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#ifdef CONFIG_HAVE_GENERIC_TIF_BITS
15#define EXIT_TO_USER_MODE_WORK_LOOP (EXIT_TO_USER_MODE_WORK & ~_TIF_RSEQ)
16#else
17#define EXIT_TO_USER_MODE_WORK_LOOP (EXIT_TO_USER_MODE_WORK)
18#endif
19
20static __always_inline unsigned long __exit_to_user_mode_loop(struct pt_regs *regs,
21 unsigned long ti_work)
22{
23 /*
24 * Before returning to user space ensure that all pending work
25 * items have been completed.
26 */
27 while (ti_work & EXIT_TO_USER_MODE_WORK_LOOP) {
28
29 local_irq_enable_exit_to_user(ti_work);
30
31 if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
32 schedule();
33
34 if (ti_work & _TIF_UPROBE)
35 uprobe_notify_resume(regs);
36
37 if (ti_work & _TIF_PATCH_PENDING)
38 klp_update_patch_state(current);
39
40 if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
41 arch_do_signal_or_restart(regs);
42
43 if (ti_work & _TIF_NOTIFY_RESUME)
44 resume_user_mode_work(regs);
45
46 /* Architecture specific TIF work */
47 arch_exit_to_user_mode_work(regs, ti_work);
48
49 /*
50 * Disable interrupts and reevaluate the work flags as they
51 * might have changed while interrupts and preemption was
52 * enabled above.
53 */
54 local_irq_disable_exit_to_user();
55
56 /* Check if any of the above work has queued a deferred wakeup */
57 tick_nohz_user_enter_prepare();
58
59 ti_work = read_thread_flags();
60 }
61
62 /* Return the latest work state for arch_exit_to_user_mode() */
63 return ti_work;
64}
65
66/**
67 * exit_to_user_mode_loop - do any pending work before leaving to user space
68 * @regs: Pointer to pt_regs on entry stack
69 * @ti_work: TIF work flags as read by the caller
70 */
71__always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
72 unsigned long ti_work)
73{
74 for (;;) {
75 ti_work = __exit_to_user_mode_loop(regs, ti_work);
76
77 if (likely(!rseq_exit_to_user_mode_restart(regs, ti_work)))
78 return ti_work;
79 ti_work = read_thread_flags();
80 }
81}
82
83noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
84{
85 irqentry_state_t ret = {
86 .exit_rcu = false,
87 };
88
89 if (user_mode(regs)) {
90 irqentry_enter_from_user_mode(regs);
91 return ret;
92 }
93
94 /*
95 * If this entry hit the idle task invoke ct_irq_enter() whether
96 * RCU is watching or not.
97 *
98 * Interrupts can nest when the first interrupt invokes softirq
99 * processing on return which enables interrupts.
100 *
101 * Scheduler ticks in the idle task can mark quiescent state and
102 * terminate a grace period, if and only if the timer interrupt is
103 * not nested into another interrupt.
104 *
105 * Checking for rcu_is_watching() here would prevent the nesting
106 * interrupt to invoke ct_irq_enter(). If that nested interrupt is
107 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
108 * assume that it is the first interrupt and eventually claim
109 * quiescent state and end grace periods prematurely.
110 *
111 * Unconditionally invoke ct_irq_enter() so RCU state stays
112 * consistent.
113 *
114 * TINY_RCU does not support EQS, so let the compiler eliminate
115 * this part when enabled.
116 */
117 if (!IS_ENABLED(CONFIG_TINY_RCU) &&
118 (is_idle_task(current) || arch_in_rcu_eqs())) {
119 /*
120 * If RCU is not watching then the same careful
121 * sequence vs. lockdep and tracing is required
122 * as in irqentry_enter_from_user_mode().
123 */
124 lockdep_hardirqs_off(CALLER_ADDR0);
125 ct_irq_enter();
126 instrumentation_begin();
127 kmsan_unpoison_entry_regs(regs);
128 trace_hardirqs_off_finish();
129 instrumentation_end();
130
131 ret.exit_rcu = true;
132 return ret;
133 }
134
135 /*
136 * If RCU is watching then RCU only wants to check whether it needs
137 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
138 * already contains a warning when RCU is not watching, so no point
139 * in having another one here.
