// SPDX-License-Identifier: GPL-2.0-only
/*
 * Hibernation support specific for i386 - temporary page tables
 *
 * Copyright (c) 2006 Rafael J. Wysocki <rjw@sisk.pl>
 */

#include <linux/gfp.h>
#include <linux/suspend.h>
#include <linux/memblock.h>
#include <linux/pgtable.h>

#include <asm/page.h>
#include <asm/mmzone.h>
#include <asm/sections.h>
#include <asm/suspend.h>

/* Pointer to the temporary resume page tables */
pgd_t *resume_pg_dir;

/* The following three functions are based on the analogous code in
 * arch/x86/mm/init_32.c
 */

/*
 * Create a middle page table on a resume-safe page and put a pointer to it in
 * the given global directory entry.  This only returns the gd entry
 * in non-PAE compilation mode, since the middle layer is folded.
 */
static pmd_t *resume_one_md_table_init(pgd_t *pgd)
{
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd_table;

#ifdef CONFIG_X86_PAE
        pmd_table = (pmd_t *)get_safe_page(GFP_ATOMIC);
        if (!pmd_table)
                return NULL;

        set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
        p4d = p4d_offset(pgd, 0);
        pud = pud_offset(p4d, 0);

        BUG_ON(pmd_table != pmd_offset(pud, 0));
#else
        p4d = p4d_offset(pgd, 0);
        pud = pud_offset(p4d, 0);
        pmd_table = pmd_offset(pud, 0);
#endif

        return pmd_table;
}

/*
 * Create a page table on a resume-safe page and place a pointer to it in
 * a middle page directory entry.
 */
static pte_t *resume_one_page_table_init(pmd_t *pmd)
{
        if (pmd_none(*pmd)) {
                pte_t *page_table = (pte_t *)get_safe_page(GFP_ATOMIC);
                if (!page_table)
                        return NULL;

                set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));

                BUG_ON(page_table != pte_offset_kernel(pmd, 0));

                return page_table;
        }

        return pte_offset_kernel(pmd, 0);
}

/*
 * This maps the physical memory to kernel virtual address space, a total
 * of max_low_pfn pages, by creating page tables starting from address
 * PAGE_OFFSET.  The page tables are allocated out of resume-safe pages.
 */
static int resume_physical_mapping_init(pgd_t *pgd_base)
{
        unsigned long pfn;
        pgd_t *pgd;
        pmd_t *pmd;
        pte_t *pte;
        int pgd_idx, pmd_idx;

        pgd_idx = pgd_index(PAGE_OFFSET);
        pgd = pgd_base + pgd_idx;
        pfn = 0;

        for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
                pmd = resume_one_md_table_init(pgd);
                if (!pmd)
                        return -ENOMEM;

                if (pfn >= max_low_pfn)
                        continue;

                for (pmd_idx = 0; pmd_idx < PTRS_PER_PMD; pmd++, pmd_idx++) {
                        if (pfn >= max_low_pfn)
                                break;

                        /* Map with big pages if possible, otherwise create
                         * normal page tables.
                         * NOTE: We can mark everything as executable here
                         */
                        if (boot_cpu_has(X86_FEATURE_PSE)) {
                                set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE_EXEC));
                                pfn += PTRS_PER_PTE;
                        } else {
                                pte_t *max_pte;

                                pte = resume_one_page_table_init(pmd);
                                if (!pte)
                                        return -ENOMEM;

                                max_pte = pte + PTRS_PER_PTE;
                                for (; pte < max_pte; pte++, pfn++) {
                                        if (pfn >= max_low_pfn)
                                                break;

                                        set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
                                }
                        }
                }
        }

        return 0;
}

static inline void resume_init_first_level_page_table(pgd_t *pg_dir)
{
#ifdef CONFIG_X86_PAE
        int i;

        /* Init entries of the first-level page table to the zero page */
        for (i = 0; i < PTRS_PER_PGD; i++)
                set_pgd(pg_dir + i,
                        __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));
#endif
}

static int set_up_temporary_text_mapping(pgd_t *pgd_base)
{
        pgd_t *pgd;
        pmd_t *pmd;
        pte_t *pte;

        pgd = pgd_base + pgd_index(restore_jump_address);

        pmd = resume_one_md_table_init(pgd);
        if (!pmd)
                return -ENOMEM;

        if (boot_cpu_has(X86_FEATURE_PSE)) {
                set_pmd(pmd + pmd_index(restore_jump_address),
                __pmd((jump_address_phys & PMD_MASK) | pgprot_val(PAGE_KERNEL_LARGE_EXEC)));
        } else {
                pte = resume_one_page_table_init(pmd);
                if (!pte)
                        return -ENOMEM;
                set_pte(pte + pte_index(restore_jump_address),
                __pte((jump_address_phys & PAGE_MASK) | pgprot_val(PAGE_KERNEL_EXEC)));
        }

        return 0;
}

asmlinkage int swsusp_arch_resume(void)
{
        int error;

        resume_pg_dir = (pgd_t *)get_safe_page(GFP_ATOMIC);
        if (!resume_pg_dir)
                return -ENOMEM;

        resume_init_first_level_page_table(resume_pg_dir);

        error = set_up_temporary_text_mapping(resume_pg_dir);
        if (error)
                return error;

        error = resume_physical_mapping_init(resume_pg_dir);
        if (error)
                return error;

        temp_pgt = __pa(resume_pg_dir);

        error = relocate_restore_code();
        if (error)
                return error;

        /* We have got enough memory and from now on we cannot recover */
        restore_image();
        return 0;
}