// SPDX-License-Identifier: GPL-2.0

#include <linux/context_tracking.h>
#include <linux/entry-common.h>
#include <linux/highmem.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>

/* See comment for enter_from_user_mode() in entry-common.h */
static __always_inline void __enter_from_user_mode(struct pt_regs *regs)
{
        arch_check_user_regs(regs);
        lockdep_hardirqs_off(CALLER_ADDR0);

        CT_WARN_ON(ct_state() != CONTEXT_USER);
        user_exit_irqoff();

        instrumentation_begin();
        trace_hardirqs_off_finish();
        instrumentation_end();
}

void noinstr enter_from_user_mode(struct pt_regs *regs)
{
        __enter_from_user_mode(regs);
}

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]);
        }
}

static 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 = arch_syscall_enter_tracehook(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);

        syscall_enter_audit(regs, syscall);

        return ret ? : syscall;
}

static __always_inline long
__syscall_enter_from_user_work(struct pt_regs *regs, long syscall)
{
        unsigned long work = READ_ONCE(current_thread_info()->syscall_work);

        if (work & SYSCALL_WORK_ENTER)
                syscall = syscall_trace_enter(regs, syscall, work);

        return syscall;
}

long syscall_enter_from_user_mode_work(struct pt_regs *regs, long syscall)
{
        return __syscall_enter_from_user_work(regs, syscall);
}

noinstr long syscall_enter_from_user_mode(struct pt_regs *regs, long syscall)
{
        long ret;

        __enter_from_user_mode(regs);

        instrumentation_begin();
        local_irq_enable();
        ret = __syscall_enter_from_user_work(regs, syscall);
        instrumentation_end();

        return ret;
}

noinstr void syscall_enter_from_user_mode_prepare(struct pt_regs *regs)
{
        __enter_from_user_mode(regs);
        instrumentation_begin();
        local_irq_enable();
        instrumentation_end();
}

/* See comment for exit_to_user_mode() in entry-common.h */
static __always_inline void __exit_to_user_mode(void)
{
        instrumentation_begin();
        trace_hardirqs_on_prepare();
        lockdep_hardirqs_on_prepare(CALLER_ADDR0);
        instrumentation_end();

        user_enter_irqoff();
        arch_exit_to_user_mode();
        lockdep_hardirqs_on(CALLER_ADDR0);
}

void noinstr exit_to_user_mode(void)
{
        __exit_to_user_mode();
}

/* Workaround to allow gradual conversion of architecture code */
void __weak arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) { }

static void handle_signal_work(struct pt_regs *regs, unsigned long ti_work)
{
        if (ti_work & _TIF_NOTIFY_SIGNAL)
                tracehook_notify_signal();

        arch_do_signal_or_restart(regs, ti_work & _TIF_SIGPENDING);
}

static 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) {

                local_irq_enable_exit_to_user(ti_work);

                if (ti_work & _TIF_NEED_RESCHED)
                        schedule();

                if (ti_work & _TIF_UPROBE)
                        uprobe_notify_resume(regs);

                if (ti_work & _TIF_PATCH_PENDING)
                        klp_update_patch_state(current);

                if (ti_work & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
                        handle_signal_work(regs, ti_work);

                if (ti_work & _TIF_NOTIFY_RESUME)
                        tracehook_notify_resume(regs);

                /* Architecture specific TIF work */
                arch_exit_to_user_mode_work(regs, ti_work);

                /*
                 * Disable interrupts and reevaluate the work flags as they
                 * might have changed while interrupts and preemption was
                 * enabled above.
                 */
                local_irq_disable_exit_to_user();

                /* Check if any of the above work has queued a deferred wakeup */
                tick_nohz_user_enter_prepare();

                ti_work = READ_ONCE(current_thread_info()->flags);
        }

        /* Return the latest work state for arch_exit_to_user_mode() */
        return ti_work;
}

static void exit_to_user_mode_prepare(struct pt_regs *regs)
{
        unsigned long ti_work = READ_ONCE(current_thread_info()->flags);

        lockdep_assert_irqs_disabled();

        /* Flush pending rcuog wakeup before the last need_resched() check */
        tick_nohz_user_enter_prepare();

        if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
                ti_work = exit_to_user_mode_loop(regs, ti_work);

        arch_exit_to_user_mode_prepare(regs, ti_work);

        /* Ensure that the address limit is intact and no locks are held */
        addr_limit_user_check();
        kmap_assert_nomap();
        lockdep_assert_irqs_disabled();
        lockdep_sys_exit();
}

/*
 * 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)
                arch_syscall_exit_tracehook(regs, step);
}

/*
 * Syscall specific exit to user mode preparation. Runs with interrupts
 * enabled.
 */
static void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
{
        unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
        unsigned long nr = syscall_get_nr(current, regs);

        CT_WARN_ON(ct_state() != CONTEXT_KERNEL);

        if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
                if (WARN(irqs_disabled(), "syscall %lu left IRQs disabled", nr))
                        local_irq_enable();
        }

        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_enter_from_user_mode(regs);
                return ret;
        }

        /*
         * If this entry hit the idle task invoke rcu_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 rcu_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 rcu_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);
                rcu_irq_enter();
                instrumentation_begin();
                trace_hardirqs_off_finish();
                instrumentation_end();

                ret.exit_rcu = true;
                return ret;
        }

        /*
         * 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();
        rcu_irq_enter_check_tick();
        trace_hardirqs_off_finish();
        instrumentation_end();

        return ret;
}

void irqentry_exit_cond_resched(void)
{
        if (!preempt_count()) {
                /* Sanity check RCU and thread stack */
                rcu_irq_exit_check_preempt();
                if (IS_ENABLED(CONFIG_DEBUG_ENTRY))
                        WARN_ON_ONCE(!on_thread_stack());
                if (need_resched())
                        preempt_schedule_irq();
        }
}
#ifdef CONFIG_PREEMPT_DYNAMIC
DEFINE_STATIC_CALL(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
#endif

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)) {
                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(CALLER_ADDR0);
                        instrumentation_end();
                        rcu_irq_exit();
                        lockdep_hardirqs_on(CALLER_ADDR0);
                        return;
                }

                instrumentation_begin();
                if (IS_ENABLED(CONFIG_PREEMPTION)) {
#ifdef CONFIG_PREEMPT_DYNAMIC
                        static_call(irqentry_exit_cond_resched)();
#else
                        irqentry_exit_cond_resched();
#endif
                }
                /* 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)
                        rcu_irq_exit();
        }
}

irqentry_state_t noinstr irqentry_nmi_enter(struct pt_regs *regs)
{
        irqentry_state_t irq_state;

        irq_state.lockdep = lockdep_hardirqs_enabled();

        __nmi_enter();
        lockdep_hardirqs_off(CALLER_ADDR0);
        lockdep_hardirq_enter();
        rcu_nmi_enter();

        instrumentation_begin();
        trace_hardirqs_off_finish();
        ftrace_nmi_enter();
        instrumentation_end();

        return irq_state;
}

void noinstr irqentry_nmi_exit(struct pt_regs *regs, irqentry_state_t irq_state)
{
        instrumentation_begin();
        ftrace_nmi_exit();
        if (irq_state.lockdep) {
                trace_hardirqs_on_prepare();
                lockdep_hardirqs_on_prepare(CALLER_ADDR0);
        }
        instrumentation_end();

        rcu_nmi_exit();
        lockdep_hardirq_exit();
        if (irq_state.lockdep)
                lockdep_hardirqs_on(CALLER_ADDR0);
        __nmi_exit();
}