// Copyright 2016 The Fuchsia Authors
// Copyright (c) 2009 Corey Tabaka
// Copyright (c) 2015 Intel Corporation
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#include <arch/exception.h>
#include <arch/user_copy.h>
#include <arch/x86.h>
#include <arch/x86/apic.h>
#include <arch/x86/descriptor.h>
#include <arch/x86/feature.h>
#include <arch/x86/interrupts.h>
#include <arch/x86/perf_mon.h>
#include <arch/x86/registers.h>

#include <debug.h>

#include <kernel/interrupt.h>
#include <kernel/thread.h>

#include <lib/crashlog.h>

#include <platform.h>
#include <trace.h>
#include <vm/fault.h>
#include <vm/vm.h>

#include <fbl/auto_call.h>

#include <lib/counters.h>
#include <lib/ktrace.h>

#include <zircon/syscalls/exception.h>
#include <zircon/types.h>

// Returns whether the register state indicates that the CPU was executing
// userland code.
static bool is_from_user(const x86_iframe_t* frame) {
    return SELECTOR_PL(frame->cs) != 0;
}

static void dump_fault_frame(x86_iframe_t* frame) {
    dprintf(CRITICAL, " CS:  %#18" PRIx64 " RIP: %#18" PRIx64 " EFL: %#18" PRIx64 " CR2: %#18lx\n",
            frame->cs, frame->ip, frame->flags, x86_get_cr2());
    dprintf(CRITICAL, " RAX: %#18" PRIx64 " RBX: %#18" PRIx64 " RCX: %#18" PRIx64 " RDX: %#18" PRIx64 "\n",
            frame->rax, frame->rbx, frame->rcx, frame->rdx);
    dprintf(CRITICAL, " RSI: %#18" PRIx64 " RDI: %#18" PRIx64 " RBP: %#18" PRIx64 " RSP: %#18" PRIx64 "\n",
            frame->rsi, frame->rdi, frame->rbp, frame->user_sp);
    dprintf(CRITICAL, "  R8: %#18" PRIx64 "  R9: %#18" PRIx64 " R10: %#18" PRIx64 " R11: %#18" PRIx64 "\n",
            frame->r8, frame->r9, frame->r10, frame->r11);
    dprintf(CRITICAL, " R12: %#18" PRIx64 " R13: %#18" PRIx64 " R14: %#18" PRIx64 " R15: %#18" PRIx64 "\n",
            frame->r12, frame->r13, frame->r14, frame->r15);
    dprintf(CRITICAL, "errc: %#18" PRIx64 "\n",
            frame->err_code);

    // dump the bottom of the current stack
    void* stack = frame;

    if (frame->cs == CODE_64_SELECTOR) {
        dprintf(CRITICAL, "bottom of kernel stack at %p:\n", stack);
        hexdump(stack, 128);
    }
}

KCOUNTER(exceptions_debug, "kernel.exceptions.debug");
KCOUNTER(exceptions_nmi, "kernel.exceptions.nmi");
KCOUNTER(exceptions_brkpt, "kernel.exceptions.breakpoint");
KCOUNTER(exceptions_invop, "kernel.exceptions.inv_opcode");
KCOUNTER(exceptions_dev_na, "kernel.exceptions.dev_na");
KCOUNTER(exceptions_dfault, "kernel.exceptions.double_fault");
KCOUNTER(exceptions_fpu, "kernel.exceptions.fpu");
KCOUNTER(exceptions_simd, "kernel.exceptions.simd");
KCOUNTER(exceptions_gpf, "kernel.exceptions.gpf");
KCOUNTER(exceptions_page, "kernel.exceptions.page_fault");
KCOUNTER(exceptions_apic_err, "kernel.exceptions.apic_error");
KCOUNTER(exceptions_irq, "kernel.exceptions.irq");
KCOUNTER(exceptions_unhandled, "kernel.exceptions.unhandled");
KCOUNTER(exceptions_user, "kernel.exceptions.user");

__NO_RETURN static void exception_die(x86_iframe_t* frame, const char* msg) {
    platform_panic_start();

    printf("vector %lu\n", (ulong)frame->vector);
    dprintf(CRITICAL, "%s", msg);
    dump_fault_frame(frame);
    crashlog.iframe = frame;

