1// SPDX-License-Identifier: GPL-2.0
2
3#include <linux/irq-entry-common.h>
4#include <linux/resume_user_mode.h>
5#include <linux/highmem.h>
6#include <linux/jump_label.h>
7#include <linux/kmsan.h>
8#include <linux/livepatch.h>
9#include <linux/tick.h>
10
11/* Workaround to allow gradual conversion of architecture code */
12void __weak arch_do_signal_or_restart(struct pt_regs *regs) { }
13
14/**
15 * exit_to_user_mode_loop - do any pending work before leaving to user space
16 * @regs: Pointer to pt_regs on entry stack
17 * @ti_work: TIF work flags as read by the caller
18 */
19__always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
20 unsigned long ti_work)
21{
22 /*
23 * Before returning to user space ensure that all pending work
24 * items have been completed.
25 */
26 while (ti_work & EXIT_TO_USER_MODE_WORK) {
27
28 local_irq_enable_exit_to_user(ti_work);
29
30 if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
31 schedule();
32
33 if (ti_work & _TIF_UPROBE)
34 uprobe_notify_resume(regs);
35
36 if (ti_work & _TIF_PATCH_PENDING)
37 klp_update_patch_state(current);
38
39 if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
40 arch_do_signal_or_restart(regs);
41
42 if (ti_work & _TIF_NOTIFY_RESUME)
43 resume_user_mode_work(regs);
44
45 /* Architecture specific TIF work */
46 arch_exit_to_user_mode_work(regs, ti_work);
47
48 /*
49 * Disable interrupts and reevaluate the work flags as they
50 * might have changed while interrupts and preemption was
51 * enabled above.
52 */
53 local_irq_disable_exit_to_user();
54
55 /* Check if any of the above work has queued a deferred wakeup */
56 tick_nohz_user_enter_prepare();
57
58 ti_work = read_thread_flags();
59 }
60
61 /* Return the latest work state for arch_exit_to_user_mode() */
62 return ti_work;
63}
64
65noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
66{
67 enter_from_user_mode(regs);
68}
69
70noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
71{
72 instrumentation_begin();
73 exit_to_user_mode_prepare(regs);
74 instrumentation_end();
75 exit_to_user_mode();
76}
77
78noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
79{
80 irqentry_state_t ret = {
81 .exit_rcu = false,
82 };
83
84 if (user_mode(regs)) {
85 irqentry_enter_from_user_mode(regs);
86 return ret;
87 }
88
89 /*
90 * If this entry hit the idle task invoke ct_irq_enter() whether
91 * RCU is watching or not.
92 *
93 * Interrupts can nest when the first interrupt invokes softirq
94 * processing on return which enables interrupts.
95 *
96 * Scheduler ticks in the idle task can mark quiescent state and
97 * terminate a grace period, if and only if the timer interrupt is
98 * not nested into another interrupt.
99 *
100 * Checking for rcu_is_watching() here would prevent the nesting
101 * interrupt to invoke ct_irq_enter(). If that nested interrupt is
102 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
103 * assume that it is the first interrupt and eventually claim
104 * quiescent state and end grace periods prematurely.
105 *
106 * Unconditionally invoke ct_irq_enter() so RCU state stays
107 * consistent.
108 *
109 * TINY_RCU does not support EQS, so let the compiler eliminate
110 * this part when enabled.
111 */
112 if (!IS_ENABLED(CONFIG_TINY_RCU) &&
113 (is_idle_task(current) || arch_in_rcu_eqs())) {
114 /*
115 * If RCU is not watching then the same careful
116 * sequence vs. lockdep and tracing is required
117 * as in irqentry_enter_from_user_mode().
118 */
119 lockdep_hardirqs_off(CALLER_ADDR0);
120 ct_irq_enter();
121 instrumentation_begin();
122 kmsan_unpoison_entry_regs(regs);
123 trace_hardirqs_off_finish();
124 instrumentation_end();
125
126 ret.exit_rcu = true;
127 return ret;
128 }
129
130 /*
131 * If RCU is watching then RCU only wants to check whether it needs
132 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
133 * already contains a warning when RCU is not watching, so no point
134 * in having another one here.
