// SPDX-License-Identifier: GPL-2.0
/*
 * Exception handling code
 *
 * Copyright (C) 2019 ARM Ltd.
 */

#include <linux/context_tracking.h>
#include <linux/linkage.h>
#include <linux/lockdep.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/thread_info.h>

#include <asm/cpufeature.h>
#include <asm/daifflags.h>
#include <asm/esr.h>
#include <asm/exception.h>
#include <asm/kprobes.h>
#include <asm/mmu.h>
#include <asm/processor.h>
#include <asm/sdei.h>
#include <asm/stacktrace.h>
#include <asm/sysreg.h>
#include <asm/system_misc.h>

/*
 * This is intended to match the logic in irqentry_enter(), handling the kernel
 * mode transitions only.
 */
static void noinstr enter_from_kernel_mode(struct pt_regs *regs)
{
        regs->exit_rcu = false;

        if (!IS_ENABLED(CONFIG_TINY_RCU) && is_idle_task(current)) {
                lockdep_hardirqs_off(CALLER_ADDR0);
                rcu_irq_enter();
                trace_hardirqs_off_finish();

                regs->exit_rcu = true;
                return;
        }

        lockdep_hardirqs_off(CALLER_ADDR0);
        rcu_irq_enter_check_tick();
        trace_hardirqs_off_finish();

        mte_check_tfsr_entry();
}

/*
 * This is intended to match the logic in irqentry_exit(), handling the kernel
 * mode transitions only, and with preemption handled elsewhere.
 */
static void noinstr exit_to_kernel_mode(struct pt_regs *regs)
{
        lockdep_assert_irqs_disabled();

        mte_check_tfsr_exit();

        if (interrupts_enabled(regs)) {
                if (regs->exit_rcu) {
                        trace_hardirqs_on_prepare();
                        lockdep_hardirqs_on_prepare(CALLER_ADDR0);
                        rcu_irq_exit();
                        lockdep_hardirqs_on(CALLER_ADDR0);
                        return;
                }

                trace_hardirqs_on();
        } else {
                if (regs->exit_rcu)
                        rcu_irq_exit();
        }
}

static void noinstr arm64_enter_nmi(struct pt_regs *regs)
{
        regs->lockdep_hardirqs = lockdep_hardirqs_enabled();

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

        trace_hardirqs_off_finish();
        ftrace_nmi_enter();
}

static void noinstr arm64_exit_nmi(struct pt_regs *regs)
{
        bool restore = regs->lockdep_hardirqs;

        ftrace_nmi_exit();
        if (restore) {
                trace_hardirqs_on_prepare();
                lockdep_hardirqs_on_prepare(CALLER_ADDR0);
        }

        rcu_nmi_exit();
        lockdep_hardirq_exit();
        if (restore)
                lockdep_hardirqs_on(CALLER_ADDR0);
        __nmi_exit();
}

static void noinstr enter_el1_irq_or_nmi(struct pt_regs *regs)
{
        if (IS_ENABLED(CONFIG_ARM64_PSEUDO_NMI) && !interrupts_enabled(regs))
                arm64_enter_nmi(regs);
        else
                enter_from_kernel_mode(regs);
}

static void noinstr exit_el1_irq_or_nmi(struct pt_regs *regs)
{
        if (IS_ENABLED(CONFIG_ARM64_PSEUDO_NMI) && !interrupts_enabled(regs))
                arm64_exit_nmi(regs);
        else
                exit_to_kernel_mode(regs);
}

static void __sched arm64_preempt_schedule_irq(void)
{
        lockdep_assert_irqs_disabled();

        /*
         * DAIF.DA are cleared at the start of IRQ/FIQ handling, and when GIC
         * priority masking is used the GIC irqchip driver will clear DAIF.IF
         * using gic_arch_enable_irqs() for normal IRQs. If anything is set in
         * DAIF we must have handled an NMI, so skip preemption.
         */
        if (system_uses_irq_prio_masking() && read_sysreg(daif))
                return;

        /*
         * Preempting a task from an IRQ means we leave copies of PSTATE
         * on the stack. cpufeature's enable calls may modify PSTATE, but
         * resuming one of these preempted tasks would undo those changes.
         *
         * Only allow a task to be preempted once cpufeatures have been
         * enabled.
         */
        if (system_capabilities_finalized())
                preempt_schedule_irq();
}

static void do_interrupt_handler(struct pt_regs *regs,
                                 void (*handler)(struct pt_regs *))
{
        if (on_thread_stack())
                call_on_irq_stack(regs, handler);
        else
                handler(regs);
}

extern void (*handle_arch_irq)(struct pt_regs *);
extern void (*handle_arch_fiq)(struct pt_regs *);

static void noinstr __panic_unhandled(struct pt_regs *regs, const char *vector,
                                      unsigned int esr)
{
        arm64_enter_nmi(regs);

        console_verbose();

        pr_crit("Unhandled %s exception on CPU%d, ESR 0x%08x -- %s\n",
                vector, smp_processor_id(), esr,
                esr_get_class_string(esr));