    // try to dump the user stack
    if (is_user_address(frame->user_sp)) {
        uint8_t buf[256];
        if (arch_copy_from_user(buf, (void*)frame->user_sp, sizeof(buf)) == ZX_OK) {
            printf("bottom of user stack at 0x%lx:\n", (vaddr_t)frame->user_sp);
            hexdump_ex(buf, sizeof(buf), frame->user_sp);
        }
    }

    platform_halt(HALT_ACTION_HALT, HALT_REASON_SW_PANIC);
}

static zx_status_t call_dispatch_user_exception(uint kind,
                                                struct arch_exception_context* context,
                                                x86_iframe_t* frame) {
    thread_t* thread = get_current_thread();
    x86_set_suspended_general_regs(&thread->arch, X86_GENERAL_REGS_IFRAME, frame);
    zx_status_t status = dispatch_user_exception(kind, context);
    x86_reset_suspended_general_regs(&thread->arch);
    return status;
}

static bool try_dispatch_user_exception(x86_iframe_t* frame, uint kind) {
    if (is_from_user(frame)) {
        struct arch_exception_context context = {false, frame, 0};
        thread_preempt_reenable_no_resched();
        arch_set_blocking_disallowed(false);
        arch_enable_ints();
        zx_status_t erc = call_dispatch_user_exception(kind, &context, frame);
        arch_disable_ints();
        arch_set_blocking_disallowed(true);
        thread_preempt_disable();
        if (erc == ZX_OK)
            return true;
    }

    return false;
}

static void x86_debug_handler(x86_iframe_t* frame) {
    // We now need to keep track of the debug registers.
    thread_t* thread = get_current_thread();

    // DR6 is the status register that explains what exception happened (single step, hardware
    // breakpoint, etc.).
    // We only need to keep track of DR6 because the other state doesn't change and the only way
    // to actually change the debug registers for a thread is through the thread_write_state
    // syscall.
    x86_read_debug_status(&thread->arch.debug_state);

    // NOTE: a HW breakpoint exception can also represent a single step.
    // TODO(ZX-3037): Is it worth separating this into two separate exceptions?
    if (try_dispatch_user_exception(frame, ZX_EXCP_HW_BREAKPOINT))
        return;

    exception_die(frame, "unhandled hw breakpoint, halting\n");
}

static void x86_nmi_handler(x86_iframe_t* frame) {
}

static void x86_breakpoint_handler(x86_iframe_t* frame) {
    if (try_dispatch_user_exception(frame, ZX_EXCP_SW_BREAKPOINT))
        return;

    exception_die(frame, "unhandled sw breakpoint, halting\n");
}

static void x86_gpf_handler(x86_iframe_t* frame) {
    DEBUG_ASSERT(arch_ints_disabled());

    // Check if we were doing a GPF test, e.g. to check if an MSR exists.
    struct x86_percpu* percpu = x86_get_percpu();
    if (unlikely(percpu->gpf_return_target)) {
        ASSERT(!is_from_user(frame));

        // Set up return to new address
        frame->ip = percpu->gpf_return_target;
        percpu->gpf_return_target = 0;
        return;
    }

    if (try_dispatch_user_exception(frame, ZX_EXCP_GENERAL))
        return;

    exception_die(frame, "unhandled gpf, halting\n");
}

static void x86_invop_handler(x86_iframe_t* frame) {
    if (try_dispatch_user_exception(frame, ZX_EXCP_UNDEFINED_INSTRUCTION))
        return;

    exception_die(frame, "invalid opcode, halting\n");
}

static void x86_df_handler(x86_iframe_t* frame) {
    // Do not give the user exception handler the opportunity to handle double
    // faults, since they indicate an unexpected system state and cannot be
    // recovered from.
    exception_die(frame, "double fault, halting\n");
}

static void x86_unhandled_exception(x86_iframe_t* frame) {
    if (try_dispatch_user_exception(frame, ZX_EXCP_GENERAL))
        return;

    exception_die(frame, "unhandled exception, halting\n");
}

static void x86_dump_pfe(x86_iframe_t* frame, ulong cr2) {
    uint64_t error_code = frame->err_code;

