-sets the profiling
391 * interrupt frequency, on architectures that support this.
392 */
write_profile(struct file * file,const char __user * buf,size_t count,loff_t * ppos)393 static ssize_t write_profile(struct file *file, const char __user *buf,
394 size_t count, loff_t *ppos)
395 {
396 #ifdef CONFIG_SMP
397 if (count == sizeof(int)) {
398 unsigned int multiplier;
399
400 if (copy_from_user(&multiplier, buf, sizeof(int)))
401 return -EFAULT;
402
403 if (setup_profiling_timer(multiplier))
404 return -EINVAL;
405 }
406 #endif
407 profile_discard_flip_buffers();
408 memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
409 return count;
410 }
411
412 static const struct proc_ops profile_proc_ops = {
413 .proc_read = read_profile,
414 .proc_write = write_profile,
415 .proc_lseek = default_llseek,
416 };
417
create_proc_profile(void)418 int __ref create_proc_profile(void)
419 {
420 struct proc_dir_entry *entry;
421 #ifdef CONFIG_SMP
422 enum cpuhp_state online_state;
423 #endif
424
425 int err = 0;
426
427 if (!prof_on)
428 return 0;
429 #ifdef CONFIG_SMP
430 err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
431 profile_prepare_cpu, profile_dead_cpu);
432 if (err)
433 return err;
434
435 err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
436 profile_online_cpu, NULL);
437 if (err < 0)
438 goto err_state_prep;
439 online_state = err;
440 err = 0;
441 #endif
442 entry = proc_create("profile", S_IWUSR | S_IRUGO,
443 NULL, &profile_proc_ops);
444 if (!entry)
445 goto err_state_onl;
446 proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
447
448 return err;
449 err_state_onl:
450 #ifdef CONFIG_SMP
451 cpuhp_remove_state(online_state);
452 err_state_prep:
453 cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
454 #endif
455 return err;
456 }
457 subsys_initcall(create_proc_profile);
458 #endif /* CONFIG_PROC_FS */
459