1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include <linux/context_tracking.h>
4 #include <linux/entry-common.h>
5 #include <linux/highmem.h>
6 #include <linux/livepatch.h>
7 #include <linux/audit.h>
8 #include <linux/tick.h>
9 
10 #include "common.h"
11 
12 #define CREATE_TRACE_POINTS
13 #include <trace/events/syscalls.h>
14 
15 /* See comment for enter_from_user_mode() in entry-common.h */
__enter_from_user_mode(struct pt_regs * regs)16 static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
17 {
18 	arch_check_user_regs(regs);
19 	lockdep_hardirqs_off(CALLER_ADDR0);
20 
21 	CT_WARN_ON(ct_state() != CONTEXT_USER);
22 	user_exit_irqoff();
23 
24 	instrumentation_begin();
25 	trace_hardirqs_off_finish();
26 	instrumentation_end();
27 }
28 
enter_from_user_mode(struct pt_regs * regs)29 void noinstr enter_from_user_mode(struct pt_regs *regs)
30 {
31 	__enter_from_user_mode(regs);
32 }
33 
syscall_enter_audit(struct pt_regs * regs,long syscall)34 static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
35 {
36 	if (unlikely(audit_context())) {
37 		unsigned long args[6];
38 
39 		syscall_get_arguments(current, regs, args);
40 		audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
41 	}
42 }
43 
syscall_trace_enter(struct pt_regs * regs,long syscall,unsigned long work)44 static long syscall_trace_enter(struct pt_regs *regs, long syscall,
45 				unsigned long work)
46 {
47 	long ret = 0;
48 
49 	/*
50 	 * Handle Syscall User Dispatch.  This must comes first, since
51 	 * the ABI here can be something that doesn't make sense for
52 	 * other syscall_work features.
53 	 */
54 	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
55 		if (syscall_user_dispatch(regs))
56 			return -1L;
57 	}
58 
59 	/* Handle ptrace */
60 	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
61 		ret = arch_syscall_enter_tracehook(regs);
62 		if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
63 			return -1L;
64 	}
65 
66 	/* Do seccomp after ptrace, to catch any tracer changes. */
67 	if (work & SYSCALL_WORK_SECCOMP) {
68 		ret = __secure_computing(NULL);
69 		if (ret == -1L)
70 			return ret;
71 	}
72 
73 	/* Either of the above might have changed the syscall number */
74 	syscall = syscall_get_nr(current, regs);
75 
76 	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
77 		trace_sys_enter(regs, syscall);
78 
79 	syscall_enter_audit(regs, syscall);
80 
81 	return ret ? : syscall;
82 }
83 
84 static __always_inline long
__syscall_enter_from_user_work(struct pt_regs * regs,long syscall)85 __syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
86 {
87 	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
88 
89 	if (work & SYSCALL_WORK_ENTER)
90 		syscall = syscall_trace_enter(regs, syscall, work);
91 
92 	return syscall;
93 }
94 
syscall_enter_from_user_mode_work(struct pt_regs * regs,long syscall)95 long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
96 {
97 	return __syscall_enter_from_user_work(regs, syscall);
98 }
99 
syscall_enter_from_user_mode(struct pt_regs * regs,long syscall)100 noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
101 {
102 	long ret;
103 
104 	__enter_from_user_mode(regs);
105 
106 	instrumentation_begin();
107 	local_irq_enable();
108 	ret = __syscall_enter_from_user_work(regs, syscall);
109 	instrumentation_end();
110 
111 	return ret;
112 }
113 
syscall_enter_from_user_mode_prepare(struct pt_regs * regs)114 noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
115 {
116 	__enter_from_user_mode(regs);
117 	instrumentation_begin();
118 	local_irq_enable();
119 	instrumentation_end();
120 }
121 
122 /* See comment for exit_to_user_mode() in entry-common.h */
__exit_to_user_mode(void)123 static __always_inline void __exit_to_user_mode(void)
124 {
125 	instrumentation_begin();
126 	trace_hardirqs_on_prepare();
127 	lockdep_hardirqs_on_prepare(CALLER_ADDR0);
128 	instrumentation_end();
129 
130 	user_enter_irqoff();
131 	arch_exit_to_user_mode();
132 	lockdep_hardirqs_on(CALLER_ADDR0);
133 }
134 
exit_to_user_mode(void)135 void noinstr exit_to_user_mode(void)
136 {
137 	__exit_to_user_mode();
138 }
139 
140 /* Workaround to allow gradual conversion of architecture code */
arch_do_signal_or_restart(struct pt_regs * regs,bool has_signal)141 void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }
142 
handle_signal_work(struct pt_regs * regs,unsigned long ti_work)143 static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work)
144 {
145 	if (ti_work & _TIF_NOTIFY_SIGNAL)
146 		tracehook_notify_signal();
147 
148 	arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING);
149 }
150 
exit_to_user_mode_loop(struct pt_regs * regs,unsigned long ti_work)151 static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
152 					    unsigned long ti_work)
153 {
154 	/*
155 	 * Before returning to user space ensure that all pending work
156 	 * items have been completed.
