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1// SPDX-License-Identifier: GPL-2.0
2
3#include <linux/context_tracking.h>
4#include <linux/entry-common.h>
5#include <linux/livepatch.h>
6#include <linux/audit.h>
7
8#define CREATE_TRACE_POINTS
9#include <trace/events/syscalls.h>
10
11/**
12 * enter_from_user_mode - Establish state when coming from user mode
13 *
14 * Syscall/interrupt entry disables interrupts, but user mode is traced as
15 * interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
16 *
17 * 1) Tell lockdep that interrupts are disabled
18 * 2) Invoke context tracking if enabled to reactivate RCU
19 * 3) Trace interrupts off state
20 */
21static __always_inline void enter_from_user_mode(struct pt_regs *regs)
22{
23 arch_check_user_regs(regs);
24 lockdep_hardirqs_off(CALLER_ADDR0);
25
26 CT_WARN_ON(ct_state() != CONTEXT_USER);
27 user_exit_irqoff();
28
29 instrumentation_begin();
30 trace_hardirqs_off_finish();
31 instrumentation_end();
32}
33
34static 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
44static long syscall_trace_enter(struct pt_regs *regs, long syscall,
45 unsigned long ti_work)
46{
47 long ret = 0;
48
49 /* Handle ptrace */
50 if (ti_work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
51 ret = arch_syscall_enter_tracehook(regs);
52 if (ret || (ti_work & _TIF_SYSCALL_EMU))
53 return -1L;
54 }
55
56 /* Do seccomp after ptrace, to catch any tracer changes. */
57 if (ti_work & _TIF_SECCOMP) {
58 ret = __secure_computing(NULL);
59 if (ret == -1L)
60 return ret;
61 }
62
63 /* Either of the above might have changed the syscall number */
64 syscall = syscall_get_nr(current, regs);
65
66 if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
67 trace_sys_enter(regs, syscall);
68
69 syscall_enter_audit(regs, syscall);
70
71 return ret ? : syscall;
72}
73
74static __always_inline long
75__syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
76{
77 unsigned long ti_work;
78
79 ti_work = READ_ONCE(current_thread_info()->flags);
80 if (ti_work & SYSCALL_ENTER_WORK)
81 syscall = syscall_trace_enter(regs, syscall, ti_work);
82
83 return syscall;
84}
85
86long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
87{
88 return __syscall_enter_from_user_work(regs, syscall);
89}
90
91noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
92{
93 long ret;
94
95 enter_from_user_mode(regs);
96
97 instrumentation_begin();
98 local_irq_enable();
99 ret = __syscall_enter_from_user_work(regs, syscall);
100 instrumentation_end();
101
102 return ret;
103}
104
105noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
106{
107 enter_from_user_mode(regs);
108 instrumentation_begin();
109 local_irq_enable();
110 instrumentation_end();
111}
112
113/**
114 * exit_to_user_mode - Fixup state when exiting to user mode
115 *
116 * Syscall/interupt exit enables interrupts, but the kernel state is
117 * interrupts disabled when this is invoked. Also tell RCU about it.
118 *
119 * 1) Trace interrupts on state
120 * 2) Invoke context tracking if enabled to adjust RCU state
121 * 3) Invoke architecture specific last minute exit code, e.g. speculation
122 * mitigations, etc.
123 * 4) Tell lockdep that interrupts are enabled
124 */
125static __always_inline void exit_to_user_mode(void)
126{
127 instrumentation_begin();
128 trace_hardirqs_on_prepare();
129 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
130 instrumentation_end();
131
132 user_enter_irqoff();
133 arch_exit_to_user_mode();
134 lockdep_hardirqs_on(CALLER_ADDR0);
135}
136
137/* Workaround to allow gradual conversion of architecture code */
138void __weak arch_do_signal(struct pt_regs *regs) { }
139
140static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
141 unsigned long ti_work)
142{
143 /*
144 * Before returning to user space ensure that all pending work
145 * items have been completed.
