// SPDX-License-Identifier: GPL-2.0
/*
 * Kernel probes (kprobes) for SuperH
 *
 * Copyright (C) 2007 Chris Smith <chris.smith@st.com>
 * Copyright (C) 2006 Lineo Solutions, Inc.
 */
#include <linux/kprobes.h>
#include <linux/extable.h>
#include <linux/ptrace.h>
#include <linux/preempt.h>
#include <linux/kdebug.h>
#include <linux/slab.h>
#include <asm/cacheflush.h>
#include <linux/uaccess.h>

DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

static DEFINE_PER_CPU(struct kprobe, saved_current_opcode);
static DEFINE_PER_CPU(struct kprobe, saved_next_opcode);
static DEFINE_PER_CPU(struct kprobe, saved_next_opcode2);

#define OPCODE_JMP(x)   (((x) & 0xF0FF) == 0x402b)
#define OPCODE_JSR(x)   (((x) & 0xF0FF) == 0x400b)
#define OPCODE_BRA(x)   (((x) & 0xF000) == 0xa000)
#define OPCODE_BRAF(x)  (((x) & 0xF0FF) == 0x0023)
#define OPCODE_BSR(x)   (((x) & 0xF000) == 0xb000)
#define OPCODE_BSRF(x)  (((x) & 0xF0FF) == 0x0003)

#define OPCODE_BF_S(x)  (((x) & 0xFF00) == 0x8f00)
#define OPCODE_BT_S(x)  (((x) & 0xFF00) == 0x8d00)

#define OPCODE_BF(x)    (((x) & 0xFF00) == 0x8b00)
#define OPCODE_BT(x)    (((x) & 0xFF00) == 0x8900)

#define OPCODE_RTS(x)   (((x) & 0x000F) == 0x000b)
#define OPCODE_RTE(x)   (((x) & 0xFFFF) == 0x002b)

int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
        kprobe_opcode_t opcode = *p->addr;

        if (OPCODE_RTE(opcode))
                return -EFAULT; /* Bad breakpoint */

        memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
        p->opcode = opcode;

        return 0;
}

void __kprobes arch_arm_kprobe(struct kprobe *p)
{
        *p->addr = BREAKPOINT_INSTRUCTION;
        flush_icache_range((unsigned long)p->addr,
                           (unsigned long)p->addr + sizeof(kprobe_opcode_t));
}

void __kprobes arch_disarm_kprobe(struct kprobe *p)
{
        *p->addr = p->opcode;
        flush_icache_range((unsigned long)p->addr,
                           (unsigned long)p->addr + sizeof(kprobe_opcode_t));
}

int __kprobes arch_trampoline_kprobe(struct kprobe *p)
{
        if (*p->addr == BREAKPOINT_INSTRUCTION)
                return 1;

        return 0;
}

/**
 * If an illegal slot instruction exception occurs for an address
 * containing a kprobe, remove the probe.
 *
 * Returns 0 if the exception was handled successfully, 1 otherwise.
 */
int __kprobes kprobe_handle_illslot(unsigned long pc)
{
        struct kprobe *p = get_kprobe((kprobe_opcode_t *) pc + 1);

        if (p != NULL) {
                printk("Warning: removing kprobe from delay slot: 0x%.8x\n",
                       (unsigned int)pc + 2);
                unregister_kprobe(p);
                return 0;
        }

        return 1;
}

void __kprobes arch_remove_kprobe(struct kprobe *p)
{
        struct kprobe *saved = this_cpu_ptr(&saved_next_opcode);

        if (saved->addr) {
                arch_disarm_kprobe(p);
                arch_disarm_kprobe(saved);

                saved->addr = NULL;
                saved->opcode = 0;

                saved = this_cpu_ptr(&saved_next_opcode2);
                if (saved->addr) {
                        arch_disarm_kprobe(saved);

                        saved->addr = NULL;
                        saved->opcode = 0;
                }
        }
}

static void __kprobes save_previous_kprobe(struct kprobe_ctlblk *kcb)
{
        kcb->prev_kprobe.kp = kprobe_running();
        kcb->prev_kprobe.status = kcb->kprobe_status;
}

static void __kprobes restore_previous_kprobe(struct kprobe_ctlblk *kcb)
{
        __this_cpu_write(current_kprobe, kcb->prev_kprobe.kp);
        kcb->kprobe_status = kcb->prev_kprobe.status;
}

static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
                                         struct kprobe_ctlblk *kcb)
{
        __this_cpu_write(current_kprobe, p);
}

