1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __LINUX_IRQENTRYCOMMON_H
3#define __LINUX_IRQENTRYCOMMON_H
4
5#include <linux/context_tracking.h>
6#include <linux/kmsan.h>
7#include <linux/rseq_entry.h>
8#include <linux/static_call_types.h>
9#include <linux/syscalls.h>
10#include <linux/tick.h>
11#include <linux/unwind_deferred.h>
12
13#include <asm/entry-common.h>
14
15/*
16 * Define dummy _TIF work flags if not defined by the architecture or for
17 * disabled functionality.
18 */
19#ifndef _TIF_PATCH_PENDING
20# define _TIF_PATCH_PENDING (0)
21#endif
22
23/*
24 * TIF flags handled in exit_to_user_mode_loop()
25 */
26#ifndef ARCH_EXIT_TO_USER_MODE_WORK
27# define ARCH_EXIT_TO_USER_MODE_WORK (0)
28#endif
29
30#define EXIT_TO_USER_MODE_WORK \
31 (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
32 _TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY | \
33 _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | _TIF_RSEQ | \
34 ARCH_EXIT_TO_USER_MODE_WORK)
35
36/**
37 * arch_enter_from_user_mode - Architecture specific sanity check for user mode regs
38 * @regs: Pointer to currents pt_regs
39 *
40 * Defaults to an empty implementation. Can be replaced by architecture
41 * specific code.
42 *
43 * Invoked from syscall_enter_from_user_mode() in the non-instrumentable
44 * section. Use __always_inline so the compiler cannot push it out of line
45 * and make it instrumentable.
46 */
47static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs);
48
49#ifndef arch_enter_from_user_mode
50static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs) {}
51#endif
52
53/**
54 * arch_in_rcu_eqs - Architecture specific check for RCU extended quiescent
55 * states.
56 *
57 * Returns: true if the CPU is potentially in an RCU EQS, false otherwise.
58 *
59 * Architectures only need to define this if threads other than the idle thread
60 * may have an interruptible EQS. This does not need to handle idle threads. It
61 * is safe to over-estimate at the cost of redundant RCU management work.
62 *
63 * Invoked from irqentry_enter()
64 */
65#ifndef arch_in_rcu_eqs
66static __always_inline bool arch_in_rcu_eqs(void) { return false; }
67#endif
68
69/**
70 * enter_from_user_mode - Establish state when coming from user mode
71 * @regs: Pointer to currents pt_regs
72 *
73 * Syscall/interrupt entry disables interrupts, but user mode is traced as
74 * interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
75 *
76 * 1) Tell lockdep that interrupts are disabled
77 * 2) Invoke context tracking if enabled to reactivate RCU
78 * 3) Trace interrupts off state
79 *
80 * Invoked from architecture specific syscall entry code with interrupts
81 * disabled. The calling code has to be non-instrumentable. When the
82 * function returns all state is correct and interrupts are still
83 * disabled. The subsequent functions can be instrumented.
84 *
85 * This is invoked when there is architecture specific functionality to be
86 * done between establishing state and enabling interrupts. The caller must
87 * enable interrupts before invoking syscall_enter_from_user_mode_work().
88 */
89static __always_inline void enter_from_user_mode(struct pt_regs *regs)
90{
91 arch_enter_from_user_mode(regs);
92 lockdep_hardirqs_off(CALLER_ADDR0);
93
94 CT_WARN_ON(__ct_state() != CT_STATE_USER);
95 user_exit_irqoff();
96
97 instrumentation_begin();
98 kmsan_unpoison_entry_regs(regs);
99 trace_hardirqs_off_finish();
100 instrumentation_end();
101}
102
103/**
104 * local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable()
105 * @ti_work: Cached TIF flags gathered with interrupts disabled
106 *
107 * Defaults to local_irq_enable(). Can be supplied by architecture specific
108 * code.
109 */
110static inline void local_irq_enable_exit_to_user(unsigned long ti_work);
111
112#ifndef local_irq_enable_exit_to_user
113static __always_inline void local_irq_enable_exit_to_user(unsigned long ti_work)
114{
115 local_irq_enable();
116}
117#endif
118
119/**
120 * local_irq_disable_exit_to_user - Exit to user variant of local_irq_disable()
121 *
122 * Defaults to local_irq_disable(). Can be supplied by architecture specific
123 * code.
