/*
 *  Copyright (C) 2014 ARM Limited
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/cpu.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/perf_event.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/sysctl.h>

#include <asm/alternative.h>
#include <asm/cpufeature.h>
#include <asm/insn.h>
#include <asm/opcodes.h>
#include <asm/sysreg.h>
#include <asm/system_misc.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
#include <asm/cpufeature.h>

#define CREATE_TRACE_POINTS
#include "trace-events-emulation.h"

/*
 * The runtime support for deprecated instruction support can be in one of
 * following three states -
 *
 * 0 = undef
 * 1 = emulate (software emulation)
 * 2 = hw (supported in hardware)
 */
enum insn_emulation_mode {
        INSN_UNDEF,
        INSN_EMULATE,
        INSN_HW,
};

enum legacy_insn_status {
        INSN_DEPRECATED,
        INSN_OBSOLETE,
};

struct insn_emulation_ops {
        const char              *name;
        enum legacy_insn_status status;
        struct undef_hook       *hooks;
        int                     (*set_hw_mode)(bool enable);
};

struct insn_emulation {
        struct list_head node;
        struct insn_emulation_ops *ops;
        int current_mode;
        int min;
        int max;
};

static LIST_HEAD(insn_emulation);
static int nr_insn_emulated __initdata;
static DEFINE_RAW_SPINLOCK(insn_emulation_lock);

static void register_emulation_hooks(struct insn_emulation_ops *ops)
{
        struct undef_hook *hook;

        BUG_ON(!ops->hooks);

        for (hook = ops->hooks; hook->instr_mask; hook++)
                register_undef_hook(hook);

        pr_notice("Registered %s emulation handler\n", ops->name);
}

static void remove_emulation_hooks(struct insn_emulation_ops *ops)
{
        struct undef_hook *hook;

        BUG_ON(!ops->hooks);

        for (hook = ops->hooks; hook->instr_mask; hook++)
                unregister_undef_hook(hook);

        pr_notice("Removed %s emulation handler\n", ops->name);
}

static void enable_insn_hw_mode(void *data)
{
        struct insn_emulation *insn = (struct insn_emulation *)data;
        if (insn->ops->set_hw_mode)
                insn->ops->set_hw_mode(true);
}

static void disable_insn_hw_mode(void *data)
{
        struct insn_emulation *insn = (struct insn_emulation *)data;
        if (insn->ops->set_hw_mode)
                insn->ops->set_hw_mode(false);
}

/* Run set_hw_mode(mode) on all active CPUs */
static int run_all_cpu_set_hw_mode(struct insn_emulation *insn, bool enable)
{
        if (!insn->ops->set_hw_mode)
                return -EINVAL;
        if (enable)
                on_each_cpu(enable_insn_hw_mode, (void *)insn, true);
        else
                on_each_cpu(disable_insn_hw_mode, (void *)insn, true);
        return 0;
}

/*
 * Run set_hw_mode for all insns on a starting CPU.
 * Returns:
 *  0           - If all the hooks ran successfully.
 * -EINVAL      - At least one hook is not supported by the CPU.
 */
static int run_all_insn_set_hw_mode(unsigned long cpu)
{
        int rc = 0;
        unsigned long flags;
        struct insn_emulation *insn;

        raw_spin_lock_irqsave(&insn_emulation_lock, flags);
        list_for_each_entry(insn, &insn_emulation, node) {
                bool enable = (insn->current_mode == INSN_HW);
                if (insn->ops->set_hw_mode && insn->ops->set_hw_mode(enable)) {
                        pr_warn("CPU[%ld] cannot support the emulation of %s",
                                cpu, insn->ops->name);
                        rc = -EINVAL;
                }
        }
        raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);
        return rc;
}

static int update_insn_emulation_mode(struct insn_emulation *insn,
                                       enum insn_emulation_mode prev)
{
        int ret = 0;

        switch (prev) {
        case INSN_UNDEF: /* Nothing to be done */
                break;
        case INSN_EMULATE:
                remove_emulation_hooks(insn->ops);
                break;
        case INSN_HW:
                if (!run_all_cpu_set_hw_mode(insn, false))
                        pr_notice("Disabled %s support\n", insn->ops->name);
                break;
        }