146 */
147 while (ti_work & EXIT_TO_USER_MODE_WORK) {
148
149 local_irq_enable_exit_to_user(ti_work);
150
151 if (ti_work & _TIF_NEED_RESCHED)
152 schedule();
153
154 if (ti_work & _TIF_UPROBE)
155 uprobe_notify_resume(regs);
156
157 if (ti_work & _TIF_PATCH_PENDING)
158 klp_update_patch_state(current);
159
160 if (ti_work & _TIF_SIGPENDING)
161 arch_do_signal(regs);
162
163 if (ti_work & _TIF_NOTIFY_RESUME) {
164 clear_thread_flag(TIF_NOTIFY_RESUME);
165 tracehook_notify_resume(regs);
166 rseq_handle_notify_resume(NULL, regs);
167 }
168
169 /* Architecture specific TIF work */
170 arch_exit_to_user_mode_work(regs, ti_work);
171
172 /*
173 * Disable interrupts and reevaluate the work flags as they
174 * might have changed while interrupts and preemption was
175 * enabled above.
176 */
177 local_irq_disable_exit_to_user();
178 ti_work = READ_ONCE(current_thread_info()->flags);
179 }
180
181 /* Return the latest work state for arch_exit_to_user_mode() */
182 return ti_work;
183}
184
185static void exit_to_user_mode_prepare(struct pt_regs *regs)
186{
187 unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
188
189 lockdep_assert_irqs_disabled();
190
191 if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
192 ti_work = exit_to_user_mode_loop(regs, ti_work);
193
194 arch_exit_to_user_mode_prepare(regs, ti_work);
195
196 /* Ensure that the address limit is intact and no locks are held */
197 addr_limit_user_check();
198 lockdep_assert_irqs_disabled();
199 lockdep_sys_exit();
200}
201
202#ifndef _TIF_SINGLESTEP
203static inline bool report_single_step(unsigned long ti_work)
204{
205 return false;
206}
207#else
208/*
209 * If TIF_SYSCALL_EMU is set, then the only reason to report is when
210 * TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
211 * instruction has been already reported in syscall_enter_from_usermode().
212 */
213#define SYSEMU_STEP (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU)
214
215static inline bool report_single_step(unsigned long ti_work)
216{
217 return (ti_work & SYSEMU_STEP) == _TIF_SINGLESTEP;
218}
219#endif
220
221static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work)
222{
223 bool step;
224
225 audit_syscall_exit(regs);
226
227 if (ti_work & _TIF_SYSCALL_TRACEPOINT)
228 trace_sys_exit(regs, syscall_get_return_value(current, regs));
229
230 step = report_single_step(ti_work);
231 if (step || ti_work & _TIF_SYSCALL_TRACE)
232 arch_syscall_exit_tracehook(regs, step);
233}
234
235/*
236 * Syscall specific exit to user mode preparation. Runs with interrupts
237 * enabled.
238 */
239static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
240{
241 u32 cached_flags = READ_ONCE(current_thread_info()->flags);
242 unsigned long nr = syscall_get_nr(current, regs);
243
244 CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
245
246 if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
247 if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
248 local_irq_enable();
249 }
250
251 rseq_syscall(regs);
252
253 /*
254 * Do one-time syscall specific work. If these work items are
255 * enabled, we want to run them exactly once per syscall exit with
256 * interrupts enabled.
257 */
258 if (unlikely(cached_flags & SYSCALL_EXIT_WORK))
259 syscall_exit_work(regs, cached_flags);
260}
261
262__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
263{
264 instrumentation_begin();
265 syscall_exit_to_user_mode_prepare(regs);
266 local_irq_disable_exit_to_user();
267 exit_to_user_mode_prepare(regs);
268 instrumentation_end();
269 exit_to_user_mode();
270}
271
272noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
273{
274 enter_from_user_mode(regs);
275}
276
277noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
278{
279 instrumentation_begin();
280 exit_to_user_mode_prepare(regs);
281 instrumentation_end();
282 exit_to_user_mode();
283}
284
285noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
286{
287 irqentry_state_t ret = {
288 .exit_rcu = false,
289 };
290
291 if (user_mode(regs)) {
292 irqentry_enter_from_user_mode(regs);
293 return ret;
294 }
295
296 /*
297 * If this entry hit the idle task invoke rcu_irq_enter() whether
298 * RCU is watching or not.
