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 return ret ? : syscall;
71 noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
73 unsigned long ti_work;
75 enter_from_user_mode(regs);
76 instrumentation_begin();
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 instrumentation_end();
88 * exit_to_user_mode - Fixup state when exiting to user mode
90 * Syscall/interupt exit enables interrupts, but the kernel state is
91 * interrupts disabled when this is invoked. Also tell RCU about it.
93 * 1) Trace interrupts on state
94 * 2) Invoke context tracking if enabled to adjust RCU state
95 * 3) Invoke architecture specific last minute exit code, e.g. speculation
97 * 4) Tell lockdep that interrupts are enabled
99 static __always_inline void exit_to_user_mode(void)
101 instrumentation_begin();
102 trace_hardirqs_on_prepare();
103 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
104 instrumentation_end();
107 arch_exit_to_user_mode();
108 lockdep_hardirqs_on(CALLER_ADDR0);
111 /* Workaround to allow gradual conversion of architecture code */
112 void __weak arch_do_signal(struct pt_regs *regs) { }
114 static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
115 unsigned long ti_work)
118 * Before returning to user space ensure that all pending work
119 * items have been completed.
121 while (ti_work & EXIT_TO_USER_MODE_WORK) {
123 local_irq_enable_exit_to_user(ti_work);
125 if (ti_work & _TIF_NEED_RESCHED)
128 if (ti_work & _TIF_UPROBE)
129 uprobe_notify_resume(regs);
131 if (ti_work & _TIF_PATCH_PENDING)
132 klp_update_patch_state(current);
134 if (ti_work & _TIF_SIGPENDING)
135 arch_do_signal(regs);
137 if (ti_work & _TIF_NOTIFY_RESUME) {
138 clear_thread_flag(TIF_NOTIFY_RESUME);
139 tracehook_notify_resume(regs);
140 rseq_handle_notify_resume(NULL, regs);
143 /* Architecture specific TIF work */
144 arch_exit_to_user_mode_work(regs, ti_work);
147 * Disable interrupts and reevaluate the work flags as they
148 * might have changed while interrupts and preemption was
151 local_irq_disable_exit_to_user();
152 ti_work = READ_ONCE(current_thread_info()->flags);
155 /* Return the latest work state for arch_exit_to_user_mode() */
159 static void exit_to_user_mode_prepare(struct pt_regs *regs)
161 unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
163 lockdep_assert_irqs_disabled();
165 if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
166 ti_work = exit_to_user_mode_loop(regs, ti_work);
168 arch_exit_to_user_mode_prepare(regs, ti_work);
170 /* Ensure that the address limit is intact and no locks are held */
171 addr_limit_user_check();
172 lockdep_assert_irqs_disabled();
176 #ifndef _TIF_SINGLESTEP
177 static inline bool report_single_step(unsigned long ti_work)
183 * If TIF_SYSCALL_EMU is set, then the only reason to report is when
184 * TIF_SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP). This syscall
185 * instruction has been already reported in syscall_enter_from_usermode().
187 #define SYSEMU_STEP (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU)
189 static inline bool report_single_step(unsigned long ti_work)
191 return (ti_work & SYSEMU_STEP) == _TIF_SINGLESTEP;
195 static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work)
199 audit_syscall_exit(regs);
201 if (ti_work & _TIF_SYSCALL_TRACEPOINT)
202 trace_sys_exit(regs, syscall_get_return_value(current, regs));
204 step = report_single_step(ti_work);
205 if (step || ti_work & _TIF_SYSCALL_TRACE)
206 arch_syscall_exit_tracehook(regs, step);
210 * Syscall specific exit to user mode preparation. Runs with interrupts
213 static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
215 u32 cached_flags = READ_ONCE(current_thread_info()->flags);
216 unsigned long nr = syscall_get_nr(current, regs);
218 CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
220 if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
221 if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
228 * Do one-time syscall specific work. If these work items are
229 * enabled, we want to run them exactly once per syscall exit with
230 * interrupts enabled.
232 if (unlikely(cached_flags & SYSCALL_EXIT_WORK))
233 syscall_exit_work(regs, cached_flags);
236 __visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
238 instrumentation_begin();
239 syscall_exit_to_user_mode_prepare(regs);
240 local_irq_disable_exit_to_user();
241 exit_to_user_mode_prepare(regs);
242 instrumentation_end();
246 noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
248 enter_from_user_mode(regs);
251 noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
253 instrumentation_begin();
254 exit_to_user_mode_prepare(regs);
255 instrumentation_end();
259 noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
261 irqentry_state_t ret = {
265 if (user_mode(regs)) {
266 irqentry_enter_from_user_mode(regs);
271 * If this entry hit the idle task invoke rcu_irq_enter() whether
272 * RCU is watching or not.
274 * Interupts can nest when the first interrupt invokes softirq
275 * processing on return which enables interrupts.
277 * Scheduler ticks in the idle task can mark quiescent state and
278 * terminate a grace period, if and only if the timer interrupt is
279 * not nested into another interrupt.
281 * Checking for __rcu_is_watching() here would prevent the nesting
282 * interrupt to invoke rcu_irq_enter(). If that nested interrupt is
283 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
284 * assume that it is the first interupt and eventually claim
285 * quiescient state and end grace periods prematurely.
287 * Unconditionally invoke rcu_irq_enter() so RCU state stays
290 * TINY_RCU does not support EQS, so let the compiler eliminate
291 * this part when enabled.
293 if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
295 * If RCU is not watching then the same careful
296 * sequence vs. lockdep and tracing is required
297 * as in irq_enter_from_user_mode().
299 lockdep_hardirqs_off(CALLER_ADDR0);
301 instrumentation_begin();
302 trace_hardirqs_off_finish();
303 instrumentation_end();
310 * If RCU is watching then RCU only wants to check whether it needs
311 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
312 * already contains a warning when RCU is not watching, so no point
313 * in having another one here.
315 instrumentation_begin();
316 rcu_irq_enter_check_tick();
317 /* Use the combo lockdep/tracing function */
318 trace_hardirqs_off();
319 instrumentation_end();
324 void irqentry_exit_cond_resched(void)
326 if (!preempt_count()) {
327 /* Sanity check RCU and thread stack */
328 rcu_irq_exit_check_preempt();
329 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
330 WARN_ON_ONCE(!on_thread_stack());
332 preempt_schedule_irq();
336 noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
338 lockdep_assert_irqs_disabled();
340 /* Check whether this returns to user mode */
341 if (user_mode(regs)) {
342 irqentry_exit_to_user_mode(regs);
343 } else if (!regs_irqs_disabled(regs)) {
345 * If RCU was not watching on entry this needs to be done
346 * carefully and needs the same ordering of lockdep/tracing
347 * and RCU as the return to user mode path.
349 if (state.exit_rcu) {
350 instrumentation_begin();
351 /* Tell the tracer that IRET will enable interrupts */
352 trace_hardirqs_on_prepare();
353 lockdep_hardirqs_on_prepare(CALLER_ADDR0);
354 instrumentation_end();
356 lockdep_hardirqs_on(CALLER_ADDR0);
360 instrumentation_begin();
361 if (IS_ENABLED(CONFIG_PREEMPTION))
362 irqentry_exit_cond_resched();
363 /* Covers both tracing and lockdep */
365 instrumentation_end();
368 * IRQ flags state is correct already. Just tell RCU if it
369 * was not watching on entry.