1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_ENTRYCOMMON_H
3 #define __LINUX_ENTRYCOMMON_H
4
5 #include <linux/static_call_types.h>
6 #include <linux/tracehook.h>
7 #include <linux/syscalls.h>
8 #include <linux/seccomp.h>
9 #include <linux/sched.h>
10
11 #include <asm/entry-common.h>
12
13 /*
14 * Define dummy _TIF work flags if not defined by the architecture or for
15 * disabled functionality.
16 */
17 #ifndef _TIF_PATCH_PENDING
18 # define _TIF_PATCH_PENDING (0)
19 #endif
20
21 #ifndef _TIF_UPROBE
22 # define _TIF_UPROBE (0)
23 #endif
24
25 /*
26 * SYSCALL_WORK flags handled in syscall_enter_from_user_mode()
27 */
28 #ifndef ARCH_SYSCALL_WORK_ENTER
29 # define ARCH_SYSCALL_WORK_ENTER (0)
30 #endif
31
32 /*
33 * SYSCALL_WORK flags handled in syscall_exit_to_user_mode()
34 */
35 #ifndef ARCH_SYSCALL_WORK_EXIT
36 # define ARCH_SYSCALL_WORK_EXIT (0)
37 #endif
38
39 #define SYSCALL_WORK_ENTER (SYSCALL_WORK_SECCOMP | \
40 SYSCALL_WORK_SYSCALL_TRACEPOINT | \
41 SYSCALL_WORK_SYSCALL_TRACE | \
42 SYSCALL_WORK_SYSCALL_EMU | \
43 SYSCALL_WORK_SYSCALL_AUDIT | \
44 SYSCALL_WORK_SYSCALL_USER_DISPATCH | \
45 ARCH_SYSCALL_WORK_ENTER)
46 #define SYSCALL_WORK_EXIT (SYSCALL_WORK_SYSCALL_TRACEPOINT | \
47 SYSCALL_WORK_SYSCALL_TRACE | \
48 SYSCALL_WORK_SYSCALL_AUDIT | \
49 SYSCALL_WORK_SYSCALL_USER_DISPATCH | \
50 SYSCALL_WORK_SYSCALL_EXIT_TRAP | \
51 ARCH_SYSCALL_WORK_EXIT)
52
53 /*
54 * TIF flags handled in exit_to_user_mode_loop()
55 */
56 #ifndef ARCH_EXIT_TO_USER_MODE_WORK
57 # define ARCH_EXIT_TO_USER_MODE_WORK (0)
58 #endif
59
60 #define EXIT_TO_USER_MODE_WORK \
61 (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
62 _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \
63 ARCH_EXIT_TO_USER_MODE_WORK)
64
65 /**
66 * arch_check_user_regs - Architecture specific sanity check for user mode regs
67 * @regs: Pointer to currents pt_regs
68 *
69 * Defaults to an empty implementation. Can be replaced by architecture
70 * specific code.
71 *
72 * Invoked from syscall_enter_from_user_mode() in the non-instrumentable
73 * section. Use __always_inline so the compiler cannot push it out of line
74 * and make it instrumentable.
75 */
76 static __always_inline void arch_check_user_regs(struct pt_regs *regs);
77
78 #ifndef arch_check_user_regs
arch_check_user_regs(struct pt_regs * regs)79 static __always_inline void arch_check_user_regs(struct pt_regs *regs) {}
80 #endif
81
82 /**
83 * arch_syscall_enter_tracehook - Wrapper around tracehook_report_syscall_entry()
84 * @regs: Pointer to currents pt_regs
85 *
86 * Returns: 0 on success or an error code to skip the syscall.
87 *
88 * Defaults to tracehook_report_syscall_entry(). Can be replaced by
89 * architecture specific code.