140 */
141 lockdep_hardirqs_off(CALLER_ADDR0);
142 instrumentation_begin();
143 kmsan_unpoison_entry_regs(regs);
144 rcu_irq_enter_check_tick();
145 trace_hardirqs_off_finish();
146 instrumentation_end();
147
148 return ret;
149}
150
151/**
152 * arch_irqentry_exit_need_resched - Architecture specific need resched function
153 *
154 * Invoked from raw_irqentry_exit_cond_resched() to check if resched is needed.
155 * Defaults return true.
156 *
157 * The main purpose is to permit arch to avoid preemption of a task from an IRQ.
158 */
159static inline bool arch_irqentry_exit_need_resched(void);
160
161#ifndef arch_irqentry_exit_need_resched
162static inline bool arch_irqentry_exit_need_resched(void) { return true; }
163#endif
164
165void raw_irqentry_exit_cond_resched(void)
166{
167 if (!preempt_count()) {
168 /* Sanity check RCU and thread stack */
169 rcu_irq_exit_check_preempt();
170 if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
171 WARN_ON_ONCE(!on_thread_stack());
172 if (need_resched() && arch_irqentry_exit_need_resched())
173 preempt_schedule_irq();
174 }
175}
176#ifdef CONFIG_PREEMPT_DYNAMIC
177#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
178DEFINE_STATIC_CALL(irqentry_exit_cond_resched, raw_irqentry_exit_cond_resched);
179#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
180DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched);
181void dynamic_irqentry_exit_cond_resched(void)
182{
183 if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
184 return;
185 raw_irqentry_exit_cond_resched();
186}
187#endif
188#endif
189
190noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
191{
192 lockdep_assert_irqs_disabled();
193
194 /* Check whether this returns to user mode */
195 if (user_mode(regs)) {
196 irqentry_exit_to_user_mode(regs);
197 } else if (!regs_irqs_disabled(regs)) {
198 /*
199 * If RCU was not watching on entry this needs to be done
200 * carefully and needs the same ordering of lockdep/tracing
201 * and RCU as the return to user mode path.
202 */
203 if (state.exit_rcu) {
204 instrumentation_begin();
205 /* Tell the tracer that IRET will enable interrupts */
206 trace_hardirqs_on_prepare();
207 lockdep_hardirqs_on_prepare();
208 instrumentation_end();
209 ct_irq_exit();
210 lockdep_hardirqs_on(CALLER_ADDR0);
211 return;
212 }
213
214 instrumentation_begin();
215 if (IS_ENABLED(CONFIG_PREEMPTION))
216 irqentry_exit_cond_resched();
217
218 /* Covers both tracing and lockdep */
219 trace_hardirqs_on();
220 instrumentation_end();
221 } else {
222 /*
223 * IRQ flags state is correct already. Just tell RCU if it
224 * was not watching on entry.
225 */
226 if (state.exit_rcu)
227 ct_irq_exit();
228 }
229}
230
231irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
232{
233 irqentry_state_t irq_state;
234
235 irq_state.lockdep = lockdep_hardirqs_enabled();
236
237 __nmi_enter();
238 lockdep_hardirqs_off(CALLER_ADDR0);
239 lockdep_hardirq_enter();
240 ct_nmi_enter();
241
242 instrumentation_begin();
243 kmsan_unpoison_entry_regs(regs);
244 trace_hardirqs_off_finish();
245 ftrace_nmi_enter();
246 instrumentation_end();
247
248 return irq_state;
249}
250
251void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
252{
253 instrumentation_begin();
254 ftrace_nmi_exit();
255 if (irq_state.lockdep) {
256 trace_hardirqs_on_prepare();
257 lockdep_hardirqs_on_prepare();
258 }
259 instrumentation_end();
260
261 ct_nmi_exit();
262 lockdep_hardirq_exit();
263 if (irq_state.lockdep)
264 lockdep_hardirqs_on(CALLER_ADDR0);
265 __nmi_exit();
266}
267

source code of linux/kernel/entry/common.c