/*
 *  qemu user cpu loop
 *
 *  Copyright (c) 2003-2008 Fabrice Bellard
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include "qemu/osdep.h"
#include "qemu.h"
#include "qemu/timer.h"
#include "user-internals.h"
#include "user/cpu_loop.h"
#include "signal-common.h"
#include "user-mmap.h"

/***********************************************************/
/* CPUX86 core interface */

uint64_t cpu_get_tsc(CPUX86State *env)
{
    return cpu_get_host_ticks();
}

static void write_dt(void *ptr, unsigned long addr, unsigned long limit,
              int flags)
{
    unsigned int e1, e2;
    uint32_t *p;
    e1 = (addr << 16) | (limit & 0xffff);
    e2 = ((addr >> 16) & 0xff) | (addr & 0xff000000) | (limit & 0x000f0000);
    e2 |= flags;
    p = ptr;
    p[0] = tswap32(e1);
    p[1] = tswap32(e2);
}

static uint64_t *idt_table;

static void set_gate64(void *ptr, unsigned int type, unsigned int dpl,
                       uint64_t addr, unsigned int sel)
{
    uint32_t *p, e1, e2;
    e1 = (addr & 0xffff) | (sel << 16);
    e2 = (addr & 0xffff0000) | 0x8000 | (dpl << 13) | (type << 8);
    p = ptr;
    p[0] = tswap32(e1);
    p[1] = tswap32(e2);
    p[2] = tswap32(addr >> 32);
    p[3] = 0;
}

#ifdef TARGET_X86_64
/* only dpl matters as we do only user space emulation */
static void set_idt(int n, unsigned int dpl, bool is64)
{
    set_gate64(idt_table + n * 2, 0, dpl, 0, 0);
}
#else
static void set_gate(void *ptr, unsigned int type, unsigned int dpl,
                     uint32_t addr, unsigned int sel)
{
    uint32_t *p, e1, e2;
    e1 = (addr & 0xffff) | (sel << 16);
    e2 = (addr & 0xffff0000) | 0x8000 | (dpl << 13) | (type << 8);
    p = ptr;
    p[0] = tswap32(e1);
    p[1] = tswap32(e2);
}

/* only dpl matters as we do only user space emulation */
static void set_idt(int n, unsigned int dpl, bool is64)
{
    if (is64) {
        set_gate64(idt_table + n * 2, 0, dpl, 0, 0);
    } else {
        set_gate(idt_table + n, 0, dpl, 0, 0);
    }
}
#endif

#ifdef TARGET_X86_64
static bool write_ok_or_segv(CPUX86State *env, abi_ptr addr, size_t len)
{
    /*
     * For all the vsyscalls, NULL means "don't write anything" not
     * "write it at address 0".
     */
    if (addr == 0 || access_ok(env_cpu(env), VERIFY_WRITE, addr, len)) {
        return true;
    }

    env->error_code = PG_ERROR_W_MASK | PG_ERROR_U_MASK;
    force_sig_fault(TARGET_SIGSEGV, TARGET_SEGV_MAPERR, addr);
    return false;
}

/*
 * Since v3.1, the kernel traps and emulates the vsyscall page.
 * Entry points other than the official generate SIGSEGV.
 */
static void emulate_vsyscall(CPUX86State *env)
{
    int syscall;
    abi_ulong ret;
    uint64_t caller;

    /*
     * Validate the entry point.  We have already validated the page
     * during translation to get here; now verify the offset.
     */
    switch (env->eip & ~TARGET_PAGE_MASK) {
    case 0x000:
        syscall = TARGET_NR_gettimeofday;
        break;
    case 0x400:
        syscall = TARGET_NR_time;
        break;
    case 0x800:
        syscall = TARGET_NR_getcpu;
        break;
    default:
        goto sigsegv;
    }

    /*
     * Validate the return address.
     * Note that the kernel treats this the same as an invalid entry point.
     */
    if (get_user_u64(caller, env->regs[R_ESP])) {
        goto sigsegv;
    }

    /*
     * Validate the pointer arguments.
     */
    switch (syscall) {
    case TARGET_NR_gettimeofday:
        if (!write_ok_or_segv(env, env->regs[R_EDI],
                              sizeof(struct target_timeval)) ||
            !write_ok_or_segv(env, env->regs[R_ESI],
                              sizeof(struct target_timezone))) {
            return;
        }
        break;
    case TARGET_NR_time:
        if (!write_ok_or_segv(env, env->regs[R_EDI], sizeof(abi_long))) {
            return;
        }
        break;
    case TARGET_NR_getcpu:
        if (!write_ok_or_segv(env, env->regs[R_EDI], sizeof(uint32_t)) ||
            !write_ok_or_segv(env, env->regs[R_ESI], sizeof(uint32_t))) {
            return;
        }
        break;
    default:
        g_assert_not_reached();
    }

