/* kgdb support for MN10300
 *
 * Copyright (C) 2010 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/slab.h>
#include <linux/ptrace.h>
#include <linux/kgdb.h>
#include <linux/uaccess.h>
#include <unit/leds.h>
#include <unit/serial.h>
#include <asm/debugger.h>
#include <asm/serial-regs.h>
#include "internal.h"

/*
 * Software single-stepping breakpoint save (used by __switch_to())
 */
static struct thread_info *kgdb_sstep_thread;
u8 *kgdb_sstep_bp_addr[2];
u8 kgdb_sstep_bp[2];

/*
 * Copy kernel exception frame registers to the GDB register file
 */
void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
{
        unsigned long ssp = (unsigned long) (regs + 1);

        gdb_regs[GDB_FR_D0]     = regs->d0;
        gdb_regs[GDB_FR_D1]     = regs->d1;
        gdb_regs[GDB_FR_D2]     = regs->d2;
        gdb_regs[GDB_FR_D3]     = regs->d3;
        gdb_regs[GDB_FR_A0]     = regs->a0;
        gdb_regs[GDB_FR_A1]     = regs->a1;
        gdb_regs[GDB_FR_A2]     = regs->a2;
        gdb_regs[GDB_FR_A3]     = regs->a3;
        gdb_regs[GDB_FR_SP]     = (regs->epsw & EPSW_nSL) ? regs->sp : ssp;
        gdb_regs[GDB_FR_PC]     = regs->pc;
        gdb_regs[GDB_FR_MDR]    = regs->mdr;
        gdb_regs[GDB_FR_EPSW]   = regs->epsw;
        gdb_regs[GDB_FR_LIR]    = regs->lir;
        gdb_regs[GDB_FR_LAR]    = regs->lar;
        gdb_regs[GDB_FR_MDRQ]   = regs->mdrq;
        gdb_regs[GDB_FR_E0]     = regs->e0;
        gdb_regs[GDB_FR_E1]     = regs->e1;
        gdb_regs[GDB_FR_E2]     = regs->e2;
        gdb_regs[GDB_FR_E3]     = regs->e3;
        gdb_regs[GDB_FR_E4]     = regs->e4;
        gdb_regs[GDB_FR_E5]     = regs->e5;
        gdb_regs[GDB_FR_E6]     = regs->e6;
        gdb_regs[GDB_FR_E7]     = regs->e7;
        gdb_regs[GDB_FR_SSP]    = ssp;
        gdb_regs[GDB_FR_MSP]    = 0;
        gdb_regs[GDB_FR_USP]    = regs->sp;
        gdb_regs[GDB_FR_MCRH]   = regs->mcrh;
        gdb_regs[GDB_FR_MCRL]   = regs->mcrl;
        gdb_regs[GDB_FR_MCVF]   = regs->mcvf;
        gdb_regs[GDB_FR_DUMMY0] = 0;
        gdb_regs[GDB_FR_DUMMY1] = 0;
        gdb_regs[GDB_FR_FS0]    = 0;
}

/*
 * Extracts kernel SP/PC values understandable by gdb from the values
 * saved by switch_to().
 */
void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
{
        gdb_regs[GDB_FR_SSP]    = p->thread.sp;
        gdb_regs[GDB_FR_PC]     = p->thread.pc;
        gdb_regs[GDB_FR_A3]     = p->thread.a3;
        gdb_regs[GDB_FR_USP]    = p->thread.usp;
        gdb_regs[GDB_FR_FPCR]   = p->thread.fpu_state.fpcr;
}