    addr_t v_addr = cr2;
    addr_t ssp = frame->user_ss & X86_8BYTE_MASK;
    addr_t sp = frame->user_sp;
    addr_t cs = frame->cs & X86_8BYTE_MASK;
    addr_t ip = frame->ip;

    dprintf(CRITICAL, "<PAGE FAULT> Instruction Pointer   = 0x%lx:0x%lx\n",
            (ulong)cs,
            (ulong)ip);
    dprintf(CRITICAL, "<PAGE FAULT> Stack Pointer         = 0x%lx:0x%lx\n",
            (ulong)ssp,
            (ulong)sp);
    dprintf(CRITICAL, "<PAGE FAULT> Fault Linear Address  = 0x%lx\n",
            (ulong)v_addr);
    dprintf(CRITICAL, "<PAGE FAULT> Error Code Value      = 0x%lx\n",
            (ulong)error_code);
    dprintf(CRITICAL, "<PAGE FAULT> Error Code Type       = %s %s %s%s, %s\n",
            error_code & PFEX_U ? "user" : "supervisor",
            error_code & PFEX_W ? "write" : "read",
            error_code & PFEX_I ? "instruction" : "data",
            error_code & PFEX_RSV ? " rsv" : "",
            error_code & PFEX_P ? "protection violation" : "page not present");
}

__NO_RETURN static void x86_fatal_pfe_handler(x86_iframe_t* frame, ulong cr2) {
    x86_dump_pfe(frame, cr2);

    uint64_t error_code = frame->err_code;

    dump_thread_during_panic(get_current_thread(), true);

    if (error_code & PFEX_U) {
        // User mode page fault
        switch (error_code) {
        case 4:
        case 5:
        case 6:
        case 7:
            exception_die(frame, "User Page Fault exception, halting\n");
            break;
        }
    } else {
        // Supervisor mode page fault
        switch (error_code) {

        case 0:
        case 1:
        case 2:
        case 3:
            exception_die(frame, "Supervisor Page Fault exception, halting\n");
            break;
        }
    }

    exception_die(frame, "unhandled page fault, halting\n");
}

static zx_status_t x86_pfe_handler(x86_iframe_t* frame) {
    /* Handle a page fault exception */
    uint64_t error_code = frame->err_code;
    vaddr_t va = x86_get_cr2();

    /* reenable interrupts */
    thread_preempt_reenable_no_resched();
    arch_set_blocking_disallowed(false);
    arch_enable_ints();

    /* make sure we put interrupts back as we exit */
    auto ac = fbl::MakeAutoCall([]() {
        arch_disable_ints();
        arch_set_blocking_disallowed(true);
        thread_preempt_disable();
    });

    /* check for flags we're not prepared to handle */
    if (unlikely(error_code & ~(PFEX_I | PFEX_U | PFEX_W | PFEX_P))) {
        printf("x86_pfe_handler: unhandled error code bits set, error code %#" PRIx64 "\n", error_code);
        return ZX_ERR_NOT_SUPPORTED;
    }

    /* check for a potential SMAP failure */
    if (unlikely(
            !(error_code & PFEX_U) &&
            (error_code & PFEX_P) &&
            x86_feature_test(X86_FEATURE_SMAP) &&
            !(frame->flags & X86_FLAGS_AC) &&
            is_user_address(va))) {
        /* supervisor mode page-present access failure with the AC bit clear (SMAP enabled) */
        printf("x86_pfe_handler: potential SMAP failure, supervisor access at address %#" PRIxPTR "\n", va);
        return ZX_ERR_ACCESS_DENIED;
    }

    /* convert the PF error codes to page fault flags */
    uint flags = 0;
    flags |= (error_code & PFEX_W) ? VMM_PF_FLAG_WRITE : 0;
    flags |= (error_code & PFEX_U) ? VMM_PF_FLAG_USER : 0;
    flags |= (error_code & PFEX_I) ? VMM_PF_FLAG_INSTRUCTION : 0;
    flags |= (error_code & PFEX_P) ? 0 : VMM_PF_FLAG_NOT_PRESENT;