90 *
91 * Invoked from syscall_enter_from_user_mode()
92 */
93 static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs);
94
95 #ifndef arch_syscall_enter_tracehook
arch_syscall_enter_tracehook(struct pt_regs * regs)96 static inline __must_check int arch_syscall_enter_tracehook(struct pt_regs *regs)
97 {
98 return tracehook_report_syscall_entry(regs);
99 }
100 #endif
101
102 /**
103 * enter_from_user_mode - Establish state when coming from user mode
104 *
105 * Syscall/interrupt entry disables interrupts, but user mode is traced as
106 * interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
107 *
108 * 1) Tell lockdep that interrupts are disabled
109 * 2) Invoke context tracking if enabled to reactivate RCU
110 * 3) Trace interrupts off state
111 *
112 * Invoked from architecture specific syscall entry code with interrupts
113 * disabled. The calling code has to be non-instrumentable. When the
114 * function returns all state is correct and interrupts are still
115 * disabled. The subsequent functions can be instrumented.
116 *
117 * This is invoked when there is architecture specific functionality to be
118 * done between establishing state and enabling interrupts. The caller must
119 * enable interrupts before invoking syscall_enter_from_user_mode_work().
120 */
121 void enter_from_user_mode(struct pt_regs *regs);
122
123 /**
124 * syscall_enter_from_user_mode_prepare - Establish state and enable interrupts
125 * @regs: Pointer to currents pt_regs
126 *
127 * Invoked from architecture specific syscall entry code with interrupts
128 * disabled. The calling code has to be non-instrumentable. When the
129 * function returns all state is correct, interrupts are enabled and the
130 * subsequent functions can be instrumented.
131 *
132 * This handles lockdep, RCU (context tracking) and tracing state, i.e.
133 * the functionality provided by enter_from_user_mode().
134 *
135 * This is invoked when there is extra architecture specific functionality
136 * to be done between establishing state and handling user mode entry work.
137 */
138 void syscall_enter_from_user_mode_prepare(struct pt_regs *regs);
139
140 /**
141 * syscall_enter_from_user_mode_work - Check and handle work before invoking
142 * a syscall
143 * @regs: Pointer to currents pt_regs
144 * @syscall: The syscall number
145 *
146 * Invoked from architecture specific syscall entry code with interrupts
147 * enabled after invoking syscall_enter_from_user_mode_prepare() and extra
148 * architecture specific work.
149 *
150 * Returns: The original or a modified syscall number
151 *
152 * If the returned syscall number is -1 then the syscall should be
153 * skipped. In this case the caller may invoke syscall_set_error() or
154 * syscall_set_return_value() first. If neither of those are called and -1
155 * is returned, then the syscall will fail with ENOSYS.
156 *
157 * It handles the following work items:
158 *
159 * 1) syscall_work flag dependent invocations of
160 * arch_syscall_enter_tracehook(), __secure_computing(), trace_sys_enter()
161 * 2) Invocation of audit_syscall_entry()
162 */
163 long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall);
164
165 /**
166 * syscall_enter_from_user_mode - Establish state and check and handle work
167 * before invoking a syscall
168 * @regs: Pointer to currents pt_regs
169 * @syscall: The syscall number
170 *
171 * Invoked from architecture specific syscall entry code with interrupts
172 * disabled. The calling code has to be non-instrumentable. When the
173 * function returns all state is correct, interrupts are enabled and the
174 * subsequent functions can be instrumented.
175 *
176 * This is combination of syscall_enter_from_user_mode_prepare() and
177 * syscall_enter_from_user_mode_work().
178 *
179 * Returns: The original or a modified syscall number. See
180 * syscall_enter_from_user_mode_work() for further explanation.
181 */
182 long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall);
183
184 /**
185 * local_irq_enable_exit_to_user - Exit to user variant of local_irq_enable()
186 * @ti_work: Cached TIF flags gathered with interrupts disabled
187 *
188 * Defaults to local_irq_enable(). Can be supplied by architecture specific
189 * code.