/*
 * Fill kernel exception frame registers from the GDB register file
 */
void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
{
        regs->d0        = gdb_regs[GDB_FR_D0];
        regs->d1        = gdb_regs[GDB_FR_D1];
        regs->d2        = gdb_regs[GDB_FR_D2];
        regs->d3        = gdb_regs[GDB_FR_D3];
        regs->a0        = gdb_regs[GDB_FR_A0];
        regs->a1        = gdb_regs[GDB_FR_A1];
        regs->a2        = gdb_regs[GDB_FR_A2];
        regs->a3        = gdb_regs[GDB_FR_A3];
        regs->sp        = gdb_regs[GDB_FR_SP];
        regs->pc        = gdb_regs[GDB_FR_PC];
        regs->mdr       = gdb_regs[GDB_FR_MDR];
        regs->epsw      = gdb_regs[GDB_FR_EPSW];
        regs->lir       = gdb_regs[GDB_FR_LIR];
        regs->lar       = gdb_regs[GDB_FR_LAR];
        regs->mdrq      = gdb_regs[GDB_FR_MDRQ];
        regs->e0        = gdb_regs[GDB_FR_E0];
        regs->e1        = gdb_regs[GDB_FR_E1];
        regs->e2        = gdb_regs[GDB_FR_E2];
        regs->e3        = gdb_regs[GDB_FR_E3];
        regs->e4        = gdb_regs[GDB_FR_E4];
        regs->e5        = gdb_regs[GDB_FR_E5];
        regs->e6        = gdb_regs[GDB_FR_E6];
        regs->e7        = gdb_regs[GDB_FR_E7];
        regs->sp        = gdb_regs[GDB_FR_SSP];
        /* gdb_regs[GDB_FR_MSP]; */
        // regs->usp    = gdb_regs[GDB_FR_USP];
        regs->mcrh      = gdb_regs[GDB_FR_MCRH];
        regs->mcrl      = gdb_regs[GDB_FR_MCRL];
        regs->mcvf      = gdb_regs[GDB_FR_MCVF];
        /* gdb_regs[GDB_FR_DUMMY0]; */
        /* gdb_regs[GDB_FR_DUMMY1]; */

        // regs->fpcr   = gdb_regs[GDB_FR_FPCR];
        // regs->fs0    = gdb_regs[GDB_FR_FS0];
}

struct kgdb_arch arch_kgdb_ops = {
        .gdb_bpt_instr  = { 0xff },
        .flags          = KGDB_HW_BREAKPOINT,
};

static const unsigned char mn10300_kgdb_insn_sizes[256] =
{
        /* 1  2  3  4  5  6  7  8  9  a  b  c  d  e  f */
        1, 3, 3, 3, 1, 3, 3, 3, 1, 3, 3, 3, 1, 3, 3, 3, /* 0 */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 1 */
        2, 2, 2, 2, 3, 3, 3, 3, 2, 2, 2, 2, 3, 3, 3, 3, /* 2 */
        3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 1, 1, 1, 1, /* 3 */
        1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, 1, 1, 2, 2, /* 4 */
        1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, /* 5 */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 6 */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* 7 */
        2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* 8 */
        2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* 9 */
        2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* a */
        2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, /* b */
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 2, 2, /* c */
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, /* d */
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, /* e */
        0, 2, 2, 2, 2, 2, 2, 4, 0, 3, 0, 4, 0, 6, 7, 1  /* f */
};

/*
 * Attempt to emulate single stepping by means of breakpoint instructions.
 * Although there is a single-step trace flag in EPSW, its use is not
 * sufficiently documented and is only intended for use with the JTAG debugger.
 */
static int kgdb_arch_do_singlestep(struct pt_regs *regs)
{
        unsigned long arg;
        unsigned size;
        u8 *pc = (u8 *)regs->pc, *sp = (u8 *)(regs + 1), cur;
        u8 *x = NULL, *y = NULL;
        int ret;

        ret = probe_kernel_read(&cur, pc, 1);
        if (ret < 0)
                return ret;

        size = mn10300_kgdb_insn_sizes[cur];
        if (size > 0) {
                x = pc + size;
                goto set_x;
        }

        switch (cur) {
                /* Bxx (d8,PC) */
        case 0xc0 ... 0xca:
                ret = probe_kernel_read(&arg, pc + 1, 1);
                if (ret < 0)
                        return ret;
                x = pc + 2;
                if (arg >= 0 && arg <= 2)
                        goto set_x;
                y = pc + (s8)arg;
                goto set_x_and_y;

                /* LXX (d8,PC) */
        case 0xd0 ... 0xda:
                x = pc + 1;
                if (regs->pc == regs->lar)
                        goto set_x;
                y = (u8 *)regs->lar;
                goto set_x_and_y;

                /* SETLB - loads the next four bytes into the LIR register
                 * (which mustn't include a breakpoint instruction) */
        case 0xdb:
                x = pc + 5;
                goto set_x;

                /* JMP (d16,PC) or CALL (d16,PC) */
        case 0xcc:
        case 0xcd:
                ret = probe_kernel_read(&arg, pc + 1, 2);
                if (ret < 0)
                        return ret;
                x = pc + (s16)arg;
                goto set_x;

