xref: /openbmc/linux/kernel/trace/trace_syscalls.c (revision d3c4db86)
1 // SPDX-License-Identifier: GPL-2.0
2 #include <trace/syscall.h>
3 #include <trace/events/syscalls.h>
4 #include <linux/syscalls.h>
5 #include <linux/slab.h>
6 #include <linux/kernel.h>
7 #include <linux/module.h>	/* for MODULE_NAME_LEN via KSYM_SYMBOL_LEN */
8 #include <linux/ftrace.h>
9 #include <linux/perf_event.h>
10 #include <linux/xarray.h>
11 #include <asm/syscall.h>
12 
13 #include "trace_output.h"
14 #include "trace.h"
15 
16 static DEFINE_MUTEX(syscall_trace_lock);
17 
18 static int syscall_enter_register(struct trace_event_call *event,
19 				 enum trace_reg type, void *data);
20 static int syscall_exit_register(struct trace_event_call *event,
21 				 enum trace_reg type, void *data);
22 
23 static struct list_head *
syscall_get_enter_fields(struct trace_event_call * call)24 syscall_get_enter_fields(struct trace_event_call *call)
25 {
26 	struct syscall_metadata *entry = call->data;
27 
28 	return &entry->enter_fields;
29 }
30 
31 extern struct syscall_metadata *__start_syscalls_metadata[];
32 extern struct syscall_metadata *__stop_syscalls_metadata[];
33 
34 static DEFINE_XARRAY(syscalls_metadata_sparse);
35 static struct syscall_metadata **syscalls_metadata;
36 
37 #ifndef ARCH_HAS_SYSCALL_MATCH_SYM_NAME
arch_syscall_match_sym_name(const char * sym,const char * name)38 static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
39 {
40 	/*
41 	 * Only compare after the "sys" prefix. Archs that use
42 	 * syscall wrappers may have syscalls symbols aliases prefixed
43 	 * with ".SyS" or ".sys" instead of "sys", leading to an unwanted
44 	 * mismatch.
45 	 */
46 	return !strcmp(sym + 3, name + 3);
47 }
48 #endif
49 
50 #ifdef ARCH_TRACE_IGNORE_COMPAT_SYSCALLS
51 /*
52  * Some architectures that allow for 32bit applications
53  * to run on a 64bit kernel, do not map the syscalls for
54  * the 32bit tasks the same as they do for 64bit tasks.
55  *
56  *     *cough*x86*cough*
57  *
58  * In such a case, instead of reporting the wrong syscalls,
59  * simply ignore them.
60  *
61  * For an arch to ignore the compat syscalls it needs to
62  * define ARCH_TRACE_IGNORE_COMPAT_SYSCALLS as well as
63  * define the function arch_trace_is_compat_syscall() to let
64  * the tracing system know that it should ignore it.
65  */
66 static int
trace_get_syscall_nr(struct task_struct * task,struct pt_regs * regs)67 trace_get_syscall_nr(struct task_struct *task, struct pt_regs *regs)
68 {
69 	if (unlikely(arch_trace_is_compat_syscall(regs)))
70 		return -1;
71 
72 	return syscall_get_nr(task, regs);
73 }
74 #else
75 static inline int
trace_get_syscall_nr(struct task_struct * task,struct pt_regs * regs)76 trace_get_syscall_nr(struct task_struct *task, struct pt_regs *regs)
77 {
78 	return syscall_get_nr(task, regs);
79 }
80 #endif /* ARCH_TRACE_IGNORE_COMPAT_SYSCALLS */
81 
82 static __init struct syscall_metadata *
find_syscall_meta(unsigned long syscall)83 find_syscall_meta(unsigned long syscall)
84 {
85 	struct syscall_metadata **start;
86 	struct syscall_metadata **stop;
87 	char str[KSYM_SYMBOL_LEN];
88 
89 
90 	start = __start_syscalls_metadata;
91 	stop = __stop_syscalls_metadata;
92 	kallsyms_lookup(syscall, NULL, NULL, NULL, str);
93 
94 	if (arch_syscall_match_sym_name(str, "sys_ni_syscall"))
95 		return NULL;
96 
97 	for ( ; start < stop; start++) {
98 		if ((*start)->name && arch_syscall_match_sym_name(str, (*start)->name))
99 			return *start;
100 	}
101 	return NULL;
102 }
103 
syscall_nr_to_meta(int nr)104 static struct syscall_metadata *syscall_nr_to_meta(int nr)
105 {
106 	if (IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR))
