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