summaryrefslogtreecommitdiff
path: root/include/linux/entry-common.h
blob: d95ab85f96ba5a41527722cd9f4a6f6a29554c2e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_ENTRYCOMMON_H
#define __LINUX_ENTRYCOMMON_H

#include <linux/static_call_types.h>
#include <linux/ptrace.h>
#include <linux/syscalls.h>
#include <linux/seccomp.h>
#include <linux/sched.h>

#include <asm/entry-common.h>

/*
 * Define dummy _TIF work flags if not defined by the architecture or for
 * disabled functionality.
 */
#ifndef _TIF_PATCH_PENDING
# define _TIF_PATCH_PENDING		(0)
#endif

#ifndef _TIF_UPROBE
# define _TIF_UPROBE			(0)
#endif

/*
 * SYSCALL_WORK flags handled in syscall_enter_from_user_mode()
 */
#ifndef ARCH_SYSCALL_WORK_ENTER
# define ARCH_SYSCALL_WORK_ENTER	(0)
#endif

/*
 * SYSCALL_WORK flags handled in syscall_exit_to_user_mode()
 */
#ifndef ARCH_SYSCALL_WORK_EXIT
# define ARCH_SYSCALL_WORK_EXIT		(0)
#endif

#define SYSCALL_WORK_ENTER	(SYSCALL_WORK_SECCOMP |			\
				 SYSCALL_WORK_SYSCALL_TRACEPOINT |	\
				 SYSCALL_WORK_SYSCALL_TRACE |		\
				 SYSCALL_WORK_SYSCALL_EMU |		\
				 SYSCALL_WORK_SYSCALL_AUDIT |		\
				 SYSCALL_WORK_SYSCALL_USER_DISPATCH |	\
				 ARCH_SYSCALL_WORK_ENTER)
#define SYSCALL_WORK_EXIT	(SYSCALL_WORK_SYSCALL_TRACEPOINT |	\
				 SYSCALL_WORK_SYSCALL_TRACE |		\
				 SYSCALL_WORK_SYSCALL_AUDIT |		\
				 SYSCALL_WORK_SYSCALL_USER_DISPATCH |	\
				 SYSCALL_WORK_SYSCALL_EXIT_TRAP	|	\
				 ARCH_SYSCALL_WORK_EXIT)

/*
 * TIF flags handled in exit_to_user_mode_loop()
 */
#ifndef ARCH_EXIT_TO_USER_MODE_WORK
# define ARCH_EXIT_TO_USER_MODE_WORK		(0)
#endif

#define EXIT_TO_USER_MODE_WORK						\
	(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE |		\
	 _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL |	\
	 ARCH_EXIT_TO_USER_MODE_WORK)

/**
 * arch_enter_from_user_mode - Architecture specific sanity check for user mode regs
 * @regs:	Pointer to currents pt_regs
 *
 * Defaults to an empty implementation. Can be replaced by architecture
 * specific code.
 *
 * Invoked from syscall_enter_from_user_mode() in the non-instrumentable
 * section. Use __always_inline so the compiler cannot push it out of line
 * and make it instrumentable.
 */
static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs);

#ifndef arch_enter_from_user_mode
static __always_inline void arch_enter_from_user_mode(struct pt_regs *regs) {}
#endif

/**
 * enter_from_user_mode - Establish state when coming from user mode
 *
 * Syscall/interrupt entry disables interrupts, but user mode is traced as
 * interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
 *
 * 1) Tell lockdep that interrupts are disabled
 * 2) Invoke context tracking if enabled to reactivate RCU
 * 3) Trace interrupts off state
 *
 * Invoked from architecture specific syscall entry code with interrupts
 * disabled. The calling code has to be non-instrumentable. When the
 * function returns all state is correct and interrupts are still
 * disabled. The subsequent functions can be instrumented.
 *
 * This is invoked when there is architecture specific functionality to be
 * done between establishing state and enabling interrupts. The caller must
 * enable interrupts before invoking syscall_enter_from_user_mode_work().
 */
void enter_from_user_mode(struct pt_regs *regs);