        switch (insn->current_mode) {
        case INSN_UNDEF:
                break;
        case INSN_EMULATE:
                register_emulation_hooks(insn->ops);
                break;
        case INSN_HW:
                ret = run_all_cpu_set_hw_mode(insn, true);
                if (!ret)
                        pr_notice("Enabled %s support\n", insn->ops->name);
                break;
        }

        return ret;
}

static void __init register_insn_emulation(struct insn_emulation_ops *ops)
{
        unsigned long flags;
        struct insn_emulation *insn;

        insn = kzalloc(sizeof(*insn), GFP_KERNEL);
        insn->ops = ops;
        insn->min = INSN_UNDEF;

        switch (ops->status) {
        case INSN_DEPRECATED:
                insn->current_mode = INSN_EMULATE;
                /* Disable the HW mode if it was turned on at early boot time */
                run_all_cpu_set_hw_mode(insn, false);
                insn->max = INSN_HW;
                break;
        case INSN_OBSOLETE:
                insn->current_mode = INSN_UNDEF;
                insn->max = INSN_EMULATE;
                break;
        }

        raw_spin_lock_irqsave(&insn_emulation_lock, flags);
        list_add(&insn->node, &insn_emulation);
        nr_insn_emulated++;
        raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);

        /* Register any handlers if required */
        update_insn_emulation_mode(insn, INSN_UNDEF);
}

static int emulation_proc_handler(struct ctl_table *table, int write,
                                  void __user *buffer, size_t *lenp,
                                  loff_t *ppos)
{
        int ret = 0;
        struct insn_emulation *insn = (struct insn_emulation *) table->data;
        enum insn_emulation_mode prev_mode = insn->current_mode;

        table->data = &insn->current_mode;
        ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);

        if (ret || !write || prev_mode == insn->current_mode)
                goto ret;

        ret = update_insn_emulation_mode(insn, prev_mode);
        if (ret) {
                /* Mode change failed, revert to previous mode. */
                insn->current_mode = prev_mode;
                update_insn_emulation_mode(insn, INSN_UNDEF);
        }
ret:
        table->data = insn;
        return ret;
}

static struct ctl_table ctl_abi[] = {
        {
                .procname = "abi",
                .mode = 0555,
        },
        { }
};

static void __init register_insn_emulation_sysctl(struct ctl_table *table)
{
        unsigned long flags;
        int i = 0;
        struct insn_emulation *insn;
        struct ctl_table *insns_sysctl, *sysctl;

        insns_sysctl = kzalloc(sizeof(*sysctl) * (nr_insn_emulated + 1),
                              GFP_KERNEL);

        raw_spin_lock_irqsave(&insn_emulation_lock, flags);
        list_for_each_entry(insn, &insn_emulation, node) {
                sysctl = &insns_sysctl[i];

                sysctl->mode = 0644;
                sysctl->maxlen = sizeof(int);

                sysctl->procname = insn->ops->name;
                sysctl->data = insn;
                sysctl->extra1 = &insn->min;
                sysctl->extra2 = &insn->max;
                sysctl->proc_handler = emulation_proc_handler;
                i++;
        }
        raw_spin_unlock_irqrestore(&insn_emulation_lock, flags);

        table->child = insns_sysctl;
        register_sysctl_table(table);
}

/*
 *  Implement emulation of the SWP/SWPB instructions using load-exclusive and
 *  store-exclusive.
 *
 *  Syntax of SWP{B} instruction: SWP{B}<c> <Rt>, <Rt2>, [<Rn>]
 *  Where: Rt  = destination
 *         Rt2 = source
 *         Rn  = address
 */

