xref: /linux/kernel/trace/trace_syscalls.c (revision 06afb0f36106ecb839c5e2509905e68c1e2677de)
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 	/*
303 	 * Syscall probe called with preemption enabled, but the ring
304 	 * buffer and per-cpu data require preemption to be disabled.
305 	 */
306 	might_fault();
307 	guard(preempt_notrace)();
308 
309 	syscall_nr = trace_get_syscall_nr(current, regs);
310 	if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
311 		return;
312 
313 	/* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE) */
314 	trace_file = rcu_dereference_sched(tr->enter_syscall_files[syscall_nr]);
315 	if (!trace_file)
316 		return;
317 
318 	if (trace_trigger_soft_disabled(trace_file))
319 		return;
320 
321 	sys_data = syscall_nr_to_meta(syscall_nr);
322 	if (!sys_data)
323 		return;
324 
325 	size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
326 
327 	entry = trace_event_buffer_reserve(&fbuffer, trace_file, size);
328 	if (!entry)
329 		return;
330 
331 	entry = ring_buffer_event_data(fbuffer.event);
332 	entry->nr = syscall_nr;
333 	syscall_get_arguments(current, regs, args);
334 	memcpy(entry->args, args, sizeof(unsigned long) * sys_data->nb_args);
335 
336 	trace_event_buffer_commit(&fbuffer);
337 }
338 
ftrace_syscall_exit(void * data,struct pt_regs * regs,long ret)339 static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
340 {
341 	struct trace_array *tr = data;
342 	struct trace_event_file *trace_file;
343 	struct syscall_trace_exit *entry;
344 	struct syscall_metadata *sys_data;
345 	struct trace_event_buffer fbuffer;
346 	int syscall_nr;
347 
348 	/*
349 	 * Syscall probe called with preemption enabled, but the ring
350 	 * buffer and per-cpu data require preemption to be disabled.
351 	 */
352 	might_fault();
353 	guard(preempt_notrace)();
354 
355 	syscall_nr = trace_get_syscall_nr(current, regs);
356 	if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
357 		return;
358 
359 	/* Here we're inside tp handler's rcu_read_lock_sched (__DO_TRACE()) */
360 	trace_file = rcu_dereference_sched(tr->exit_syscall_files[syscall_nr]);
361 	if (!trace_file)
362 		return;
363 
364 	if (trace_trigger_soft_disabled(trace_file))
365 		return;
366 
367 	sys_data = syscall_nr_to_meta(syscall_nr);
368 	if (!sys_data)
369 		return;
370 
371 	entry = trace_event_buffer_reserve(&fbuffer, trace_file, sizeof(*entry));
372 	if (!entry)
373 		return;
374 
375 	entry = ring_buffer_event_data(fbuffer.event);
376 	entry->nr = syscall_nr;
377 	entry->ret = syscall_get_return_value(current, regs);
378 
379 	trace_event_buffer_commit(&fbuffer);
380 }
381 
reg_event_syscall_enter(struct trace_event_file * file,struct trace_event_call * call)382 static int reg_event_syscall_enter(struct trace_event_file *file,
383 				   struct trace_event_call *call)
384 {
385 	struct trace_array *tr = file->tr;
386 	int ret = 0;
387 	int num;
388 
389 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
390 	if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
391 		return -ENOSYS;
392 	mutex_lock(&syscall_trace_lock);
393 	if (!tr->sys_refcount_enter)
394 		ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
395 	if (!ret) {
396 		rcu_assign_pointer(tr->enter_syscall_files[num], file);
397 		tr->sys_refcount_enter++;
398 	}
