1 files changed, 69 insertions, 271 deletions

diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index e33691d5adf7..19d2244a9fef 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -1,105 +1,58 @@
 // SPDX-License-Identifier: GPL-2.0
 
-#include <linux/context_tracking.h>
-#include <linux/entry-common.h>
+#include <linux/irq-entry-common.h>
 #include <linux/resume_user_mode.h>
 #include <linux/highmem.h>
 #include <linux/jump_label.h>
 #include <linux/kmsan.h>
 #include <linux/livepatch.h>
-#include <linux/audit.h>
 #include <linux/tick.h>
 
-#include "common.h"
-
-#define CREATE_TRACE_POINTS
-#include <trace/events/syscalls.h>
-
-static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
-{
-	if (unlikely(audit_context())) {
-		unsigned long args[6];
-
-		syscall_get_arguments(current, regs, args);
-		audit_syscall_entry(syscall, args[0], args[1], args[2], args[3]);
-	}
-}
-
-long syscall_trace_enter(struct pt_regs *regs, long syscall,
-				unsigned long work)
-{
-	long ret = 0;
-
-	/*
-	 * Handle Syscall User Dispatch.  This must comes first, since
-	 * the ABI here can be something that doesn't make sense for
-	 * other syscall_work features.
-	 */
-	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
-		if (syscall_user_dispatch(regs))
-			return -1L;
-	}
-
-	/* Handle ptrace */
-	if (work & (SYSCALL_WORK_SYSCALL_TRACE | SYSCALL_WORK_SYSCALL_EMU)) {
-		ret = ptrace_report_syscall_entry(regs);
-		if (ret || (work & SYSCALL_WORK_SYSCALL_EMU))
-			return -1L;
-	}
-
-	/* Do seccomp after ptrace, to catch any tracer changes. */
-	if (work & SYSCALL_WORK_SECCOMP) {
-		ret = __secure_computing(NULL);
-		if (ret == -1L)
-			return ret;
-	}
-
-	/* Either of the above might have changed the syscall number */
-	syscall = syscall_get_nr(current, regs);
-
-	if (unlikely(work & SYSCALL_WORK_SYSCALL_TRACEPOINT)) {
-		trace_sys_enter(regs, syscall);
-		/*
-		 * Probes or BPF hooks in the tracepoint may have changed the
-		 * system call number as well.
-		 */
-		syscall = syscall_get_nr(current, regs);
-	}
-
-	syscall_enter_audit(regs, syscall);
-
-	return ret ? : syscall;
-}
-
-noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
-{
-	enter_from_user_mode(regs);
-	instrumentation_begin();
-	local_irq_enable();
-	instrumentation_end();
-}
-
 /* Workaround to allow gradual conversion of architecture code */
 void __weak arch_do_signal_or_restart(struct pt_regs *regs) { }
 
-/**
- * exit_to_user_mode_loop - do any pending work before leaving to user space
- * @regs:	Pointer to pt_regs on entry stack
- * @ti_work:	TIF work flags as read by the caller
+#ifdef CONFIG_HAVE_GENERIC_TIF_BITS
+#define EXIT_TO_USER_MODE_WORK_LOOP	(EXIT_TO_USER_MODE_WORK & ~_TIF_RSEQ)
+#else
+#define EXIT_TO_USER_MODE_WORK_LOOP	(EXIT_TO_USER_MODE_WORK)
+#endif
+
+/* TIF bits, which prevent a time slice extension. */
+#ifdef CONFIG_PREEMPT_RT
+/*
+ * Since rseq slice ext has a direct correlation to the worst case
+ * scheduling latency (schedule is delayed after all), only have it affect
+ * LAZY reschedules on PREEMPT_RT for now.
+ *
+ * However, since this delay is only applicable to userspace, a value
+ * for rseq_slice_extension_nsec that is strictly less than the worst case
+ * kernel space preempt_disable() region, should mean the scheduling latency
+ * is not affected, even for !LAZY.
+ *
+ * However, since this value depends on the hardware at hand, it cannot be
+ * pre-determined in any sensible way. Hence punt on this problem for now.
  */
-__always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
-						     unsigned long ti_work)
+# define TIF_SLICE_EXT_SCHED	(_TIF_NEED_RESCHED_LAZY)
+#else
+# define TIF_SLICE_EXT_SCHED	(_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)
+#endif
+#define TIF_SLICE_EXT_DENY	(EXIT_TO_USER_MODE_WORK & ~TIF_SLICE_EXT_SCHED)
+
+static __always_inline unsigned long __exit_to_user_mode_loop(struct pt_regs *regs,
+							      unsigned long ti_work)
 {
 	/*
 	 * Before returning to user space ensure that all pending work
 	 * items have been completed.
 	 */
-	while (ti_work & EXIT_TO_USER_MODE_WORK) {
+	while (ti_work & EXIT_TO_USER_MODE_WORK_LOOP) {
 