135 */
136 lockdep_hardirqs_off(CALLER_ADDR0);
137 instrumentation_begin();
138 kmsan_unpoison_entry_regs(regs);
139 rcu_irq_enter_check_tick();
140 trace_hardirqs_off_finish();
141 instrumentation_end();
142
143 return ret;
144}
145
146/**
147 * arch_irqentry_exit_need_resched - Architecture specific need resched function
148 *
149 * Invoked from raw_irqentry_exit_cond_resched() to check if resched is needed.
150 * Defaults return true.
151 *
152 * The main purpose is to permit arch to avoid preemption of a task from an IRQ.
153 */
154static inline bool arch_irqentry_exit_need_resched(void);
155
156#ifndef arch_irqentry_exit_need_resched
157static inline bool arch_irqentry_exit_need_resched(void) { return true; }
158#endif
159
160void raw_irqentry_exit_cond_resched(void)
161{
162 if (!preempt_count()) {
163 /* Sanity check RCU and thread stack */
164 rcu_irq_exit_check_preempt();
165 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
166 WARN_ON_ONCE(!on_thread_stack());
167 if (need_resched() && arch_irqentry_exit_need_resched())
168 preempt_schedule_irq();
169 }
170}
171#ifdef CONFIG_PREEMPT_DYNAMIC
172#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
173DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
174#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
175DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
176void dynamic_irqentry_exit_cond_resched(void)
177{
178 if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
179 return;
180 raw_irqentry_exit_cond_resched();
181}
182#endif
183#endif
184
185noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
186{
187 lockdep_assert_irqs_disabled();
188
189 /* Check whether this returns to user mode */
190 if (user_mode(regs)) {
191 irqentry_exit_to_user_mode(regs);
192 } else if (!regs_irqs_disabled(regs)) {
193 /*
194 * If RCU was not watching on entry this needs to be done
195 * carefully and needs the same ordering of lockdep/tracing
196 * and RCU as the return to user mode path.
197 */
198 if (state.exit_rcu) {
199 instrumentation_begin();
200 /* Tell the tracer that IRET will enable interrupts */
201 trace_hardirqs_on_prepare();
202 lockdep_hardirqs_on_prepare();
203 instrumentation_end();
204 ct_irq_exit();
205 lockdep_hardirqs_on(CALLER_ADDR0);
206 return;
207 }
208
209 instrumentation_begin();
210 if (IS_ENABLED(CONFIG_PREEMPTION))
211 irqentry_exit_cond_resched();
212
213 /* Covers both tracing and lockdep */
214 trace_hardirqs_on();
215 instrumentation_end();
216 } else {
217 /*
218 * IRQ flags state is correct already. Just tell RCU if it
219 * was not watching on entry.
220 */
221 if (state.exit_rcu)
222 ct_irq_exit();
223 }
224}
225
226irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
227{
228 irqentry_state_t irq_state;
229
230 irq_state.lockdep = lockdep_hardirqs_enabled();
231
232 __nmi_enter();
233 lockdep_hardirqs_off(CALLER_ADDR0);
234 lockdep_hardirq_enter();
235 ct_nmi_enter();
236
237 instrumentation_begin();
238 kmsan_unpoison_entry_regs(regs);
239 trace_hardirqs_off_finish();
240 ftrace_nmi_enter();
241 instrumentation_end();
242
243 return irq_state;
244}
245
246void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
247{
248 instrumentation_begin();
249 ftrace_nmi_exit();
250 if (irq_state.lockdep) {
251 trace_hardirqs_on_prepare();
252 lockdep_hardirqs_on_prepare();
253 }
254 instrumentation_end();
255
256 ct_nmi_exit();
257 lockdep_hardirq_exit();
258 if (irq_state.lockdep)
259 lockdep_hardirqs_on(CALLER_ADDR0);
260 __nmi_exit();
261}
262