399 	mutex_unlock(&syscall_trace_lock);
400 	return ret;
401 }
402 
unreg_event_syscall_enter(struct trace_event_file * file,struct trace_event_call * call)403 static void unreg_event_syscall_enter(struct trace_event_file *file,
404 				      struct trace_event_call *call)
405 {
406 	struct trace_array *tr = file->tr;
407 	int num;
408 
409 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
410 	if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
411 		return;
412 	mutex_lock(&syscall_trace_lock);
413 	tr->sys_refcount_enter--;
414 	RCU_INIT_POINTER(tr->enter_syscall_files[num], NULL);
415 	if (!tr->sys_refcount_enter)
416 		unregister_trace_sys_enter(ftrace_syscall_enter, tr);
417 	mutex_unlock(&syscall_trace_lock);
418 }
419 
reg_event_syscall_exit(struct trace_event_file * file,struct trace_event_call * call)420 static int reg_event_syscall_exit(struct trace_event_file *file,
421 				  struct trace_event_call *call)
422 {
423 	struct trace_array *tr = file->tr;
424 	int ret = 0;
425 	int num;
426 
427 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
428 	if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
429 		return -ENOSYS;
430 	mutex_lock(&syscall_trace_lock);
431 	if (!tr->sys_refcount_exit)
432 		ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
433 	if (!ret) {
434 		rcu_assign_pointer(tr->exit_syscall_files[num], file);
435 		tr->sys_refcount_exit++;
436 	}
437 	mutex_unlock(&syscall_trace_lock);
438 	return ret;
439 }
440 
unreg_event_syscall_exit(struct trace_event_file * file,struct trace_event_call * call)441 static void unreg_event_syscall_exit(struct trace_event_file *file,
442 				     struct trace_event_call *call)
443 {
444 	struct trace_array *tr = file->tr;
445 	int num;
446 
447 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
448 	if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
449 		return;
450 	mutex_lock(&syscall_trace_lock);
451 	tr->sys_refcount_exit--;
452 	RCU_INIT_POINTER(tr->exit_syscall_files[num], NULL);
453 	if (!tr->sys_refcount_exit)
454 		unregister_trace_sys_exit(ftrace_syscall_exit, tr);
455 	mutex_unlock(&syscall_trace_lock);
456 }
457 
init_syscall_trace(struct trace_event_call * call)458 static int __init init_syscall_trace(struct trace_event_call *call)
459 {
460 	int id;
461 	int num;
462 
463 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
464 	if (num < 0 || num >= NR_syscalls) {
465 		pr_debug("syscall %s metadata not mapped, disabling ftrace event\n",
466 				((struct syscall_metadata *)call->data)->name);
467 		return -ENOSYS;
468 	}
469 
470 	if (set_syscall_print_fmt(call) < 0)
471 		return -ENOMEM;
472 
473 	id = trace_event_raw_init(call);
474 
475 	if (id < 0) {
476 		free_syscall_print_fmt(call);
477 		return id;
478 	}
479 
480 	return id;
481 }
482 
483 static struct trace_event_fields __refdata syscall_enter_fields_array[] = {
484 	SYSCALL_FIELD(int, __syscall_nr),
485 	{ .type = TRACE_FUNCTION_TYPE,
486 	  .define_fields = syscall_enter_define_fields },
487 	{}
488 };
489 
490 struct trace_event_functions enter_syscall_print_funcs = {
491 	.trace		= print_syscall_enter,
492 };
493 
494 struct trace_event_functions exit_syscall_print_funcs = {
495 	.trace		= print_syscall_exit,
496 };
497 
498 struct trace_event_class __refdata event_class_syscall_enter = {
