// SPDX-License-Identifier: GPL-2.0
/*
 * SuperH KGDB support
 *
 * Copyright (C) 2008 - 2012  Paul Mundt
 *
 * Single stepping taken from the old stub by Henry Bell and Jeremy Siegel.
 */
#include <linux/kgdb.h>
#include <linux/kdebug.h>
#include <linux/irq.h>
#include <linux/io.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>

#include <asm/cacheflush.h>
#include <asm/traps.h>

/* Macros for single step instruction identification */
#define OPCODE_BT(op)           (((op) & 0xff00) == 0x8900)
#define OPCODE_BF(op)           (((op) & 0xff00) == 0x8b00)
#define OPCODE_BTF_DISP(op)     (((op) & 0x80) ? (((op) | 0xffffff80) << 1) : \
                                 (((op) & 0x7f ) << 1))
#define OPCODE_BFS(op)          (((op) & 0xff00) == 0x8f00)
#define OPCODE_BTS(op)          (((op) & 0xff00) == 0x8d00)
#define OPCODE_BRA(op)          (((op) & 0xf000) == 0xa000)
#define OPCODE_BRA_DISP(op)     (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
                                 (((op) & 0x7ff) << 1))
#define OPCODE_BRAF(op)         (((op) & 0xf0ff) == 0x0023)
#define OPCODE_BRAF_REG(op)     (((op) & 0x0f00) >> 8)
#define OPCODE_BSR(op)          (((op) & 0xf000) == 0xb000)
#define OPCODE_BSR_DISP(op)     (((op) & 0x800) ? (((op) | 0xfffff800) << 1) : \
                                 (((op) & 0x7ff) << 1))
#define OPCODE_BSRF(op)         (((op) & 0xf0ff) == 0x0003)
#define OPCODE_BSRF_REG(op)     (((op) >> 8) & 0xf)
#define OPCODE_JMP(op)          (((op) & 0xf0ff) == 0x402b)
#define OPCODE_JMP_REG(op)      (((op) >> 8) & 0xf)
#define OPCODE_JSR(op)          (((op) & 0xf0ff) == 0x400b)
#define OPCODE_JSR_REG(op)      (((op) >> 8) & 0xf)
#define OPCODE_RTS(op)          ((op) == 0xb)
#define OPCODE_RTE(op)          ((op) == 0x2b)

#define SR_T_BIT_MASK           0x1
#define STEP_OPCODE             0xc33d

/* Calculate the new address for after a step */
static short *get_step_address(struct pt_regs *linux_regs)
{
        insn_size_t op = __raw_readw(linux_regs->pc);
        long addr;

        /* BT */
        if (OPCODE_BT(op)) {
                if (linux_regs->sr & SR_T_BIT_MASK)
                        addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
                else
                        addr = linux_regs->pc + 2;
        }

        /* BTS */
        else if (OPCODE_BTS(op)) {
                if (linux_regs->sr & SR_T_BIT_MASK)
                        addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
                else
                        addr = linux_regs->pc + 4;      /* Not in delay slot */
        }

        /* BF */
        else if (OPCODE_BF(op)) {
                if (!(linux_regs->sr & SR_T_BIT_MASK))
                        addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
                else
                        addr = linux_regs->pc + 2;
        }

        /* BFS */
        else if (OPCODE_BFS(op)) {
                if (!(linux_regs->sr & SR_T_BIT_MASK))
                        addr = linux_regs->pc + 4 + OPCODE_BTF_DISP(op);
                else
                        addr = linux_regs->pc + 4;      /* Not in delay slot */
        }

        /* BRA */
        else if (OPCODE_BRA(op))
                addr = linux_regs->pc + 4 + OPCODE_BRA_DISP(op);

        /* BRAF */
        else if (OPCODE_BRAF(op))
                addr = linux_regs->pc + 4
                    + linux_regs->regs[OPCODE_BRAF_REG(op)];

        /* BSR */
        else if (OPCODE_BSR(op))
                addr = linux_regs->pc + 4 + OPCODE_BSR_DISP(op);

        /* BSRF */
        else if (OPCODE_BSRF(op))
                addr = linux_regs->pc + 4
                    + linux_regs->regs[OPCODE_BSRF_REG(op)];

        /* JMP */
        else if (OPCODE_JMP(op))
                addr = linux_regs->regs[OPCODE_JMP_REG(op)];

        /* JSR */
        else if (OPCODE_JSR(op))
                addr = linux_regs->regs[OPCODE_JSR_REG(op)];

        /* RTS */
        else if (OPCODE_RTS(op))
                addr = linux_regs->pr;

        /* RTE */
        else if (OPCODE_RTE(op))
                addr = linux_regs->regs[15];

        /* Other */
        else
                addr = linux_regs->pc + instruction_size(op);

        flush_icache_range(addr, addr + instruction_size(op));
        return (short *)addr;
}

/*
 * Replace the instruction immediately after the current instruction
 * (i.e. next in the expected flow of control) with a trap instruction,
 * so that returning will cause only a single instruction to be executed.
 * Note that this model is slightly broken for instructions with delay
 * slots (e.g. B[TF]S, BSR, BRA etc), where both the branch and the
 * instruction in the delay slot will be executed.
 */

static unsigned long stepped_address;
static insn_size_t stepped_opcode;

static void do_single_step(struct pt_regs *linux_regs)
{
        /* Determine where the target instruction will send us to */
        unsigned short *addr = get_step_address(linux_regs);

        stepped_address = (int)addr;

