/*
 * AArch64 KGDB support
 *
 * Based on arch/arm/kernel/kgdb.c
 *
 * Copyright (C) 2013 Cavium Inc.
 * Author: Vijaya Kumar K <vijaya.kumar@caviumnetworks.com>
 *
 * 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.
 *
 * 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 <linux/bug.h>
#include <linux/irq.h>
#include <linux/kdebug.h>
#include <linux/kgdb.h>
#include <linux/kprobes.h>
#include <linux/sched/task_stack.h>

#include <asm/debug-monitors.h>
#include <asm/insn.h>
#include <asm/traps.h>

struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
        { "x0", 8, offsetof(struct pt_regs, regs[0])},
        { "x1", 8, offsetof(struct pt_regs, regs[1])},
        { "x2", 8, offsetof(struct pt_regs, regs[2])},
        { "x3", 8, offsetof(struct pt_regs, regs[3])},
        { "x4", 8, offsetof(struct pt_regs, regs[4])},
        { "x5", 8, offsetof(struct pt_regs, regs[5])},
        { "x6", 8, offsetof(struct pt_regs, regs[6])},
        { "x7", 8, offsetof(struct pt_regs, regs[7])},
        { "x8", 8, offsetof(struct pt_regs, regs[8])},
        { "x9", 8, offsetof(struct pt_regs, regs[9])},
        { "x10", 8, offsetof(struct pt_regs, regs[10])},
        { "x11", 8, offsetof(struct pt_regs, regs[11])},
        { "x12", 8, offsetof(struct pt_regs, regs[12])},
        { "x13", 8, offsetof(struct pt_regs, regs[13])},
        { "x14", 8, offsetof(struct pt_regs, regs[14])},
        { "x15", 8, offsetof(struct pt_regs, regs[15])},
        { "x16", 8, offsetof(struct pt_regs, regs[16])},
        { "x17", 8, offsetof(struct pt_regs, regs[17])},
        { "x18", 8, offsetof(struct pt_regs, regs[18])},
        { "x19", 8, offsetof(struct pt_regs, regs[19])},
        { "x20", 8, offsetof(struct pt_regs, regs[20])},
        { "x21", 8, offsetof(struct pt_regs, regs[21])},
        { "x22", 8, offsetof(struct pt_regs, regs[22])},
        { "x23", 8, offsetof(struct pt_regs, regs[23])},
        { "x24", 8, offsetof(struct pt_regs, regs[24])},
        { "x25", 8, offsetof(struct pt_regs, regs[25])},
        { "x26", 8, offsetof(struct pt_regs, regs[26])},
        { "x27", 8, offsetof(struct pt_regs, regs[27])},
        { "x28", 8, offsetof(struct pt_regs, regs[28])},
        { "x29", 8, offsetof(struct pt_regs, regs[29])},
        { "x30", 8, offsetof(struct pt_regs, regs[30])},
        { "sp", 8, offsetof(struct pt_regs, sp)},
        { "pc", 8, offsetof(struct pt_regs, pc)},
        /*
         * struct pt_regs thinks PSTATE is 64-bits wide but gdb remote
         * protocol disagrees. Therefore we must extract only the lower
         * 32-bits. Look for the big comment in asm/kgdb.h for more
         * detail.
         */
        { "pstate", 4, offsetof(struct pt_regs, pstate)
#ifdef CONFIG_CPU_BIG_ENDIAN
                                                        + 4
#endif
        },
        { "v0", 16, -1 },
        { "v1", 16, -1 },
        { "v2", 16, -1 },
        { "v3", 16, -1 },
        { "v4", 16, -1 },
        { "v5", 16, -1 },
        { "v6", 16, -1 },
        { "v7", 16, -1 },
        { "v8", 16, -1 },
        { "v9", 16, -1 },
        { "v10", 16, -1 },
        { "v11", 16, -1 },
        { "v12", 16, -1 },
        { "v13", 16, -1 },
        { "v14", 16, -1 },
        { "v15", 16, -1 },
        { "v16", 16, -1 },
        { "v17", 16, -1 },
        { "v18", 16, -1 },
        { "v19", 16, -1 },
        { "v20", 16, -1 },
        { "v21", 16, -1 },
        { "v22", 16, -1 },
        { "v23", 16, -1 },
        { "v24", 16, -1 },
        { "v25", 16, -1 },
        { "v26", 16, -1 },
        { "v27", 16, -1 },
        { "v28", 16, -1 },
        { "v29", 16, -1 },
        { "v30", 16, -1 },
        { "v31", 16, -1 },
        { "fpsr", 4, -1 },
        { "fpcr", 4, -1 },
};

