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

#include <linux/stddef.h>
#include <linux/module.h>
#include <linux/memblock.h>
#include <linux/highmem.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <asm/fixmap.h>
#include <asm/page.h>
#include <as-layout.h>
#include <init.h>
#include <kern.h>
#include <kern_util.h>
#include <mem_user.h>
#include <os.h>

/* allocated in paging_init, zeroed in mem_init, and unchanged thereafter */
unsigned long *empty_zero_page = NULL;
EXPORT_SYMBOL(empty_zero_page);

/*
 * Initialized during boot, and readonly for initializing page tables
 * afterwards
 */
pgd_t swapper_pg_dir[PTRS_PER_PGD];

/* Initialized at boot time, and readonly after that */
unsigned long long highmem;
EXPORT_SYMBOL(highmem);
int kmalloc_ok = 0;

/* Used during early boot */
static unsigned long brk_end;

void __init mem_init(void)
{
        /* clear the zero-page */
        memset(empty_zero_page, 0, PAGE_SIZE);

        /* Map in the area just after the brk now that kmalloc is about
         * to be turned on.
         */
        brk_end = (unsigned long) UML_ROUND_UP(sbrk(0));
        map_memory(brk_end, __pa(brk_end), uml_reserved - brk_end, 1, 1, 0);
        memblock_free(__pa(brk_end), uml_reserved - brk_end);
        uml_reserved = brk_end;

        /* this will put all low memory onto the freelists */
        memblock_free_all();
        max_low_pfn = totalram_pages();
        max_pfn = max_low_pfn;
        mem_init_print_info(NULL);
        kmalloc_ok = 1;
}

/*
 * Create a page table and place a pointer to it in a middle page
 * directory entry.
 */
static void __init one_page_table_init(pmd_t *pmd)
{
        if (pmd_none(*pmd)) {
                pte_t *pte = (pte_t *) memblock_alloc_low(PAGE_SIZE,
                                                          PAGE_SIZE);
                if (!pte)
                        panic("%s: Failed to allocate %lu bytes align=%lx\n",
                              __func__, PAGE_SIZE, PAGE_SIZE);

                set_pmd(pmd, __pmd(_KERNPG_TABLE +
                                           (unsigned long) __pa(pte)));
                if (pte != pte_offset_kernel(pmd, 0))
                        BUG();
        }
}

static void __init one_md_table_init(pud_t *pud)
{
#ifdef CONFIG_3_LEVEL_PGTABLES
        pmd_t *pmd_table = (pmd_t *) memblock_alloc_low(PAGE_SIZE, PAGE_SIZE);
        if (!pmd_table)
                panic("%s: Failed to allocate %lu bytes align=%lx\n",
                      __func__, PAGE_SIZE, PAGE_SIZE);

        set_pud(pud, __pud(_KERNPG_TABLE + (unsigned long) __pa(pmd_table)));
        if (pmd_table != pmd_offset(pud, 0))
                BUG();
#endif
}

static void __init fixrange_init(unsigned long start, unsigned long end,
                                 pgd_t *pgd_base)
{
        pgd_t *pgd;
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;
        int i, j;
        unsigned long vaddr;

        vaddr = start;
        i = pgd_index(vaddr);
        j = pmd_index(vaddr);
        pgd = pgd_base + i;

        for ( ; (i < PTRS_PER_PGD) && (vaddr < end); pgd++, i++) {
                p4d = p4d_offset(pgd, vaddr);
                pud = pud_offset(p4d, vaddr);
                if (pud_none(*pud))
                        one_md_table_init(pud);
                pmd = pmd_offset(pud, vaddr);
                for (; (j < PTRS_PER_PMD) && (vaddr < end); pmd++, j++) {
                        one_page_table_init(pmd);
                        vaddr += PMD_SIZE;
                }
                j = 0;
        }
}

static void __init fixaddr_user_init( void)
{
#ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
        long size = FIXADDR_USER_END - FIXADDR_USER_START;
        pgd_t *pgd;
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;
        phys_t p;
        unsigned long v, vaddr = FIXADDR_USER_START;

        if (!size)
                return;

        fixrange_init( FIXADDR_USER_START, FIXADDR_USER_END, swapper_pg_dir);
        v = (unsigned long) memblock_alloc_low(size, PAGE_SIZE);
        if (!v)
                panic("%s: Failed to allocate %lu bytes align=%lx\n",
                      __func__, size, PAGE_SIZE);

        memcpy((void *) v , (void *) FIXADDR_USER_START, size);
        p = __pa(v);
        for ( ; size > 0; size -= PAGE_SIZE, vaddr += PAGE_SIZE,
                      p += PAGE_SIZE) {
                pgd = swapper_pg_dir + pgd_index(vaddr);
                p4d = p4d_offset(pgd, vaddr);
                pud = pud_offset(p4d, vaddr);
                pmd = pmd_offset(pud, vaddr);
                pte = pte_offset_kernel(pmd, vaddr);
                pte_set_val(*pte, p, PAGE_READONLY);
        }
#endif
}

void __init paging_init(void)
{
        unsigned long zones_size[MAX_NR_ZONES], vaddr;
        int i;

        empty_zero_page = (unsigned long *) memblock_alloc_low(PAGE_SIZE,
                                                               PAGE_SIZE);
        if (!empty_zero_page)
                panic("%s: Failed to allocate %lu bytes align=%lx\n",
                      __func__, PAGE_SIZE, PAGE_SIZE);

        for (i = 0; i < ARRAY_SIZE(zones_size); i++)
                zones_size[i] = 0;

        zones_size[ZONE_NORMAL] = (end_iomem >> PAGE_SHIFT) -
                (uml_physmem >> PAGE_SHIFT);
        free_area_init(zones_size);

        /*
         * Fixed mappings, only the page table structure has to be
         * created - mappings will be set by set_fixmap():
         */
        vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
        fixrange_init(vaddr, FIXADDR_TOP, swapper_pg_dir);

        fixaddr_user_init();
}

/*
 * This can't do anything because nothing in the kernel image can be freed
 * since it's not in kernel physical memory.
 */

void free_initmem(void)
{
}

/* Allocate and free page tables. */

pgd_t *pgd_alloc(struct mm_struct *mm)
{
        pgd_t *pgd = (pgd_t *)__get_free_page(GFP_KERNEL);

        if (pgd) {
                memset(pgd, 0, USER_PTRS_PER_PGD * sizeof(pgd_t));
                memcpy(pgd + USER_PTRS_PER_PGD,
                       swapper_pg_dir + USER_PTRS_PER_PGD,
                       (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
        }
        return pgd;
}

void pgd_free(struct mm_struct *mm, pgd_t *pgd)
{
        free_page((unsigned long) pgd);
}

#ifdef CONFIG_3_LEVEL_PGTABLES
pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address)
{
        pmd_t *pmd = (pmd_t *) __get_free_page(GFP_KERNEL);

        if (pmd)
                memset(pmd, 0, PAGE_SIZE);

        return pmd;
}
#endif

void *uml_kmalloc(int size, int flags)
{
        return kmalloc(size, flags);
}