/**
 * syscall_enter_from_user_mode_prepare - Establish state and enable interrupts
 * @regs:	Pointer to currents pt_regs
 *
 * Invoked from architecture specific syscall entry code with interrupts
 * disabled. The calling code has to be non-instrumentable. When the
 * function returns all state is correct, interrupts are enabled and the
 * subsequent functions can be instrumented.
 *
 * This handles lockdep, RCU (context tracking) and tracing state, i.e.
 * the functionality provided by enter_from_user_mode().
 *
 * This is invoked when there is extra architecture specific functionality
 * to be done between establishing state and handling user mode entry work.
 */
void syscall_enter_from_user_mode_prepare(struct pt_regs *regs);

/**
 * syscall_enter_from_user_mode_work - Check and handle work before invoking
 *				       a syscall
 * @regs:	Pointer to currents pt_regs
 * @syscall:	The syscall number
 *
 * Invoked from architecture specific syscall entry code with interrupts
 * enabled after invoking syscall_enter_from_user_mode_prepare() and extra
 * architecture specific work.
 *
 * Returns: The original or a modified syscall number
 *
 * If the returned syscall number is -1 then the syscall should be
 * skipped. In this case the caller may invoke syscall_set_error() or
 * syscall_set_return_value() first.  If neither of those are called and -1
 * is returned, then the syscall will fail with ENOSYS.
 *
 * It handles the following work items:
 *
 *  1) syscall_work flag dependent invocations of
 *     ptrace_report_syscall_entry(), __secure_computing(), trace_sys_enter()
 *  2) Invocation of audit_syscall_entry()
 */
long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall);

/**
 * syscall_enter_from_user_mode - Establish state and check and handle work
 *				  before invoking a syscall
 * @regs:	Pointer to currents pt_regs
 * @syscall:	The syscall number
 *
 * Invoked from architecture specific syscall entry code with interrupts
 * disabled. The calling code has to be non-instrumentable. When the
 * function returns all state is correct, interrupts are enabled and the
 * subsequent functions can be instrumented.
 *
 * This is combination of syscall_enter_from_user_mode_prepare() and
 * syscall_enter_from_user_mode_work().
 *
 * Returns: The original or a modified syscall number. See
 * syscall_enter_from_user_mode_work() for further explanation.
 */
long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall);

/**
 * local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable()
 * @ti_work:	Cached TIF flags gathered with interrupts disabled
 *
 * Defaults to local_irq_enable(). Can be supplied by architecture specific
 * code.
 */
static inline void local_irq_enable_exit_to_user(unsigned long ti_work);

#ifndef local_irq_enable_exit_to_user
static inline void local_irq_enable_exit_to_user(unsigned long ti_work)
{
	local_irq_enable();
}
#endif

/**
 * local_irq_disable_exit_to_user - Exit to user variant of local_irq_disable()
 *
 * Defaults to local_irq_disable(). Can be supplied by architecture specific
 * code.
 */
static inline void local_irq_disable_exit_to_user(void);

#ifndef local_irq_disable_exit_to_user
static inline void local_irq_disable_exit_to_user(void)
{
	local_irq_disable();
}
#endif

/**
 * arch_exit_to_user_mode_work - Architecture specific TIF work for exit
 *				 to user mode.
 * @regs:	Pointer to currents pt_regs
 * @ti_work:	Cached TIF flags gathered with interrupts disabled
 *
 * Invoked from exit_to_user_mode_loop() with interrupt enabled
 *
 * Defaults to NOOP. Can be supplied by architecture specific code.
 */
static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
					       unsigned long ti_work);

#ifndef arch_exit_to_user_mode_work
static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
					       unsigned long ti_work)
{
}
#endif

/**
 * arch_exit_to_user_mode_prepare - Architecture specific preparation for
 *				    exit to user mode.
 * @regs:	Pointer to currents pt_regs
 * @ti_work:	Cached TIF flags gathered with interrupts disabled
 *
 * Invoked from exit_to_user_mode_prepare() with interrupt disabled as the last
 * function before return. Defaults to NOOP.
 */
static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
						  unsigned long ti_work);

#ifndef arch_exit_to_user_mode_prepare
static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
						  unsigned long ti_work)
{
}
#endif

/**
 * arch_exit_to_user_mode - Architecture specific final work before
 *			    exit to user mode.
 *
 * Invoked from exit_to_user_mode() with interrupt disabled as the last
 * function before return. Defaults to NOOP.
 *
 * This needs to be __always_inline because it is non-instrumentable code
 * invoked after context tracking switched to user mode.
 *
 * An architecture implementation must not do anything complex, no locking
 * etc. The main purpose is for speculation mitigations.
 */
static __always_inline void arch_exit_to_user_mode(void);

