projects/linux·blob v5.12 · refs

478 lines · 12.0 KiB

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
9#include "common.h"
10
11#define CREATE_TRACE_POINTS
12#include <trace/events/syscalls.h>
13
14/* See comment for enter_from_user_mode() in entry-common.h */
15static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
16{
17 arch_check_user_regs(regs);
18 lockdep_hardirqs_off(CALLER_ADDR0);
19
20 CT_WARN_ON(ct_state() != CONTEXT_USER);
21 user_exit_irqoff();
22
23 instrumentation_begin();
24 trace_hardirqs_off_finish();
25 instrumentation_end();
26}
27
28void noinstr enter_from_user_mode(struct pt_regs *regs)
29{
30 __enter_from_user_mode(regs);
31}
32
33static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
34{
35 if (unlikely(audit_context())) {
36 unsigned long args[6];
37
38 syscall_get_arguments(current, regs, args);
39 audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
40 }
41}
42
43static long syscall_trace_enter(struct pt_regs *regs, long syscall,
44 unsigned long work)
45{
46 long ret = 0;
47
48 /*
49 * Handle Syscall User Dispatch. This must comes first, since
50 * the ABI here can be something that doesn't make sense for
51 * other syscall_work features.
52 */
53 if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
54 if (syscall_user_dispatch(regs))
55 return -1L;
56 }
57
58 /* Handle ptrace */
59 if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
60 ret = arch_syscall_enter_tracehook(regs);
61 if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
62 return -1L;
63 }
64
65 /* Do seccomp after ptrace, to catch any tracer changes. */
66 if (work & SYSCALL_WORK_SECCOMP) {
67 ret = __secure_computing(NULL);
68 if (ret == -1L)
69 return ret;
70 }
71
72 /* Either of the above might have changed the syscall number */
73 syscall = syscall_get_nr(current, regs);
74
75 if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT))
76 trace_sys_enter(regs, syscall);
77
78 syscall_enter_audit(regs, syscall);
79
80 return ret ? : syscall;
81}
82
83static __always_inline long
84__syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
85{
86 unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
87
88 if (work & SYSCALL_WORK_ENTER)
89 syscall = syscall_trace_enter(regs, syscall, work);
90
91 return syscall;
92}
93
94long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
95{
96 return __syscall_enter_from_user_work(regs, syscall);
97}
98
99noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
100{
101 long ret;
102
103 __enter_from_user_mode(regs);
104
105 instrumentation_begin();
106 local_irq_enable();
107 ret = __syscall_enter_from_user_work(regs, syscall);
108 instrumentation_end();
109
110 return ret;
111}
112
113noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
114{
115 __enter_from_user_mode(regs);
116 instrumentation_begin();
117 local_irq_enable();
118 instrumentation_end();
119}
120
121/* See comment for exit_to_user_mode() in entry-common.h */
122static __always_inline void __exit_to_user_mode(void)
123{
124 instrumentation_begin();
125 trace_hardirqs_on_prepare();
126 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
127 instrumentation_end();
128
129 user_enter_irqoff();
130 arch_exit_to_user_mode();
131 lockdep_hardirqs_on(CALLER_ADDR0);
132}
133
134void noinstr exit_to_user_mode(void)
135{
136 __exit_to_user_mode();
137}
138
139/* Workaround to allow gradual conversion of architecture code */
140void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }
141
142static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work)
143{
144 if (ti_work & _TIF_NOTIFY_SIGNAL)
145 tracehook_notify_signal();
146
147 arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING);
148}
149
150static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
151 unsigned long ti_work)
152{
153 /*
154 * Before returning to user space ensure that all pending work
155 * items have been completed.
156 */
157 while (ti_work & EXIT_TO_USER_MODE_WORK) {
158
159 local_irq_enable_exit_to_user(ti_work);
160
161 if (ti_work & _TIF_NEED_RESCHED)
162 schedule();
163
164 if (ti_work & _TIF_UPROBE)
165 uprobe_notify_resume(regs);
166
167 if (ti_work & _TIF_PATCH_PENDING)
168 klp_update_patch_state(current);
169
170 if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
171 handle_signal_work(regs, ti_work);
172
173 if (ti_work & _TIF_NOTIFY_RESUME) {
174 tracehook_notify_resume(regs);
175 rseq_handle_notify_resume(NULL, regs);
176 }
177
178 /* Architecture specific TIF work */
179 arch_exit_to_user_mode_work(regs, ti_work);
180
181 /*
182 * Disable interrupts and reevaluate the work flags as they
183 * might have changed while interrupts and preemption was
184 * enabled above.