        __show_regs(regs);
        panic("Unhandled exception");
}

#define UNHANDLED(el, regsize, vector)                                                  \
asmlinkage void noinstr el##_##regsize##_##vector##_handler(struct pt_regs *regs)       \
{                                                                                       \
        const char *desc = #regsize "-bit " #el " " #vector;                            \
        __panic_unhandled(regs, desc, read_sysreg(esr_el1));                            \
}

#ifdef CONFIG_ARM64_ERRATUM_1463225
static DEFINE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa);

static void cortex_a76_erratum_1463225_svc_handler(void)
{
        u32 reg, val;

        if (!unlikely(test_thread_flag(TIF_SINGLESTEP)))
                return;

        if (!unlikely(this_cpu_has_cap(ARM64_WORKAROUND_1463225)))
                return;

        __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 1);
        reg = read_sysreg(mdscr_el1);
        val = reg | DBG_MDSCR_SS | DBG_MDSCR_KDE;
        write_sysreg(val, mdscr_el1);
        asm volatile("msr daifclr, #8");
        isb();

        /* We will have taken a single-step exception by this point */

        write_sysreg(reg, mdscr_el1);
        __this_cpu_write(__in_cortex_a76_erratum_1463225_wa, 0);
}

static bool cortex_a76_erratum_1463225_debug_handler(struct pt_regs *regs)
{
        if (!__this_cpu_read(__in_cortex_a76_erratum_1463225_wa))
                return false;

        /*
         * We've taken a dummy step exception from the kernel to ensure
         * that interrupts are re-enabled on the syscall path. Return back
         * to cortex_a76_erratum_1463225_svc_handler() with debug exceptions
         * masked so that we can safely restore the mdscr and get on with
         * handling the syscall.
         */
        regs->pstate |= PSR_D_BIT;
        return true;
}
#else /* CONFIG_ARM64_ERRATUM_1463225 */
static void cortex_a76_erratum_1463225_svc_handler(void) { }
static bool cortex_a76_erratum_1463225_debug_handler(struct pt_regs *regs)
{
        return false;
}
#endif /* CONFIG_ARM64_ERRATUM_1463225 */

UNHANDLED(el1t, 64, sync)
UNHANDLED(el1t, 64, irq)
UNHANDLED(el1t, 64, fiq)
UNHANDLED(el1t, 64, error)

static void noinstr el1_abort(struct pt_regs *regs, unsigned long esr)
{
        unsigned long far = read_sysreg(far_el1);

        enter_from_kernel_mode(regs);
        local_daif_inherit(regs);
        do_mem_abort(far, esr, regs);
        local_daif_mask();
        exit_to_kernel_mode(regs);
}

static void noinstr el1_pc(struct pt_regs *regs, unsigned long esr)
{
        unsigned long far = read_sysreg(far_el1);

        enter_from_kernel_mode(regs);
        local_daif_inherit(regs);
        do_sp_pc_abort(far, esr, regs);
        local_daif_mask();
        exit_to_kernel_mode(regs);
}

static void noinstr el1_undef(struct pt_regs *regs)
{
        enter_from_kernel_mode(regs);
        local_daif_inherit(regs);
        do_undefinstr(regs);
        local_daif_mask();
        exit_to_kernel_mode(regs);
}

static void noinstr arm64_enter_el1_dbg(struct pt_regs *regs)
{
        regs->lockdep_hardirqs = lockdep_hardirqs_enabled();

        lockdep_hardirqs_off(CALLER_ADDR0);
        rcu_nmi_enter();

        trace_hardirqs_off_finish();
}

static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs)
{
        bool restore = regs->lockdep_hardirqs;

        if (restore) {
                trace_hardirqs_on_prepare();
                lockdep_hardirqs_on_prepare(CALLER_ADDR0);
        }

        rcu_nmi_exit();
        if (restore)
                lockdep_hardirqs_on(CALLER_ADDR0);
}

static void noinstr el1_dbg(struct pt_regs *regs, unsigned long esr)
{
        unsigned long far = read_sysreg(far_el1);

        arm64_enter_el1_dbg(regs);
        if (!cortex_a76_erratum_1463225_debug_handler(regs))
                do_debug_exception(far, esr, regs);
        arm64_exit_el1_dbg(regs);
}