#ifndef arch_exit_to_user_mode
static __always_inline void arch_exit_to_user_mode(void) { }
#endif

/**
 * arch_do_signal_or_restart -  Architecture specific signal delivery function
 * @regs:	Pointer to currents pt_regs
 *
 * Invoked from exit_to_user_mode_loop().
 */
void arch_do_signal_or_restart(struct pt_regs *regs);

/**
 * exit_to_user_mode - Fixup state when exiting to user mode
 *
 * Syscall/interrupt exit enables interrupts, but the kernel state is
 * interrupts disabled when this is invoked. Also tell RCU about it.
 *
 * 1) Trace interrupts on state
 * 2) Invoke context tracking if enabled to adjust RCU state
 * 3) Invoke architecture specific last minute exit code, e.g. speculation
 *    mitigations, etc.: arch_exit_to_user_mode()
 * 4) Tell lockdep that interrupts are enabled
 *
 * Invoked from architecture specific code when syscall_exit_to_user_mode()
 * is not suitable as the last step before returning to userspace. Must be
 * invoked with interrupts disabled and the caller must be
 * non-instrumentable.
 * The caller has to invoke syscall_exit_to_user_mode_work() before this.
 */
void exit_to_user_mode(void);

/**
 * syscall_exit_to_user_mode_work - Handle work before returning to user mode
 * @regs:	Pointer to currents pt_regs
 *
 * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
 * exit_to_user_mode() to perform the final transition to user mode.
 *
 * Calling convention is the same as for syscall_exit_to_user_mode() and it
 * returns with all work handled and interrupts disabled. The caller must
 * invoke exit_to_user_mode() before actually switching to user mode to
 * make the final state transitions. Interrupts must stay disabled between
 * return from this function and the invocation of exit_to_user_mode().
 */
void syscall_exit_to_user_mode_work(struct pt_regs *regs);

/**
 * syscall_exit_to_user_mode - Handle work before returning to user mode
 * @regs:	Pointer to currents pt_regs
 *
 * Invoked with interrupts enabled and fully valid regs. Returns with all
 * work handled, interrupts disabled such that the caller can immediately
 * switch to user mode. Called from architecture specific syscall and ret
 * from fork code.
 *
 * The call order is:
 *  1) One-time syscall exit work:
 *	- rseq syscall exit
 *      - audit
 *	- syscall tracing
 *	- ptrace (single stepping)
 *
 *  2) Preparatory work
 *	- Exit to user mode loop (common TIF handling). Invokes
 *	  arch_exit_to_user_mode_work() for architecture specific TIF work
 *	- Architecture specific one time work arch_exit_to_user_mode_prepare()
 *	- Address limit and lockdep checks
 *
 *  3) Final transition (lockdep, tracing, context tracking, RCU), i.e. the
 *     functionality in exit_to_user_mode().
 *
 * This is a combination of syscall_exit_to_user_mode_work() (1,2) and
 * exit_to_user_mode(). This function is preferred unless there is a
 * compelling architectural reason to use the separate functions.
 */
void syscall_exit_to_user_mode(struct pt_regs *regs);

/**
 * irqentry_enter_from_user_mode - Establish state before invoking the irq handler
 * @regs:	Pointer to currents pt_regs
 *
 * Invoked from architecture specific entry code with interrupts disabled.
 * Can only be called when the interrupt entry came from user mode. The
 * calling code must be non-instrumentable.  When the function returns all
 * state is correct and the subsequent functions can be instrumented.
 *
 * The function establishes state (lockdep, RCU (context tracking), tracing)
 */
void irqentry_enter_from_user_mode(struct pt_regs *regs);

/**
 * irqentry_exit_to_user_mode - Interrupt exit work
 * @regs:	Pointer to current's pt_regs
 *
 * Invoked with interrupts disabled and fully valid regs. Returns with all
 * work handled, interrupts disabled such that the caller can immediately
 * switch to user mode. Called from architecture specific interrupt
 * handling code.
 *
 * The call order is #2 and #3 as described in syscall_exit_to_user_mode().
 * Interrupt exit is not invoking #1 which is the syscall specific one time
 * work.
 */
void irqentry_exit_to_user_mode(struct pt_regs *regs);