                /* JMP (d32,PC) or CALL (d32,PC) */
        case 0xdc:
        case 0xdd:
                ret = probe_kernel_read(&arg, pc + 1, 4);
                if (ret < 0)
                        return ret;
                x = pc + (s32)arg;
                goto set_x;

                /* RETF */
        case 0xde:
                x = (u8 *)regs->mdr;
                goto set_x;

                /* RET */
        case 0xdf:
                ret = probe_kernel_read(&arg, pc + 2, 1);
                if (ret < 0)
                        return ret;
                ret = probe_kernel_read(&x, sp + (s8)arg, 4);
                if (ret < 0)
                        return ret;
                goto set_x;

        case 0xf0:
                ret = probe_kernel_read(&cur, pc + 1, 1);
                if (ret < 0)
                        return ret;

                if (cur >= 0xf0 && cur <= 0xf7) {
                        /* JMP (An) / CALLS (An) */
                        switch (cur & 3) {
                        case 0: x = (u8 *)regs->a0; break;
                        case 1: x = (u8 *)regs->a1; break;
                        case 2: x = (u8 *)regs->a2; break;
                        case 3: x = (u8 *)regs->a3; break;
                        }
                        goto set_x;
                } else if (cur == 0xfc) {
                        /* RETS */
                        ret = probe_kernel_read(&x, sp, 4);
                        if (ret < 0)
                                return ret;
                        goto set_x;
                } else if (cur == 0xfd) {
                        /* RTI */
                        ret = probe_kernel_read(&x, sp + 4, 4);
                        if (ret < 0)
                                return ret;
                        goto set_x;
                } else {
                        x = pc + 2;
                        goto set_x;
                }
                break;

                /* potential 3-byte conditional branches */
        case 0xf8:
                ret = probe_kernel_read(&cur, pc + 1, 1);
                if (ret < 0)
                        return ret;
                x = pc + 3;

                if (cur >= 0xe8 && cur <= 0xeb) {
                        ret = probe_kernel_read(&arg, pc + 2, 1);
                        if (ret < 0)
                                return ret;
                        if (arg >= 0 && arg <= 3)
                                goto set_x;
                        y = pc + (s8)arg;
                        goto set_x_and_y;
                }
                goto set_x;

        case 0xfa:
                ret = probe_kernel_read(&cur, pc + 1, 1);
                if (ret < 0)
                        return ret;

                if (cur == 0xff) {
                        /* CALLS (d16,PC) */
                        ret = probe_kernel_read(&arg, pc + 2, 2);
                        if (ret < 0)
                                return ret;
                        x = pc + (s16)arg;
                        goto set_x;
                }

                x = pc + 4;
                goto set_x;

        case 0xfc:
                ret = probe_kernel_read(&cur, pc + 1, 1);
                if (ret < 0)
                        return ret;

                if (cur == 0xff) {
                        /* CALLS (d32,PC) */
                        ret = probe_kernel_read(&arg, pc + 2, 4);
                        if (ret < 0)
                                return ret;
                        x = pc + (s32)arg;
                        goto set_x;
                }

                x = pc + 6;
                goto set_x;
        }

        return 0;

set_x:
        kgdb_sstep_bp_addr[0] = x;
        kgdb_sstep_bp_addr[1] = NULL;
        ret = probe_kernel_read(&kgdb_sstep_bp[0], x, 1);
        if (ret < 0)
                return ret;
        ret = probe_kernel_write(x, &arch_kgdb_ops.gdb_bpt_instr, 1);
        if (ret < 0)
                return ret;
        kgdb_sstep_thread = current_thread_info();
        debugger_local_cache_flushinv_one(x);
        return ret;

set_x_and_y:
        kgdb_sstep_bp_addr[0] = x;
        kgdb_sstep_bp_addr[1] = y;
        ret = probe_kernel_read(&kgdb_sstep_bp[0], x, 1);
        if (ret < 0)
                return ret;
        ret = probe_kernel_read(&kgdb_sstep_bp[1], y, 1);
        if (ret < 0)
                return ret;
        ret = probe_kernel_write(x, &arch_kgdb_ops.gdb_bpt_instr, 1);
        if (ret < 0)
                return ret;
        ret = probe_kernel_write(y, &arch_kgdb_ops.gdb_bpt_instr, 1);
        if (ret < 0) {
                probe_kernel_write(kgdb_sstep_bp_addr[0],
                                   &kgdb_sstep_bp[0], 1);
        } else {
                kgdb_sstep_thread = current_thread_info();
        }
        debugger_local_cache_flushinv_one(x);
        debugger_local_cache_flushinv_one(y);
        return ret;
}