499 	.system		= "syscalls",
500 	.reg		= syscall_enter_register,
501 	.fields_array	= syscall_enter_fields_array,
502 	.get_fields	= syscall_get_enter_fields,
503 	.raw_init	= init_syscall_trace,
504 };
505 
506 struct trace_event_class __refdata event_class_syscall_exit = {
507 	.system		= "syscalls",
508 	.reg		= syscall_exit_register,
509 	.fields_array	= (struct trace_event_fields[]){
510 		SYSCALL_FIELD(int, __syscall_nr),
511 		SYSCALL_FIELD(long, ret),
512 		{}
513 	},
514 	.fields		= LIST_HEAD_INIT(event_class_syscall_exit.fields),
515 	.raw_init	= init_syscall_trace,
516 };
517 
arch_syscall_addr(int nr)518 unsigned long __init __weak arch_syscall_addr(int nr)
519 {
520 	return (unsigned long)sys_call_table[nr];
521 }
522 
init_ftrace_syscalls(void)523 void __init init_ftrace_syscalls(void)
524 {
525 	struct syscall_metadata *meta;
526 	unsigned long addr;
527 	int i;
528 	void *ret;
529 
530 	if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
531 		syscalls_metadata = kcalloc(NR_syscalls,
532 					sizeof(*syscalls_metadata),
533 					GFP_KERNEL);
534 		if (!syscalls_metadata) {
535 			WARN_ON(1);
536 			return;
537 		}
538 	}
539 
540 	for (i = 0; i < NR_syscalls; i++) {
541 		addr = arch_syscall_addr(i);
542 		meta = find_syscall_meta(addr);
543 		if (!meta)
544 			continue;
545 
546 		meta->syscall_nr = i;
547 
548 		if (!IS_ENABLED(CONFIG_HAVE_SPARSE_SYSCALL_NR)) {
549 			syscalls_metadata[i] = meta;
550 		} else {
551 			ret = xa_store(&syscalls_metadata_sparse, i, meta,
552 					GFP_KERNEL);
553 			WARN(xa_is_err(ret),
554 				"Syscall memory allocation failed\n");
555 		}
556 
557 	}
558 }
559 
560 #ifdef CONFIG_PERF_EVENTS
561 
562 static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
563 static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
564 static int sys_perf_refcount_enter;
565 static int sys_perf_refcount_exit;
566 
perf_call_bpf_enter(struct trace_event_call * call,struct pt_regs * regs,struct syscall_metadata * sys_data,struct syscall_trace_enter * rec)567 static int perf_call_bpf_enter(struct trace_event_call *call, struct pt_regs *regs,
568 			       struct syscall_metadata *sys_data,
569 			       struct syscall_trace_enter *rec)
570 {
571 	struct syscall_tp_t {
572 		struct trace_entry ent;
573 		int syscall_nr;
574 		unsigned long args[SYSCALL_DEFINE_MAXARGS];
575 	} __aligned(8) param;
576 	int i;
577 
578 	BUILD_BUG_ON(sizeof(param.ent) < sizeof(void *));
579 
580 	/* bpf prog requires 'regs' to be the first member in the ctx (a.k.a. &param) */
581 	perf_fetch_caller_regs(regs);
582 	*(struct pt_regs **)&param = regs;
583 	param.syscall_nr = rec->nr;
584 	for (i = 0; i < sys_data->nb_args; i++)
585 		param.args[i] = rec->args[i];
586 	return trace_call_bpf(call, &param);
587 }
588 
perf_syscall_enter(void * ignore,struct pt_regs * regs,long id)589 static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
590 {
591 	struct syscall_metadata *sys_data;
592 	struct syscall_trace_enter *rec;
593 	struct pt_regs *fake_regs;
594 	struct hlist_head *head;
595 	unsigned long args[6];
596 	bool valid_prog_array;
597 	int syscall_nr;
598 	int rctx;
599 	int size;
600 
601 	/*
602 	 * Syscall probe called with preemption enabled, but the ring
603 	 * buffer and per-cpu data require preemption to be disabled.