static void noinstr el1_fpac(struct pt_regs *regs, unsigned long esr)
{
        enter_from_kernel_mode(regs);
        local_daif_inherit(regs);
        do_ptrauth_fault(regs, esr);
        local_daif_mask();
        exit_to_kernel_mode(regs);
}

asmlinkage void noinstr el1h_64_sync_handler(struct pt_regs *regs)
{
        unsigned long esr = read_sysreg(esr_el1);

        switch (ESR_ELx_EC(esr)) {
        case ESR_ELx_EC_DABT_CUR:
        case ESR_ELx_EC_IABT_CUR:
                el1_abort(regs, esr);
                break;
        /*
         * We don't handle ESR_ELx_EC_SP_ALIGN, since we will have hit a
         * recursive exception when trying to push the initial pt_regs.
         */
        case ESR_ELx_EC_PC_ALIGN:
                el1_pc(regs, esr);
                break;
        case ESR_ELx_EC_SYS64:
        case ESR_ELx_EC_UNKNOWN:
                el1_undef(regs);
                break;
        case ESR_ELx_EC_BREAKPT_CUR:
        case ESR_ELx_EC_SOFTSTP_CUR:
        case ESR_ELx_EC_WATCHPT_CUR:
        case ESR_ELx_EC_BRK64:
                el1_dbg(regs, esr);
                break;
        case ESR_ELx_EC_FPAC:
                el1_fpac(regs, esr);
                break;
        default:
                __panic_unhandled(regs, "64-bit el1h sync", esr);
        }
}

static void noinstr el1_interrupt(struct pt_regs *regs,
                                  void (*handler)(struct pt_regs *))
{
        write_sysreg(DAIF_PROCCTX_NOIRQ, daif);

        enter_el1_irq_or_nmi(regs);
        do_interrupt_handler(regs, handler);

        /*
         * Note: thread_info::preempt_count includes both thread_info::count
         * and thread_info::need_resched, and is not equivalent to
         * preempt_count().
         */
        if (IS_ENABLED(CONFIG_PREEMPTION) &&
            READ_ONCE(current_thread_info()->preempt_count) == 0)
                arm64_preempt_schedule_irq();

        exit_el1_irq_or_nmi(regs);
}

asmlinkage void noinstr el1h_64_irq_handler(struct pt_regs *regs)
{
        el1_interrupt(regs, handle_arch_irq);
}

asmlinkage void noinstr el1h_64_fiq_handler(struct pt_regs *regs)
{
        el1_interrupt(regs, handle_arch_fiq);
}

asmlinkage void noinstr el1h_64_error_handler(struct pt_regs *regs)
{
        unsigned long esr = read_sysreg(esr_el1);

        local_daif_restore(DAIF_ERRCTX);
        arm64_enter_nmi(regs);
        do_serror(regs, esr);
        arm64_exit_nmi(regs);
}

asmlinkage void noinstr enter_from_user_mode(void)
{
        lockdep_hardirqs_off(CALLER_ADDR0);
        CT_WARN_ON(ct_state() != CONTEXT_USER);
        user_exit_irqoff();
        trace_hardirqs_off_finish();
}

asmlinkage void noinstr exit_to_user_mode(void)
{
        mte_check_tfsr_exit();

        trace_hardirqs_on_prepare();
        lockdep_hardirqs_on_prepare(CALLER_ADDR0);
        user_enter_irqoff();
        lockdep_hardirqs_on(CALLER_ADDR0);
}

static void noinstr el0_da(struct pt_regs *regs, unsigned long esr)
{
        unsigned long far = read_sysreg(far_el1);

        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_mem_abort(far, esr, regs);
}

static void noinstr el0_ia(struct pt_regs *regs, unsigned long esr)
{
        unsigned long far = read_sysreg(far_el1);

        /*
         * We've taken an instruction abort from userspace and not yet
         * re-enabled IRQs. If the address is a kernel address, apply
         * BP hardening prior to enabling IRQs and pre-emption.
         */
        if (!is_ttbr0_addr(far))
                arm64_apply_bp_hardening();

        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_mem_abort(far, esr, regs);
}

static void noinstr el0_fpsimd_acc(struct pt_regs *regs, unsigned long esr)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_fpsimd_acc(esr, regs);
}

static void noinstr el0_sve_acc(struct pt_regs *regs, unsigned long esr)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_sve_acc(esr, regs);
}

static void noinstr el0_fpsimd_exc(struct pt_regs *regs, unsigned long esr)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_fpsimd_exc(esr, regs);
}

static void noinstr el0_sys(struct pt_regs *regs, unsigned long esr)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_sysinstr(esr, regs);
}

static void noinstr el0_pc(struct pt_regs *regs, unsigned long esr)
{
        unsigned long far = read_sysreg(far_el1);

        if (!is_ttbr0_addr(instruction_pointer(regs)))
                arm64_apply_bp_hardening();