    /*
     * Perform the syscall.  None of the vsyscalls should need restarting.
     */
    get_task_state(env_cpu(env))->orig_ax = syscall;
    ret = do_syscall(env, syscall, env->regs[R_EDI], env->regs[R_ESI],
                     env->regs[R_EDX], env->regs[10], env->regs[8],
                     env->regs[9], 0, 0);
    g_assert(ret != -QEMU_ERESTARTSYS);
    g_assert(ret != -QEMU_ESIGRETURN);
    if (ret == -TARGET_EFAULT) {
        goto sigsegv;
    }
    env->regs[R_EAX] = ret;

    /* Emulate a ret instruction to leave the vsyscall page.  */
    env->eip = caller;
    env->regs[R_ESP] += 8;
    return;

 sigsegv:
    force_sig(TARGET_SIGSEGV);
}
#endif

static bool maybe_handle_vm86_trap(CPUX86State *env, int trapnr)
{
#ifndef TARGET_X86_64
    if (env->eflags & VM_MASK) {
        handle_vm86_trap(env, trapnr);
        return true;
    }
#endif
    return false;
}

void cpu_loop(CPUX86State *env)
{
    CPUState *cs = env_cpu(env);
    int trapnr;
    abi_ulong ret;

    for(;;) {
        cpu_exec_start(cs);
        trapnr = cpu_exec(cs);
        cpu_exec_end(cs);
        qemu_process_cpu_events(cs);

        switch(trapnr) {
        case 0x80:
#ifndef TARGET_X86_64
        case EXCP_SYSCALL:
#endif
            /* linux syscall from int $0x80 */
            get_task_state(cs)->orig_ax = env->regs[R_EAX];
            ret = do_syscall(env,
                             env->regs[R_EAX],
                             env->regs[R_EBX],
                             env->regs[R_ECX],
                             env->regs[R_EDX],
                             env->regs[R_ESI],
                             env->regs[R_EDI],
                             env->regs[R_EBP],
                             0, 0);
            if (ret == -QEMU_ERESTARTSYS) {
                env->eip -= 2;
            } else if (ret != -QEMU_ESIGRETURN) {
                env->regs[R_EAX] = ret;
            }
            break;
#ifdef TARGET_X86_64
        case EXCP_SYSCALL:
            /* linux syscall from syscall instruction.  */
            get_task_state(cs)->orig_ax = env->regs[R_EAX];
            ret = do_syscall(env,
                             env->regs[R_EAX],
                             env->regs[R_EDI],
                             env->regs[R_ESI],
                             env->regs[R_EDX],
                             env->regs[10],
                             env->regs[8],
                             env->regs[9],
                             0, 0);
            if (ret == -QEMU_ERESTARTSYS) {
                env->eip -= 2;
            } else if (ret != -QEMU_ESIGRETURN) {
                env->regs[R_EAX] = ret;
            }
            break;
        case EXCP_VSYSCALL:
            emulate_vsyscall(env);
            break;
#endif
        case EXCP0B_NOSEG:
        case EXCP0C_STACK:
            force_sig(TARGET_SIGBUS);
            break;
        case EXCP0D_GPF:
            /* XXX: potential problem if ABI32 */
            if (maybe_handle_vm86_trap(env, trapnr)) {
                break;
            }
            force_sig(TARGET_SIGSEGV);
            break;
        case EXCP0E_PAGE:
            force_sig_fault(TARGET_SIGSEGV,
                            (env->error_code & PG_ERROR_P_MASK ?
                             TARGET_SEGV_ACCERR : TARGET_SEGV_MAPERR),
                            env->cr[2]);
            break;
        case EXCP00_DIVZ:
            if (maybe_handle_vm86_trap(env, trapnr)) {
                break;
            }
            force_sig_fault(TARGET_SIGFPE, TARGET_FPE_INTDIV, env->eip);
            break;
        case EXCP01_DB:
            if (maybe_handle_vm86_trap(env, trapnr)) {
                break;
            }
            force_sig_fault(TARGET_SIGTRAP, TARGET_TRAP_BRKPT, env->eip);
            break;
        case EXCP03_INT3:
            if (maybe_handle_vm86_trap(env, trapnr)) {
                break;
            }
            force_sig(TARGET_SIGTRAP);
            break;
        case EXCP04_INTO:
        case EXCP05_BOUND:
            if (maybe_handle_vm86_trap(env, trapnr)) {
                break;
            }
            force_sig(TARGET_SIGSEGV);
            break;
        case EXCP06_ILLOP:
            force_sig_fault(TARGET_SIGILL, TARGET_ILL_ILLOPN, env->eip);
            break;
        case EXCP_INTERRUPT:
            /* just indicate that signals should be handled asap */
            break;
        case EXCP_DEBUG:
            force_sig_fault(TARGET_SIGTRAP, TARGET_TRAP_BRKPT, env->eip);
            break;
        case EXCP_ATOMIC:
            cpu_exec_step_atomic(cs);
            break;
        default:
            EXCP_DUMP(env, "qemu: unhandled CPU exception 0x%x - aborting\n",
                      trapnr);
            abort();
        }
        process_pending_signals(env);
    }
}

static void target_cpu_free(void *obj)
{
    target_munmap(cpu_env(obj)->gdt.base,
                  sizeof(uint64_t) * TARGET_GDT_ENTRIES);
    g_free(obj);
}

void init_main_thread(CPUState *cpu, struct image_info *info)
{
    CPUArchState *env = cpu_env(cpu);
    bool is64 = (env->features[FEAT_8000_0001_EDX] & CPUID_EXT2_LM) != 0;