/*
 * Error-checking SWP macros implemented using ldxr{b}/stxr{b}
 */
#define __user_swpX_asm(data, addr, res, temp, B)               \
        __asm__ __volatile__(                                   \
        ALTERNATIVE("nop", SET_PSTATE_PAN(0), ARM64_HAS_PAN,    \
                    CONFIG_ARM64_PAN)                           \
        "0:     ldxr"B"         %w2, [%3]\n"                    \
        "1:     stxr"B"         %w0, %w1, [%3]\n"               \
        "       cbz             %w0, 2f\n"                      \
        "       mov             %w0, %w4\n"                     \
        "       b               3f\n"                           \
        "2:\n"                                                  \
        "       mov             %w1, %w2\n"                     \
        "3:\n"                                                  \
        "       .pushsection     .fixup,\"ax\"\n"               \
        "       .align          2\n"                            \
        "4:     mov             %w0, %w5\n"                     \
        "       b               3b\n"                           \
        "       .popsection"                                    \
        _ASM_EXTABLE(0b, 4b)                                    \
        _ASM_EXTABLE(1b, 4b)                                    \
        ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN,    \
                CONFIG_ARM64_PAN)                               \
        : "=&r" (res), "+r" (data), "=&r" (temp)                \
        : "r" (addr), "i" (-EAGAIN), "i" (-EFAULT)              \
        : "memory")

#define __user_swp_asm(data, addr, res, temp) \
        __user_swpX_asm(data, addr, res, temp, "")
#define __user_swpb_asm(data, addr, res, temp) \
        __user_swpX_asm(data, addr, res, temp, "b")

/*
 * Bit 22 of the instruction encoding distinguishes between
 * the SWP and SWPB variants (bit set means SWPB).
 */
#define TYPE_SWPB (1 << 22)

/*
 * Set up process info to signal segmentation fault - called on access error.
 */
static void set_segfault(struct pt_regs *regs, unsigned long addr)
{
        siginfo_t info;

        down_read(&current->mm->mmap_sem);
        if (find_vma(current->mm, addr) == NULL)
                info.si_code = SEGV_MAPERR;
        else
                info.si_code = SEGV_ACCERR;
        up_read(&current->mm->mmap_sem);

        info.si_signo = SIGSEGV;
        info.si_errno = 0;
        info.si_addr  = (void *) instruction_pointer(regs);

        pr_debug("SWP{B} emulation: access caused memory abort!\n");
        arm64_notify_die("Illegal memory access", regs, &info, 0);
}

static int emulate_swpX(unsigned int address, unsigned int *data,
                        unsigned int type)
{
        unsigned int res = 0;

        if ((type != TYPE_SWPB) && (address & 0x3)) {
                /* SWP to unaligned address not permitted */
                pr_debug("SWP instruction on unaligned pointer!\n");
                return -EFAULT;
        }

        while (1) {
                unsigned long temp;

                if (type == TYPE_SWPB)
                        __user_swpb_asm(*data, address, res, temp);
                else
                        __user_swp_asm(*data, address, res, temp);

                if (likely(res != -EAGAIN) || signal_pending(current))
                        break;

                cond_resched();
        }

        return res;
}

/*
 * swp_handler logs the id of calling process, dissects the instruction, sanity
 * checks the memory location, calls emulate_swpX for the actual operation and
 * deals with fixup/error handling before returning
 */
static int swp_handler(struct pt_regs *regs, u32 instr)
{
        u32 destreg, data, type, address = 0;
        int rn, rt2, res = 0;

        perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);

        type = instr & TYPE_SWPB;

        switch (arm_check_condition(instr, regs->pstate)) {
        case ARM_OPCODE_CONDTEST_PASS:
                break;
        case ARM_OPCODE_CONDTEST_FAIL:
                /* Condition failed - return to next instruction */
                goto ret;
        case ARM_OPCODE_CONDTEST_UNCOND:
                /* If unconditional encoding - not a SWP, undef */
                return -EFAULT;
        default:
                return -EINVAL;
        }

        rn = aarch32_insn_extract_reg_num(instr, A32_RN_OFFSET);
        rt2 = aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET);

        address = (u32)regs->user_regs.regs[rn];
        data    = (u32)regs->user_regs.regs[rt2];
        destreg = aarch32_insn_extract_reg_num(instr, A32_RT_OFFSET);

        pr_debug("addr in r%d->0x%08x, dest is r%d, source in r%d->0x%08x)\n",
                rn, address, destreg,
                aarch32_insn_extract_reg_num(instr, A32_RT2_OFFSET), data);