        /* Replace it */
        stepped_opcode = __raw_readw((long)addr);
        *addr = STEP_OPCODE;

        /* Flush and return */
        flush_icache_range((long)addr, (long)addr +
                           instruction_size(stepped_opcode));
}

/* Undo a single step */
static void undo_single_step(struct pt_regs *linux_regs)
{
        /* If we have stepped, put back the old instruction */
        /* Use stepped_address in case we stopped elsewhere */
        if (stepped_opcode != 0) {
                __raw_writew(stepped_opcode, stepped_address);
                flush_icache_range(stepped_address, stepped_address + 2);
        }

        stepped_opcode = 0;
}

struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
        { "r0",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[0]) },
        { "r1",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[1]) },
        { "r2",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[2]) },
        { "r3",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[3]) },
        { "r4",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[4]) },
        { "r5",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[5]) },
        { "r6",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[6]) },
        { "r7",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[7]) },
        { "r8",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[8]) },
        { "r9",         GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[9]) },
        { "r10",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[10]) },
        { "r11",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[11]) },
        { "r12",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[12]) },
        { "r13",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[13]) },
        { "r14",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[14]) },
        { "r15",        GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[15]) },
        { "pc",         GDB_SIZEOF_REG, offsetof(struct pt_regs, pc) },
        { "pr",         GDB_SIZEOF_REG, offsetof(struct pt_regs, pr) },
        { "sr",         GDB_SIZEOF_REG, offsetof(struct pt_regs, sr) },
        { "gbr",        GDB_SIZEOF_REG, offsetof(struct pt_regs, gbr) },
        { "mach",       GDB_SIZEOF_REG, offsetof(struct pt_regs, mach) },
        { "macl",       GDB_SIZEOF_REG, offsetof(struct pt_regs, macl) },
        { "vbr",        GDB_SIZEOF_REG, -1 },
};

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

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

        switch (regno) {
        case GDB_VBR:
                __asm__ __volatile__ ("stc vbr, %0" : "=r" (mem));
                break;
        }

        return dbg_reg_def[regno].name;
}

void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
{
        struct pt_regs *thread_regs = task_pt_regs(p);
        int reg;

        /* Initialize to zero */
        for (reg = 0; reg < DBG_MAX_REG_NUM; reg++)
                gdb_regs[reg] = 0;

        /*
         * Copy out GP regs 8 to 14.
         *
         * switch_to() relies on SR.RB toggling, so regs 0->7 are banked
         * and need privileged instructions to get to. The r15 value we
         * fetch from the thread info directly.
         */
        for (reg = GDB_R8; reg < GDB_R15; reg++)
                gdb_regs[reg] = thread_regs->regs[reg];

        gdb_regs[GDB_R15] = p->thread.sp;
        gdb_regs[GDB_PC] = p->thread.pc;

        /*
         * Additional registers we have context for
         */
        gdb_regs[GDB_PR] = thread_regs->pr;
        gdb_regs[GDB_GBR] = thread_regs->gbr;
}

int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
                               char *remcomInBuffer, char *remcomOutBuffer,
                               struct pt_regs *linux_regs)
{
        unsigned long addr;
        char *ptr;

        /* Undo any stepping we may have done */
        undo_single_step(linux_regs);

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

                if (remcomInBuffer[0] == 's') {
                        do_single_step(linux_regs);
                        kgdb_single_step = 1;

                        atomic_set(&kgdb_cpu_doing_single_step,
                                   raw_smp_processor_id());
                }

                return 0;
        }

        /* this means that we do not want to exit from the handler: */
        return -1;
}

unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
{
        if (exception == 60)
                return instruction_pointer(regs) - 2;
        return instruction_pointer(regs);
}

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

/*
 * The primary entry points for the kgdb debug trap table entries.
 */
BUILD_TRAP_HANDLER(singlestep)
{
        unsigned long flags;
        TRAP_HANDLER_DECL;

        local_irq_save(flags);
        regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
        kgdb_handle_exception(0, SIGTRAP, 0, regs);
        local_irq_restore(flags);
}

static int __kgdb_notify(struct die_args *args, unsigned long cmd)
{
        int ret;

        switch (cmd) {
        case DIE_BREAKPOINT:
                /*
                 * This means a user thread is single stepping
                 * a system call which should be ignored
                 */
                if (test_thread_flag(TIF_SINGLESTEP))
                        return NOTIFY_DONE;

                ret = kgdb_handle_exception(args->trapnr & 0xff, args->signr,
                                            args->err, args->regs);
                if (ret)
                        return NOTIFY_DONE;

                break;
        }

        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,

        /*
         * Lowest-prio notifier priority, we want to be notified last:
         */
        .priority       = -INT_MAX,
};

int kgdb_arch_init(void)
{
        return register_die_notifier(&kgdb_notifier);
}

void kgdb_arch_exit(void)
{
        unregister_die_notifier(&kgdb_notifier);
}

const struct kgdb_arch arch_kgdb_ops = {
        /* Breakpoint instruction: trapa #0x3c */
#ifdef CONFIG_CPU_LITTLE_ENDIAN
        .gdb_bpt_instr          = { 0x3c, 0xc3 },
#else
        .gdb_bpt_instr          = { 0xc3, 0x3c },
#endif
};