    OBJECT(cpu)->free = target_cpu_free;
    env->cr[0] = CR0_PG_MASK | CR0_WP_MASK | CR0_PE_MASK;
    env->hflags |= HF_PE_MASK | HF_CPL_MASK;
    if (env->features[FEAT_1_EDX] & CPUID_SSE) {
        env->cr[4] |= CR4_OSFXSR_MASK;
        env->hflags |= HF_OSFXSR_MASK;
    }

    /* enable 64 bit mode if possible */
    if (is64) {
        env->cr[4] |= CR4_PAE_MASK;
        env->efer |= MSR_EFER_LMA | MSR_EFER_LME;
        env->hflags |= HF_LMA_MASK;
    }
#ifndef TARGET_ABI32
    else {
        fprintf(stderr, "The selected x86 CPU does not support 64 bit mode\n");
        exit(EXIT_FAILURE);
    }
#endif

    /* flags setup : we activate the IRQs by default as in user mode */
    env->eflags |= IF_MASK;

    /*
     * Linux register setup.
     *
     * SVR4/i386 ABI (pages 3-31, 3-32) says that when the program
     * starts %edx contains a pointer to a function which might be
     * registered using `atexit'.  This provides a mean for the
     * dynamic linker to call DT_FINI functions for shared libraries
     * that have been loaded before the code runs.
     * A value of 0 tells we have no such handler.
     *
     * This applies to x86_64 as well as i386.
     *
     * That said, the kernel's ELF_PLAT_INIT simply zeros all of the general
     * registers.  Note that x86_cpu_reset_hold will set %edx to cpuid_version;
     * clear all general registers defensively.
     */
    memset(env->regs, 0, sizeof(env->regs));
    env->regs[R_ESP] = info->start_stack;
    env->eip = info->entry;

    /* linux interrupt setup */
#ifndef TARGET_ABI32
    env->idt.limit = 511;
#else
    env->idt.limit = 255;
#endif
    env->idt.base = target_mmap(0, sizeof(uint64_t) * (env->idt.limit + 1),
                                PROT_READ|PROT_WRITE,
                                MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
    idt_table = g2h_untagged(env->idt.base);
    for (int i = 0; i < 20; i++) {
        set_idt(i, 0, is64);
    }
    set_idt(3, 3, is64);
    set_idt(4, 3, is64);
    set_idt(0x80, 3, is64);

    /* linux segment setup */
    {
        uint64_t *gdt_table;
        env->gdt.base = target_mmap(0, sizeof(uint64_t) * TARGET_GDT_ENTRIES,
                                    PROT_READ|PROT_WRITE,
                                    MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
        env->gdt.limit = sizeof(uint64_t) * TARGET_GDT_ENTRIES - 1;
        gdt_table = g2h_untagged(env->gdt.base);
#ifdef TARGET_ABI32
        write_dt(&gdt_table[__USER_CS >> 3], 0, 0xfffff,
                 DESC_G_MASK | DESC_B_MASK | DESC_P_MASK | DESC_S_MASK |
                 (3 << DESC_DPL_SHIFT) | (0xa << DESC_TYPE_SHIFT));
#else
        /* 64 bit code segment */
        write_dt(&gdt_table[__USER_CS >> 3], 0, 0xfffff,
                 DESC_G_MASK | DESC_B_MASK | DESC_P_MASK | DESC_S_MASK |
                 DESC_L_MASK |
                 (3 << DESC_DPL_SHIFT) | (0xa << DESC_TYPE_SHIFT));
#endif
        write_dt(&gdt_table[__USER_DS >> 3], 0, 0xfffff,
                 DESC_G_MASK | DESC_B_MASK | DESC_P_MASK | DESC_S_MASK |
                 (3 << DESC_DPL_SHIFT) | (0x2 << DESC_TYPE_SHIFT));
    }
    cpu_x86_load_seg(env, R_CS, __USER_CS);
    cpu_x86_load_seg(env, R_SS, __USER_DS);
#ifdef TARGET_ABI32
    cpu_x86_load_seg(env, R_DS, __USER_DS);
    cpu_x86_load_seg(env, R_ES, __USER_DS);
    cpu_x86_load_seg(env, R_FS, __USER_DS);
    cpu_x86_load_seg(env, R_GS, __USER_DS);
    /* This hack makes Wine work... */
    env->segs[R_FS].selector = 0;
#else
    cpu_x86_load_seg(env, R_DS, 0);
    cpu_x86_load_seg(env, R_ES, 0);
    cpu_x86_load_seg(env, R_FS, 0);
    cpu_x86_load_seg(env, R_GS, 0);
#endif
}