        /* Check access in reasonable access range for both SWP and SWPB */
        if (!access_ok(VERIFY_WRITE, (address & ~3), 4)) {
                pr_debug("SWP{B} emulation: access to 0x%08x not allowed!\n",
                        address);
                goto fault;
        }

        res = emulate_swpX(address, &data, type);
        if (res == -EFAULT)
                goto fault;
        else if (res == 0)
                regs->user_regs.regs[destreg] = data;

ret:
        if (type == TYPE_SWPB)
                trace_instruction_emulation("swpb", regs->pc);
        else
                trace_instruction_emulation("swp", regs->pc);

        pr_warn_ratelimited("\"%s\" (%ld) uses obsolete SWP{B} instruction at 0x%llx\n",
                        current->comm, (unsigned long)current->pid, regs->pc);

        regs->pc += 4;
        return 0;

fault:
        set_segfault(regs, address);

        return 0;
}

/*
 * Only emulate SWP/SWPB executed in ARM state/User mode.
 * The kernel must be SWP free and SWP{B} does not exist in Thumb.
 */
static struct undef_hook swp_hooks[] = {
        {
                .instr_mask     = 0x0fb00ff0,
                .instr_val      = 0x01000090,
                .pstate_mask    = COMPAT_PSR_MODE_MASK,
                .pstate_val     = COMPAT_PSR_MODE_USR,
                .fn             = swp_handler
        },
        { }
};

static struct insn_emulation_ops swp_ops = {
        .name = "swp",
        .status = INSN_OBSOLETE,
        .hooks = swp_hooks,
        .set_hw_mode = NULL,
};

static int cp15barrier_handler(struct pt_regs *regs, u32 instr)
{
        perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);

        switch (arm_check_condition(instr, regs->pstate)) {
        case ARM_OPCODE_CONDTEST_PASS:
                break;
        case ARM_OPCODE_CONDTEST_FAIL:
                /* Condition failed - return to next instruction */
                goto ret;
        case ARM_OPCODE_CONDTEST_UNCOND:
                /* If unconditional encoding - not a barrier instruction */
                return -EFAULT;
        default:
                return -EINVAL;
        }

        switch (aarch32_insn_mcr_extract_crm(instr)) {
        case 10:
                /*
                 * dmb - mcr p15, 0, Rt, c7, c10, 5
                 * dsb - mcr p15, 0, Rt, c7, c10, 4
                 */
                if (aarch32_insn_mcr_extract_opc2(instr) == 5) {
                        dmb(sy);
                        trace_instruction_emulation(
                                "mcr p15, 0, Rt, c7, c10, 5 ; dmb", regs->pc);
                } else {
                        dsb(sy);
                        trace_instruction_emulation(
                                "mcr p15, 0, Rt, c7, c10, 4 ; dsb", regs->pc);
                }
                break;
        case 5:
                /*
                 * isb - mcr p15, 0, Rt, c7, c5, 4
                 *
                 * Taking an exception or returning from one acts as an
                 * instruction barrier. So no explicit barrier needed here.
                 */
                trace_instruction_emulation(
                        "mcr p15, 0, Rt, c7, c5, 4 ; isb", regs->pc);
                break;
        }

ret:
        pr_warn_ratelimited("\"%s\" (%ld) uses deprecated CP15 Barrier instruction at 0x%llx\n",
                        current->comm, (unsigned long)current->pid, regs->pc);

        regs->pc += 4;
        return 0;
}

static int cp15_barrier_set_hw_mode(bool enable)
{
        if (enable)
                config_sctlr_el1(0, SCTLR_EL1_CP15BEN);
        else
                config_sctlr_el1(SCTLR_EL1_CP15BEN, 0);
        return 0;
}

static struct undef_hook cp15_barrier_hooks[] = {
        {
                .instr_mask     = 0x0fff0fdf,
                .instr_val      = 0x0e070f9a,
                .pstate_mask    = COMPAT_PSR_MODE_MASK,
                .pstate_val     = COMPAT_PSR_MODE_USR,
                .fn             = cp15barrier_handler,
        },
        {
                .instr_mask     = 0x0fff0fff,
                .instr_val      = 0x0e070f95,
                .pstate_mask    = COMPAT_PSR_MODE_MASK,
                .pstate_val     = COMPAT_PSR_MODE_USR,
                .fn             = cp15barrier_handler,
        },
        { }
};