604 	 */
605 	might_fault();
606 	guard(preempt_notrace)();
607 
608 	syscall_nr = trace_get_syscall_nr(current, regs);
609 	if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
610 		return;
611 	if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
612 		return;
613 
614 	sys_data = syscall_nr_to_meta(syscall_nr);
615 	if (!sys_data)
616 		return;
617 
618 	head = this_cpu_ptr(sys_data->enter_event->perf_events);
619 	valid_prog_array = bpf_prog_array_valid(sys_data->enter_event);
620 	if (!valid_prog_array && hlist_empty(head))
621 		return;
622 
623 	/* get the size after alignment with the u32 buffer size field */
624 	size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
625 	size = ALIGN(size + sizeof(u32), sizeof(u64));
626 	size -= sizeof(u32);
627 
628 	rec = perf_trace_buf_alloc(size, &fake_regs, &rctx);
629 	if (!rec)
630 		return;
631 
632 	rec->nr = syscall_nr;
633 	syscall_get_arguments(current, regs, args);
634 	memcpy(&rec->args, args, sizeof(unsigned long) * sys_data->nb_args);
635 
636 	if ((valid_prog_array &&
637 	     !perf_call_bpf_enter(sys_data->enter_event, fake_regs, sys_data, rec)) ||
638 	    hlist_empty(head)) {
639 		perf_swevent_put_recursion_context(rctx);
640 		return;
641 	}
642 
643 	perf_trace_buf_submit(rec, size, rctx,
644 			      sys_data->enter_event->event.type, 1, regs,
645 			      head, NULL);
646 }
647 
perf_sysenter_enable(struct trace_event_call * call)648 static int perf_sysenter_enable(struct trace_event_call *call)
649 {
650 	int ret = 0;
651 	int num;
652 
653 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
654 
655 	mutex_lock(&syscall_trace_lock);
656 	if (!sys_perf_refcount_enter)
657 		ret = register_trace_sys_enter(perf_syscall_enter, NULL);
658 	if (ret) {
659 		pr_info("event trace: Could not activate syscall entry trace point");
660 	} else {
661 		set_bit(num, enabled_perf_enter_syscalls);
662 		sys_perf_refcount_enter++;
663 	}
664 	mutex_unlock(&syscall_trace_lock);
665 	return ret;
666 }
667 
perf_sysenter_disable(struct trace_event_call * call)668 static void perf_sysenter_disable(struct trace_event_call *call)
669 {
670 	int num;
671 
672 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
673 
674 	mutex_lock(&syscall_trace_lock);
675 	sys_perf_refcount_enter--;
676 	clear_bit(num, enabled_perf_enter_syscalls);
677 	if (!sys_perf_refcount_enter)
678 		unregister_trace_sys_enter(perf_syscall_enter, NULL);
679 	mutex_unlock(&syscall_trace_lock);
680 }
681 
perf_call_bpf_exit(struct trace_event_call * call,struct pt_regs * regs,struct syscall_trace_exit * rec)682 static int perf_call_bpf_exit(struct trace_event_call *call, struct pt_regs *regs,
683 			      struct syscall_trace_exit *rec)
684 {
685 	struct syscall_tp_t {
686 		struct trace_entry ent;
687 		int syscall_nr;
688 		unsigned long ret;
689 	} __aligned(8) param;
690 
691 	/* bpf prog requires 'regs' to be the first member in the ctx (a.k.a. &param) */
692 	perf_fetch_caller_regs(regs);
693 	*(struct pt_regs **)&param = regs;
694 	param.syscall_nr = rec->nr;
695 	param.ret = rec->ret;
696 	return trace_call_bpf(call, &param);
697 }
698 
perf_syscall_exit(void * ignore,struct pt_regs * regs,long ret)699 static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
700 {
701 	struct syscall_metadata *sys_data;
702 	struct syscall_trace_exit *rec;
703 	struct pt_regs *fake_regs;
704 	struct hlist_head *head;
705 	bool valid_prog_array;
706 	int syscall_nr;
707 	int rctx;
708 	int size;
709 
710 	/*
711 	 * Syscall probe called with preemption enabled, but the ring
712 	 * buffer and per-cpu data require preemption to be disabled.