char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
{
        if (regno >= DBG_MAX_REG_NUM || regno < 0)
                return NULL;

        if (dbg_reg_def[regno].offset != -1)
                memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
                       dbg_reg_def[regno].size);
        else
                memset(mem, 0, dbg_reg_def[regno].size);
        return dbg_reg_def[regno].name;
}

int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
{
        if (regno >= DBG_MAX_REG_NUM || regno < 0)
                return -EINVAL;

        if (dbg_reg_def[regno].offset != -1)
                memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
                       dbg_reg_def[regno].size);
        return 0;
}

void
sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
{
        struct pt_regs *thread_regs;

        /* Initialize to zero */
        memset((char *)gdb_regs, 0, NUMREGBYTES);
        thread_regs = task_pt_regs(task);
        memcpy((void *)gdb_regs, (void *)thread_regs->regs, GP_REG_BYTES);
        /* Special case for PSTATE (check comments in asm/kgdb.h for details) */
        dbg_get_reg(33, gdb_regs + GP_REG_BYTES, thread_regs);
}

void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
{
        regs->pc = pc;
}

static int compiled_break;

static void kgdb_arch_update_addr(struct pt_regs *regs,
                                char *remcom_in_buffer)
{
        unsigned long addr;
        char *ptr;

        ptr = &remcom_in_buffer[1];
        if (kgdb_hex2long(&ptr, &addr))
                kgdb_arch_set_pc(regs, addr);
        else if (compiled_break == 1)
                kgdb_arch_set_pc(regs, regs->pc + 4);

        compiled_break = 0;
}

int kgdb_arch_handle_exception(int exception_vector, int signo,
                               int err_code, char *remcom_in_buffer,
                               char *remcom_out_buffer,
                               struct pt_regs *linux_regs)
{
        int err;

        switch (remcom_in_buffer[0]) {
        case 'D':
        case 'k':
                /*
                 * Packet D (Detach), k (kill). No special handling
                 * is required here. Handle same as c packet.
                 */
        case 'c':
                /*
                 * Packet c (Continue) to continue executing.
                 * Set pc to required address.
                 * Try to read optional parameter and set pc.
                 * If this was a compiled breakpoint, we need to move
                 * to the next instruction else we will just breakpoint
                 * over and over again.
                 */
                kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
                atomic_set(&kgdb_cpu_doing_single_step, -1);
                kgdb_single_step =  0;

                /*
                 * Received continue command, disable single step
                 */
                if (kernel_active_single_step())
                        kernel_disable_single_step();

                err = 0;
                break;
        case 's':
                /*
                 * Update step address value with address passed
                 * with step packet.
                 * On debug exception return PC is copied to ELR
                 * So just update PC.
                 * If no step address is passed, resume from the address
                 * pointed by PC. Do not update PC
                 */
                kgdb_arch_update_addr(linux_regs, remcom_in_buffer);
                atomic_set(&kgdb_cpu_doing_single_step, raw_smp_processor_id());
                kgdb_single_step =  1;