107 		return xa_load(&syscalls_metadata_sparse, (unsigned long)nr);
108 
109 	if (!syscalls_metadata || nr >= NR_syscalls || nr < 0)
110 		return NULL;
111 
112 	return syscalls_metadata[nr];
113 }
114 
get_syscall_name(int syscall)115 const char *get_syscall_name(int syscall)
116 {
117 	struct syscall_metadata *entry;
118 
119 	entry = syscall_nr_to_meta(syscall);
120 	if (!entry)
121 		return NULL;
122 
123 	return entry->name;
124 }
125 
126 static enum print_line_t
print_syscall_enter(struct trace_iterator * iter,int flags,struct trace_event * event)127 print_syscall_enter(struct trace_iterator *iter, int flags,
128 		    struct trace_event *event)
129 {
130 	struct trace_array *tr = iter->tr;
131 	struct trace_seq *s = &iter->seq;
132 	struct trace_entry *ent = iter->ent;
133 	struct syscall_trace_enter *trace;
134 	struct syscall_metadata *entry;
135 	int i, syscall;
136 
137 	trace = (typeof(trace))ent;
138 	syscall = trace->nr;
139 	entry = syscall_nr_to_meta(syscall);
140 
141 	if (!entry)
142 		goto end;
143 
144 	if (entry->enter_event->event.type != ent->type) {
145 		WARN_ON_ONCE(1);
146 		goto end;
147 	}
148 
149 	trace_seq_printf(s, "%s(", entry->name);
150 
151 	for (i = 0; i < entry->nb_args; i++) {
152 
153 		if (trace_seq_has_overflowed(s))
154 			goto end;
155 
156 		/* parameter types */
157 		if (tr && tr->trace_flags & TRACE_ITER_VERBOSE)
158 			trace_seq_printf(s, "%s ", entry->types[i]);
159 
160 		/* parameter values */
161 		trace_seq_printf(s, "%s: %lx%s", entry->args[i],
162 				 trace->args[i],
163 				 i == entry->nb_args - 1 ? "" : ", ");
164 	}
165 
166 	trace_seq_putc(s, ')');
167 end:
168 	trace_seq_putc(s, '\n');
169 
170 	return trace_handle_return(s);
171 }
172 
173 static enum print_line_t
print_syscall_exit(struct trace_iterator * iter,int flags,struct trace_event * event)174 print_syscall_exit(struct trace_iterator *iter, int flags,
175 		   struct trace_event *event)
176 {
177 	struct trace_seq *s = &iter->seq;
178 	struct trace_entry *ent = iter->ent;
179 	struct syscall_trace_exit *trace;
180 	int syscall;
181 	struct syscall_metadata *entry;
182 
183 	trace = (typeof(trace))ent;
184 	syscall = trace->nr;
185 	entry = syscall_nr_to_meta(syscall);
186 
187 	if (!entry) {
188 		trace_seq_putc(s, '\n');
189 		goto out;
190 	}
191 
192 	if (entry->exit_event->event.type != ent->type) {
193 		WARN_ON_ONCE(1);
194 		return TRACE_TYPE_UNHANDLED;
195 	}
196 
197 	trace_seq_printf(s, "%s -> 0x%lx\n", entry->name,
198 				trace->ret);
199 
200  out:
201 	return trace_handle_return(s);
202 }
203 
204 #define SYSCALL_FIELD(_type, _name) {					\
205 	.type = #_type, .name = #_name,					\
206 	.size = sizeof(_type), .align = __alignof__(_type),		\
207 	.is_signed = is_signed_type(_type), .filter_type = FILTER_OTHER }
208 
209 static int __init
__set_enter_print_fmt(struct syscall_metadata * entry,char * buf,int len)210 __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len)
211 {
212 	int i;
213 	int pos = 0;
214 
215 	/* When len=0, we just calculate the needed length */
216 #define LEN_OR_ZERO (len ? len - pos : 0)
217 
218 	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
219 	for (i = 0; i < entry->nb_args; i++) {
220 		pos += snprintf(buf + pos, LEN_OR_ZERO, "%s: 0x%%0%zulx%s",
221 				entry->args[i], sizeof(unsigned long),
222 				i == entry->nb_args - 1 ? "" : ", ");
223 	}
224 	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
225 
226 	for (i = 0; i < entry->nb_args; i++) {
227 		pos += snprintf(buf + pos, LEN_OR_ZERO,
228 				", ((unsigned long)(REC->%s))", entry->args[i]);
229 	}
230 
231 #undef LEN_OR_ZERO
232 
233 	/* return the length of print_fmt */
234 	return pos;
235 }