        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_sp_pc_abort(far, esr, regs);
}

static void noinstr el0_sp(struct pt_regs *regs, unsigned long esr)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_sp_pc_abort(regs->sp, esr, regs);
}

static void noinstr el0_undef(struct pt_regs *regs)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_undefinstr(regs);
}

static void noinstr el0_bti(struct pt_regs *regs)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_bti(regs);
}

static void noinstr el0_inv(struct pt_regs *regs, unsigned long esr)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        bad_el0_sync(regs, 0, esr);
}

static void noinstr el0_dbg(struct pt_regs *regs, unsigned long esr)
{
        /* Only watchpoints write FAR_EL1, otherwise its UNKNOWN */
        unsigned long far = read_sysreg(far_el1);

        enter_from_user_mode();
        do_debug_exception(far, esr, regs);
        local_daif_restore(DAIF_PROCCTX);
}

static void noinstr el0_svc(struct pt_regs *regs)
{
        enter_from_user_mode();
        cortex_a76_erratum_1463225_svc_handler();
        do_el0_svc(regs);
}

static void noinstr el0_fpac(struct pt_regs *regs, unsigned long esr)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_ptrauth_fault(regs, esr);
}

asmlinkage void noinstr el0t_64_sync_handler(struct pt_regs *regs)
{
        unsigned long esr = read_sysreg(esr_el1);

        switch (ESR_ELx_EC(esr)) {
        case ESR_ELx_EC_SVC64:
                el0_svc(regs);
                break;
        case ESR_ELx_EC_DABT_LOW:
                el0_da(regs, esr);
                break;
        case ESR_ELx_EC_IABT_LOW:
                el0_ia(regs, esr);
                break;
        case ESR_ELx_EC_FP_ASIMD:
                el0_fpsimd_acc(regs, esr);
                break;
        case ESR_ELx_EC_SVE:
                el0_sve_acc(regs, esr);
                break;
        case ESR_ELx_EC_FP_EXC64:
                el0_fpsimd_exc(regs, esr);
                break;
        case ESR_ELx_EC_SYS64:
        case ESR_ELx_EC_WFx:
                el0_sys(regs, esr);
                break;
        case ESR_ELx_EC_SP_ALIGN:
                el0_sp(regs, esr);
                break;
        case ESR_ELx_EC_PC_ALIGN:
                el0_pc(regs, esr);
                break;
        case ESR_ELx_EC_UNKNOWN:
                el0_undef(regs);
                break;
        case ESR_ELx_EC_BTI:
                el0_bti(regs);
                break;
        case ESR_ELx_EC_BREAKPT_LOW:
        case ESR_ELx_EC_SOFTSTP_LOW:
        case ESR_ELx_EC_WATCHPT_LOW:
        case ESR_ELx_EC_BRK64:
                el0_dbg(regs, esr);
                break;
        case ESR_ELx_EC_FPAC:
                el0_fpac(regs, esr);
                break;
        default:
                el0_inv(regs, esr);
        }
}

static void noinstr el0_interrupt(struct pt_regs *regs,
                                  void (*handler)(struct pt_regs *))
{
        enter_from_user_mode();

        write_sysreg(DAIF_PROCCTX_NOIRQ, daif);

        if (regs->pc & BIT(55))
                arm64_apply_bp_hardening();

        do_interrupt_handler(regs, handler);
}

static void noinstr __el0_irq_handler_common(struct pt_regs *regs)
{
        el0_interrupt(regs, handle_arch_irq);
}

asmlinkage void noinstr el0t_64_irq_handler(struct pt_regs *regs)
{
        __el0_irq_handler_common(regs);
}

static void noinstr __el0_fiq_handler_common(struct pt_regs *regs)
{
        el0_interrupt(regs, handle_arch_fiq);
}

asmlinkage void noinstr el0t_64_fiq_handler(struct pt_regs *regs)
{
        __el0_fiq_handler_common(regs);
}

static void noinstr __el0_error_handler_common(struct pt_regs *regs)
{
        unsigned long esr = read_sysreg(esr_el1);

        enter_from_user_mode();
        local_daif_restore(DAIF_ERRCTX);
        arm64_enter_nmi(regs);
        do_serror(regs, esr);
        arm64_exit_nmi(regs);
        local_daif_restore(DAIF_PROCCTX);
}

asmlinkage void noinstr el0t_64_error_handler(struct pt_regs *regs)
{
        __el0_error_handler_common(regs);
}

