1 // SPDX-License-Identifier: GPL-2.0
3 #include <linux/context_tracking.h>
4 #include <linux/entry-common.h>
5 #include <linux/livepatch.h>
6 #include <linux/audit.h>
8 #define CREATE_TRACE_POINTS
9 #include <trace/events/syscalls.h>
12 * enter_from_user_mode - Establish state when coming from user mode
14 * Syscall/interrupt entry disables interrupts, but user mode is traced as
15 * interrupts enabled. Also with NO_HZ_FULL RCU might be idle.
17 * 1) Tell lockdep that interrupts are disabled
18 * 2) Invoke context tracking if enabled to reactivate RCU
19 * 3) Trace interrupts off state
21 static __always_inline void enter_from_user_mode(struct pt_regs *regs)
23 arch_check_user_regs(regs);
24 lockdep_hardirqs_off(CALLER_ADDR0);
26 CT_WARN_ON(ct_state() != CONTEXT_USER);
29 instrumentation_begin();
30 trace_hardirqs_off_finish();
31 instrumentation_end();
34 static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
36 if (unlikely(audit_context())) {
37 unsigned long args[6];
39 syscall_get_arguments(current, regs, args);
40 audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
44 static long syscall_trace_enter(struct pt_regs *regs, long syscall,
45 unsigned long ti_work)
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))
56 /* Do seccomp after ptrace, to catch any tracer changes. */
57 if (ti_work & _TIF_SECCOMP) {
58 ret = __secure_computing(NULL);
63 if (unlikely(ti_work & _TIF_SYSCALL_TRACEPOINT))
64 trace_sys_enter(regs, syscall);
66 syscall_enter_audit(regs, syscall);
68 /* The above might have changed the syscall number */
69 return ret ? : syscall_get_nr(current, regs);
72 noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
74 unsigned long ti_work;
76 enter_from_user_mode(regs);
77 instrumentation_begin();
80 ti_work = READ_ONCE(current_thread_info()->flags);
81 if (ti_work & SYSCALL_ENTER_WORK)
82 syscall = syscall_trace_enter(regs, syscall, ti_work);
83 instrumentation_end();
89 * exit_to_user_mode - Fixup state when exiting to user mode
91 * Syscall/interupt exit enables interrupts, but the kernel state is
92 * interrupts disabled when this is invoked. Also tell RCU about it.
94 * 1) Trace interrupts on state
95 * 2) Invoke context tracking if enabled to adjust RCU state
96 * 3) Invoke architecture specific last minute exit code, e.g. speculation
98 * 4) Tell lockdep that interrupts are enabled
100 static __always_inline void exit_to_user_mode(void)
102 instrumentation_begin();
103 trace_hardirqs_on_prepare();
104 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
105 instrumentation_end();
108 arch_exit_to_user_mode();
109 lockdep_hardirqs_on(CALLER_ADDR0);
112 /* Workaround to allow gradual conversion of architecture code */
113 void __weak arch_do_signal(struct pt_regs *regs) { }
115 static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
116 unsigned long ti_work)
119 * Before returning to user space ensure that all pending work
120 * items have been completed.
122 while (ti_work & EXIT_TO_USER_MODE_WORK) {
124 local_irq_enable_exit_to_user(ti_work);
126 if (ti_work & _TIF_NEED_RESCHED)
129 if (ti_work & _TIF_UPROBE)
130 uprobe_notify_resume(regs);
132 if (ti_work & _TIF_PATCH_PENDING)
133 klp_update_patch_state(current);
135 if (ti_work & _TIF_SIGPENDING)
136 arch_do_signal(regs);
138 if (ti_work & _TIF_NOTIFY_RESUME) {
139 clear_thread_flag(TIF_NOTIFY_RESUME);
140 tracehook_notify_resume(regs);
141 rseq_handle_notify_resume(NULL, regs);
144 /* Architecture specific TIF work */
145 arch_exit_to_user_mode_work(regs, ti_work);
148 * Disable interrupts and reevaluate the work flags as they
149 * might have changed while interrupts and preemption was
152 local_irq_disable_exit_to_user();
153 ti_work = READ_ONCE(current_thread_info()->flags);
156 /* Return the latest work state for arch_exit_to_user_mode() */
160 static void exit_to_user_mode_prepare(struct pt_regs *regs)
162 unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
164 lockdep_assert_irqs_disabled();
166 if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
167 ti_work = exit_to_user_mode_loop(regs, ti_work);
169 arch_exit_to_user_mode_prepare(regs, ti_work);
171 /* Ensure that the address limit is intact and no locks are held */
172 addr_limit_user_check();
173 lockdep_assert_irqs_disabled();
177 #ifndef _TIF_SINGLESTEP
178 static inline bool report_single_step(unsigned long ti_work)
184 * If TIF_SYSCALL_EMU is set, then the only reason to report is when
185 * TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
186 * instruction has been already reported in syscall_enter_from_usermode().