236 
set_syscall_print_fmt(struct trace_event_call * call)237 static int __init set_syscall_print_fmt(struct trace_event_call *call)
238 {
239 	char *print_fmt;
240 	int len;
241 	struct syscall_metadata *entry = call->data;
242 
243 	if (entry->enter_event != call) {
244 		call->print_fmt = "\"0x%lx\", REC->ret";
245 		return 0;
246 	}
247 
248 	/* First: called with 0 length to calculate the needed length */
249 	len = __set_enter_print_fmt(entry, NULL, 0);
250 
251 	print_fmt = kmalloc(len + 1, GFP_KERNEL);
252 	if (!print_fmt)
253 		return -ENOMEM;
254 
255 	/* Second: actually write the @print_fmt */
256 	__set_enter_print_fmt(entry, print_fmt, len + 1);
257 	call->print_fmt = print_fmt;
258 
259 	return 0;
260 }
261 
free_syscall_print_fmt(struct trace_event_call * call)262 static void __init free_syscall_print_fmt(struct trace_event_call *call)
263 {
264 	struct syscall_metadata *entry = call->data;
265 
266 	if (entry->enter_event == call)
267 		kfree(call->print_fmt);
268 }
269 
syscall_enter_define_fields(struct trace_event_call * call)270 static int __init syscall_enter_define_fields(struct trace_event_call *call)
271 {
272 	struct syscall_trace_enter trace;
273 	struct syscall_metadata *meta = call->data;
274 	int offset = offsetof(typeof(trace), args);
275 	int ret = 0;
276 	int i;
277 
278 	for (i = 0; i < meta->nb_args; i++) {
279 		ret = trace_define_field(call, meta->types[i],
280 					 meta->args[i], offset,
281 					 sizeof(unsigned long), 0,
282 					 FILTER_OTHER);
283 		if (ret)
284 			break;
285 		offset += sizeof(unsigned long);
286 	}
287 
288 	return ret;
289 }
290 
ftrace_syscall_enter(void * data,struct pt_regs * regs,long id)291 static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
292 {
293 	struct trace_array *tr = data;
294 	struct trace_event_file *trace_file;
295 	struct syscall_trace_enter *entry;
296 	struct syscall_metadata *sys_data;
297 	struct trace_event_buffer fbuffer;
298 	unsigned long args[6];
299 	int syscall_nr;
300 	int size;
301 
302 	syscall_nr = trace_get_syscall_nr(current, regs);
303 	if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
304 		return;
305 
306 	/* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE) */
307 	trace_file = rcu_dereference_sched(tr->enter_syscall_files[syscall_nr]);
308 	if (!trace_file)
309 		return;
310 
311 	if (trace_trigger_soft_disabled(trace_file))
312 		return;
313 
314 	sys_data = syscall_nr_to_meta(syscall_nr);
315 	if (!sys_data)
316 		return;
317 
318 	size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
319 
320 	entry = trace_event_buffer_reserve(&fbuffer, trace_file, size);
321 	if (!entry)
322 		return;
323 
324 	entry = ring_buffer_event_data(fbuffer.event);
325 	entry->nr = syscall_nr;
326 	syscall_get_arguments(current, regs, args);
327 	memcpy(entry->args, args, sizeof(unsigned long) * sys_data->nb_args);
328 
329 	trace_event_buffer_commit(&fbuffer);
330 }
331 
ftrace_syscall_exit(void * data,struct pt_regs * regs,long ret)332 static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
333 {
334 	struct trace_array *tr = data;
335 	struct trace_event_file *trace_file;
336 	struct syscall_trace_exit *entry;
337 	struct syscall_metadata *sys_data;
338 	struct trace_event_buffer fbuffer;
339 	int syscall_nr;
340 
341 	syscall_nr = trace_get_syscall_nr(current, regs);
342 	if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
343 		return;
344 
345 	/* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE()) */
346 	trace_file = rcu_dereference_sched(tr->exit_syscall_files[syscall_nr]);
347 	if (!trace_file)
348 		return;
349 
350 	if (trace_trigger_soft_disabled(trace_file))
351 		return;
352 