/*
 * Singlestep is implemented by disabling the current kprobe and setting one
 * on the next instruction, following branches. Two probes are set if the
 * branch is conditional.
 */
static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{
        __this_cpu_write(saved_current_opcode.addr, (kprobe_opcode_t *)regs->pc);

        if (p != NULL) {
                struct kprobe *op1, *op2;

                arch_disarm_kprobe(p);

                op1 = this_cpu_ptr(&saved_next_opcode);
                op2 = this_cpu_ptr(&saved_next_opcode2);

                if (OPCODE_JSR(p->opcode) || OPCODE_JMP(p->opcode)) {
                        unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
                        op1->addr = (kprobe_opcode_t *) regs->regs[reg_nr];
                } else if (OPCODE_BRA(p->opcode) || OPCODE_BSR(p->opcode)) {
                        unsigned long disp = (p->opcode & 0x0FFF);
                        op1->addr =
                            (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);

                } else if (OPCODE_BRAF(p->opcode) || OPCODE_BSRF(p->opcode)) {
                        unsigned int reg_nr = ((p->opcode >> 8) & 0x000F);
                        op1->addr =
                            (kprobe_opcode_t *) (regs->pc + 4 +
                                                 regs->regs[reg_nr]);

                } else if (OPCODE_RTS(p->opcode)) {
                        op1->addr = (kprobe_opcode_t *) regs->pr;

                } else if (OPCODE_BF(p->opcode) || OPCODE_BT(p->opcode)) {
                        unsigned long disp = (p->opcode & 0x00FF);
                        /* case 1 */
                        op1->addr = p->addr + 1;
                        /* case 2 */
                        op2->addr =
                            (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
                        op2->opcode = *(op2->addr);
                        arch_arm_kprobe(op2);

                } else if (OPCODE_BF_S(p->opcode) || OPCODE_BT_S(p->opcode)) {
                        unsigned long disp = (p->opcode & 0x00FF);
                        /* case 1 */
                        op1->addr = p->addr + 2;
                        /* case 2 */
                        op2->addr =
                            (kprobe_opcode_t *) (regs->pc + 4 + disp * 2);
                        op2->opcode = *(op2->addr);
                        arch_arm_kprobe(op2);

                } else {
                        op1->addr = p->addr + 1;
                }

                op1->opcode = *(op1->addr);
                arch_arm_kprobe(op1);
        }
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
                                      struct pt_regs *regs)
{
        ri->ret_addr = (kprobe_opcode_t *) regs->pr;
        ri->fp = NULL;

        /* Replace the return addr with trampoline addr */
        regs->pr = (unsigned long)__kretprobe_trampoline;
}

static int __kprobes kprobe_handler(struct pt_regs *regs)
{
        struct kprobe *p;
        int ret = 0;
        kprobe_opcode_t *addr = NULL;
        struct kprobe_ctlblk *kcb;

        /*
         * We don't want to be preempted for the entire
         * duration of kprobe processing
         */
        preempt_disable();
        kcb = get_kprobe_ctlblk();

        addr = (kprobe_opcode_t *) (regs->pc);

        /* Check we're not actually recursing */
        if (kprobe_running()) {
                p = get_kprobe(addr);
                if (p) {
                        if (kcb->kprobe_status == KPROBE_HIT_SS &&
                            *p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
                                goto no_kprobe;
                        }
                        /* We have reentered the kprobe_handler(), since
                         * another probe was hit while within the handler.
                         * We here save the original kprobes variables and
                         * just single step on the instruction of the new probe
                         * without calling any user handlers.
                         */
                        save_previous_kprobe(kcb);
                        set_current_kprobe(p, regs, kcb);
                        kprobes_inc_nmissed_count(p);
                        prepare_singlestep(p, regs);
                        kcb->kprobe_status = KPROBE_REENTER;
                        return 1;
                }
                goto no_kprobe;
        }

        p = get_kprobe(addr);
        if (!p) {
                /* Not one of ours: let kernel handle it */
                if (*addr != BREAKPOINT_INSTRUCTION) {
                        /*
                         * The breakpoint instruction was removed right
                         * after we hit it. Another cpu has removed
                         * either a probepoint or a debugger breakpoint
                         * at this address. In either case, no further
                         * handling of this interrupt is appropriate.
                         */
                        ret = 1;
                }

                goto no_kprobe;
        }

        set_current_kprobe(p, regs, kcb);
        kcb->kprobe_status = KPROBE_HIT_ACTIVE;

        if (p->pre_handler && p->pre_handler(p, regs)) {
                /* handler has already set things up, so skip ss setup */
                reset_current_kprobe();
                preempt_enable_no_resched();
                return 1;
        }

        prepare_singlestep(p, regs);
        kcb->kprobe_status = KPROBE_HIT_SS;
        return 1;

no_kprobe:
        preempt_enable_no_resched();
        return ret;
}

/*
 * For function-return probes, init_kprobes() establishes a probepoint
 * here. When a retprobed function returns, this probe is hit and
 * trampoline_probe_handler() runs, calling the kretprobe's handler.
 */
static void __used kretprobe_trampoline_holder(void)
{
        asm volatile (".globl __kretprobe_trampoline\n"
                      "__kretprobe_trampoline:\n\t"
                      "nop\n");
}