-		local_irq_enable_exit_to_user(ti_work);
+		local_irq_enable();
 
-		if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY))
-			schedule();
+		if (ti_work & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) {
+			if (!rseq_grant_slice_extension(ti_work, TIF_SLICE_EXT_DENY))
+				schedule();
+		}
 
 		if (ti_work & _TIF_UPROBE)
 			uprobe_notify_resume(regs);
@@ -121,7 +74,7 @@ __always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
 		 * might have changed while interrupts and preemption was
 		 * enabled above.
 		 */
-		local_irq_disable_exit_to_user();
+		local_irq_disable();
 
 		/* Check if any of the above work has queued a deferred wakeup */
 		tick_nohz_user_enter_prepare();
@@ -133,172 +86,50 @@ __always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
 	return ti_work;
 }
 
-/*
- * If SYSCALL_EMU is set, then the only reason to report is when
- * SINGLESTEP is set (i.e. PTRACE_SYSEMU_SINGLESTEP).  This syscall
- * instruction has been already reported in syscall_enter_from_user_mode().
- */
-static inline bool report_single_step(unsigned long work)
-{
-	if (work & SYSCALL_WORK_SYSCALL_EMU)
-		return false;
-
-	return work & SYSCALL_WORK_SYSCALL_EXIT_TRAP;
-}
-
-static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
-{
-	bool step;
-
-	/*
-	 * If the syscall was rolled back due to syscall user dispatching,
-	 * then the tracers below are not invoked for the same reason as
-	 * the entry side was not invoked in syscall_trace_enter(): The ABI
-	 * of these syscalls is unknown.
-	 */
-	if (work & SYSCALL_WORK_SYSCALL_USER_DISPATCH) {
-		if (unlikely(current->syscall_dispatch.on_dispatch)) {
-			current->syscall_dispatch.on_dispatch = false;
-			return;
-		}
-	}
-
-	audit_syscall_exit(regs);
-
-	if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
-		trace_sys_exit(regs, syscall_get_return_value(current, regs));
-
-	step = report_single_step(work);
-	if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
-		ptrace_report_syscall_exit(regs, step);
-}
-
-/*
- * Syscall specific exit to user mode preparation. Runs with interrupts
- * enabled.
+/**
+ * exit_to_user_mode_loop - do any pending work before leaving to user space
+ * @regs:	Pointer to pt_regs on entry stack
+ * @ti_work:	TIF work flags as read by the caller
  */
-static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
+__always_inline unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
+						     unsigned long ti_work)
 {
-	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
-	unsigned long nr = syscall_get_nr(current, regs);
-
-	CT_WARN_ON(ct_state() != CT_STATE_KERNEL);
+	for (;;) {
+		ti_work = __exit_to_user_mode_loop(regs, ti_work);
 
-	if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
-		if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
-			local_irq_enable();
+		if (likely(!rseq_exit_to_user_mode_restart(regs, ti_work)))
+			return ti_work;
+		ti_work = read_thread_flags();
 	}
-
-	rseq_syscall(regs);
-
-	/*
-	 * Do one-time syscall specific work. If these work items are
-	 * enabled, we want to run them exactly once per syscall exit with
-	 * interrupts enabled.
-	 */
-	if (unlikely(work & SYSCALL_WORK_EXIT))
-		syscall_exit_work(regs, work);
-}
-
-static __always_inline void __syscall_exit_to_user_mode_work(struct pt_regs *regs)
-{
-	syscall_exit_to_user_mode_prepare(regs);
-	local_irq_disable_exit_to_user();
-	exit_to_user_mode_prepare(regs);
-}
-
-void syscall_exit_to_user_mode_work(struct pt_regs *regs)
-{
-	__syscall_exit_to_user_mode_work(regs);
-}
-
-__visible noinstr void syscall_exit_to_user_mode(struct pt_regs *regs)
-{
-	instrumentation_begin();
-	__syscall_exit_to_user_mode_work(regs);
-	instrumentation_end();
-	exit_to_user_mode();
-}
-
-noinstr void irqentry_enter_from_user_mode(struct pt_regs *regs)
-{
-	enter_from_user_mode(regs);
-}
-
-noinstr void irqentry_exit_to_user_mode(struct pt_regs *regs)
-{
-	instrumentation_begin();
-	exit_to_user_mode_prepare(regs);
-	instrumentation_end();
-	exit_to_user_mode();
 }
 
 noinstr irqentry_state_t irqentry_enter(struct pt_regs *regs)
 {
-	irqentry_state_t ret = {
-		.exit_rcu = false,
-	};
-
 	if (user_mode(regs)) {
+		irqentry_state_t ret = {
+			.exit_rcu = false,
+		};
+
 		irqentry_enter_from_user_mode(regs);
 		return ret;
 	}
 