353 	sys_data = syscall_nr_to_meta(syscall_nr);
354 	if (!sys_data)
355 		return;
356 
357 	entry = trace_event_buffer_reserve(&fbuffer, trace_file, sizeof(*entry));
358 	if (!entry)
359 		return;
360 
361 	entry = ring_buffer_event_data(fbuffer.event);
362 	entry->nr = syscall_nr;
363 	entry->ret = syscall_get_return_value(current, regs);
364 
365 	trace_event_buffer_commit(&fbuffer);
366 }
367 
reg_event_syscall_enter(struct trace_event_file * file,struct trace_event_call * call)368 static int reg_event_syscall_enter(struct trace_event_file *file,
369 				   struct trace_event_call *call)
370 {
371 	struct trace_array *tr = file->tr;
372 	int ret = 0;
373 	int num;
374 
375 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
376 	if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
377 		return -ENOSYS;
378 	mutex_lock(&syscall_trace_lock);
379 	if (!tr->sys_refcount_enter)
380 		ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
381 	if (!ret) {
382 		rcu_assign_pointer(tr->enter_syscall_files[num], file);
383 		tr->sys_refcount_enter++;
384 	}
385 	mutex_unlock(&syscall_trace_lock);
386 	return ret;
387 }
388 
unreg_event_syscall_enter(struct trace_event_file * file,struct trace_event_call * call)389 static void unreg_event_syscall_enter(struct trace_event_file *file,
390 				      struct trace_event_call *call)
391 {
392 	struct trace_array *tr = file->tr;
393 	int num;
394 
395 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
396 	if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
397 		return;
398 	mutex_lock(&syscall_trace_lock);
399 	tr->sys_refcount_enter--;
400 	RCU_INIT_POINTER(tr->enter_syscall_files[num], NULL);
401 	if (!tr->sys_refcount_enter)
402 		unregister_trace_sys_enter(ftrace_syscall_enter, tr);
403 	mutex_unlock(&syscall_trace_lock);
404 }
405 
reg_event_syscall_exit(struct trace_event_file * file,struct trace_event_call * call)406 static int reg_event_syscall_exit(struct trace_event_file *file,
407 				  struct trace_event_call *call)
408 {
409 	struct trace_array *tr = file->tr;
410 	int ret = 0;
411 	int num;
412 
413 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
414 	if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
415 		return -ENOSYS;
416 	mutex_lock(&syscall_trace_lock);
417 	if (!tr->sys_refcount_exit)
418 		ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
419 	if (!ret) {
420 		rcu_assign_pointer(tr->exit_syscall_files[num], file);
421 		tr->sys_refcount_exit++;
422 	}
423 	mutex_unlock(&syscall_trace_lock);
424 	return ret;
425 }
426 
unreg_event_syscall_exit(struct trace_event_file * file,struct trace_event_call * call)427 static void unreg_event_syscall_exit(struct trace_event_file *file,
428 				     struct trace_event_call *call)
429 {
430 	struct trace_array *tr = file->tr;
431 	int num;
432 
433 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
434 	if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
435 		return;
436 	mutex_lock(&syscall_trace_lock);
437 	tr->sys_refcount_exit--;
438 	RCU_INIT_POINTER(tr->exit_syscall_files[num], NULL);
439 	if (!tr->sys_refcount_exit)
440 		unregister_trace_sys_exit(ftrace_syscall_exit, tr);
441 	mutex_unlock(&syscall_trace_lock);
442 }
443 
init_syscall_trace(struct trace_event_call * call)444 static int __init init_syscall_trace(struct trace_event_call *call)
445 {
446 	int id;
447 	int num;
448 
449 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
450 	if (num < 0 || num >= NR_syscalls) {
451 		pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
452 				((struct syscall_metadata *)call->data)->name);
453 		return -ENOSYS;
454 	}
455 
456 	if (set_syscall_print_fmt(call) < 0)
457 		return -ENOMEM;
