projects/linux·blob v5.9 · refs

400 lines · 10.2 KiB

1// SPDX-License-Identifier: GPL-2.0
2
3#include <linux/context_tracking.h>
4#include <linux/entry-common.h>
5#include <linux/livepatch.h>
6#include <linux/audit.h>
7
8#define CREATE_TRACE_POINTS
9#include <trace/events/syscalls.h>
10
11/**
12 * enter_from_user_mode - Establish state when coming from user mode
13 *
14 * Syscall/interrupt entry disables interrupts, but user mode is traced as
15 * interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
16 *
17 * 1) Tell lockdep that interrupts are disabled
18 * 2) Invoke context tracking if enabled to reactivate RCU
19 * 3) Trace interrupts off state
20 */
21static __always_inline void enter_from_user_mode(struct pt_regs *regs)
22{
23 arch_check_user_regs(regs);
24 lockdep_hardirqs_off(CALLER_ADDR0);
25
26 CT_WARN_ON(ct_state() != CONTEXT_USER);
27 user_exit_irqoff();
28
29 instrumentation_begin();
30 trace_hardirqs_off_finish();
31 instrumentation_end();
32}
33
34static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
35{
36 if (unlikely(audit_context())) {
37 unsigned long args[6];
38
39 syscall_get_arguments(current, regs, args);
40 audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
41 }
42}
43
44static long syscall_trace_enter(struct pt_regs *regs, long syscall,
45 unsigned long ti_work)
46{
47 long ret = 0;
48
49 /* Handle ptrace */
50 if (ti_work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
51 ret = arch_syscall_enter_tracehook(regs);
52 if (ret || (ti_work & _TIF_SYSCALL_EMU))
53 return -1L;
54 }
55
56 /* Do seccomp after ptrace, to catch any tracer changes. */
57 if (ti_work & _TIF_SECCOMP) {
58 ret = __secure_computing(NULL);
59 if (ret == -1L)
60 return ret;
61 }
62
63 /* Either of the above might have changed the syscall number */
64 syscall = syscall_get_nr(current, regs);
65
66 if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
67 trace_sys_enter(regs, syscall);
68
69 syscall_enter_audit(regs, syscall);
70
71 return ret ? : syscall;
72}
73
74static __always_inline long
75__syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
76{
77 unsigned long ti_work;
78
79 ti_work = READ_ONCE(current_thread_info()->flags);
80 if (ti_work & SYSCALL_ENTER_WORK)
81 syscall = syscall_trace_enter(regs, syscall, ti_work);
82
83 return syscall;
84}
85
86long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
87{
88 return __syscall_enter_from_user_work(regs, syscall);
89}
90
91noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
92{
93 long ret;
94
95 enter_from_user_mode(regs);
96
97 instrumentation_begin();
98 local_irq_enable();
99 ret = __syscall_enter_from_user_work(regs, syscall);
100 instrumentation_end();
101
102 return ret;
103}
104
105noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
106{
107 enter_from_user_mode(regs);
108 instrumentation_begin();
109 local_irq_enable();
110 instrumentation_end();
111}
112
113/**
114 * exit_to_user_mode - Fixup state when exiting to user mode
115 *
116 * Syscall/interupt exit enables interrupts, but the kernel state is
117 * interrupts disabled when this is invoked. Also tell RCU about it.
118 *
119 * 1) Trace interrupts on state
120 * 2) Invoke context tracking if enabled to adjust RCU state
121 * 3) Invoke architecture specific last minute exit code, e.g. speculation
122 * mitigations, etc.
123 * 4) Tell lockdep that interrupts are enabled
124 */
125static __always_inline void exit_to_user_mode(void)
126{
127 instrumentation_begin();
128 trace_hardirqs_on_prepare();
129 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
130 instrumentation_end();
131
132 user_enter_irqoff();
133 arch_exit_to_user_mode();
134 lockdep_hardirqs_on(CALLER_ADDR0);
135}
136
137/* Workaround to allow gradual conversion of architecture code */
138void __weak arch_do_signal(struct pt_regs *regs) { }
139
140static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
141 unsigned long ti_work)
142{
143 /*
144 * Before returning to user space ensure that all pending work
145 * items have been completed.
