// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/arch/m68k/mm/fault.c
 *
 *  Copyright (C) 1995  Hamish Macdonald
 */

#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/uaccess.h>
#include <linux/perf_event.h>

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

#include "fault.h"

extern void die_if_kernel(char *, struct pt_regs *, long);

int send_fault_sig(struct pt_regs *regs)
{
        int signo, si_code;
        void __user *addr;

        signo = current->thread.signo;
        si_code = current->thread.code;
        addr = (void __user *)current->thread.faddr;
        pr_debug("send_fault_sig: %p,%d,%d\n", addr, signo, si_code);

        if (user_mode(regs)) {
                force_sig_fault(signo, si_code, addr);
        } else {
                if (fixup_exception(regs))
                        return -1;

                //if (signo == SIGBUS)
                //      force_sig_fault(si_signo, si_code, addr);

                /*
                 * Oops. The kernel tried to access some bad page. We'll have to
                 * terminate things with extreme prejudice.
                 */
                if ((unsigned long)addr < PAGE_SIZE)
                        pr_alert("Unable to handle kernel NULL pointer dereference");
                else
                        pr_alert("Unable to handle kernel access");
                pr_cont(" at virtual address %p\n", addr);
                die_if_kernel("Oops", regs, 0 /*error_code*/);
                make_task_dead(SIGKILL);
        }

        return 1;
}

/*
 * This routine handles page faults.  It determines the problem, and
 * then passes it off to one of the appropriate routines.
 *
 * error_code:
 *      bit 0 == 0 means no page found, 1 means protection fault
 *      bit 1 == 0 means read, 1 means write
 *
 * If this routine detects a bad access, it returns 1, otherwise it
 * returns 0.
 */
int do_page_fault(struct pt_regs *regs, unsigned long address,
                              unsigned long error_code)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct * vma;
        vm_fault_t fault;
        unsigned int flags = FAULT_FLAG_DEFAULT;

        pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
                regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL);

        /*
         * If we're in an interrupt or have no user
         * context, we must not take the fault..
         */
        if (faulthandler_disabled() || !mm)
                goto no_context;

        if (user_mode(regs))
                flags |= FAULT_FLAG_USER;

        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
retry:
        mmap_read_lock(mm);

        vma = find_vma(mm, address);
        if (!vma)
                goto map_err;
        if (vma->vm_start <= address)
                goto good_area;
        if (!(vma->vm_flags & VM_GROWSDOWN))
                goto map_err;
        if (user_mode(regs)) {
                /* Accessing the stack below usp is always a bug.  The
                   "+ 256" is there due to some instructions doing
                   pre-decrement on the stack and that doesn't show up
                   until later.  */
                if (address + 256 < rdusp())
                        goto map_err;
        }
        vma = expand_stack(mm, address);
        if (!vma)
                goto map_err_nosemaphore;

/*
 * Ok, we have a good vm_area for this memory access, so
 * we can handle it..
 */
good_area:
        pr_debug("do_page_fault: good_area\n");
        switch (error_code & 3) {
                default:        /* 3: write, present */
                        fallthrough;
                case 2:         /* write, not present */
                        if (!(vma->vm_flags & VM_WRITE))
                                goto acc_err;
                        flags |= FAULT_FLAG_WRITE;
                        break;
                case 1:         /* read, present */
                        goto acc_err;
                case 0:         /* read, not present */
                        if (unlikely(!vma_is_accessible(vma)))
                                goto acc_err;
        }

        /*
         * If for any reason at all we couldn't handle the fault,
         * make sure we exit gracefully rather than endlessly redo
         * the fault.
         */

        fault = handle_mm_fault(vma, address, flags, regs);
        pr_debug("handle_mm_fault returns %x\n", fault);

        if (fault_signal_pending(fault, regs)) {
                if (!user_mode(regs))
                        goto no_context;
                return 0;
        }

        /* The fault is fully completed (including releasing mmap lock) */
        if (fault & VM_FAULT_COMPLETED)
                return 0;

        if (unlikely(fault & VM_FAULT_ERROR)) {
                if (fault & VM_FAULT_OOM)
                        goto out_of_memory;
                else if (fault & VM_FAULT_SIGSEGV)
                        goto map_err;
                else if (fault & VM_FAULT_SIGBUS)
                        goto bus_err;
                BUG();
        }

        if (fault & VM_FAULT_RETRY) {
                flags |= FAULT_FLAG_TRIED;

                /*
                 * No need to mmap_read_unlock(mm) as we would
                 * have already released it in __lock_page_or_retry
                 * in mm/filemap.c.
                 */

                goto retry;
        }

        mmap_read_unlock(mm);
        return 0;

/*
 * We ran out of memory, or some other thing happened to us that made
 * us unable to handle the page fault gracefully.
 */
out_of_memory:
        mmap_read_unlock(mm);
        if (!user_mode(regs))
                goto no_context;
        pagefault_out_of_memory();
        return 0;

no_context:
        current->thread.signo = SIGBUS;
        current->thread.faddr = address;
        return send_fault_sig(regs);

bus_err:
        current->thread.signo = SIGBUS;
        current->thread.code = BUS_ADRERR;
        current->thread.faddr = address;
        goto send_sig;

map_err:
        mmap_read_unlock(mm);
map_err_nosemaphore:
        current->thread.signo = SIGSEGV;
        current->thread.code = SEGV_MAPERR;
        current->thread.faddr = address;
        return send_fault_sig(regs);

acc_err:
        current->thread.signo = SIGSEGV;
        current->thread.code = SEGV_ACCERR;
        current->thread.faddr = address;

send_sig:
        mmap_read_unlock(mm);
        return send_fault_sig(regs);
}