458 
459 	id = trace_event_raw_init(call);
460 
461 	if (id < 0) {
462 		free_syscall_print_fmt(call);
463 		return id;
464 	}
465 
466 	return id;
467 }
468 
469 static struct trace_event_fields __refdata syscall_enter_fields_array[] = {
470 	SYSCALL_FIELD(int, __syscall_nr),
471 	{ .type = TRACE_FUNCTION_TYPE,
472 	  .define_fields = syscall_enter_define_fields },
473 	{}
474 };
475 
476 struct trace_event_functions enter_syscall_print_funcs = {
477 	.trace		= print_syscall_enter,
478 };
479 
480 struct trace_event_functions exit_syscall_print_funcs = {
481 	.trace		= print_syscall_exit,
482 };
483 
484 struct trace_event_class __refdata event_class_syscall_enter = {
485 	.system		= "syscalls",
486 	.reg		= syscall_enter_register,
487 	.fields_array	= syscall_enter_fields_array,
488 	.get_fields	= syscall_get_enter_fields,
489 	.raw_init	= init_syscall_trace,
490 };
491 
492 struct trace_event_class __refdata event_class_syscall_exit = {
493 	.system		= "syscalls",
494 	.reg		= syscall_exit_register,
495 	.fields_array	= (struct trace_event_fields[]){
496 		SYSCALL_FIELD(int, __syscall_nr),
497 		SYSCALL_FIELD(long, ret),
498 		{}
499 	},
500 	.fields		= LIST_HEAD_INIT(event_class_syscall_exit.fields),
501 	.raw_init	= init_syscall_trace,
502 };
503 
arch_syscall_addr(int nr)504 unsigned long __init __weak arch_syscall_addr(int nr)
505 {
506 	return (unsigned long)sys_call_table[nr];
507 }
508 
init_ftrace_syscalls(void)509 void __init init_ftrace_syscalls(void)
510 {
511 	struct syscall_metadata *meta;
512 	unsigned long addr;
513 	int i;
514 	void *ret;
515 
516 	if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
517 		syscalls_metadata = kcalloc(NR_syscalls,
518 					sizeof(*syscalls_metadata),
519 					GFP_KERNEL);
520 		if (!syscalls_metadata) {
521 			WARN_ON(1);
522 			return;
523 		}
524 	}
525 
526 	for (i = 0; i < NR_syscalls; i++) {
527 		addr = arch_syscall_addr(i);
528 		meta = find_syscall_meta(addr);
529 		if (!meta)
530 			continue;
531 
532 		meta->syscall_nr = i;
533 
534 		if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
535 			syscalls_metadata[i] = meta;
536 		} else {
537 			ret = xa_store(&syscalls_metadata_sparse, i, meta,
538 					GFP_KERNEL);
539 			WARN(xa_is_err(ret),
540 				"Syscall memory allocation failed\n");
541 		}
542 
543 	}
544 }
545 
546 #ifdef CONFIG_PERF_EVENTS
547 
548 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
549 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
550 static int sys_perf_refcount_enter;
551 static int sys_perf_refcount_exit;
552 
perf_call_bpf_enter(struct trace_event_call * call,struct pt_regs * regs,struct syscall_metadata * sys_data,struct syscall_trace_enter * rec)553 static int perf_call_bpf_enter(struct trace_event_call *call, struct pt_regs *regs,
554 			       struct syscall_metadata *sys_data,
555 			       struct syscall_trace_enter *rec)
556 {
557 	struct syscall_tp_t {
558 		struct trace_entry ent;
559 		unsigned long syscall_nr;
560 		unsigned long args[SYSCALL_DEFINE_MAXARGS];
561 	} __aligned(8) param;
562 	int i;
563 
564 	BUILD_BUG_ON(sizeof(param.ent) < sizeof(void *));
565 
566 	/* bpf prog requires 'regs' to be the first member in the ctx (a.k.a. &param) */
567 	*(struct pt_regs **)&param = regs;
568 	param.syscall_nr = rec->nr;
569 	for (i = 0; i < sys_data->nb_args; i++)
570 		param.args[i] = rec->args[i];
571 	return trace_call_bpf(call, &param);
572 }
573 
perf_syscall_enter(void * ignore,struct pt_regs * regs,long id)574 static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
575 {
576 	struct syscall_metadata *sys_data;
577 	struct syscall_trace_enter *rec;
578 	struct hlist_head *head;
579 	unsigned long args[6];