static struct insn_emulation_ops cp15_barrier_ops = {
        .name = "cp15_barrier",
        .status = INSN_DEPRECATED,
        .hooks = cp15_barrier_hooks,
        .set_hw_mode = cp15_barrier_set_hw_mode,
};

static int setend_set_hw_mode(bool enable)
{
        if (!cpu_supports_mixed_endian_el0())
                return -EINVAL;

        if (enable)
                config_sctlr_el1(SCTLR_EL1_SED, 0);
        else
                config_sctlr_el1(0, SCTLR_EL1_SED);
        return 0;
}

static int compat_setend_handler(struct pt_regs *regs, u32 big_endian)
{
        char *insn;

        perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->pc);

        if (big_endian) {
                insn = "setend be";
                regs->pstate |= COMPAT_PSR_E_BIT;
        } else {
                insn = "setend le";
                regs->pstate &= ~COMPAT_PSR_E_BIT;
        }

        trace_instruction_emulation(insn, regs->pc);
        pr_warn_ratelimited("\"%s\" (%ld) uses deprecated setend instruction at 0x%llx\n",
                        current->comm, (unsigned long)current->pid, regs->pc);

        return 0;
}

static int a32_setend_handler(struct pt_regs *regs, u32 instr)
{
        int rc = compat_setend_handler(regs, (instr >> 9) & 1);
        regs->pc += 4;
        return rc;
}

static int t16_setend_handler(struct pt_regs *regs, u32 instr)
{
        int rc = compat_setend_handler(regs, (instr >> 3) & 1);
        regs->pc += 2;
        return rc;
}

static struct undef_hook setend_hooks[] = {
        {
                .instr_mask     = 0xfffffdff,
                .instr_val      = 0xf1010000,
                .pstate_mask    = COMPAT_PSR_MODE_MASK,
                .pstate_val     = COMPAT_PSR_MODE_USR,
                .fn             = a32_setend_handler,
        },
        {
                /* Thumb mode */
                .instr_mask     = 0x0000fff7,
                .instr_val      = 0x0000b650,
                .pstate_mask    = (COMPAT_PSR_T_BIT | COMPAT_PSR_MODE_MASK),
                .pstate_val     = (COMPAT_PSR_T_BIT | COMPAT_PSR_MODE_USR),
                .fn             = t16_setend_handler,
        },
        {}
};

static struct insn_emulation_ops setend_ops = {
        .name = "setend",
        .status = INSN_DEPRECATED,
        .hooks = setend_hooks,
        .set_hw_mode = setend_set_hw_mode,
};

static int insn_cpu_hotplug_notify(struct notifier_block *b,
                              unsigned long action, void *hcpu)
{
        int rc = 0;
        if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)
                rc = run_all_insn_set_hw_mode((unsigned long)hcpu);

        return notifier_from_errno(rc);
}

static struct notifier_block insn_cpu_hotplug_notifier = {
        .notifier_call = insn_cpu_hotplug_notify,
};

/*
 * Invoked as late_initcall, since not needed before init spawned.
 */
static int __init armv8_deprecated_init(void)
{
        if (IS_ENABLED(CONFIG_SWP_EMULATION))
                register_insn_emulation(&swp_ops);

        if (IS_ENABLED(CONFIG_CP15_BARRIER_EMULATION))
                register_insn_emulation(&cp15_barrier_ops);

        if (IS_ENABLED(CONFIG_SETEND_EMULATION)) {
                if(system_supports_mixed_endian_el0())
                        register_insn_emulation(&setend_ops);
                else
                        pr_info("setend instruction emulation is not supported on the system");
        }

        register_cpu_notifier(&insn_cpu_hotplug_notifier);
        register_insn_emulation_sysctl(ctl_abi);

        return 0;
}

late_initcall(armv8_deprecated_init);