124 */
125static inline void local_irq_disable_exit_to_user(void);
126
127#ifndef local_irq_disable_exit_to_user
128static __always_inline void local_irq_disable_exit_to_user(void)
129{
130 local_irq_disable();
131}
132#endif
133
134/**
135 * arch_exit_to_user_mode_work - Architecture specific TIF work for exit
136 * to user mode.
137 * @regs: Pointer to currents pt_regs
138 * @ti_work: Cached TIF flags gathered with interrupts disabled
139 *
140 * Invoked from exit_to_user_mode_loop() with interrupt enabled
141 *
142 * Defaults to NOOP. Can be supplied by architecture specific code.
143 */
144static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
145 unsigned long ti_work);
146
147#ifndef arch_exit_to_user_mode_work
148static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
149 unsigned long ti_work)
150{
151}
152#endif
153
154/**
155 * arch_exit_to_user_mode_prepare - Architecture specific preparation for
156 * exit to user mode.
157 * @regs: Pointer to currents pt_regs
158 * @ti_work: Cached TIF flags gathered with interrupts disabled
159 *
160 * Invoked from exit_to_user_mode_prepare() with interrupt disabled as the last
161 * function before return. Defaults to NOOP.
162 */
163static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
164 unsigned long ti_work);
165
166#ifndef arch_exit_to_user_mode_prepare
167static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
168 unsigned long ti_work)
169{
170}
171#endif
172
173/**
174 * arch_exit_to_user_mode - Architecture specific final work before
175 * exit to user mode.
176 *
177 * Invoked from exit_to_user_mode() with interrupt disabled as the last
178 * function before return. Defaults to NOOP.
179 *
180 * This needs to be __always_inline because it is non-instrumentable code
181 * invoked after context tracking switched to user mode.
182 *
183 * An architecture implementation must not do anything complex, no locking
184 * etc. The main purpose is for speculation mitigations.
185 */
186static __always_inline void arch_exit_to_user_mode(void);
187
188#ifndef arch_exit_to_user_mode
189static __always_inline void arch_exit_to_user_mode(void) { }
190#endif
191
192/**
193 * arch_do_signal_or_restart - Architecture specific signal delivery function
194 * @regs: Pointer to currents pt_regs
195 *
196 * Invoked from exit_to_user_mode_loop().
197 */
198void arch_do_signal_or_restart(struct pt_regs *regs);
199
200/* Handle pending TIF work */
201unsigned long exit_to_user_mode_loop(struct pt_regs *regs, unsigned long ti_work);
202
203/**
204 * __exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required
205 * @regs: Pointer to pt_regs on entry stack
206 *
207 * 1) check that interrupts are disabled
208 * 2) call tick_nohz_user_enter_prepare()
209 * 3) call exit_to_user_mode_loop() if any flags from
210 * EXIT_TO_USER_MODE_WORK are set
211 * 4) check that interrupts are still disabled
212 *
213 * Don't invoke directly, use the syscall/irqentry_ prefixed variants below
214 */
215static __always_inline void __exit_to_user_mode_prepare(struct pt_regs *regs)
216{
217 unsigned long ti_work;
218
219 lockdep_assert_irqs_disabled();
220
221 /* Flush pending rcuog wakeup before the last need_resched() check */
222 tick_nohz_user_enter_prepare();
223
224 ti_work = read_thread_flags();
225 if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
226 ti_work = exit_to_user_mode_loop(regs, ti_work);
227
228 arch_exit_to_user_mode_prepare(regs, ti_work);
229}
230
231static __always_inline void __exit_to_user_mode_validate(void)
232{
233 /* Ensure that kernel state is sane for a return to userspace */
234 kmap_assert_nomap();
235 lockdep_assert_irqs_disabled();
236 lockdep_sys_exit();
237}
238
239/* Temporary workaround to keep ARM64 alive */
240static __always_inline void exit_to_user_mode_prepare_legacy(struct pt_regs *regs)
241{
242 __exit_to_user_mode_prepare(regs);
243 rseq_exit_to_user_mode_legacy();
244 __exit_to_user_mode_validate();
245}
246
247/**
248 * syscall_exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required
249 * @regs: Pointer to pt_regs on entry stack
250 *
251 * Wrapper around __exit_to_user_mode_prepare() to separate the exit work for
252 * syscalls and interrupts.