157 	 */
158 	while (ti_work & EXIT_TO_USER_MODE_WORK) {
159 
160 		local_irq_enable_exit_to_user(ti_work);
161 
162 		if (ti_work & _TIF_NEED_RESCHED)
163 			schedule();
164 
165 		if (ti_work & _TIF_UPROBE)
166 			uprobe_notify_resume(regs);
167 
168 		if (ti_work & _TIF_PATCH_PENDING)
169 			klp_update_patch_state(current);
170 
171 		if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
172 			handle_signal_work(regs, ti_work);
173 
174 		if (ti_work & _TIF_NOTIFY_RESUME)
175 			tracehook_notify_resume(regs);
176 
177 		/* Architecture specific TIF work */
178 		arch_exit_to_user_mode_work(regs, ti_work);
179 
180 		/*
181 		 * Disable interrupts and reevaluate the work flags as they
182 		 * might have changed while interrupts and preemption was
183 		 * enabled above.
184 		 */
185 		local_irq_disable_exit_to_user();
186 
187 		/* Check if any of the above work has queued a deferred wakeup */
188 		tick_nohz_user_enter_prepare();
189 
190 		ti_work = READ_ONCE(current_thread_info()->flags);
191 	}
192 
193 	/* Return the latest work state for arch_exit_to_user_mode() */
194 	return ti_work;
195 }
196 
exit_to_user_mode_prepare(struct pt_regs * regs)197 static void exit_to_user_mode_prepare(struct pt_regs *regs)
198 {
199 	unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
200 
201 	lockdep_assert_irqs_disabled();
202 
203 	/* Flush pending rcuog wakeup before the last need_resched() check */
204 	tick_nohz_user_enter_prepare();
205 
206 	if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
207 		ti_work = exit_to_user_mode_loop(regs, ti_work);
208 
209 	arch_exit_to_user_mode_prepare(regs, ti_work);
210 
211 	/* Ensure that the address limit is intact and no locks are held */
212 	addr_limit_user_check();
213 	kmap_assert_nomap();
214 	lockdep_assert_irqs_disabled();
215 	lockdep_sys_exit();
216 }
217 
218 /*
219  * If SYSCALL_EMU is set, then the only reason to report is when
220  * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP).  This syscall
221  * instruction has been already reported in syscall_enter_from_user_mode().
222  */
report_single_step(unsigned long work)223 static inline bool report_single_step(unsigned long work)
224 {
225 	if (work & SYSCALL_WORK_SYSCALL_EMU)
226 		return false;
227 
228 	return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
229 }
230 
syscall_exit_work(struct pt_regs * regs,unsigned long work)231 static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
232 {
233 	bool step;
234 
235 	/*
236 	 * If the syscall was rolled back due to syscall user dispatching,
237 	 * then the tracers below are not invoked for the same reason as
238 	 * the entry side was not invoked in syscall_trace_enter(): The ABI
239 	 * of these syscalls is unknown.