188 #define SYSEMU_STEP (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU)
190 static inline bool report_single_step(unsigned long ti_work)
192 return (ti_work & SYSEMU_STEP) == _TIF_SINGLESTEP;
196 static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work)
200 audit_syscall_exit(regs);
202 if (ti_work & _TIF_SYSCALL_TRACEPOINT)
203 trace_sys_exit(regs, syscall_get_return_value(current, regs));
205 step = report_single_step(ti_work);
206 if (step || ti_work & _TIF_SYSCALL_TRACE)
207 arch_syscall_exit_tracehook(regs, step);
211 * Syscall specific exit to user mode preparation. Runs with interrupts
214 static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
216 u32 cached_flags = READ_ONCE(current_thread_info()->flags);
217 unsigned long nr = syscall_get_nr(current, regs);
219 CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
221 if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
222 if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
229 * Do one-time syscall specific work. If these work items are
230 * enabled, we want to run them exactly once per syscall exit with
231 * interrupts enabled.
233 if (unlikely(cached_flags & SYSCALL_EXIT_WORK))
234 syscall_exit_work(regs, cached_flags);
237 __visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
239 instrumentation_begin();
240 syscall_exit_to_user_mode_prepare(regs);
241 local_irq_disable_exit_to_user();
242 exit_to_user_mode_prepare(regs);
243 instrumentation_end();
247 noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
249 enter_from_user_mode(regs);
252 noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
254 instrumentation_begin();
255 exit_to_user_mode_prepare(regs);
256 instrumentation_end();
260 noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
262 irqentry_state_t ret = {
266 if (user_mode(regs)) {
267 irqentry_enter_from_user_mode(regs);
272 * If this entry hit the idle task invoke rcu_irq_enter() whether
273 * RCU is watching or not.
275 * Interupts can nest when the first interrupt invokes softirq
276 * processing on return which enables interrupts.
278 * Scheduler ticks in the idle task can mark quiescent state and
279 * terminate a grace period, if and only if the timer interrupt is
280 * not nested into another interrupt.
282 * Checking for __rcu_is_watching() here would prevent the nesting
283 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
284 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
285 * assume that it is the first interupt and eventually claim
286 * quiescient state and end grace periods prematurely.
288 * Unconditionally invoke rcu_irq_enter() so RCU state stays
291 * TINY_RCU does not support EQS, so let the compiler eliminate
292 * this part when enabled.
294 if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
296 * If RCU is not watching then the same careful
297 * sequence vs. lockdep and tracing is required
298 * as in irq_enter_from_user_mode().
300 lockdep_hardirqs_off(CALLER_ADDR0);
302 instrumentation_begin();
303 trace_hardirqs_off_finish();
304 instrumentation_end();
311 * If RCU is watching then RCU only wants to check whether it needs
312 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
313 * already contains a warning when RCU is not watching, so no point
314 * in having another one here.
316 instrumentation_begin();
317 rcu_irq_enter_check_tick();
318 /* Use the combo lockdep/tracing function */
319 trace_hardirqs_off();
320 instrumentation_end();
325 void irqentry_exit_cond_resched(void)
327 if (!preempt_count()) {
328 /* Sanity check RCU and thread stack */
329 rcu_irq_exit_check_preempt();
330 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
331 WARN_ON_ONCE(!on_thread_stack());
333 preempt_schedule_irq();
337 noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
339 lockdep_assert_irqs_disabled();
341 /* Check whether this returns to user mode */
342 if (user_mode(regs)) {
343 irqentry_exit_to_user_mode(regs);
344 } else if (!regs_irqs_disabled(regs)) {
346 * If RCU was not watching on entry this needs to be done
347 * carefully and needs the same ordering of lockdep/tracing
348 * and RCU as the return to user mode path.
350 if (state.exit_rcu) {
351 instrumentation_begin();
352 /* Tell the tracer that IRET will enable interrupts */
353 trace_hardirqs_on_prepare();
354 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
355 instrumentation_end();
357 lockdep_hardirqs_on(CALLER_ADDR0);
361 instrumentation_begin();
362 if (IS_ENABLED(CONFIG_PREEMPTION))
363 irqentry_exit_cond_resched();
364 /* Covers both tracing and lockdep */
366 instrumentation_end();
369 * IRQ flags state is correct already. Just tell RCU if it
370 * was not watching on entry.