253 */
254static __always_inline void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
255{
256 __exit_to_user_mode_prepare(regs);
257 rseq_syscall_exit_to_user_mode();
258 __exit_to_user_mode_validate();
259}
260
261/**
262 * irqentry_exit_to_user_mode_prepare - call exit_to_user_mode_loop() if required
263 * @regs: Pointer to pt_regs on entry stack
264 *
265 * Wrapper around __exit_to_user_mode_prepare() to separate the exit work for
266 * syscalls and interrupts.
267 */
268static __always_inline void irqentry_exit_to_user_mode_prepare(struct pt_regs *regs)
269{
270 __exit_to_user_mode_prepare(regs);
271 rseq_irqentry_exit_to_user_mode();
272 __exit_to_user_mode_validate();
273}
274
275/**
276 * exit_to_user_mode - Fixup state when exiting to user mode
277 *
278 * Syscall/interrupt exit enables interrupts, but the kernel state is
279 * interrupts disabled when this is invoked. Also tell RCU about it.
280 *
281 * 1) Trace interrupts on state
282 * 2) Invoke context tracking if enabled to adjust RCU state
283 * 3) Invoke architecture specific last minute exit code, e.g. speculation
284 * mitigations, etc.: arch_exit_to_user_mode()
285 * 4) Tell lockdep that interrupts are enabled
286 *
287 * Invoked from architecture specific code when syscall_exit_to_user_mode()
288 * is not suitable as the last step before returning to userspace. Must be
289 * invoked with interrupts disabled and the caller must be
290 * non-instrumentable.
291 * The caller has to invoke syscall_exit_to_user_mode_work() before this.
292 */
293static __always_inline void exit_to_user_mode(void)
294{
295 instrumentation_begin();
296 unwind_reset_info();
297 trace_hardirqs_on_prepare();
298 lockdep_hardirqs_on_prepare();
299 instrumentation_end();
300
301 user_enter_irqoff();
302 arch_exit_to_user_mode();
303 lockdep_hardirqs_on(CALLER_ADDR0);
304}
305
306/**
307 * irqentry_enter_from_user_mode - Establish state before invoking the irq handler
308 * @regs: Pointer to currents pt_regs
309 *
310 * Invoked from architecture specific entry code with interrupts disabled.
311 * Can only be called when the interrupt entry came from user mode. The
312 * calling code must be non-instrumentable. When the function returns all
313 * state is correct and the subsequent functions can be instrumented.
314 *
315 * The function establishes state (lockdep, RCU (context tracking), tracing)
316 */
317static __always_inline void irqentry_enter_from_user_mode(struct pt_regs *regs)
318{
319 enter_from_user_mode(regs);
320 rseq_note_user_irq_entry();
321}
322
323/**
324 * irqentry_exit_to_user_mode - Interrupt exit work
325 * @regs: Pointer to current's pt_regs
326 *
327 * Invoked with interrupts disabled and fully valid regs. Returns with all
328 * work handled, interrupts disabled such that the caller can immediately
329 * switch to user mode. Called from architecture specific interrupt
330 * handling code.
331 *
332 * The call order is #2 and #3 as described in syscall_exit_to_user_mode().
333 * Interrupt exit is not invoking #1 which is the syscall specific one time
334 * work.
335 */
336static __always_inline void irqentry_exit_to_user_mode(struct pt_regs *regs)
337{
338 instrumentation_begin();
339 irqentry_exit_to_user_mode_prepare(regs);
340 instrumentation_end();
341 exit_to_user_mode();
342}
343
344#ifndef irqentry_state
345/**
346 * struct irqentry_state - Opaque object for exception state storage
347 * @exit_rcu: Used exclusively in the irqentry_*() calls; signals whether the
348 * exit path has to invoke ct_irq_exit().
349 * @lockdep: Used exclusively in the irqentry_nmi_*() calls; ensures that
350 * lockdep state is restored correctly on exit from nmi.