/*
 * Remove emplaced single-step breakpoints, returning true if we hit one of
 * them.
 */
static bool kgdb_arch_undo_singlestep(struct pt_regs *regs)
{
        bool hit = false;
        u8 *x = kgdb_sstep_bp_addr[0], *y = kgdb_sstep_bp_addr[1];
        u8 opcode;

        if (kgdb_sstep_thread == current_thread_info()) {
                if (x) {
                        if (x == (u8 *)regs->pc)
                                hit = true;
                        if (probe_kernel_read(&opcode, x,
                                              1) < 0 ||
                            opcode != 0xff)
                                BUG();
                        probe_kernel_write(x, &kgdb_sstep_bp[0], 1);
                        debugger_local_cache_flushinv_one(x);
                }
                if (y) {
                        if (y == (u8 *)regs->pc)
                                hit = true;
                        if (probe_kernel_read(&opcode, y,
                                              1) < 0 ||
                            opcode != 0xff)
                                BUG();
                        probe_kernel_write(y, &kgdb_sstep_bp[1], 1);
                        debugger_local_cache_flushinv_one(y);
                }
        }

        kgdb_sstep_bp_addr[0] = NULL;
        kgdb_sstep_bp_addr[1] = NULL;
        kgdb_sstep_thread = NULL;
        return hit;
}

/*
 * Catch a single-step-pending thread being deleted and make sure the global
 * single-step state is cleared.  At this point the breakpoints should have
 * been removed by __switch_to().
 */
void arch_release_thread_info(struct thread_info *ti)
{
        if (kgdb_sstep_thread == ti) {
                kgdb_sstep_thread = NULL;

                /* However, we may now be running in degraded mode, with most
                 * of the CPUs disabled until such a time as KGDB is reentered,
                 * so force immediate reentry */
                kgdb_breakpoint();
        }
}

/*
 * Handle unknown packets and [CcsDk] packets
 * - at this point breakpoints have been installed
 */
int kgdb_arch_handle_exception(int vector, int signo, int err_code,
                               char *remcom_in_buffer, char *remcom_out_buffer,
                               struct pt_regs *regs)
{
        long addr;
        char *ptr;

        switch (remcom_in_buffer[0]) {
        case 'c':
        case 's':
                /* try to read optional parameter, pc unchanged if no parm */
                ptr = &remcom_in_buffer[1];
                if (kgdb_hex2long(&ptr, &addr))
                        regs->pc = addr;
        case 'D':
        case 'k':
                atomic_set(&kgdb_cpu_doing_single_step, -1);

                if (remcom_in_buffer[0] == 's') {
                        kgdb_arch_do_singlestep(regs);
                        kgdb_single_step = 1;
                        atomic_set(&kgdb_cpu_doing_single_step,
                                   raw_smp_processor_id());
                }
                return 0;
        }
        return -1; /* this means that we do not want to exit from the handler */
}

/*
 * Handle event interception
 * - returns 0 if the exception should be skipped, -ERROR otherwise.
 */
int debugger_intercept(enum exception_code excep, int signo, int si_code,
                       struct pt_regs *regs)
{
        int ret;

        if (kgdb_arch_undo_singlestep(regs)) {
                excep = EXCEP_TRAP;
                signo = SIGTRAP;
                si_code = TRAP_TRACE;
        }

        ret = kgdb_handle_exception(excep, signo, si_code, regs);

        debugger_local_cache_flushinv();

        return ret;
}

/*
 * Determine if we've hit a debugger special breakpoint
 */
int at_debugger_breakpoint(struct pt_regs *regs)
{
        return regs->pc == (unsigned long)&__arch_kgdb_breakpoint;
}

/*
 * Initialise kgdb
 */
int kgdb_arch_init(void)
{
        return 0;
}

/*
 * Do something, perhaps, but don't know what.
 */
void kgdb_arch_exit(void)
{
}

#ifdef CONFIG_SMP
void debugger_nmi_interrupt(struct pt_regs *regs, enum exception_code code)
{
        kgdb_nmicallback(arch_smp_processor_id(), regs);
        debugger_local_cache_flushinv();
}

void kgdb_roundup_cpus(unsigned long flags)
{
        smp_jump_to_debugger();
}
#endif