580 	bool valid_prog_array;
581 	int syscall_nr;
582 	int rctx;
583 	int size;
584 
585 	syscall_nr = trace_get_syscall_nr(current, regs);
586 	if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
587 		return;
588 	if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
589 		return;
590 
591 	sys_data = syscall_nr_to_meta(syscall_nr);
592 	if (!sys_data)
593 		return;
594 
595 	head = this_cpu_ptr(sys_data->enter_event->perf_events);
596 	valid_prog_array = bpf_prog_array_valid(sys_data->enter_event);
597 	if (!valid_prog_array && hlist_empty(head))
598 		return;
599 
600 	/* get the size after alignment with the u32 buffer size field */
601 	size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
602 	size = ALIGN(size + sizeof(u32), sizeof(u64));
603 	size -= sizeof(u32);
604 
605 	rec = perf_trace_buf_alloc(size, NULL, &rctx);
606 	if (!rec)
607 		return;
608 
609 	rec->nr = syscall_nr;
610 	syscall_get_arguments(current, regs, args);
611 	memcpy(&rec->args, args, sizeof(unsigned long) * sys_data->nb_args);
612 
613 	if ((valid_prog_array &&
614 	     !perf_call_bpf_enter(sys_data->enter_event, regs, sys_data, rec)) ||
615 	    hlist_empty(head)) {
616 		perf_swevent_put_recursion_context(rctx);
617 		return;
618 	}
619 
620 	perf_trace_buf_submit(rec, size, rctx,
621 			      sys_data->enter_event->event.type, 1, regs,
622 			      head, NULL);
623 }
624 
perf_sysenter_enable(struct trace_event_call * call)625 static int perf_sysenter_enable(struct trace_event_call *call)
626 {
627 	int ret = 0;
628 	int num;
629 
630 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
631 
632 	mutex_lock(&syscall_trace_lock);
633 	if (!sys_perf_refcount_enter)
634 		ret = register_trace_sys_enter(perf_syscall_enter, NULL);
635 	if (ret) {
636 		pr_info("event trace: Could not activate syscall entry trace point");
637 	} else {
638 		set_bit(num, enabled_perf_enter_syscalls);
639 		sys_perf_refcount_enter++;
640 	}
641 	mutex_unlock(&syscall_trace_lock);
642 	return ret;
643 }
644 
perf_sysenter_disable(struct trace_event_call * call)645 static void perf_sysenter_disable(struct trace_event_call *call)
646 {
647 	int num;
648 
649 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
650 
651 	mutex_lock(&syscall_trace_lock);
652 	sys_perf_refcount_enter--;
653 	clear_bit(num, enabled_perf_enter_syscalls);
654 	if (!sys_perf_refcount_enter)
655 		unregister_trace_sys_enter(perf_syscall_enter, NULL);
656 	mutex_unlock(&syscall_trace_lock);
657 }
658 
perf_call_bpf_exit(struct trace_event_call * call,struct pt_regs * regs,struct syscall_trace_exit * rec)659 static int perf_call_bpf_exit(struct trace_event_call *call, struct pt_regs *regs,
660 			      struct syscall_trace_exit *rec)
661 {
662 	struct syscall_tp_t {
663 		struct trace_entry ent;
664 		unsigned long syscall_nr;
665 		unsigned long ret;
666 	} __aligned(8) param;
667 
668 	/* bpf prog requires 'regs' to be the first member in the ctx (a.k.a. &param) */
669 	*(struct pt_regs **)&param = regs;
670 	param.syscall_nr = rec->nr;
671 	param.ret = rec->ret;
672 	return trace_call_bpf(call, &param);
673 }
674 
perf_syscall_exit(void * ignore,struct pt_regs * regs,long ret)675 static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
676 {
677 	struct syscall_metadata *sys_data;
678 	struct syscall_trace_exit *rec;
679 	struct hlist_head *head;
680 	bool valid_prog_array;
681 	int syscall_nr;
682 	int rctx;
683 	int size;
684 
685 	syscall_nr = trace_get_syscall_nr(current, regs);
686 	if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
687 		return;
688 	if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
689 		return;
690 
691 	sys_data = syscall_nr_to_meta(syscall_nr);