185 */
186 local_irq_disable_exit_to_user();
187
188 /* Check if any of the above work has queued a deferred wakeup */
189 rcu_nocb_flush_deferred_wakeup();
190
191 ti_work = READ_ONCE(current_thread_info()->flags);
192 }
193
194 /* Return the latest work state for arch_exit_to_user_mode() */
195 return ti_work;
196}
197
198static void exit_to_user_mode_prepare(struct pt_regs *regs)
199{
200 unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
201
202 lockdep_assert_irqs_disabled();
203
204 /* Flush pending rcuog wakeup before the last need_resched() check */
205 rcu_nocb_flush_deferred_wakeup();
206
207 if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
208 ti_work = exit_to_user_mode_loop(regs, ti_work);
209
210 arch_exit_to_user_mode_prepare(regs, ti_work);
211
212 /* Ensure that the address limit is intact and no locks are held */
213 addr_limit_user_check();
214 kmap_assert_nomap();
215 lockdep_assert_irqs_disabled();
216 lockdep_sys_exit();
217}
218
219/*
220 * If SYSCALL_EMU is set, then the only reason to report is when
221 * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
222 * instruction has been already reported in syscall_enter_from_user_mode().
223 */
224static inline bool report_single_step(unsigned long work)
225{
226 if (work & SYSCALL_WORK_SYSCALL_EMU)
227 return false;
228
229 return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
230}
231
232static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
233{
234 bool step;
235
236 /*
237 * If the syscall was rolled back due to syscall user dispatching,
238 * then the tracers below are not invoked for the same reason as
239 * the entry side was not invoked in syscall_trace_enter(): The ABI
240 * of these syscalls is unknown.
241 */
242 if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
243 if (unlikely(current->syscall_dispatch.on_dispatch)) {
244 current->syscall_dispatch.on_dispatch = false;
245 return;
246 }
247 }
248
249 audit_syscall_exit(regs);
250
251 if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
252 trace_sys_exit(regs, syscall_get_return_value(current, regs));
253
254 step = report_single_step(work);
255 if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
256 arch_syscall_exit_tracehook(regs, step);
257}
258
259/*
260 * Syscall specific exit to user mode preparation. Runs with interrupts
261 * enabled.
262 */
263static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
264{
265 unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
266 unsigned long nr = syscall_get_nr(current, regs);
267
268 CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
269
270 if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
271 if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
272 local_irq_enable();
273 }
274
275 rseq_syscall(regs);
276
277 /*
278 * Do one-time syscall specific work. If these work items are
279 * enabled, we want to run them exactly once per syscall exit with
280 * interrupts enabled.
281 */
282 if (unlikely(work & SYSCALL_WORK_EXIT))
283 syscall_exit_work(regs, work);
284}
285
286static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
287{
288 syscall_exit_to_user_mode_prepare(regs);
289 local_irq_disable_exit_to_user();
290 exit_to_user_mode_prepare(regs);
291}
292
293void syscall_exit_to_user_mode_work(struct pt_regs *regs)
294{
295 __syscall_exit_to_user_mode_work(regs);
296}
297
298__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
299{
300 instrumentation_begin();
301 __syscall_exit_to_user_mode_work(regs);
302 instrumentation_end();
303 __exit_to_user_mode();
304}
305
306noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
307{
308 __enter_from_user_mode(regs);
309}
310
311noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
312{
313 instrumentation_begin();
314 exit_to_user_mode_prepare(regs);
315 instrumentation_end();
316 __exit_to_user_mode();
317}
318
319noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
320{
321 irqentry_state_t ret = {
322 .exit_rcu = false,
323 };
324
325 if (user_mode(regs)) {
326 irqentry_enter_from_user_mode(regs);
327 return ret;
328 }
329
330 /*
331 * If this entry hit the idle task invoke rcu_irq_enter() whether
332 * RCU is watching or not.
333 *
334 * Interrupts can nest when the first interrupt invokes softirq
335 * processing on return which enables interrupts.