                /*
                 * Enable single step handling
                 */
                if (!kernel_active_single_step())
                        kernel_enable_single_step(linux_regs);
                err = 0;
                break;
        default:
                err = -1;
        }
        return err;
}

static int kgdb_brk_fn(struct pt_regs *regs, unsigned int esr)
{
        kgdb_handle_exception(1, SIGTRAP, 0, regs);
        return 0;
}
NOKPROBE_SYMBOL(kgdb_brk_fn)

static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int esr)
{
        compiled_break = 1;
        kgdb_handle_exception(1, SIGTRAP, 0, regs);

        return 0;
}
NOKPROBE_SYMBOL(kgdb_compiled_brk_fn);

static int kgdb_step_brk_fn(struct pt_regs *regs, unsigned int esr)
{
        if (!kgdb_single_step)
                return DBG_HOOK_ERROR;

        kgdb_handle_exception(1, SIGTRAP, 0, regs);
        return 0;
}
NOKPROBE_SYMBOL(kgdb_step_brk_fn);

static struct break_hook kgdb_brkpt_hook = {
        .esr_mask       = 0xffffffff,
        .esr_val        = (u32)ESR_ELx_VAL_BRK64(KGDB_DYN_DBG_BRK_IMM),
        .fn             = kgdb_brk_fn
};

static struct break_hook kgdb_compiled_brkpt_hook = {
        .esr_mask       = 0xffffffff,
        .esr_val        = (u32)ESR_ELx_VAL_BRK64(KGDB_COMPILED_DBG_BRK_IMM),
        .fn             = kgdb_compiled_brk_fn
};

static struct step_hook kgdb_step_hook = {
        .fn             = kgdb_step_brk_fn
};

static void kgdb_call_nmi_hook(void *ignored)
{
        kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
}

void kgdb_roundup_cpus(unsigned long flags)
{
        local_irq_enable();
        smp_call_function(kgdb_call_nmi_hook, NULL, 0);
        local_irq_disable();
}

static int __kgdb_notify(struct die_args *args, unsigned long cmd)
{
        struct pt_regs *regs = args->regs;

        if (kgdb_handle_exception(1, args->signr, cmd, regs))
                return NOTIFY_DONE;
        return NOTIFY_STOP;
}

static int
kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
{
        unsigned long flags;
        int ret;

        local_irq_save(flags);
        ret = __kgdb_notify(ptr, cmd);
        local_irq_restore(flags);

        return ret;
}

static struct notifier_block kgdb_notifier = {
        .notifier_call  = kgdb_notify,
        /*
         * Want to be lowest priority
         */
        .priority       = -INT_MAX,
};

/*
 * kgdb_arch_init - Perform any architecture specific initialization.
 * This function will handle the initialization of any architecture
 * specific callbacks.
 */
int kgdb_arch_init(void)
{
        int ret = register_die_notifier(&kgdb_notifier);

        if (ret != 0)
                return ret;

        register_break_hook(&kgdb_brkpt_hook);
        register_break_hook(&kgdb_compiled_brkpt_hook);
        register_step_hook(&kgdb_step_hook);
        return 0;
}

/*
 * kgdb_arch_exit - Perform any architecture specific uninitalization.
 * This function will handle the uninitalization of any architecture
 * specific callbacks, for dynamic registration and unregistration.
 */
void kgdb_arch_exit(void)
{
        unregister_break_hook(&kgdb_brkpt_hook);
        unregister_break_hook(&kgdb_compiled_brkpt_hook);
        unregister_step_hook(&kgdb_step_hook);
        unregister_die_notifier(&kgdb_notifier);
}

struct kgdb_arch arch_kgdb_ops;

int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
{
        int err;

        BUILD_BUG_ON(AARCH64_INSN_SIZE != BREAK_INSTR_SIZE);

        err = aarch64_insn_read((void *)bpt->bpt_addr, (u32 *)bpt->saved_instr);
        if (err)
                return err;

        return aarch64_insn_write((void *)bpt->bpt_addr,
                        (u32)AARCH64_BREAK_KGDB_DYN_DBG);
}

int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
{
        return aarch64_insn_write((void *)bpt->bpt_addr,
                        *(u32 *)bpt->saved_instr);
}