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