299 *
300 * Interupts can nest when the first interrupt invokes softirq
301 * processing on return which enables interrupts.
302 *
303 * Scheduler ticks in the idle task can mark quiescent state and
304 * terminate a grace period, if and only if the timer interrupt is
305 * not nested into another interrupt.
306 *
307 * Checking for __rcu_is_watching() here would prevent the nesting
308 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
309 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
310 * assume that it is the first interupt and eventually claim
311 * quiescient state and end grace periods prematurely.
312 *
313 * Unconditionally invoke rcu_irq_enter() so RCU state stays
314 * consistent.
315 *
316 * TINY_RCU does not support EQS, so let the compiler eliminate
317 * this part when enabled.
318 */
319 if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
320 /*
321 * If RCU is not watching then the same careful
322 * sequence vs. lockdep and tracing is required
323 * as in irq_enter_from_user_mode().
324 */
325 lockdep_hardirqs_off(CALLER_ADDR0);
326 rcu_irq_enter();
327 instrumentation_begin();
328 trace_hardirqs_off_finish();
329 instrumentation_end();
330
331 ret.exit_rcu = true;
332 return ret;
333 }
334
335 /*
336 * If RCU is watching then RCU only wants to check whether it needs
337 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
338 * already contains a warning when RCU is not watching, so no point
339 * in having another one here.
340 */
341 instrumentation_begin();
342 rcu_irq_enter_check_tick();
343 /* Use the combo lockdep/tracing function */
344 trace_hardirqs_off();
345 instrumentation_end();
346
347 return ret;
348}
349
350void irqentry_exit_cond_resched(void)
351{
352 if (!preempt_count()) {
353 /* Sanity check RCU and thread stack */
354 rcu_irq_exit_check_preempt();
355 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
356 WARN_ON_ONCE(!on_thread_stack());
357 if (need_resched())
358 preempt_schedule_irq();
359 }
360}
361
362noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
363{
364 lockdep_assert_irqs_disabled();
365
366 /* Check whether this returns to user mode */
367 if (user_mode(regs)) {
368 irqentry_exit_to_user_mode(regs);
369 } else if (!regs_irqs_disabled(regs)) {
370 /*
371 * If RCU was not watching on entry this needs to be done
372 * carefully and needs the same ordering of lockdep/tracing
373 * and RCU as the return to user mode path.
374 */
375 if (state.exit_rcu) {
376 instrumentation_begin();
377 /* Tell the tracer that IRET will enable interrupts */
378 trace_hardirqs_on_prepare();
379 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
380 instrumentation_end();
381 rcu_irq_exit();
382 lockdep_hardirqs_on(CALLER_ADDR0);
383 return;
384 }
385
386 instrumentation_begin();
387 if (IS_ENABLED(CONFIG_PREEMPTION))
388 irqentry_exit_cond_resched();
389 /* Covers both tracing and lockdep */
390 trace_hardirqs_on();
391 instrumentation_end();
392 } else {
393 /*
394 * IRQ flags state is correct already. Just tell RCU if it
395 * was not watching on entry.
396 */
397 if (state.exit_rcu)
398 rcu_irq_exit();
399 }
400}
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 */
16static __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
29void noinstr enter_from_user_mode(struct pt_regs *regs)
30{
31 __enter_from_user_mode(regs);
32}
33
34static 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
44static 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
84static __always_inline long
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
95long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
96{
97 return __syscall_enter_from_user_work(regs, syscall);
98}
99
100noinstr 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
114noinstr 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 */
123static __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
135void noinstr exit_to_user_mode(void)
136{
137 __exit_to_user_mode();
138}
139
140/* Workaround to allow gradual conversion of architecture code */
141void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }
142
143static 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
151static 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 rseq_handle_notify_resume(NULL, regs);
177 }
178
179 /* Architecture specific TIF work */
180 arch_exit_to_user_mode_work(regs, ti_work);
181
182 /*
183 * Disable interrupts and reevaluate the work flags as they
184 * might have changed while interrupts and preemption was
185 * enabled above.