    /* call the high level page fault handler */
    zx_status_t pf_err = vmm_page_fault_handler(va, flags);
    if (likely(pf_err == ZX_OK))
        return ZX_OK;

    /* if the high level page fault handler can't deal with it,
     * resort to trying to recover first, before bailing */

    /* Check if a resume address is specified, and just return to it if so */
    thread_t* current_thread = get_current_thread();
    if (unlikely(current_thread->arch.page_fault_resume)) {
        frame->ip = (uintptr_t)current_thread->arch.page_fault_resume;
        return ZX_OK;
    }

    /* let high level code deal with this */
    if (is_from_user(frame)) {
        kcounter_add(exceptions_user, 1);
        struct arch_exception_context context = {true, frame, va};
        return call_dispatch_user_exception(ZX_EXCP_FATAL_PAGE_FAULT,
                                            &context, frame);
    }

    /* fall through to fatal path */
    return ZX_ERR_NOT_SUPPORTED;
}

static void x86_iframe_process_pending_signals(x86_iframe_t* frame) {
    thread_t* thread = get_current_thread();
    if (unlikely(thread_is_signaled(thread))) {
        x86_set_suspended_general_regs(&thread->arch, X86_GENERAL_REGS_IFRAME, frame);
        thread_process_pending_signals();
        x86_reset_suspended_general_regs(&thread->arch);
    }
}

static void handle_exception_types(x86_iframe_t* frame) {
    switch (frame->vector) {
    case X86_INT_DEBUG:
        kcounter_add(exceptions_debug, 1);
        x86_debug_handler(frame);
        break;
    case X86_INT_NMI:
        kcounter_add(exceptions_nmi, 1);
        x86_nmi_handler(frame);
        break;
    case X86_INT_BREAKPOINT:
        kcounter_add(exceptions_brkpt, 1);
        x86_breakpoint_handler(frame);
        break;

    case X86_INT_INVALID_OP:
        kcounter_add(exceptions_invop, 1);
        x86_invop_handler(frame);
        break;

    case X86_INT_DEVICE_NA:
        kcounter_add(exceptions_dev_na, 1);
        exception_die(frame, "device na fault\n");
        break;

    case X86_INT_DOUBLE_FAULT:
        x86_df_handler(frame);
        break;
    case X86_INT_FPU_FP_ERROR:
        kcounter_add(exceptions_fpu, 1);
        x86_unhandled_exception(frame);
        break;
    case X86_INT_SIMD_FP_ERROR:
        kcounter_add(exceptions_simd, 1);
        x86_unhandled_exception(frame);
        break;
    case X86_INT_GP_FAULT:
        kcounter_add(exceptions_gpf, 1);
        x86_gpf_handler(frame);
        break;

    case X86_INT_PAGE_FAULT:
        kcounter_add(exceptions_page, 1);
        CPU_STATS_INC(page_faults);
        if (x86_pfe_handler(frame) != ZX_OK)
            x86_fatal_pfe_handler(frame, x86_get_cr2());
        break;

    /* ignore spurious APIC irqs */
    case X86_INT_APIC_SPURIOUS:
        break;
    case X86_INT_APIC_ERROR: {
        kcounter_add(exceptions_apic_err, 1);
        apic_error_interrupt_handler();
        apic_issue_eoi();
        break;
    }
    case X86_INT_APIC_TIMER: {
        apic_timer_interrupt_handler();
        apic_issue_eoi();
        break;
    }
    case X86_INT_IPI_GENERIC: {
        mp_mbx_generic_irq(nullptr);
        apic_issue_eoi();
        break;
    }
    case X86_INT_IPI_RESCHEDULE: {
        mp_mbx_reschedule_irq(nullptr);
        apic_issue_eoi();
        break;
    }
    case X86_INT_IPI_INTERRUPT: {
        mp_mbx_interrupt_irq(nullptr);
        apic_issue_eoi();
        break;
    }
    case X86_INT_IPI_HALT: {
        x86_ipi_halt_handler(nullptr);
        /* no return */
        break;
    }
    case X86_INT_APIC_PMI: {
        apic_pmi_interrupt_handler(frame);
        // Note: apic_pmi_interrupt_handler calls apic_issue_eoi().
        break;
    }
    /* pass all other non-Intel defined irq vectors to the platform */
    case X86_INT_PLATFORM_BASE ... X86_INT_PLATFORM_MAX: {
        kcounter_add(exceptions_irq, 1);
        platform_irq(frame);
        break;
    }