#ifndef irqentry_state
/**
 * struct irqentry_state - Opaque object for exception state storage
 * @exit_rcu: Used exclusively in the irqentry_*() calls; signals whether the
 *            exit path has to invoke ct_irq_exit().
 * @lockdep: Used exclusively in the irqentry_nmi_*() calls; ensures that
 *           lockdep state is restored correctly on exit from nmi.
 *
 * This opaque object is filled in by the irqentry_*_enter() functions and
 * must be passed back into the corresponding irqentry_*_exit() functions
 * when the exception is complete.
 *
 * Callers of irqentry_*_[enter|exit]() must consider this structure opaque
 * and all members private.  Descriptions of the members are provided to aid in
 * the maintenance of the irqentry_*() functions.
 */
typedef struct irqentry_state {
	union {
		bool	exit_rcu;
		bool	lockdep;
	};
} irqentry_state_t;
#endif

/**
 * irqentry_enter - Handle state tracking on ordinary interrupt entries
 * @regs:	Pointer to pt_regs of interrupted context
 *
 * Invokes:
 *  - lockdep irqflag state tracking as low level ASM entry disabled
 *    interrupts.
 *
 *  - Context tracking if the exception hit user mode.
 *
 *  - The hardirq tracer to keep the state consistent as low level ASM
 *    entry disabled interrupts.
 *
 * As a precondition, this requires that the entry came from user mode,
 * idle, or a kernel context in which RCU is watching.
 *
 * For kernel mode entries RCU handling is done conditional. If RCU is
 * watching then the only RCU requirement is to check whether the tick has
 * to be restarted. If RCU is not watching then ct_irq_enter() has to be
 * invoked on entry and ct_irq_exit() on exit.
 *
 * Avoiding the ct_irq_enter/exit() calls is an optimization but also
 * solves the problem of kernel mode pagefaults which can schedule, which
 * is not possible after invoking ct_irq_enter() without undoing it.
 *
 * For user mode entries irqentry_enter_from_user_mode() is invoked to
 * establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
 * would not be possible.
 *
 * Returns: An opaque object that must be passed to idtentry_exit()
 */
irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);

/**
 * irqentry_exit_cond_resched - Conditionally reschedule on return from interrupt
 *
 * Conditional reschedule with additional sanity checks.
 */
void raw_irqentry_exit_cond_resched(void);
#ifdef CONFIG_PREEMPT_DYNAMIC
#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
#define irqentry_exit_cond_resched_dynamic_enabled	raw_irqentry_exit_cond_resched
#define irqentry_exit_cond_resched_dynamic_disabled	NULL
DECLARE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
#define irqentry_exit_cond_resched()	static_call(irqentry_exit_cond_resched)()
#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
void dynamic_irqentry_exit_cond_resched(void);
#define irqentry_exit_cond_resched()	dynamic_irqentry_exit_cond_resched()
#endif
#else /* CONFIG_PREEMPT_DYNAMIC */
#define irqentry_exit_cond_resched()	raw_irqentry_exit_cond_resched()
#endif /* CONFIG_PREEMPT_DYNAMIC */

/**
 * irqentry_exit - Handle return from exception that used irqentry_enter()
 * @regs:	Pointer to pt_regs (exception entry regs)
 * @state:	Return value from matching call to irqentry_enter()
 *
 * Depending on the return target (kernel/user) this runs the necessary
 * preemption and work checks if possible and required and returns to
 * the caller with interrupts disabled and no further work pending.
 *
 * This is the last action before returning to the low level ASM code which
 * just needs to return to the appropriate context.
 *
 * Counterpart to irqentry_enter().
 */
void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t state);

/**
 * irqentry_nmi_enter - Handle NMI entry
 * @regs:	Pointer to currents pt_regs
 *
 * Similar to irqentry_enter() but taking care of the NMI constraints.
 */
irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);

/**
 * irqentry_nmi_exit - Handle return from NMI handling
 * @regs:	Pointer to pt_regs (NMI entry regs)
 * @irq_state:	Return value from matching call to irqentry_nmi_enter()
 *
 * Last action before returning to the low level assembly code.
 *
 * Counterpart to irqentry_nmi_enter().
 */
void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);

#endif