336 *
337 * Scheduler ticks in the idle task can mark quiescent state and
338 * terminate a grace period, if and only if the timer interrupt is
339 * not nested into another interrupt.
340 *
341 * Checking for rcu_is_watching() here would prevent the nesting
342 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
343 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
344 * assume that it is the first interupt and eventually claim
345 * quiescent state and end grace periods prematurely.
346 *
347 * Unconditionally invoke rcu_irq_enter() so RCU state stays
348 * consistent.
349 *
350 * TINY_RCU does not support EQS, so let the compiler eliminate
351 * this part when enabled.
352 */
353 if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
354 /*
355 * If RCU is not watching then the same careful
356 * sequence vs. lockdep and tracing is required
357 * as in irqentry_enter_from_user_mode().
358 */
359 lockdep_hardirqs_off(CALLER_ADDR0);
360 rcu_irq_enter();
361 instrumentation_begin();
362 trace_hardirqs_off_finish();
363 instrumentation_end();
364
365 ret.exit_rcu = true;
366 return ret;
367 }
368
369 /*
370 * If RCU is watching then RCU only wants to check whether it needs
371 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
372 * already contains a warning when RCU is not watching, so no point
373 * in having another one here.
374 */
375 lockdep_hardirqs_off(CALLER_ADDR0);
376 instrumentation_begin();
377 rcu_irq_enter_check_tick();
378 trace_hardirqs_off_finish();
379 instrumentation_end();
380
381 return ret;
382}
383
384void irqentry_exit_cond_resched(void)
385{
386 if (!preempt_count()) {
387 /* Sanity check RCU and thread stack */
388 rcu_irq_exit_check_preempt();
389 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
390 WARN_ON_ONCE(!on_thread_stack());
391 if (need_resched())
392 preempt_schedule_irq();
393 }
394}
395#ifdef CONFIG_PREEMPT_DYNAMIC
396DEFINE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
397#endif
398
399noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
400{
401 lockdep_assert_irqs_disabled();
402
403 /* Check whether this returns to user mode */
404 if (user_mode(regs)) {
405 irqentry_exit_to_user_mode(regs);
406 } else if (!regs_irqs_disabled(regs)) {
407 /*
408 * If RCU was not watching on entry this needs to be done
409 * carefully and needs the same ordering of lockdep/tracing
410 * and RCU as the return to user mode path.
411 */
412 if (state.exit_rcu) {
413 instrumentation_begin();
414 /* Tell the tracer that IRET will enable interrupts */
415 trace_hardirqs_on_prepare();
416 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
417 instrumentation_end();
418 rcu_irq_exit();
419 lockdep_hardirqs_on(CALLER_ADDR0);
420 return;
421 }
422
423 instrumentation_begin();
424 if (IS_ENABLED(CONFIG_PREEMPTION)) {
425#ifdef CONFIG_PREEMPT_DYNAMIC
426 static_call(irqentry_exit_cond_resched)();
427#else
428 irqentry_exit_cond_resched();
429#endif
430 }
431 /* Covers both tracing and lockdep */
432 trace_hardirqs_on();
433 instrumentation_end();
434 } else {
435 /*
436 * IRQ flags state is correct already. Just tell RCU if it
437 * was not watching on entry.
438 */
439 if (state.exit_rcu)
440 rcu_irq_exit();
441 }
442}
443
444irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
445{
446 irqentry_state_t irq_state;
447
448 irq_state.lockdep = lockdep_hardirqs_enabled();
449
450 __nmi_enter();
451 lockdep_hardirqs_off(CALLER_ADDR0);
452 lockdep_hardirq_enter();
453 rcu_nmi_enter();
454
455 instrumentation_begin();
456 trace_hardirqs_off_finish();
457 ftrace_nmi_enter();
458 instrumentation_end();
459
460 return irq_state;
461}
462
463void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
464{
465 instrumentation_begin();
466 ftrace_nmi_exit();
467 if (irq_state.lockdep) {
468 trace_hardirqs_on_prepare();
469 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
470 }
471 instrumentation_end();
472
473 rcu_nmi_exit();
474 lockdep_hardirq_exit();
475 if (irq_state.lockdep)
476 lockdep_hardirqs_on(CALLER_ADDR0);
477 __nmi_exit();
478}