// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2014-2016 Pratyush Anand <panand@redhat.com>
 */
#include <linux/highmem.h>
#include <linux/ptrace.h>
#include <linux/uprobes.h>
#include <asm/cacheflush.h>

#include "decode-insn.h"

#define UPROBE_INV_FAULT_CODE   UINT_MAX

void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
                void *src, unsigned long len)
{
        void *xol_page_kaddr = kmap_atomic(page);
        void *dst = xol_page_kaddr + (vaddr & ~PAGE_MASK);

        /* Initialize the slot */
        memcpy(dst, src, len);

        /* flush caches (dcache/icache) */
        sync_icache_aliases((unsigned long)dst, (unsigned long)dst + len);

        kunmap_atomic(xol_page_kaddr);
}

unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
{
        return instruction_pointer(regs);
}

int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
                unsigned long addr)
{
        probe_opcode_t insn;

        /* TODO: Currently we do not support AARCH32 instruction probing */
        if (mm->context.flags & MMCF_AARCH32)
                return -EOPNOTSUPP;
        else if (!IS_ALIGNED(addr, AARCH64_INSN_SIZE))
                return -EINVAL;

        insn = *(probe_opcode_t *)(&auprobe->insn[0]);

        switch (arm_probe_decode_insn(insn, &auprobe->api)) {
        case INSN_REJECTED:
                return -EINVAL;

        case INSN_GOOD_NO_SLOT:
                auprobe->simulate = true;
                break;

        default:
                break;
        }

        return 0;
}

int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
        struct uprobe_task *utask = current->utask;

        /* Initialize with an invalid fault code to detect if ol insn trapped */
        current->thread.fault_code = UPROBE_INV_FAULT_CODE;

        /* Instruction points to execute ol */
        instruction_pointer_set(regs, utask->xol_vaddr);

        user_enable_single_step(current);

        return 0;
}

int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
        struct uprobe_task *utask = current->utask;

        WARN_ON_ONCE(current->thread.fault_code != UPROBE_INV_FAULT_CODE);

        /* Instruction points to execute next to breakpoint address */
        instruction_pointer_set(regs, utask->vaddr + 4);

        user_disable_single_step(current);

        return 0;
}
bool arch_uprobe_xol_was_trapped(struct task_struct *t)
{
        /*
         * Between arch_uprobe_pre_xol and arch_uprobe_post_xol, if an xol
         * insn itself is trapped, then detect the case with the help of
         * invalid fault code which is being set in arch_uprobe_pre_xol
         */
        if (t->thread.fault_code != UPROBE_INV_FAULT_CODE)
                return true;

        return false;
}

bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
        probe_opcode_t insn;
        unsigned long addr;

        if (!auprobe->simulate)
                return false;

        insn = *(probe_opcode_t *)(&auprobe->insn[0]);
        addr = instruction_pointer(regs);

        if (auprobe->api.handler)
                auprobe->api.handler(insn, addr, regs);

        return true;
}

void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
        struct uprobe_task *utask = current->utask;

        /*
         * Task has received a fatal signal, so reset back to probbed
         * address.
         */
        instruction_pointer_set(regs, utask->vaddr);

        user_disable_single_step(current);
}

bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
                struct pt_regs *regs)
{
        /*
         * If a simple branch instruction (B) was called for retprobed
         * assembly label then return true even when regs->sp and ret->stack
         * are same. It will ensure that cleanup and reporting of return
         * instances corresponding to callee label is done when
         * handle_trampoline for called function is executed.
         */
        if (ctx == RP_CHECK_CHAIN_CALL)
                return regs->sp <= ret->stack;
        else
                return regs->sp < ret->stack;
}

unsigned long
arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
                                  struct pt_regs *regs)
{
        unsigned long orig_ret_vaddr;

        orig_ret_vaddr = procedure_link_pointer(regs);
        /* Replace the return addr with trampoline addr */
        procedure_link_pointer_set(regs, trampoline_vaddr);

        return orig_ret_vaddr;
}

int arch_uprobe_exception_notify(struct notifier_block *self,
                                 unsigned long val, void *data)
{
        return NOTIFY_DONE;
}

static int uprobe_breakpoint_handler(struct pt_regs *regs,
                unsigned int esr)
{
        if (uprobe_pre_sstep_notifier(regs))
                return DBG_HOOK_HANDLED;

        return DBG_HOOK_ERROR;
}

static int uprobe_single_step_handler(struct pt_regs *regs,
                unsigned int esr)
{
        struct uprobe_task *utask = current->utask;

        WARN_ON(utask && (instruction_pointer(regs) != utask->xol_vaddr + 4));
        if (uprobe_post_sstep_notifier(regs))
                return DBG_HOOK_HANDLED;

        return DBG_HOOK_ERROR;
}

/* uprobe breakpoint handler hook */
static struct break_hook uprobes_break_hook = {
        .imm = UPROBES_BRK_IMM,
        .fn = uprobe_breakpoint_handler,
};

/* uprobe single step handler hook */
static struct step_hook uprobes_step_hook = {
        .fn = uprobe_single_step_handler,
};

static int __init arch_init_uprobes(void)
{
        register_user_break_hook(&uprobes_break_hook);
        register_user_step_hook(&uprobes_step_hook);

        return 0;
}

device_initcall(arch_init_uprobes);