#ifdef CONFIG_COMPAT
static void noinstr el0_cp15(struct pt_regs *regs, unsigned long esr)
{
        enter_from_user_mode();
        local_daif_restore(DAIF_PROCCTX);
        do_cp15instr(esr, regs);
}

static void noinstr el0_svc_compat(struct pt_regs *regs)
{
        enter_from_user_mode();
        cortex_a76_erratum_1463225_svc_handler();
        do_el0_svc_compat(regs);
}

asmlinkage void noinstr el0t_32_sync_handler(struct pt_regs *regs)
{
        unsigned long esr = read_sysreg(esr_el1);

        switch (ESR_ELx_EC(esr)) {
        case ESR_ELx_EC_SVC32:
                el0_svc_compat(regs);
                break;
        case ESR_ELx_EC_DABT_LOW:
                el0_da(regs, esr);
                break;
        case ESR_ELx_EC_IABT_LOW:
                el0_ia(regs, esr);
                break;
        case ESR_ELx_EC_FP_ASIMD:
                el0_fpsimd_acc(regs, esr);
                break;
        case ESR_ELx_EC_FP_EXC32:
                el0_fpsimd_exc(regs, esr);
                break;
        case ESR_ELx_EC_PC_ALIGN:
                el0_pc(regs, esr);
                break;
        case ESR_ELx_EC_UNKNOWN:
        case ESR_ELx_EC_CP14_MR:
        case ESR_ELx_EC_CP14_LS:
        case ESR_ELx_EC_CP14_64:
                el0_undef(regs);
                break;
        case ESR_ELx_EC_CP15_32:
        case ESR_ELx_EC_CP15_64:
                el0_cp15(regs, esr);
                break;
        case ESR_ELx_EC_BREAKPT_LOW:
        case ESR_ELx_EC_SOFTSTP_LOW:
        case ESR_ELx_EC_WATCHPT_LOW:
        case ESR_ELx_EC_BKPT32:
                el0_dbg(regs, esr);
                break;
        default:
                el0_inv(regs, esr);
        }
}

asmlinkage void noinstr el0t_32_irq_handler(struct pt_regs *regs)
{
        __el0_irq_handler_common(regs);
}

asmlinkage void noinstr el0t_32_fiq_handler(struct pt_regs *regs)
{
        __el0_fiq_handler_common(regs);
}

asmlinkage void noinstr el0t_32_error_handler(struct pt_regs *regs)
{
        __el0_error_handler_common(regs);
}
#else /* CONFIG_COMPAT */
UNHANDLED(el0t, 32, sync)
UNHANDLED(el0t, 32, irq)
UNHANDLED(el0t, 32, fiq)
UNHANDLED(el0t, 32, error)
#endif /* CONFIG_COMPAT */

#ifdef CONFIG_VMAP_STACK
asmlinkage void noinstr handle_bad_stack(struct pt_regs *regs)
{
        unsigned int esr = read_sysreg(esr_el1);
        unsigned long far = read_sysreg(far_el1);

        arm64_enter_nmi(regs);
        panic_bad_stack(regs, esr, far);
}
#endif /* CONFIG_VMAP_STACK */

#ifdef CONFIG_ARM_SDE_INTERFACE
asmlinkage noinstr unsigned long
__sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg)
{
        unsigned long ret;

        /*
         * We didn't take an exception to get here, so the HW hasn't
         * set/cleared bits in PSTATE that we may rely on.
         *
         * The original SDEI spec (ARM DEN 0054A) can be read ambiguously as to
         * whether PSTATE bits are inherited unchanged or generated from
         * scratch, and the TF-A implementation always clears PAN and always
         * clears UAO. There are no other known implementations.
         *
         * Subsequent revisions (ARM DEN 0054B) follow the usual rules for how
         * PSTATE is modified upon architectural exceptions, and so PAN is
         * either inherited or set per SCTLR_ELx.SPAN, and UAO is always
         * cleared.
         *
         * We must explicitly reset PAN to the expected state, including
         * clearing it when the host isn't using it, in case a VM had it set.
         */
        if (system_uses_hw_pan())
                set_pstate_pan(1);
        else if (cpu_has_pan())
                set_pstate_pan(0);

        arm64_enter_nmi(regs);
        ret = do_sdei_event(regs, arg);
        arm64_exit_nmi(regs);

        return ret;
}
#endif /* CONFIG_ARM_SDE_INTERFACE */