190 */
191 static inline void local_irq_enable_exit_to_user(unsigned long ti_work);
192
193 #ifndef local_irq_enable_exit_to_user
local_irq_enable_exit_to_user(unsigned long ti_work)194 static inline void local_irq_enable_exit_to_user(unsigned long ti_work)
195 {
196 local_irq_enable();
197 }
198 #endif
199
200 /**
201 * local_irq_disable_exit_to_user - Exit to user variant of local_irq_disable()
202 *
203 * Defaults to local_irq_disable(). Can be supplied by architecture specific
204 * code.
205 */
206 static inline void local_irq_disable_exit_to_user(void);
207
208 #ifndef local_irq_disable_exit_to_user
local_irq_disable_exit_to_user(void)209 static inline void local_irq_disable_exit_to_user(void)
210 {
211 local_irq_disable();
212 }
213 #endif
214
215 /**
216 * arch_exit_to_user_mode_work - Architecture specific TIF work for exit
217 * to user mode.
218 * @regs: Pointer to currents pt_regs
219 * @ti_work: Cached TIF flags gathered with interrupts disabled
220 *
221 * Invoked from exit_to_user_mode_loop() with interrupt enabled
222 *
223 * Defaults to NOOP. Can be supplied by architecture specific code.
224 */
225 static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
226 unsigned long ti_work);
227
228 #ifndef arch_exit_to_user_mode_work
arch_exit_to_user_mode_work(struct pt_regs * regs,unsigned long ti_work)229 static inline void arch_exit_to_user_mode_work(struct pt_regs *regs,
230 unsigned long ti_work)
231 {
232 }
233 #endif
234
235 /**
236 * arch_exit_to_user_mode_prepare - Architecture specific preparation for
237 * exit to user mode.
238 * @regs: Pointer to currents pt_regs
239 * @ti_work: Cached TIF flags gathered with interrupts disabled
240 *
241 * Invoked from exit_to_user_mode_prepare() with interrupt disabled as the last
242 * function before return. Defaults to NOOP.
243 */
244 static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
245 unsigned long ti_work);
246
247 #ifndef arch_exit_to_user_mode_prepare
arch_exit_to_user_mode_prepare(struct pt_regs * regs,unsigned long ti_work)248 static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,
249 unsigned long ti_work)
250 {
251 }
252 #endif
253
254 /**
255 * arch_exit_to_user_mode - Architecture specific final work before
256 * exit to user mode.
257 *
258 * Invoked from exit_to_user_mode() with interrupt disabled as the last
259 * function before return. Defaults to NOOP.
260 *
261 * This needs to be __always_inline because it is non-instrumentable code
262 * invoked after context tracking switched to user mode.
263 *
264 * An architecture implementation must not do anything complex, no locking
265 * etc. The main purpose is for speculation mitigations.
266 */
267 static __always_inline void arch_exit_to_user_mode(void);
268
269 #ifndef arch_exit_to_user_mode
arch_exit_to_user_mode(void)270 static __always_inline void arch_exit_to_user_mode(void) { }
271 #endif
272
273 /**
274 * arch_do_signal_or_restart - Architecture specific signal delivery function
275 * @regs: Pointer to currents pt_regs
276 * @has_signal: actual signal to handle
277 *
278 * Invoked from exit_to_user_mode_loop().
279 */
280 void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal);
281
282 /**
283 * arch_syscall_exit_tracehook - Wrapper around tracehook_report_syscall_exit()
284 * @regs: Pointer to currents pt_regs
285 * @step: Indicator for single step
286 *
287 * Defaults to tracehook_report_syscall_exit(). Can be replaced by
288 * architecture specific code.
289 *
290 * Invoked from syscall_exit_to_user_mode()
291 */
292 static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step);
293
294 #ifndef arch_syscall_exit_tracehook
arch_syscall_exit_tracehook(struct pt_regs * regs,bool step)295 static inline void arch_syscall_exit_tracehook(struct pt_regs *regs, bool step)
296 {
297 tracehook_report_syscall_exit(regs, step);
298 }
299 #endif
300
301 /**
302 * exit_to_user_mode - Fixup state when exiting to user mode
303 *
304 * Syscall/interrupt exit enables interrupts, but the kernel state is
305 * interrupts disabled when this is invoked. Also tell RCU about it.