351 *
352 * This opaque object is filled in by the irqentry_*_enter() functions and
353 * must be passed back into the corresponding irqentry_*_exit() functions
354 * when the exception is complete.
355 *
356 * Callers of irqentry_*_[enter|exit]() must consider this structure opaque
357 * and all members private. Descriptions of the members are provided to aid in
358 * the maintenance of the irqentry_*() functions.
359 */
360typedef struct irqentry_state {
361 union {
362 bool exit_rcu;
363 bool lockdep;
364 };
365} irqentry_state_t;
366#endif
367
368/**
369 * irqentry_enter - Handle state tracking on ordinary interrupt entries
370 * @regs: Pointer to pt_regs of interrupted context
371 *
372 * Invokes:
373 * - lockdep irqflag state tracking as low level ASM entry disabled
374 * interrupts.
375 *
376 * - Context tracking if the exception hit user mode.
377 *
378 * - The hardirq tracer to keep the state consistent as low level ASM
379 * entry disabled interrupts.
380 *
381 * As a precondition, this requires that the entry came from user mode,
382 * idle, or a kernel context in which RCU is watching.
383 *
384 * For kernel mode entries RCU handling is done conditional. If RCU is
385 * watching then the only RCU requirement is to check whether the tick has
386 * to be restarted. If RCU is not watching then ct_irq_enter() has to be
387 * invoked on entry and ct_irq_exit() on exit.
388 *
389 * Avoiding the ct_irq_enter/exit() calls is an optimization but also
390 * solves the problem of kernel mode pagefaults which can schedule, which
391 * is not possible after invoking ct_irq_enter() without undoing it.
392 *
393 * For user mode entries irqentry_enter_from_user_mode() is invoked to
394 * establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
395 * would not be possible.
396 *
397 * Returns: An opaque object that must be passed to idtentry_exit()
398 */
399irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
400
401/**
402 * irqentry_exit_cond_resched - Conditionally reschedule on return from interrupt
403 *
404 * Conditional reschedule with additional sanity checks.
405 */
406void raw_irqentry_exit_cond_resched(void);
407
408#ifdef CONFIG_PREEMPT_DYNAMIC
409#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
410#define irqentry_exit_cond_resched_dynamic_enabled raw_irqentry_exit_cond_resched
411#define irqentry_exit_cond_resched_dynamic_disabled NULL
412DECLARE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
413#define irqentry_exit_cond_resched() static_call(irqentry_exit_cond_resched)()
414#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
415DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
416void dynamic_irqentry_exit_cond_resched(void);
417#define irqentry_exit_cond_resched() dynamic_irqentry_exit_cond_resched()
418#endif
419#else /* CONFIG_PREEMPT_DYNAMIC */
420#define irqentry_exit_cond_resched() raw_irqentry_exit_cond_resched()
421#endif /* CONFIG_PREEMPT_DYNAMIC */
422
423/**
424 * irqentry_exit - Handle return from exception that used irqentry_enter()
425 * @regs: Pointer to pt_regs (exception entry regs)
426 * @state: Return value from matching call to irqentry_enter()
427 *
428 * Depending on the return target (kernel/user) this runs the necessary
429 * preemption and work checks if possible and required and returns to
430 * the caller with interrupts disabled and no further work pending.
431 *
432 * This is the last action before returning to the low level ASM code which
433 * just needs to return to the appropriate context.
434 *
435 * Counterpart to irqentry_enter().
436 */
437void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t state);
438
439/**
440 * irqentry_nmi_enter - Handle NMI entry
441 * @regs: Pointer to currents pt_regs
442 *
443 * Similar to irqentry_enter() but taking care of the NMI constraints.
444 */
445irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);
446
447/**
448 * irqentry_nmi_exit - Handle return from NMI handling
449 * @regs: Pointer to pt_regs (NMI entry regs)
450 * @irq_state: Return value from matching call to irqentry_nmi_enter()
451 *
452 * Last action before returning to the low level assembly code.
453 *
454 * Counterpart to irqentry_nmi_enter().
455 */
456void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);
457
458#endif
459

source code of linux/include/linux/irq-entry-common.h