240 	 */
241 	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
242 		if (unlikely(current->syscall_dispatch.on_dispatch)) {
243 			current->syscall_dispatch.on_dispatch = false;
244 			return;
245 		}
246 	}
247 
248 	audit_syscall_exit(regs);
249 
250 	if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
251 		trace_sys_exit(regs, syscall_get_return_value(current, regs));
252 
253 	step = report_single_step(work);
254 	if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
255 		arch_syscall_exit_tracehook(regs, step);
256 }
257 
258 /*
259  * Syscall specific exit to user mode preparation. Runs with interrupts
260  * enabled.
261  */
syscall_exit_to_user_mode_prepare(struct pt_regs * regs)262 static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
263 {
264 	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
265 	unsigned long nr = syscall_get_nr(current, regs);
266 
267 	CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
268 
269 	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
270 		if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
271 			local_irq_enable();
272 	}
273 
274 	rseq_syscall(regs);
275 
276 	/*
277 	 * Do one-time syscall specific work. If these work items are
278 	 * enabled, we want to run them exactly once per syscall exit with
279 	 * interrupts enabled.
280 	 */
281 	if (unlikely(work & SYSCALL_WORK_EXIT))
282 		syscall_exit_work(regs, work);
283 }
284 
__syscall_exit_to_user_mode_work(struct pt_regs * regs)285 static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
286 {
287 	syscall_exit_to_user_mode_prepare(regs);
288 	local_irq_disable_exit_to_user();
289 	exit_to_user_mode_prepare(regs);
290 }
291 
syscall_exit_to_user_mode_work(struct pt_regs * regs)292 void syscall_exit_to_user_mode_work(struct pt_regs *regs)
293 {
294 	__syscall_exit_to_user_mode_work(regs);
295 }
296 
syscall_exit_to_user_mode(struct pt_regs * regs)297 __visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
298 {
299 	instrumentation_begin();
300 	__syscall_exit_to_user_mode_work(regs);
301 	instrumentation_end();
302 	__exit_to_user_mode();
303 }
304 
irqentry_enter_from_user_mode(struct pt_regs * regs)305 noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
306 {
307 	__enter_from_user_mode(regs);
308 }
309 
irqentry_exit_to_user_mode(struct pt_regs * regs)310 noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
311 {
312 	instrumentation_begin();
313 	exit_to_user_mode_prepare(regs);
314 	instrumentation_end();
315 	__exit_to_user_mode();
316 }
317 
irqentry_enter(struct pt_regs * regs)318 noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
319 {
320 	irqentry_state_t ret = {
321 		.exit_rcu = false,
322 	};
323 
324 	if (user_mode(regs)) {
325 		irqentry_enter_from_user_mode(regs);
326 		return ret;
327 	}
328 
329 	/*
330 	 * If this entry hit the idle task invoke rcu_irq_enter() whether
331 	 * RCU is watching or not.
332 	 *
333 	 * Interrupts can nest when the first interrupt invokes softirq
334 	 * processing on return which enables interrupts.
335 	 *
336 	 * Scheduler ticks in the idle task can mark quiescent state and
337 	 * terminate a grace period, if and only if the timer interrupt is
338 	 * not nested into another interrupt.
339 	 *
340 	 * Checking for rcu_is_watching() here would prevent the nesting
341 	 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
342 	 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
343 	 * assume that it is the first interrupt and eventually claim
344 	 * quiescent state and end grace periods prematurely.
345 	 *
346 	 * Unconditionally invoke rcu_irq_enter() so RCU state stays
347 	 * consistent.
348 	 *
349 	 * TINY_RCU does not support EQS, so let the compiler eliminate
350 	 * this part when enabled.
351 	 */
352 	if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
353 		/*
354 		 * If RCU is not watching then the same careful
355 		 * sequence vs. lockdep and tracing is required
356 		 * as in irqentry_enter_from_user_mode().