    /* Integer division-by-zero */
    case X86_INT_DIVIDE_0:
    /* Overflow for INTO instruction (should be x86-32-only) */
    case X86_INT_OVERFLOW:
    /* Bound range exceeded for BOUND instruction (should be x86-32-only) */
    case X86_INT_BOUND_RANGE:
    /* Loading segment with "not present" bit set */
    case X86_INT_SEGMENT_NOT_PRESENT:
    /* Stack segment fault (should be x86-32-only) */
    case X86_INT_STACK_FAULT:
    /* Misaligned memory access when AC=1 in flags */
    case X86_INT_ALIGNMENT_CHECK:
        kcounter_add(exceptions_unhandled, 1);
        x86_unhandled_exception(frame);
        break;

    default:
        exception_die(frame, "unhandled exception type, halting\n");
        break;
    }
}

/* top level x86 exception handler for most exceptions and irqs */
void x86_exception_handler(x86_iframe_t* frame) {
    // are we recursing?
    if (unlikely(arch_blocking_disallowed()) && frame->vector != X86_INT_NMI) {
        exception_die(frame, "recursion in interrupt handler\n");
    }

    int_handler_saved_state_t state;
    int_handler_start(&state);

    // did we come from user or kernel space?
    bool from_user = is_from_user(frame);

    // deliver the interrupt
    ktrace_tiny(TAG_IRQ_ENTER, ((uint32_t)frame->vector << 8) | arch_curr_cpu_num());

    handle_exception_types(frame);

    bool do_preempt = int_handler_finish(&state);

    /* if we came from user space, check to see if we have any signals to handle */
    if (unlikely(from_user)) {
        /* in the case of receiving a kill signal, this function may not return,
         * but the scheduler would have been invoked so it's fine.
         */
        x86_iframe_process_pending_signals(frame);
    }

    if (do_preempt)
        thread_preempt();

    ktrace_tiny(TAG_IRQ_EXIT, ((uint)frame->vector << 8) | arch_curr_cpu_num());

    DEBUG_ASSERT_MSG(arch_ints_disabled(),
                     "ints disabled on way out of exception, vector %" PRIu64 " IP %#" PRIx64 "\n",
                     frame->vector, frame->ip);
}

void x86_syscall_process_pending_signals(x86_syscall_general_regs_t* gregs) {
    thread_t* thread = get_current_thread();
    x86_set_suspended_general_regs(&thread->arch, X86_GENERAL_REGS_SYSCALL, gregs);
    thread_process_pending_signals();
    x86_reset_suspended_general_regs(&thread->arch);
}

void arch_dump_exception_context(const arch_exception_context_t* context) {
    if (context->is_page_fault) {
        x86_dump_pfe(context->frame, context->cr2);
    }

    dump_fault_frame(context->frame);

    // try to dump the user stack
    if (context->frame->cs != CODE_64_SELECTOR && is_user_address(context->frame->user_sp)) {
        uint8_t buf[256];
        if (arch_copy_from_user(buf, (void*)context->frame->user_sp, sizeof(buf)) == ZX_OK) {
            printf("bottom of user stack at 0x%lx:\n", (vaddr_t)context->frame->user_sp);
            hexdump_ex(buf, sizeof(buf), context->frame->user_sp);
        }
    }
}

void arch_fill_in_exception_context(const arch_exception_context_t* arch_context,
                                    zx_exception_report_t* report) {
    zx_exception_context_t* zx_context = &report->context;

    zx_context->arch.u.x86_64.vector = arch_context->frame->vector;
    zx_context->arch.u.x86_64.err_code = arch_context->frame->err_code;
    zx_context->arch.u.x86_64.cr2 = arch_context->cr2;
}

zx_status_t arch_dispatch_user_policy_exception(void) {
    x86_iframe_t frame = {};
    arch_exception_context_t context = {};
    context.frame = &frame;
    return dispatch_user_exception(ZX_EXCP_POLICY_ERROR, &context);
}