186 */
187 local_irq_disable_exit_to_user();
188
189 /* Check if any of the above work has queued a deferred wakeup */
190 tick_nohz_user_enter_prepare();
191
192 ti_work = READ_ONCE(current_thread_info()->flags);
193 }
194
195 /* Return the latest work state for arch_exit_to_user_mode() */
196 return ti_work;
197}
198
199static void exit_to_user_mode_prepare(struct pt_regs *regs)
200{
201 unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
202
203 lockdep_assert_irqs_disabled();
204
205 /* Flush pending rcuog wakeup before the last need_resched() check */
206 tick_nohz_user_enter_prepare();
207
208 if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
209 ti_work = exit_to_user_mode_loop(regs, ti_work);
210
211 arch_exit_to_user_mode_prepare(regs, ti_work);
212
213 /* Ensure that the address limit is intact and no locks are held */
214 addr_limit_user_check();
215 kmap_assert_nomap();
216 lockdep_assert_irqs_disabled();
217 lockdep_sys_exit();
218}
219
220/*
221 * If SYSCALL_EMU is set, then the only reason to report is when
222 * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
223 * instruction has been already reported in syscall_enter_from_user_mode().
224 */
225static inline bool report_single_step(unsigned long work)
226{
227 if (work & SYSCALL_WORK_SYSCALL_EMU)
228 return false;
229
230 return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
231}
232
233static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
234{
235 bool step;
236
237 /*
238 * If the syscall was rolled back due to syscall user dispatching,
239 * then the tracers below are not invoked for the same reason as
240 * the entry side was not invoked in syscall_trace_enter(): The ABI
241 * of these syscalls is unknown.
242 */
243 if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
244 if (unlikely(current->syscall_dispatch.on_dispatch)) {
245 current->syscall_dispatch.on_dispatch = false;
246 return;
247 }
248 }
249
250 audit_syscall_exit(regs);
251
252 if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
253 trace_sys_exit(regs, syscall_get_return_value(current, regs));
254
255 step = report_single_step(work);
256 if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
257 arch_syscall_exit_tracehook(regs, step);
258}
259
260/*
261 * Syscall specific exit to user mode preparation. Runs with interrupts
262 * enabled.
263 */
264static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
265{
266 unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
267 unsigned long nr = syscall_get_nr(current, regs);
268
269 CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
270
271 if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
272 if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
273 local_irq_enable();
274 }
275
276 rseq_syscall(regs);
277
278 /*
279 * Do one-time syscall specific work. If these work items are
280 * enabled, we want to run them exactly once per syscall exit with
281 * interrupts enabled.
282 */
283 if (unlikely(work & SYSCALL_WORK_EXIT))
284 syscall_exit_work(regs, work);
285}
286
287static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
288{
289 syscall_exit_to_user_mode_prepare(regs);
290 local_irq_disable_exit_to_user();
291 exit_to_user_mode_prepare(regs);
292}
293
294void syscall_exit_to_user_mode_work(struct pt_regs *regs)
295{
296 __syscall_exit_to_user_mode_work(regs);
297}
298
299__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
300{
301 instrumentation_begin();
302 __syscall_exit_to_user_mode_work(regs);
303 instrumentation_end();
304 __exit_to_user_mode();
305}
306
307noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
308{
309 __enter_from_user_mode(regs);
310}
311
312noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
313{
314 instrumentation_begin();
315 exit_to_user_mode_prepare(regs);
316 instrumentation_end();
317 __exit_to_user_mode();
318}
319
320noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
321{
322 irqentry_state_t ret = {
323 .exit_rcu = false,
324 };
325
326 if (user_mode(regs)) {
327 irqentry_enter_from_user_mode(regs);
328 return ret;
329 }
330
331 /*
332 * If this entry hit the idle task invoke rcu_irq_enter() whether
333 * RCU is watching or not.
334 *
335 * Interrupts can nest when the first interrupt invokes softirq
336 * processing on return which enables interrupts.
337 *
338 * Scheduler ticks in the idle task can mark quiescent state and
339 * terminate a grace period, if and only if the timer interrupt is
340 * not nested into another interrupt.