306 *
307 * 1) Trace interrupts on state
308 * 2) Invoke context tracking if enabled to adjust RCU state
309 * 3) Invoke architecture specific last minute exit code, e.g. speculation
310 * mitigations, etc.: arch_exit_to_user_mode()
311 * 4) Tell lockdep that interrupts are enabled
312 *
313 * Invoked from architecture specific code when syscall_exit_to_user_mode()
314 * is not suitable as the last step before returning to userspace. Must be
315 * invoked with interrupts disabled and the caller must be
316 * non-instrumentable.
317 * The caller has to invoke syscall_exit_to_user_mode_work() before this.
318 */
319 void exit_to_user_mode(void);
320
321 /**
322 * syscall_exit_to_user_mode_work - Handle work before returning to user mode
323 * @regs: Pointer to currents pt_regs
324 *
325 * Same as step 1 and 2 of syscall_exit_to_user_mode() but without calling
326 * exit_to_user_mode() to perform the final transition to user mode.
327 *
328 * Calling convention is the same as for syscall_exit_to_user_mode() and it
329 * returns with all work handled and interrupts disabled. The caller must
330 * invoke exit_to_user_mode() before actually switching to user mode to
331 * make the final state transitions. Interrupts must stay disabled between
332 * return from this function and the invocation of exit_to_user_mode().
333 */
334 void syscall_exit_to_user_mode_work(struct pt_regs *regs);
335
336 /**
337 * syscall_exit_to_user_mode - Handle work before returning to user mode
338 * @regs: Pointer to currents pt_regs
339 *
340 * Invoked with interrupts enabled and fully valid regs. Returns with all
341 * work handled, interrupts disabled such that the caller can immediately
342 * switch to user mode. Called from architecture specific syscall and ret
343 * from fork code.
344 *
345 * The call order is:
346 * 1) One-time syscall exit work:
347 * - rseq syscall exit
348 * - audit
349 * - syscall tracing
350 * - tracehook (single stepping)
351 *
352 * 2) Preparatory work
353 * - Exit to user mode loop (common TIF handling). Invokes
354 * arch_exit_to_user_mode_work() for architecture specific TIF work
355 * - Architecture specific one time work arch_exit_to_user_mode_prepare()
356 * - Address limit and lockdep checks
357 *
358 * 3) Final transition (lockdep, tracing, context tracking, RCU), i.e. the
359 * functionality in exit_to_user_mode().
360 *
361 * This is a combination of syscall_exit_to_user_mode_work() (1,2) and
362 * exit_to_user_mode(). This function is preferred unless there is a
363 * compelling architectural reason to use the separate functions.
364 */
365 void syscall_exit_to_user_mode(struct pt_regs *regs);
366
367 /**
368 * irqentry_enter_from_user_mode - Establish state before invoking the irq handler
369 * @regs: Pointer to currents pt_regs
370 *
371 * Invoked from architecture specific entry code with interrupts disabled.
372 * Can only be called when the interrupt entry came from user mode. The
373 * calling code must be non-instrumentable. When the function returns all
374 * state is correct and the subsequent functions can be instrumented.
375 *
376 * The function establishes state (lockdep, RCU (context tracking), tracing)
377 */
378 void irqentry_enter_from_user_mode(struct pt_regs *regs);
379
380 /**
381 * irqentry_exit_to_user_mode - Interrupt exit work
382 * @regs: Pointer to current's pt_regs
383 *
384 * Invoked with interrupts disabled and fully valid regs. Returns with all
385 * work handled, interrupts disabled such that the caller can immediately
386 * switch to user mode. Called from architecture specific interrupt
387 * handling code.
388 *
389 * The call order is #2 and #3 as described in syscall_exit_to_user_mode().
390 * Interrupt exit is not invoking #1 which is the syscall specific one time
391 * work.
