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