/*
 * Called when we hit the probe point at __kretprobe_trampoline
 */
static int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
{
        regs->pc = __kretprobe_trampoline_handler(regs, NULL);

        return 1;
}

static int __kprobes post_kprobe_handler(struct pt_regs *regs)
{
        struct kprobe *cur = kprobe_running();
        struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
        kprobe_opcode_t *addr = NULL;
        struct kprobe *p = NULL;

        if (!cur)
                return 0;

        if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
                kcb->kprobe_status = KPROBE_HIT_SSDONE;
                cur->post_handler(cur, regs, 0);
        }

        p = this_cpu_ptr(&saved_next_opcode);
        if (p->addr) {
                arch_disarm_kprobe(p);
                p->addr = NULL;
                p->opcode = 0;

                addr = __this_cpu_read(saved_current_opcode.addr);
                __this_cpu_write(saved_current_opcode.addr, NULL);

                p = get_kprobe(addr);
                arch_arm_kprobe(p);

                p = this_cpu_ptr(&saved_next_opcode2);
                if (p->addr) {
                        arch_disarm_kprobe(p);
                        p->addr = NULL;
                        p->opcode = 0;
                }
        }

        /* Restore back the original saved kprobes variables and continue. */
        if (kcb->kprobe_status == KPROBE_REENTER) {
                restore_previous_kprobe(kcb);
                goto out;
        }

        reset_current_kprobe();

out:
        preempt_enable_no_resched();

        return 1;
}

int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
{
        struct kprobe *cur = kprobe_running();
        struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
        const struct exception_table_entry *entry;

        switch (kcb->kprobe_status) {
        case KPROBE_HIT_SS:
        case KPROBE_REENTER:
                /*
                 * We are here because the instruction being single
                 * stepped caused a page fault. We reset the current
                 * kprobe, point the pc back to the probe address
                 * and allow the page fault handler to continue as a
                 * normal page fault.
                 */
                regs->pc = (unsigned long)cur->addr;
                if (kcb->kprobe_status == KPROBE_REENTER)
                        restore_previous_kprobe(kcb);
                else
                        reset_current_kprobe();
                preempt_enable_no_resched();
                break;
        case KPROBE_HIT_ACTIVE:
        case KPROBE_HIT_SSDONE:
                /*
                 * In case the user-specified fault handler returned
                 * zero, try to fix up.
                 */
                if ((entry = search_exception_tables(regs->pc)) != NULL) {
                        regs->pc = entry->fixup;
                        return 1;
                }

                /*
                 * fixup_exception() could not handle it,
                 * Let do_page_fault() fix it.
                 */
                break;
        default:
                break;
        }

        return 0;
}

/*
 * Wrapper routine to for handling exceptions.
 */
int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
                                       unsigned long val, void *data)
{
        struct die_args *args = (struct die_args *)data;
        int ret = NOTIFY_DONE;
        struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();

        if (val == DIE_TRAP &&
            args->trapnr == (BREAKPOINT_INSTRUCTION & 0xff)) {
                if (!kprobe_running()) {
                        if (kprobe_handler(args->regs)) {
                                ret = NOTIFY_STOP;
                        } else {
                                /* Not a kprobe trap */
                                ret = NOTIFY_DONE;
                        }
                } else {
                        if ((kcb->kprobe_status == KPROBE_HIT_SS) ||
                            (kcb->kprobe_status == KPROBE_REENTER)) {
                                if (post_kprobe_handler(args->regs))
                                        ret = NOTIFY_STOP;
                        } else {
                                if (kprobe_handler(args->regs))
                                        ret = NOTIFY_STOP;
                        }
                }
        }

        return ret;
}

static struct kprobe trampoline_p = {
        .addr = (kprobe_opcode_t *)&__kretprobe_trampoline,
        .pre_handler = trampoline_probe_handler
};

int __init arch_init_kprobes(void)
{
        return register_kprobe(&trampoline_p);
}