146 */
147 while (ti_work & EXIT_TO_USER_MODE_WORK) {
148
149 local_irq_enable_exit_to_user(ti_work);
150
151 if (ti_work & _TIF_NEED_RESCHED)
152 schedule();
153
154 if (ti_work & _TIF_UPROBE)
155 uprobe_notify_resume(regs);
156
157 if (ti_work & _TIF_PATCH_PENDING)
158 klp_update_patch_state(current);
159
160 if (ti_work & _TIF_SIGPENDING)
161 arch_do_signal(regs);
162
163 if (ti_work & _TIF_NOTIFY_RESUME) {
164 clear_thread_flag(TIF_NOTIFY_RESUME);
165 tracehook_notify_resume(regs);
166 rseq_handle_notify_resume(NULL, regs);
167 }
168
169 /* Architecture specific TIF work */
170 arch_exit_to_user_mode_work(regs, ti_work);
171
172 /*
173 * Disable interrupts and reevaluate the work flags as they
174 * might have changed while interrupts and preemption was
175 * enabled above.
176 */
177 local_irq_disable_exit_to_user();
178 ti_work = READ_ONCE(current_thread_info()->flags);
179 }
180
181 /* Return the latest work state for arch_exit_to_user_mode() */
182 return ti_work;
183}
184
185static void exit_to_user_mode_prepare(struct pt_regs *regs)
186{
187 unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
188
189 lockdep_assert_irqs_disabled();
190
191 if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
192 ti_work = exit_to_user_mode_loop(regs, ti_work);
193
194 arch_exit_to_user_mode_prepare(regs, ti_work);
195
196 /* Ensure that the address limit is intact and no locks are held */
197 addr_limit_user_check();
198 lockdep_assert_irqs_disabled();
199 lockdep_sys_exit();
200}
201
202#ifndef _TIF_SINGLESTEP
203static inline bool report_single_step(unsigned long ti_work)
204{
205 return false;
206}
207#else
208/*
209 * If TIF_SYSCALL_EMU is set, then the only reason to report is when
210 * TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
211 * instruction has been already reported in syscall_enter_from_usermode().
212 */
213#define SYSEMU_STEP (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU)
214
215static inline bool report_single_step(unsigned long ti_work)
216{
217 return (ti_work & SYSEMU_STEP) == _TIF_SINGLESTEP;
218}
219#endif
220
221static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work)
222{
223 bool step;
224
225 audit_syscall_exit(regs);
226
227 if (ti_work & _TIF_SYSCALL_TRACEPOINT)
228 trace_sys_exit(regs, syscall_get_return_value(current, regs));
229
230 step = report_single_step(ti_work);
231 if (step || ti_work & _TIF_SYSCALL_TRACE)
232 arch_syscall_exit_tracehook(regs, step);
233}
234
235/*
236 * Syscall specific exit to user mode preparation. Runs with interrupts
237 * enabled.
238 */
239static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
240{
241 u32 cached_flags = READ_ONCE(current_thread_info()->flags);
242 unsigned long nr = syscall_get_nr(current, regs);
243
244 CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
245
246 if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
247 if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
248 local_irq_enable();
249 }
250
251 rseq_syscall(regs);
252
253 /*
254 * Do one-time syscall specific work. If these work items are
255 * enabled, we want to run them exactly once per syscall exit with
256 * interrupts enabled.