341 *
342 * Checking for rcu_is_watching() here would prevent the nesting
343 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
344 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
345 * assume that it is the first interrupt and eventually claim
346 * quiescent state and end grace periods prematurely.
347 *
348 * Unconditionally invoke rcu_irq_enter() so RCU state stays
349 * consistent.
350 *
351 * TINY_RCU does not support EQS, so let the compiler eliminate
352 * this part when enabled.
353 */
354 if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
355 /*
356 * If RCU is not watching then the same careful
357 * sequence vs. lockdep and tracing is required
358 * as in irqentry_enter_from_user_mode().
359 */
360 lockdep_hardirqs_off(CALLER_ADDR0);
361 rcu_irq_enter();
362 instrumentation_begin();
363 trace_hardirqs_off_finish();
364 instrumentation_end();
365
366 ret.exit_rcu = true;
367 return ret;
368 }
369
370 /*
371 * If RCU is watching then RCU only wants to check whether it needs
372 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
373 * already contains a warning when RCU is not watching, so no point
374 * in having another one here.
375 */
376 lockdep_hardirqs_off(CALLER_ADDR0);
377 instrumentation_begin();
378 rcu_irq_enter_check_tick();
379 trace_hardirqs_off_finish();
380 instrumentation_end();
381
382 return ret;
383}
384
385void irqentry_exit_cond_resched(void)
386{
387 if (!preempt_count()) {
388 /* Sanity check RCU and thread stack */
389 rcu_irq_exit_check_preempt();
390 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
391 WARN_ON_ONCE(!on_thread_stack());
392 if (need_resched())
393 preempt_schedule_irq();
394 }
395}
396#ifdef CONFIG_PREEMPT_DYNAMIC
397DEFINE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
398#endif
399
400noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
401{
402 lockdep_assert_irqs_disabled();
403
404 /* Check whether this returns to user mode */
405 if (user_mode(regs)) {
406 irqentry_exit_to_user_mode(regs);
407 } else if (!regs_irqs_disabled(regs)) {
408 /*
409 * If RCU was not watching on entry this needs to be done
410 * carefully and needs the same ordering of lockdep/tracing
411 * and RCU as the return to user mode path.
412 */
413 if (state.exit_rcu) {
414 instrumentation_begin();
415 /* Tell the tracer that IRET will enable interrupts */
416 trace_hardirqs_on_prepare();
417 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
418 instrumentation_end();
419 rcu_irq_exit();
420 lockdep_hardirqs_on(CALLER_ADDR0);
421 return;
422 }
423
424 instrumentation_begin();
425 if (IS_ENABLED(CONFIG_PREEMPTION)) {
426#ifdef CONFIG_PREEMPT_DYNAMIC
427 static_call(irqentry_exit_cond_resched)();
428#else
429 irqentry_exit_cond_resched();
430#endif
431 }
432 /* Covers both tracing and lockdep */
433 trace_hardirqs_on();
434 instrumentation_end();
435 } else {
436 /*
437 * IRQ flags state is correct already. Just tell RCU if it
438 * was not watching on entry.
439 */
440 if (state.exit_rcu)
441 rcu_irq_exit();
442 }
443}
444
445irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
446{
447 irqentry_state_t irq_state;
448
449 irq_state.lockdep = lockdep_hardirqs_enabled();
450
451 __nmi_enter();
452 lockdep_hardirqs_off(CALLER_ADDR0);
453 lockdep_hardirq_enter();
454 rcu_nmi_enter();
455
456 instrumentation_begin();
457 trace_hardirqs_off_finish();
458 ftrace_nmi_enter();
459 instrumentation_end();
460
461 return irq_state;
462}
463
464void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
465{
466 instrumentation_begin();
467 ftrace_nmi_exit();
468 if (irq_state.lockdep) {
469 trace_hardirqs_on_prepare();
470 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
471 }
472 instrumentation_end();
473
474 rcu_nmi_exit();
475 lockdep_hardirq_exit();
476 if (irq_state.lockdep)
477 lockdep_hardirqs_on(CALLER_ADDR0);
478 __nmi_exit();
479}