// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 Rabin Vincent <rabin at rab.in>
 */

#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/errno.h>
#include <linux/highmem.h>
#include <linux/sched.h>
#include <linux/uprobes.h>
#include <linux/notifier.h>

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

#include "../decode.h"
#include "../decode-arm.h"
#include "core.h"

#define UPROBE_TRAP_NR  UINT_MAX

bool is_swbp_insn(uprobe_opcode_t *insn)
{
        return (__mem_to_opcode_arm(*insn) & 0x0fffffff) ==
                (UPROBE_SWBP_ARM_INSN & 0x0fffffff);
}

int set_swbp(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
             unsigned long vaddr)
{
        return uprobe_write_opcode(auprobe, vma, vaddr,
                   __opcode_to_mem_arm(auprobe->bpinsn), true);
}

bool arch_uprobe_ignore(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
        if (!auprobe->asi.insn_check_cc(regs->ARM_cpsr)) {
                regs->ARM_pc += 4;
                return true;
        }

        return false;
}

bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
        probes_opcode_t opcode;

        if (!auprobe->simulate)
                return false;

        opcode = __mem_to_opcode_arm(*(unsigned int *) auprobe->insn);

        auprobe->asi.insn_singlestep(opcode, &auprobe->asi, regs);

        return true;
}

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

        orig_ret_vaddr = regs->ARM_lr;
        /* Replace the return addr with trampoline addr */
        regs->ARM_lr = trampoline_vaddr;
        return orig_ret_vaddr;
}

int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
                             unsigned long addr)
{
        unsigned int insn;
        unsigned int bpinsn;
        enum probes_insn ret;

        /* Thumb not yet support */
        if (addr & 0x3)
                return -EINVAL;

        insn = __mem_to_opcode_arm(*(unsigned int *)auprobe->insn);
        auprobe->ixol[0] = __opcode_to_mem_arm(insn);
        auprobe->ixol[1] = __opcode_to_mem_arm(UPROBE_SS_ARM_INSN);

        ret = arm_probes_decode_insn(insn, &auprobe->asi, false,
                                     uprobes_probes_actions, NULL);
        switch (ret) {
        case INSN_REJECTED:
                return -EINVAL;

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

        case INSN_GOOD:
        default:
                break;
        }

        bpinsn = UPROBE_SWBP_ARM_INSN & 0x0fffffff;
        if (insn >= 0xe0000000)
                bpinsn |= 0xe0000000;  /* Unconditional instruction */
        else
                bpinsn |= insn & 0xf0000000;  /* Copy condition from insn */

        auprobe->bpinsn = bpinsn;

        return 0;
}

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

        preempt_disable();

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

        /* flush caches (dcache/icache) */
        flush_uprobe_xol_access(page, vaddr, dst, len);

        preempt_enable();

        kunmap_local(xol_page_kaddr);
}


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

        if (auprobe->prehandler)
                auprobe->prehandler(auprobe, &utask->autask, regs);

        utask->autask.saved_trap_no = current->thread.trap_no;
        current->thread.trap_no = UPROBE_TRAP_NR;
        regs->ARM_pc = utask->xol_vaddr;

        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.trap_no != UPROBE_TRAP_NR);

        current->thread.trap_no = utask->autask.saved_trap_no;
        regs->ARM_pc = utask->vaddr + 4;

        if (auprobe->posthandler)
                auprobe->posthandler(auprobe, &utask->autask, regs);

        return 0;
}

bool arch_uprobe_xol_was_trapped(struct task_struct *t)
{
        if (t->thread.trap_no != UPROBE_TRAP_NR)
                return true;

        return false;
}

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

        current->thread.trap_no = utask->autask.saved_trap_no;
        instruction_pointer_set(regs, utask->vaddr);
}

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

static int uprobe_trap_handler(struct pt_regs *regs, unsigned int instr)
{
        unsigned long flags;

        local_irq_save(flags);
        instr &= 0x0fffffff;
        if (instr == (UPROBE_SWBP_ARM_INSN & 0x0fffffff))
                uprobe_pre_sstep_notifier(regs);
        else if (instr == (UPROBE_SS_ARM_INSN & 0x0fffffff))
                uprobe_post_sstep_notifier(regs);
        local_irq_restore(flags);

        return 0;
}

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

static struct undef_hook uprobes_arm_break_hook = {
        .instr_mask     = 0x0fffffff,
        .instr_val      = (UPROBE_SWBP_ARM_INSN & 0x0fffffff),
        .cpsr_mask      = (PSR_T_BIT | MODE_MASK),
        .cpsr_val       = USR_MODE,
        .fn             = uprobe_trap_handler,
};

static struct undef_hook uprobes_arm_ss_hook = {
        .instr_mask     = 0x0fffffff,
        .instr_val      = (UPROBE_SS_ARM_INSN & 0x0fffffff),
        .cpsr_mask      = (PSR_T_BIT | MODE_MASK),
        .cpsr_val       = USR_MODE,
        .fn             = uprobe_trap_handler,
};

static int arch_uprobes_init(void)
{
        register_undef_hook(&uprobes_arm_break_hook);
        register_undef_hook(&uprobes_arm_ss_hook);

        return 0;
}
device_initcall(arch_uprobes_init);