// SPDX-License-Identifier: GPL-2.0-only
/* Page Fault Handling for ARC (TLB Miss / ProtV)
 *
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 */

#include <linux/signal.h>
#include <linux/interrupt.h>
#include <linux/sched/signal.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/uaccess.h>
#include <linux/kdebug.h>
#include <linux/perf_event.h>
#include <linux/mm_types.h>
#include <asm/pgalloc.h>
#include <asm/mmu.h>

/*
 * kernel virtual address is required to implement vmalloc/pkmap/fixmap
 * Refer to asm/processor.h for System Memory Map
 *
 * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
 * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
 */
noinline static int handle_kernel_vaddr_fault(unsigned long address)
{
        /*
         * Synchronize this task's top level page-table
         * with the 'reference' page table.
         */
        pgd_t *pgd, *pgd_k;
        pud_t *pud, *pud_k;
        pmd_t *pmd, *pmd_k;

        pgd = pgd_offset_fast(current->active_mm, address);
        pgd_k = pgd_offset_k(address);

        if (!pgd_present(*pgd_k))
                goto bad_area;

        pud = pud_offset(pgd, address);
        pud_k = pud_offset(pgd_k, address);
        if (!pud_present(*pud_k))
                goto bad_area;

        pmd = pmd_offset(pud, address);
        pmd_k = pmd_offset(pud_k, address);
        if (!pmd_present(*pmd_k))
                goto bad_area;

        set_pmd(pmd, *pmd_k);

        /* XXX: create the TLB entry here */
        return 0;

bad_area:
        return 1;
}

void do_page_fault(unsigned long address, struct pt_regs *regs)
{
        struct vm_area_struct *vma = NULL;
        struct task_struct *tsk = current;
        struct mm_struct *mm = tsk->mm;
        int sig, si_code = SEGV_MAPERR;
        unsigned int write = 0, exec = 0, mask;
        vm_fault_t fault = VM_FAULT_SIGSEGV;    /* handle_mm_fault() output */
        unsigned int flags;                     /* handle_mm_fault() input */

        /*
         * NOTE! We MUST NOT take any locks for this case. We may
         * be in an interrupt or a critical region, and should
         * only copy the information from the master page table,
         * nothing more.
         */
        if (address >= VMALLOC_START && !user_mode(regs)) {
                if (unlikely(handle_kernel_vaddr_fault(address)))
                        goto no_context;
                else
                        return;
        }

        /*
         * 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 (regs->ecr_cause & ECR_C_PROTV_STORE)        /* ST/EX */
                write = 1;
        else if ((regs->ecr_vec == ECR_V_PROTV) &&
                 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
                exec = 1;

        flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
        if (user_mode(regs))
                flags |= FAULT_FLAG_USER;
        if (write)
                flags |= FAULT_FLAG_WRITE;

retry:
        down_read(&mm->mmap_sem);

        vma = find_vma(mm, address);
        if (!vma)
                goto bad_area;
        if (unlikely(address < vma->vm_start)) {
                if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address))
                        goto bad_area;
        }

        /*
         * vm_area is good, now check permissions for this memory access
         */
        mask = VM_READ;
        if (write)
                mask = VM_WRITE;
        if (exec)
                mask = VM_EXEC;

        if (!(vma->vm_flags & mask)) {
                si_code = SEGV_ACCERR;
                goto bad_area;
        }

        fault = handle_mm_fault(vma, address, flags);

        /*
         * Fault retry nuances
         */
        if (unlikely(fault & VM_FAULT_RETRY)) {

                /*
                 * If fault needs to be retried, handle any pending signals
                 * first (by returning to user mode).
                 * mmap_sem already relinquished by core mm for RETRY case
                 */
                if (fatal_signal_pending(current)) {
                        if (!user_mode(regs))
                                goto no_context;
                        return;
                }
                /*
                 * retry state machine
                 */
                if (flags & FAULT_FLAG_ALLOW_RETRY) {
                        flags &= ~FAULT_FLAG_ALLOW_RETRY;
                        flags |= FAULT_FLAG_TRIED;
                        goto retry;
                }
        }

bad_area:
        up_read(&mm->mmap_sem);

        /*
         * Major/minor page fault accounting
         * (in case of retry we only land here once)
         */
        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);

        if (likely(!(fault & VM_FAULT_ERROR))) {
                if (fault & VM_FAULT_MAJOR) {
                        tsk->maj_flt++;
                        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
                                      regs, address);
                } else {
                        tsk->min_flt++;
                        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
                                      regs, address);
                }

                /* Normal return path: fault Handled Gracefully */
                return;
        }

        if (!user_mode(regs))
                goto no_context;

        if (fault & VM_FAULT_OOM) {
                pagefault_out_of_memory();
                return;
        }

        if (fault & VM_FAULT_SIGBUS) {
                sig = SIGBUS;
                si_code = BUS_ADRERR;
        }
        else {
                sig = SIGSEGV;
        }

        tsk->thread.fault_address = address;
        force_sig_fault(sig, si_code, (void __user *)address);
        return;

no_context:
        if (fixup_exception(regs))
                return;

        die("Oops", regs, address);
}