392 */
393 void irqentry_exit_to_user_mode(struct pt_regs *regs);
394
395 #ifndef irqentry_state
396 /**
397 * struct irqentry_state - Opaque object for exception state storage
398 * @exit_rcu: Used exclusively in the irqentry_*() calls; signals whether the
399 * exit path has to invoke rcu_irq_exit().
400 * @lockdep: Used exclusively in the irqentry_nmi_*() calls; ensures that
401 * lockdep state is restored correctly on exit from nmi.
402 *
403 * This opaque object is filled in by the irqentry_*_enter() functions and
404 * must be passed back into the corresponding irqentry_*_exit() functions
405 * when the exception is complete.
406 *
407 * Callers of irqentry_*_[enter|exit]() must consider this structure opaque
408 * and all members private. Descriptions of the members are provided to aid in
409 * the maintenance of the irqentry_*() functions.
410 */
411 typedef struct irqentry_state {
412 union {
413 bool exit_rcu;
414 bool lockdep;
415 };
416 } irqentry_state_t;
417 #endif
418
419 /**
420 * irqentry_enter - Handle state tracking on ordinary interrupt entries
421 * @regs: Pointer to pt_regs of interrupted context
422 *
423 * Invokes:
424 * - lockdep irqflag state tracking as low level ASM entry disabled
425 * interrupts.
426 *
427 * - Context tracking if the exception hit user mode.
428 *
429 * - The hardirq tracer to keep the state consistent as low level ASM
430 * entry disabled interrupts.
431 *
432 * As a precondition, this requires that the entry came from user mode,
433 * idle, or a kernel context in which RCU is watching.
434 *
435 * For kernel mode entries RCU handling is done conditional. If RCU is
436 * watching then the only RCU requirement is to check whether the tick has
437 * to be restarted. If RCU is not watching then rcu_irq_enter() has to be
438 * invoked on entry and rcu_irq_exit() on exit.
439 *
440 * Avoiding the rcu_irq_enter/exit() calls is an optimization but also
441 * solves the problem of kernel mode pagefaults which can schedule, which
442 * is not possible after invoking rcu_irq_enter() without undoing it.
443 *
444 * For user mode entries irqentry_enter_from_user_mode() is invoked to
445 * establish the proper context for NOHZ_FULL. Otherwise scheduling on exit
446 * would not be possible.
447 *
448 * Returns: An opaque object that must be passed to idtentry_exit()
449 */
450 irqentry_state_t noinstr irqentry_enter(struct pt_regs *regs);
451
452 /**
453 * irqentry_exit_cond_resched - Conditionally reschedule on return from interrupt
454 *
455 * Conditional reschedule with additional sanity checks.
456 */
457 void irqentry_exit_cond_resched(void);
458 #ifdef CONFIG_PREEMPT_DYNAMIC
459 DECLARE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
460 #endif
461
462 /**
463 * irqentry_exit - Handle return from exception that used irqentry_enter()
464 * @regs: Pointer to pt_regs (exception entry regs)
465 * @state: Return value from matching call to irqentry_enter()
466 *
467 * Depending on the return target (kernel/user) this runs the necessary
468 * preemption and work checks if possible and required and returns to
469 * the caller with interrupts disabled and no further work pending.
470 *
471 * This is the last action before returning to the low level ASM code which
472 * just needs to return to the appropriate context.
473 *
474 * Counterpart to irqentry_enter().
475 */
476 void noinstr irqentry_exit(struct pt_regs *regs, irqentry_state_t state);
477
478 /**
479 * irqentry_nmi_enter - Handle NMI entry
480 * @regs: Pointer to currents pt_regs
481 *
482 * Similar to irqentry_enter() but taking care of the NMI constraints.
483 */
484 irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs);
485
486 /**
487 * irqentry_nmi_exit - Handle return from NMI handling
488 * @regs: Pointer to pt_regs (NMI entry regs)
489 * @irq_state: Return value from matching call to irqentry_nmi_enter()
490 *
491 * Last action before returning to the low level assembly code.
492 *
493 * Counterpart to irqentry_nmi_enter().
494 */
495 void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state);
496
497 #endif
498