257 */
258 if (unlikely(cached_flags & SYSCALL_EXIT_WORK))
259 syscall_exit_work(regs, cached_flags);
260}
261
262__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
263{
264 instrumentation_begin();
265 syscall_exit_to_user_mode_prepare(regs);
266 local_irq_disable_exit_to_user();
267 exit_to_user_mode_prepare(regs);
268 instrumentation_end();
269 exit_to_user_mode();
270}
271
272noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
273{
274 enter_from_user_mode(regs);
275}
276
277noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
278{
279 instrumentation_begin();
280 exit_to_user_mode_prepare(regs);
281 instrumentation_end();
282 exit_to_user_mode();
283}
284
285noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
286{
287 irqentry_state_t ret = {
288 .exit_rcu = false,
289 };
290
291 if (user_mode(regs)) {
292 irqentry_enter_from_user_mode(regs);
293 return ret;
294 }
295
296 /*
297 * If this entry hit the idle task invoke rcu_irq_enter() whether
298 * RCU is watching or not.
299 *
300 * Interupts can nest when the first interrupt invokes softirq
301 * processing on return which enables interrupts.
302 *
303 * Scheduler ticks in the idle task can mark quiescent state and
304 * terminate a grace period, if and only if the timer interrupt is
305 * not nested into another interrupt.
306 *
307 * Checking for __rcu_is_watching() here would prevent the nesting
308 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
309 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
310 * assume that it is the first interupt and eventually claim
311 * quiescient state and end grace periods prematurely.
312 *
313 * Unconditionally invoke rcu_irq_enter() so RCU state stays
314 * consistent.
315 *
316 * TINY_RCU does not support EQS, so let the compiler eliminate
317 * this part when enabled.
318 */
319 if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
320 /*
321 * If RCU is not watching then the same careful
322 * sequence vs. lockdep and tracing is required
323 * as in irq_enter_from_user_mode().
324 */
325 lockdep_hardirqs_off(CALLER_ADDR0);
326 rcu_irq_enter();
327 instrumentation_begin();
328 trace_hardirqs_off_finish();
329 instrumentation_end();
330
331 ret.exit_rcu = true;
332 return ret;
333 }
334
335 /*
336 * If RCU is watching then RCU only wants to check whether it needs
337 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
338 * already contains a warning when RCU is not watching, so no point
339 * in having another one here.
340 */
341 instrumentation_begin();
342 rcu_irq_enter_check_tick();
343 /* Use the combo lockdep/tracing function */
344 trace_hardirqs_off();
345 instrumentation_end();
346
347 return ret;
348}
349
350void irqentry_exit_cond_resched(void)
351{
352 if (!preempt_count()) {
353 /* Sanity check RCU and thread stack */
354 rcu_irq_exit_check_preempt();
355 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
356 WARN_ON_ONCE(!on_thread_stack());
357 if (need_resched())
358 preempt_schedule_irq();
359 }
360}
361
362noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
363{
364 lockdep_assert_irqs_disabled();
365
366 /* Check whether this returns to user mode */
367 if (user_mode(regs)) {
368 irqentry_exit_to_user_mode(regs);
369 } else if (!regs_irqs_disabled(regs)) {
370 /*
371 * If RCU was not watching on entry this needs to be done
372 * carefully and needs the same ordering of lockdep/tracing
373 * and RCU as the return to user mode path.
374 */
375 if (state.exit_rcu) {
376 instrumentation_begin();
377 /* Tell the tracer that IRET will enable interrupts */
378 trace_hardirqs_on_prepare();
379 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
380 instrumentation_end();
381 rcu_irq_exit();
382 lockdep_hardirqs_on(CALLER_ADDR0);
383 return;
384 }
385
386 instrumentation_begin();
387 if (IS_ENABLED(CONFIG_PREEMPTION))
388 irqentry_exit_cond_resched();
389 /* Covers both tracing and lockdep */
390 trace_hardirqs_on();
391 instrumentation_end();
392 } else {
393 /*
394 * IRQ flags state is correct already. Just tell RCU if it
395 * was not watching on entry.
396 */
397 if (state.exit_rcu)
398 rcu_irq_exit();
399 }
400}