713 	 */
714 	might_fault();
715 	guard(preempt_notrace)();
716 
717 	syscall_nr = trace_get_syscall_nr(current, regs);
718 	if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
719 		return;
720 	if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
721 		return;
722 
723 	sys_data = syscall_nr_to_meta(syscall_nr);
724 	if (!sys_data)
725 		return;
726 
727 	head = this_cpu_ptr(sys_data->exit_event->perf_events);
728 	valid_prog_array = bpf_prog_array_valid(sys_data->exit_event);
729 	if (!valid_prog_array && hlist_empty(head))
730 		return;
731 
732 	/* We can probably do that at build time */
733 	size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
734 	size -= sizeof(u32);
735 
736 	rec = perf_trace_buf_alloc(size, &fake_regs, &rctx);
737 	if (!rec)
738 		return;
739 
740 	rec->nr = syscall_nr;
741 	rec->ret = syscall_get_return_value(current, regs);
742 
743 	if ((valid_prog_array &&
744 	     !perf_call_bpf_exit(sys_data->exit_event, fake_regs, rec)) ||
745 	    hlist_empty(head)) {
746 		perf_swevent_put_recursion_context(rctx);
747 		return;
748 	}
749 
750 	perf_trace_buf_submit(rec, size, rctx, sys_data->exit_event->event.type,
751 			      1, regs, head, NULL);
752 }
753 
perf_sysexit_enable(struct trace_event_call * call)754 static int perf_sysexit_enable(struct trace_event_call *call)
755 {
756 	int ret = 0;
757 	int num;
758 
759 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
760 
761 	mutex_lock(&syscall_trace_lock);
762 	if (!sys_perf_refcount_exit)
763 		ret = register_trace_sys_exit(perf_syscall_exit, NULL);
764 	if (ret) {
765 		pr_info("event trace: Could not activate syscall exit trace point");
766 	} else {
767 		set_bit(num, enabled_perf_exit_syscalls);
768 		sys_perf_refcount_exit++;
769 	}
770 	mutex_unlock(&syscall_trace_lock);
771 	return ret;
772 }
773 
perf_sysexit_disable(struct trace_event_call * call)774 static void perf_sysexit_disable(struct trace_event_call *call)
775 {
776 	int num;
777 
778 	num = ((struct syscall_metadata *)call->data)->syscall_nr;
779 
780 	mutex_lock(&syscall_trace_lock);
781 	sys_perf_refcount_exit--;
782 	clear_bit(num, enabled_perf_exit_syscalls);
783 	if (!sys_perf_refcount_exit)
784 		unregister_trace_sys_exit(perf_syscall_exit, NULL);
785 	mutex_unlock(&syscall_trace_lock);
786 }
787 
788 #endif /* CONFIG_PERF_EVENTS */
789 
syscall_enter_register(struct trace_event_call * event,enum trace_reg type,void * data)790 static int syscall_enter_register(struct trace_event_call *event,
791 				 enum trace_reg type, void *data)
792 {
793 	struct trace_event_file *file = data;
794 
795 	switch (type) {
796 	case TRACE_REG_REGISTER:
797 		return reg_event_syscall_enter(file, event);
798 	case TRACE_REG_UNREGISTER:
799 		unreg_event_syscall_enter(file, event);
800 		return 0;
801 
802 #ifdef CONFIG_PERF_EVENTS
803 	case TRACE_REG_PERF_REGISTER:
804 		return perf_sysenter_enable(event);
805 	case TRACE_REG_PERF_UNREGISTER:
806 		perf_sysenter_disable(event);
807 		return 0;
808 	case TRACE_REG_PERF_OPEN:
809 	case TRACE_REG_PERF_CLOSE:
810 	case TRACE_REG_PERF_ADD:
811 	case TRACE_REG_PERF_DEL:
812 		return 0;
813 #endif
814 	}
815 	return 0;
816 }
817 
syscall_exit_register(struct trace_event_call * event,enum trace_reg type,void * data)818 static int syscall_exit_register(struct trace_event_call *event,
819 				 enum trace_reg type, void *data)
820 {
821 	struct trace_event_file *file = data;
822 
823 	switch (type) {
824 	case TRACE_REG_REGISTER:
825 		return reg_event_syscall_exit(file, event);
826 	case TRACE_REG_UNREGISTER:
827 		unreg_event_syscall_exit(file, event);
828 		return 0;
829 
830 #ifdef CONFIG_PERF_EVENTS
831 	case TRACE_REG_PERF_REGISTER:
832 		return perf_sysexit_enable(event);
833 	case TRACE_REG_PERF_UNREGISTER:
834 		perf_sysexit_disable(event);
835 		return 0;
836 	case TRACE_REG_PERF_OPEN:
837 	case TRACE_REG_PERF_CLOSE:
838 	case TRACE_REG_PERF_ADD:
839 	case TRACE_REG_PERF_DEL:
840 		return 0;
841 #endif
842 	}
843 	return 0;
844 }
845