692 	if (!sys_data)
693 		return;
694 
695 	head = this_cpu_ptr(sys_data->exit_event->perf_events);
696 	valid_prog_array = bpf_prog_array_valid(sys_data->exit_event);
697 	if (!valid_prog_array && hlist_empty(head))
698 		return;
699 
700 	/* We can probably do that at build time */
701 	size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
702 	size -= sizeof(u32);
703 
704 	rec = perf_trace_buf_alloc(size, NULL, &rctx);
705 	if (!rec)
706 		return;
707 
708 	rec->nr = syscall_nr;
709 	rec->ret = syscall_get_return_value(current, regs);
710 
711 	if ((valid_prog_array &&
712 	     !perf_call_bpf_exit(sys_data->exit_event, regs, rec)) ||
713 	    hlist_empty(head)) {
714 		perf_swevent_put_recursion_context(rctx);
715 		return;
716 	}
717 
718 	perf_trace_buf_submit(rec, size, rctx, sys_data->exit_event->event.type,
719 			      1, regs, head, NULL);
720 }
721 
perf_sysexit_enable(struct trace_event_call * call)722 static int perf_sysexit_enable(struct trace_event_call *call)
723 {
724 	int ret = 0;
725 	int num;
726 
727 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
728 
729 	mutex_lock(&syscall_trace_lock);
730 	if (!sys_perf_refcount_exit)
731 		ret = register_trace_sys_exit(perf_syscall_exit, NULL);
732 	if (ret) {
733 		pr_info("event trace: Could not activate syscall exit trace point");
734 	} else {
735 		set_bit(num, enabled_perf_exit_syscalls);
736 		sys_perf_refcount_exit++;
737 	}
738 	mutex_unlock(&syscall_trace_lock);
739 	return ret;
740 }
741 
perf_sysexit_disable(struct trace_event_call * call)742 static void perf_sysexit_disable(struct trace_event_call *call)
743 {
744 	int num;
745 
746 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
747 
748 	mutex_lock(&syscall_trace_lock);
749 	sys_perf_refcount_exit--;
750 	clear_bit(num, enabled_perf_exit_syscalls);
751 	if (!sys_perf_refcount_exit)
752 		unregister_trace_sys_exit(perf_syscall_exit, NULL);
753 	mutex_unlock(&syscall_trace_lock);
754 }
755 
756 #endif /* CONFIG_PERF_EVENTS */
757 
syscall_enter_register(struct trace_event_call * event,enum trace_reg type,void * data)758 static int syscall_enter_register(struct trace_event_call *event,
759 				 enum trace_reg type, void *data)
760 {
761 	struct trace_event_file *file = data;
762 
763 	switch (type) {
764 	case TRACE_REG_REGISTER:
765 		return reg_event_syscall_enter(file, event);
766 	case TRACE_REG_UNREGISTER:
767 		unreg_event_syscall_enter(file, event);
768 		return 0;
769 
770 #ifdef CONFIG_PERF_EVENTS
771 	case TRACE_REG_PERF_REGISTER:
772 		return perf_sysenter_enable(event);
773 	case TRACE_REG_PERF_UNREGISTER:
774 		perf_sysenter_disable(event);
775 		return 0;
776 	case TRACE_REG_PERF_OPEN:
777 	case TRACE_REG_PERF_CLOSE:
778 	case TRACE_REG_PERF_ADD:
779 	case TRACE_REG_PERF_DEL:
780 		return 0;
781 #endif
782 	}
783 	return 0;
784 }
785 
syscall_exit_register(struct trace_event_call * event,enum trace_reg type,void * data)786 static int syscall_exit_register(struct trace_event_call *event,
787 				 enum trace_reg type, void *data)
788 {
789 	struct trace_event_file *file = data;
790 
791 	switch (type) {
792 	case TRACE_REG_REGISTER:
793 		return reg_event_syscall_exit(file, event);
794 	case TRACE_REG_UNREGISTER:
795 		unreg_event_syscall_exit(file, event);
796 		return 0;
797 
798 #ifdef CONFIG_PERF_EVENTS
799 	case TRACE_REG_PERF_REGISTER:
800 		return perf_sysexit_enable(event);
801 	case TRACE_REG_PERF_UNREGISTER:
802 		perf_sysexit_disable(event);
803 		return 0;
804 	case TRACE_REG_PERF_OPEN:
805 	case TRACE_REG_PERF_CLOSE:
806 	case TRACE_REG_PERF_ADD:
807 	case TRACE_REG_PERF_DEL:
808 		return 0;
809 #endif
810 	}
811 	return 0;
812 }
813