// SPDX-License-Identifier: GPL-2.0
#include <linux/highmem.h>
#include <linux/kdebug.h>
#include <linux/types.h>
#include <linux/notifier.h>
#include <linux/sched.h>
#include <linux/uprobes.h>

#include <asm/branch.h>
#include <asm/cpu-features.h>
#include <asm/ptrace.h>

#include "probes-common.h"

static inline int insn_has_delay_slot(const union mips_instruction insn)
{
        return __insn_has_delay_slot(insn);
}

/**
 * arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
 * @mm: the probed address space.
 * @arch_uprobe: the probepoint information.
 * @addr: virtual address at which to install the probepoint
 * Return 0 on success or a -ve number on error.
 */
int arch_uprobe_analyze_insn(struct arch_uprobe *aup,
        struct mm_struct *mm, unsigned long addr)
{
        union mips_instruction inst;

        /*
         * For the time being this also blocks attempts to use uprobes with
         * MIPS16 and microMIPS.
         */
        if (addr & 0x03)
                return -EINVAL;

        inst.word = aup->insn[0];

        if (__insn_is_compact_branch(inst)) {
                pr_notice("Uprobes for compact branches are not supported\n");
                return -EINVAL;
        }

        aup->ixol[0] = aup->insn[insn_has_delay_slot(inst)];
        aup->ixol[1] = UPROBE_BRK_UPROBE_XOL;           /* NOP  */

        return 0;
}

/**
 * is_trap_insn - check if the instruction is a trap variant
 * @insn: instruction to be checked.
 * Returns true if @insn is a trap variant.
 *
 * This definition overrides the weak definition in kernel/events/uprobes.c.
 * and is needed for the case where an architecture has multiple trap
 * instructions (like PowerPC or MIPS).  We treat BREAK just like the more
 * modern conditional trap instructions.
 */
bool is_trap_insn(uprobe_opcode_t *insn)
{
        union mips_instruction inst;

        inst.word = *insn;

        switch (inst.i_format.opcode) {
        case spec_op:
                switch (inst.r_format.func) {
                case break_op:
                case teq_op:
                case tge_op:
                case tgeu_op:
                case tlt_op:
                case tltu_op:
                case tne_op:
                        return true;
                }
                break;

        case bcond_op:  /* Yes, really ...  */
                switch (inst.u_format.rt) {
                case teqi_op:
                case tgei_op:
                case tgeiu_op:
                case tlti_op:
                case tltiu_op:
                case tnei_op:
                        return true;
                }
                break;
        }

        return false;
}

#define UPROBE_TRAP_NR  ULONG_MAX

/*
 * arch_uprobe_pre_xol - prepare to execute out of line.
 * @auprobe: the probepoint information.
 * @regs: reflects the saved user state of current task.
 */
int arch_uprobe_pre_xol(struct arch_uprobe *aup, struct pt_regs *regs)
{
        struct uprobe_task *utask = current->utask;

        /*
         * Now find the EPC where to resume after the breakpoint has been
         * dealt with.  This may require emulation of a branch.
         */
        aup->resume_epc = regs->cp0_epc + 4;
        if (insn_has_delay_slot((union mips_instruction) aup->insn[0])) {
                __compute_return_epc_for_insn(regs,
                        (union mips_instruction) aup->insn[0]);
                aup->resume_epc = regs->cp0_epc;
        }
        utask->autask.saved_trap_nr = current->thread.trap_nr;
        current->thread.trap_nr = UPROBE_TRAP_NR;
        regs->cp0_epc = current->utask->xol_vaddr;

        return 0;
}

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

        current->thread.trap_nr = utask->autask.saved_trap_nr;
        regs->cp0_epc = aup->resume_epc;

        return 0;
}

/*
 * If xol insn itself traps and generates a signal(Say,
 * SIGILL/SIGSEGV/etc), then detect the case where a singlestepped
 * instruction jumps back to its own address. It is assumed that anything
 * like do_page_fault/do_trap/etc sets thread.trap_nr != -1.
 *
 * arch_uprobe_pre_xol/arch_uprobe_post_xol save/restore thread.trap_nr,
 * arch_uprobe_xol_was_trapped() simply checks that ->trap_nr is not equal to
 * UPROBE_TRAP_NR == -1 set by arch_uprobe_pre_xol().
 */
bool arch_uprobe_xol_was_trapped(struct task_struct *tsk)
{
        if (tsk->thread.trap_nr != UPROBE_TRAP_NR)
                return true;

        return false;
}

int arch_uprobe_exception_notify(struct notifier_block *self,
        unsigned long val, void *data)
{
        struct die_args *args = data;
        struct pt_regs *regs = args->regs;

        /* regs == NULL is a kernel bug */
        if (WARN_ON(!regs))
                return NOTIFY_DONE;

        /* We are only interested in userspace traps */
        if (!user_mode(regs))
                return NOTIFY_DONE;

        switch (val) {
        case DIE_UPROBE:
                if (uprobe_pre_sstep_notifier(regs))
                        return NOTIFY_STOP;
                break;
        case DIE_UPROBE_XOL:
                if (uprobe_post_sstep_notifier(regs))
                        return NOTIFY_STOP;
                break;
        default:
                break;
        }

        return 0;
}

/*
 * This function gets called when XOL instruction either gets trapped or
 * the thread has a fatal signal. Reset the instruction pointer to its
 * probed address for the potential restart or for post mortem analysis.
 */
void arch_uprobe_abort_xol(struct arch_uprobe *aup,
        struct pt_regs *regs)
{
        struct uprobe_task *utask = current->utask;

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

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

        ra = regs->regs[31];

        /* Replace the return address with the trampoline address */
        regs->regs[31] = trampoline_vaddr;

        return ra;
}

void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
                                  void *src, unsigned long len)
{
        unsigned long kaddr, kstart;

        /* Initialize the slot */
        kaddr = (unsigned long)kmap_local_page(page);
        kstart = kaddr + (vaddr & ~PAGE_MASK);
        memcpy((void *)kstart, src, len);
        flush_icache_range(kstart, kstart + len);
        kunmap_local((void *)kaddr);
}

/**
 * uprobe_get_swbp_addr - compute address of swbp given post-swbp regs
 * @regs: Reflects the saved state of the task after it has hit a breakpoint
 * instruction.
 * Return the address of the breakpoint instruction.
 *
 * This overrides the weak version in kernel/events/uprobes.c.
 */
unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
{
        return instruction_pointer(regs);
}

/*
 * See if the instruction can be emulated.
 * Returns true if instruction was emulated, false otherwise.
 *
 * For now we always emulate so this function just returns false.
 */
bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
        return false;
}