357 		 */
358 		lockdep_hardirqs_off(CALLER_ADDR0);
359 		rcu_irq_enter();
360 		instrumentation_begin();
361 		trace_hardirqs_off_finish();
362 		instrumentation_end();
363 
364 		ret.exit_rcu = true;
365 		return ret;
366 	}
367 
368 	/*
369 	 * If RCU is watching then RCU only wants to check whether it needs
370 	 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
371 	 * already contains a warning when RCU is not watching, so no point
372 	 * in having another one here.
373 	 */
374 	lockdep_hardirqs_off(CALLER_ADDR0);
375 	instrumentation_begin();
376 	rcu_irq_enter_check_tick();
377 	trace_hardirqs_off_finish();
378 	instrumentation_end();
379 
380 	return ret;
381 }
382 
irqentry_exit_cond_resched(void)383 void irqentry_exit_cond_resched(void)
384 {
385 	if (!preempt_count()) {
386 		/* Sanity check RCU and thread stack */
387 		rcu_irq_exit_check_preempt();
388 		if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
389 			WARN_ON_ONCE(!on_thread_stack());
390 		if (need_resched())
391 			preempt_schedule_irq();
392 	}
393 }
394 #ifdef CONFIG_PREEMPT_DYNAMIC
395 DEFINE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
396 #endif
397 
irqentry_exit(struct pt_regs * regs,irqentry_state_t state)398 noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
399 {
400 	lockdep_assert_irqs_disabled();
401 
402 	/* Check whether this returns to user mode */
403 	if (user_mode(regs)) {
404 		irqentry_exit_to_user_mode(regs);
405 	} else if (!regs_irqs_disabled(regs)) {
406 		/*
407 		 * If RCU was not watching on entry this needs to be done
408 		 * carefully and needs the same ordering of lockdep/tracing
409 		 * and RCU as the return to user mode path.
410 		 */
411 		if (state.exit_rcu) {
412 			instrumentation_begin();
413 			/* Tell the tracer that IRET will enable interrupts */
414 			trace_hardirqs_on_prepare();
415 			lockdep_hardirqs_on_prepare(CALLER_ADDR0);
416 			instrumentation_end();
417 			rcu_irq_exit();
418 			lockdep_hardirqs_on(CALLER_ADDR0);
419 			return;
420 		}
421 
422 		instrumentation_begin();
423 		if (IS_ENABLED(CONFIG_PREEMPTION)) {
424 #ifdef CONFIG_PREEMPT_DYNAMIC
425 			static_call(irqentry_exit_cond_resched)();
426 #else
427 			irqentry_exit_cond_resched();
428 #endif
429 		}
430 		/* Covers both tracing and lockdep */
431 		trace_hardirqs_on();
432 		instrumentation_end();
433 	} else {
434 		/*
435 		 * IRQ flags state is correct already. Just tell RCU if it
436 		 * was not watching on entry.
437 		 */
438 		if (state.exit_rcu)
439 			rcu_irq_exit();
440 	}
441 }
442 
irqentry_nmi_enter(struct pt_regs * regs)443 irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
444 {
445 	irqentry_state_t irq_state;
446 
447 	irq_state.lockdep = lockdep_hardirqs_enabled();
448 
449 	__nmi_enter();
450 	lockdep_hardirqs_off(CALLER_ADDR0);
451 	lockdep_hardirq_enter();
452 	rcu_nmi_enter();
453 
454 	instrumentation_begin();
455 	trace_hardirqs_off_finish();
456 	ftrace_nmi_enter();
457 	instrumentation_end();
458 
459 	return irq_state;
460 }
461 
irqentry_nmi_exit(struct pt_regs * regs,irqentry_state_t irq_state)462 void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
463 {
464 	instrumentation_begin();
465 	ftrace_nmi_exit();
466 	if (irq_state.lockdep) {
467 		trace_hardirqs_on_prepare();
468 		lockdep_hardirqs_on_prepare(CALLER_ADDR0);
469 	}
470 	instrumentation_end();
471 
472 	rcu_nmi_exit();
473 	lockdep_hardirq_exit();
474 	if (irq_state.lockdep)
475 		lockdep_hardirqs_on(CALLER_ADDR0);
476 	__nmi_exit();
477 }
478