// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/sched/signal.h>

#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <as-layout.h>
#include <mem_user.h>
#include <os.h>
#include <skas.h>
#include <kern_util.h>

struct vm_ops {
        struct mm_id *mm_idp;

        int (*mmap)(struct mm_id *mm_idp,
                    unsigned long virt, unsigned long len, int prot,
                    int phys_fd, unsigned long long offset);
        int (*unmap)(struct mm_id *mm_idp,
                     unsigned long virt, unsigned long len);
};

static int kern_map(struct mm_id *mm_idp,
                    unsigned long virt, unsigned long len, int prot,
                    int phys_fd, unsigned long long offset)
{
        /* TODO: Why is executable needed to be always set in the kernel? */
        return os_map_memory((void *)virt, phys_fd, offset, len,
                             prot & UM_PROT_READ, prot & UM_PROT_WRITE,
                             1);
}

static int kern_unmap(struct mm_id *mm_idp,
                      unsigned long virt, unsigned long len)
{
        return os_unmap_memory((void *)virt, len);
}

void report_enomem(void)
{
        printk(KERN_ERR "UML ran out of memory on the host side! "
                        "This can happen due to a memory limitation or "
                        "vm.max_map_count has been reached.\n");
}

static inline int update_pte_range(pmd_t *pmd, unsigned long addr,
                                   unsigned long end,
                                   struct vm_ops *ops)
{
        pte_t *pte;
        int ret = 0;

        pte = pte_offset_kernel(pmd, addr);
        do {
                if (!pte_needsync(*pte))
                        continue;

                if (pte_present(*pte)) {
                        __u64 offset;
                        unsigned long phys = pte_val(*pte) & PAGE_MASK;
                        int fd = phys_mapping(phys, &offset);
                        int r, w, x, prot;

                        r = pte_read(*pte);
                        w = pte_write(*pte);
                        x = pte_exec(*pte);
                        if (!pte_young(*pte)) {
                                r = 0;
                                w = 0;
                        } else if (!pte_dirty(*pte))
                                w = 0;

                        prot = (r ? UM_PROT_READ : 0) |
                               (w ? UM_PROT_WRITE : 0) |
                               (x ? UM_PROT_EXEC : 0);

                        ret = ops->mmap(ops->mm_idp, addr, PAGE_SIZE,
                                        prot, fd, offset);
                } else
                        ret = ops->unmap(ops->mm_idp, addr, PAGE_SIZE);

                *pte = pte_mkuptodate(*pte);
        } while (pte++, addr += PAGE_SIZE, ((addr < end) && !ret));
        return ret;
}

static inline int update_pmd_range(pud_t *pud, unsigned long addr,
                                   unsigned long end,
                                   struct vm_ops *ops)
{
        pmd_t *pmd;
        unsigned long next;
        int ret = 0;

        pmd = pmd_offset(pud, addr);
        do {
                next = pmd_addr_end(addr, end);
                if (!pmd_present(*pmd)) {
                        if (pmd_needsync(*pmd)) {
                                ret = ops->unmap(ops->mm_idp, addr,
                                                 next - addr);
                                pmd_mkuptodate(*pmd);
                        }
                }
                else ret = update_pte_range(pmd, addr, next, ops);
        } while (pmd++, addr = next, ((addr < end) && !ret));
        return ret;
}

static inline int update_pud_range(p4d_t *p4d, unsigned long addr,
                                   unsigned long end,
                                   struct vm_ops *ops)
{
        pud_t *pud;
        unsigned long next;
        int ret = 0;

        pud = pud_offset(p4d, addr);
        do {
                next = pud_addr_end(addr, end);
                if (!pud_present(*pud)) {
                        if (pud_needsync(*pud)) {
                                ret = ops->unmap(ops->mm_idp, addr,
                                                 next - addr);
                                pud_mkuptodate(*pud);
                        }
                }
                else ret = update_pmd_range(pud, addr, next, ops);
        } while (pud++, addr = next, ((addr < end) && !ret));
        return ret;
}

static inline int update_p4d_range(pgd_t *pgd, unsigned long addr,
                                   unsigned long end,
                                   struct vm_ops *ops)
{
        p4d_t *p4d;
        unsigned long next;
        int ret = 0;

        p4d = p4d_offset(pgd, addr);
        do {
                next = p4d_addr_end(addr, end);
                if (!p4d_present(*p4d)) {
                        if (p4d_needsync(*p4d)) {
                                ret = ops->unmap(ops->mm_idp, addr,
                                                 next - addr);
                                p4d_mkuptodate(*p4d);
                        }
                } else
                        ret = update_pud_range(p4d, addr, next, ops);
        } while (p4d++, addr = next, ((addr < end) && !ret));
        return ret;
}

int um_tlb_sync(struct mm_struct *mm)
{
        pgd_t *pgd;
        struct vm_ops ops;
        unsigned long addr, next;
        int ret = 0;

        guard(spinlock_irqsave)(&mm->context.sync_tlb_lock);

        if (mm->context.sync_tlb_range_to == 0)
                return 0;

        ops.mm_idp = &mm->context.id;
        if (mm == &init_mm) {
                ops.mmap = kern_map;
                ops.unmap = kern_unmap;
        } else {
                ops.mmap = map;
                ops.unmap = unmap;
        }

        addr = mm->context.sync_tlb_range_from;
        pgd = pgd_offset(mm, addr);
        do {
                next = pgd_addr_end(addr, mm->context.sync_tlb_range_to);
                if (!pgd_present(*pgd)) {
                        if (pgd_needsync(*pgd)) {
                                ret = ops.unmap(ops.mm_idp, addr,
                                                next - addr);
                                pgd_mkuptodate(*pgd);
                        }
                } else
                        ret = update_p4d_range(pgd, addr, next, &ops);
        } while (pgd++, addr = next,
                 ((addr < mm->context.sync_tlb_range_to) && !ret));

        if (ret == -ENOMEM)
                report_enomem();

        mm->context.sync_tlb_range_from = 0;
        mm->context.sync_tlb_range_to = 0;

        return ret;
}

void flush_tlb_all(void)
{
        /*
         * Don't bother flushing if this address space is about to be
         * destroyed.
         */
        if (atomic_read(&current->mm->mm_users) == 0)
                return;

        flush_tlb_mm(current->mm);
}

void flush_tlb_mm(struct mm_struct *mm)
{
        struct vm_area_struct *vma;
        VMA_ITERATOR(vmi, mm, 0);

        for_each_vma(vmi, vma)
                um_tlb_mark_sync(mm, vma->vm_start, vma->vm_end);
}