// SPDX-License-Identifier: GPL-2.0-only
/*
 * kgdb support for ARC
 *
 * Copyright (C) 2012 Synopsys, Inc. (www.synopsys.com)
 */

#include <linux/kgdb.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <asm/disasm.h>
#include <asm/cacheflush.h>

static void to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs,
                        struct callee_regs *cregs)
{
        int regno;

        for (regno = 0; regno <= 26; regno++)
                gdb_regs[_R0 + regno] = get_reg(regno, kernel_regs, cregs);

        for (regno = 27; regno < GDB_MAX_REGS; regno++)
                gdb_regs[regno] = 0;

        gdb_regs[_FP]           = kernel_regs->fp;
        gdb_regs[__SP]          = kernel_regs->sp;
        gdb_regs[_BLINK]        = kernel_regs->blink;
        gdb_regs[_RET]          = kernel_regs->ret;
        gdb_regs[_STATUS32]     = kernel_regs->status32;
        gdb_regs[_LP_COUNT]     = kernel_regs->lp_count;
        gdb_regs[_LP_END]       = kernel_regs->lp_end;
        gdb_regs[_LP_START]     = kernel_regs->lp_start;
        gdb_regs[_BTA]          = kernel_regs->bta;
        gdb_regs[_STOP_PC]      = kernel_regs->ret;
}

static void from_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs,
                        struct callee_regs *cregs)
{
        int regno;

        for (regno = 0; regno <= 26; regno++)
                set_reg(regno, gdb_regs[regno + _R0], kernel_regs, cregs);

        kernel_regs->fp         = gdb_regs[_FP];
        kernel_regs->sp         = gdb_regs[__SP];
        kernel_regs->blink      = gdb_regs[_BLINK];
        kernel_regs->ret        = gdb_regs[_RET];
        kernel_regs->status32   = gdb_regs[_STATUS32];
        kernel_regs->lp_count   = gdb_regs[_LP_COUNT];
        kernel_regs->lp_end     = gdb_regs[_LP_END];
        kernel_regs->lp_start   = gdb_regs[_LP_START];
        kernel_regs->bta        = gdb_regs[_BTA];
}


void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
{
        to_gdb_regs(gdb_regs, kernel_regs, (struct callee_regs *)
                current->thread.callee_reg);
}

void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
{
        from_gdb_regs(gdb_regs, kernel_regs, (struct callee_regs *)
                current->thread.callee_reg);
}

void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs,
                                 struct task_struct *task)
{
        if (task)
                to_gdb_regs(gdb_regs, task_pt_regs(task),
                        (struct callee_regs *) task->thread.callee_reg);
}

struct single_step_data_t {
        uint16_t opcode[2];
        unsigned long address[2];
        int is_branch;
        int armed;
} single_step_data;

static void undo_single_step(struct pt_regs *regs)
{
        if (single_step_data.armed) {
                int i;

                for (i = 0; i < (single_step_data.is_branch ? 2 : 1); i++) {
                        memcpy((void *) single_step_data.address[i],
                                &single_step_data.opcode[i],
                                BREAK_INSTR_SIZE);

                        flush_icache_range(single_step_data.address[i],
                                single_step_data.address[i] +
                                BREAK_INSTR_SIZE);
                }
                single_step_data.armed = 0;
        }
}

static void place_trap(unsigned long address, void *save)
{
        memcpy(save, (void *) address, BREAK_INSTR_SIZE);
        memcpy((void *) address, &arch_kgdb_ops.gdb_bpt_instr,
                BREAK_INSTR_SIZE);
        flush_icache_range(address, address + BREAK_INSTR_SIZE);
}

static void do_single_step(struct pt_regs *regs)
{
        single_step_data.is_branch = disasm_next_pc((unsigned long)
                regs->ret, regs, (struct callee_regs *)
                current->thread.callee_reg,
                &single_step_data.address[0],
                &single_step_data.address[1]);

        place_trap(single_step_data.address[0], &single_step_data.opcode[0]);

        if (single_step_data.is_branch) {
                place_trap(single_step_data.address[1],
                        &single_step_data.opcode[1]);
        }

        single_step_data.armed++;
}

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

        undo_single_step(regs);

        switch (remcomInBuffer[0]) {
        case 's':
        case 'c':
                ptr = &remcomInBuffer[1];
                if (kgdb_hex2long(&ptr, &addr))
                        regs->ret = addr;
                fallthrough;

        case 'D':
        case 'k':
                atomic_set(&kgdb_cpu_doing_single_step, -1);

                if (remcomInBuffer[0] == 's') {
                        do_single_step(regs);
                        atomic_set(&kgdb_cpu_doing_single_step,
                                   smp_processor_id());
                }

                return 0;
        }
        return -1;
}

int kgdb_arch_init(void)
{
        single_step_data.armed = 0;
        return 0;
}

void kgdb_trap(struct pt_regs *regs)
{
        /* trap_s 3 is used for breakpoints that overwrite existing
         * instructions, while trap_s 4 is used for compiled breakpoints.
         *
         * with trap_s 3 breakpoints the original instruction needs to be
         * restored and continuation needs to start at the location of the
         * breakpoint.
         *
         * with trap_s 4 (compiled) breakpoints, continuation needs to
         * start after the breakpoint.
         */
        if (regs->ecr.param == 3)
                instruction_pointer(regs) -= BREAK_INSTR_SIZE;

        kgdb_handle_exception(1, SIGTRAP, 0, regs);
}

void kgdb_arch_exit(void)
{
}

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

void kgdb_call_nmi_hook(void *ignored)
{
        /* Default implementation passes get_irq_regs() but we don't */
        kgdb_nmicallback(raw_smp_processor_id(), NULL);
}

const struct kgdb_arch arch_kgdb_ops = {
        /* breakpoint instruction: TRAP_S 0x3 */
#ifdef CONFIG_CPU_BIG_ENDIAN
        .gdb_bpt_instr          = {0x78, 0x7e},
#else
        .gdb_bpt_instr          = {0x7e, 0x78},
#endif
};