-	/*
-	 * If this entry hit the idle task invoke ct_irq_enter() whether
-	 * RCU is watching or not.
-	 *
-	 * Interrupts can nest when the first interrupt invokes softirq
-	 * processing on return which enables interrupts.
-	 *
-	 * Scheduler ticks in the idle task can mark quiescent state and
-	 * terminate a grace period, if and only if the timer interrupt is
-	 * not nested into another interrupt.
-	 *
-	 * Checking for rcu_is_watching() here would prevent the nesting
-	 * interrupt to invoke ct_irq_enter(). If that nested interrupt is
-	 * the tick then rcu_flavor_sched_clock_irq() would wrongfully
-	 * assume that it is the first interrupt and eventually claim
-	 * quiescent state and end grace periods prematurely.
-	 *
-	 * Unconditionally invoke ct_irq_enter() so RCU state stays
-	 * consistent.
-	 *
-	 * TINY_RCU does not support EQS, so let the compiler eliminate
-	 * this part when enabled.
-	 */
-	if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
-		/*
-		 * If RCU is not watching then the same careful
-		 * sequence vs. lockdep and tracing is required
-		 * as in irqentry_enter_from_user_mode().
-		 */
-		lockdep_hardirqs_off(CALLER_ADDR0);
-		ct_irq_enter();
-		instrumentation_begin();
-		kmsan_unpoison_entry_regs(regs);
-		trace_hardirqs_off_finish();
-		instrumentation_end();
-
-		ret.exit_rcu = true;
-		return ret;
-	}
+	return irqentry_enter_from_kernel_mode(regs);
+}
 
-	/*
-	 * If RCU is watching then RCU only wants to check whether it needs
-	 * to restart the tick in NOHZ mode. rcu_irq_enter_check_tick()
-	 * already contains a warning when RCU is not watching, so no point
-	 * in having another one here.
-	 */
-	lockdep_hardirqs_off(CALLER_ADDR0);
-	instrumentation_begin();
-	kmsan_unpoison_entry_regs(regs);
-	rcu_irq_enter_check_tick();
-	trace_hardirqs_off_finish();
-	instrumentation_end();
+/**
+ * arch_irqentry_exit_need_resched - Architecture specific need resched function
+ *
+ * Invoked from raw_irqentry_exit_cond_resched() to check if resched is needed.
+ * Defaults return true.
+ *
+ * The main purpose is to permit arch to avoid preemption of a task from an IRQ.
+ */
+static inline bool arch_irqentry_exit_need_resched(void);
 
-	return ret;
-}
+#ifndef arch_irqentry_exit_need_resched
+static inline bool arch_irqentry_exit_need_resched(void) { return true; }
+#endif
 
 void raw_irqentry_exit_cond_resched(void)
 {
@@ -307,7 +138,7 @@ void raw_irqentry_exit_cond_resched(void)
 		rcu_irq_exit_check_preempt();
 		if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
 			WARN_ON_ONCE(!on_thread_stack());
-		if (need_resched())
+		if (need_resched() && arch_irqentry_exit_need_resched())
 			preempt_schedule_irq();
 	}
 }
@@ -327,43 +158,10 @@ void dynamic_irqentry_exit_cond_resched(void)
 
 noinstr void irqentry_exit(struct pt_regs *regs, irqentry_state_t state)
 {
-	lockdep_assert_irqs_disabled();
-
-	/* Check whether this returns to user mode */
-	if (user_mode(regs)) {
+	if (user_mode(regs))
 		irqentry_exit_to_user_mode(regs);
-	} else if (!regs_irqs_disabled(regs)) {
-		/*
-		 * If RCU was not watching on entry this needs to be done
-		 * carefully and needs the same ordering of lockdep/tracing
-		 * and RCU as the return to user mode path.
-		 */
-		if (state.exit_rcu) {
-			instrumentation_begin();
-			/* Tell the tracer that IRET will enable interrupts */
-			trace_hardirqs_on_prepare();
-			lockdep_hardirqs_on_prepare();
-			instrumentation_end();
-			ct_irq_exit();
-			lockdep_hardirqs_on(CALLER_ADDR0);
-			return;
-		}
-
-		instrumentation_begin();
-		if (IS_ENABLED(CONFIG_PREEMPTION))
-			irqentry_exit_cond_resched();
-
-		/* Covers both tracing and lockdep */
-		trace_hardirqs_on();
-		instrumentation_end();
-	} else {
-		/*
-		 * IRQ flags state is correct already. Just tell RCU if it
-		 * was not watching on entry.
-		 */
-		if (state.exit_rcu)
-			ct_irq_exit();
-	}
+	else
+		irqentry_exit_to_kernel_mode(regs, state);
 }
 
 irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)