// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/arch/i386/kernel/head32.c -- prepare to run common code
 *
 *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
 *  Copyright (C) 2007 Eric Biederman <ebiederm@xmission.com>
 */

#include <linux/init.h>
#include <linux/start_kernel.h>
#include <linux/mm.h>
#include <linux/memblock.h>

#include <asm/desc.h>
#include <asm/setup.h>
#include <asm/sections.h>
#include <asm/e820/api.h>
#include <asm/page.h>
#include <asm/apic.h>
#include <asm/io_apic.h>
#include <asm/bios_ebda.h>
#include <asm/microcode.h>
#include <asm/tlbflush.h>
#include <asm/bootparam_utils.h>

static void __init i386_default_early_setup(void)
{
        /* Initialize 32bit specific setup functions */
        x86_init.resources.reserve_resources = i386_reserve_resources;
        x86_init.mpparse.setup_ioapic_ids = setup_ioapic_ids_from_mpc;
}

#ifdef CONFIG_MICROCODE_INITRD32
unsigned long __initdata initrd_start_early;
static pte_t __initdata *initrd_pl2p_start, *initrd_pl2p_end;

static void zap_early_initrd_mapping(void)
{
        pte_t *pl2p = initrd_pl2p_start;

        for (; pl2p < initrd_pl2p_end; pl2p++) {
                *pl2p = (pte_t){ .pte = 0 };

                if (!IS_ENABLED(CONFIG_X86_PAE))
                        *(pl2p + ((PAGE_OFFSET >> PGDIR_SHIFT))) = (pte_t) {.pte = 0};
        }
}
#else
static inline void zap_early_initrd_mapping(void) { }
#endif

asmlinkage __visible void __init __noreturn i386_start_kernel(void)
{
        /* Make sure IDT is set up before any exception happens */
        idt_setup_early_handler();

        load_ucode_bsp();
        zap_early_initrd_mapping();

        cr4_init_shadow();

        sanitize_boot_params(&boot_params);

        x86_early_init_platform_quirks();

        /* Call the subarch specific early setup function */
        switch (boot_params.hdr.hardware_subarch) {
        case X86_SUBARCH_INTEL_MID:
                x86_intel_mid_early_setup();
                break;
        case X86_SUBARCH_CE4100:
                x86_ce4100_early_setup();
                break;
        default:
                i386_default_early_setup();
                break;
        }

        start_kernel();
}

/*
 * Initialize page tables.  This creates a PDE and a set of page
 * tables, which are located immediately beyond __brk_base.  The variable
 * _brk_end is set up to point to the first "safe" location.
 * Mappings are created both at virtual address 0 (identity mapping)
 * and PAGE_OFFSET for up to _end.
 *
 * In PAE mode initial_page_table is statically defined to contain
 * enough entries to cover the VMSPLIT option (that is the top 1, 2 or 3
 * entries). The identity mapping is handled by pointing two PGD entries
 * to the first kernel PMD. Note the upper half of each PMD or PTE are
 * always zero at this stage.
 */
#ifdef CONFIG_X86_PAE
typedef pmd_t                   pl2_t;
#define pl2_base                initial_pg_pmd
#define SET_PL2(val)            { .pmd = (val), }
#else
typedef pgd_t                   pl2_t;
#define pl2_base                initial_page_table
#define SET_PL2(val)            { .pgd = (val), }
#endif

static __init __no_stack_protector pte_t init_map(pte_t pte, pte_t **ptep, pl2_t **pl2p,
                                                  const unsigned long limit)
{
        while ((pte.pte & PTE_PFN_MASK) < limit) {
                pl2_t pl2 = SET_PL2((unsigned long)*ptep | PDE_IDENT_ATTR);
                int i;

                **pl2p = pl2;
                if (!IS_ENABLED(CONFIG_X86_PAE)) {
                        /* Kernel PDE entry */
                        *(*pl2p + ((PAGE_OFFSET >> PGDIR_SHIFT))) = pl2;
                }

                for (i = 0; i < PTRS_PER_PTE; i++) {
                        **ptep = pte;
                        pte.pte += PAGE_SIZE;
                        (*ptep)++;
                }
                (*pl2p)++;
        }
        return pte;
}

void __init __no_stack_protector mk_early_pgtbl_32(void)
{
        /* Enough space to fit pagetables for the low memory linear map */
        unsigned long limit = __pa_nodebug(_end) + (PAGE_TABLE_SIZE(LOWMEM_PAGES) << PAGE_SHIFT);
        pte_t pte, *ptep = (pte_t *)__pa_nodebug(__brk_base);
        struct boot_params __maybe_unused *params;
        pl2_t *pl2p = (pl2_t *)__pa_nodebug(pl2_base);
        unsigned long *ptr;

        pte.pte = PTE_IDENT_ATTR;
        pte = init_map(pte, &ptep, &pl2p, limit);

        ptr = (unsigned long *)__pa_nodebug(&max_pfn_mapped);
        /* Can't use pte_pfn() since it's a call with CONFIG_PARAVIRT */
        *ptr = (pte.pte & PTE_PFN_MASK) >> PAGE_SHIFT;

        ptr = (unsigned long *)__pa_nodebug(&_brk_end);
        *ptr = (unsigned long)ptep + PAGE_OFFSET;

#ifdef CONFIG_MICROCODE_INITRD32
        params = (struct boot_params *)__pa_nodebug(&boot_params);
        if (!params->hdr.ramdisk_size || !params->hdr.ramdisk_image)
                return;

        /* Save the virtual start address */
        ptr = (unsigned long *)__pa_nodebug(&initrd_start_early);
        *ptr = (pte.pte & PTE_PFN_MASK) + PAGE_OFFSET;
        *ptr += ((unsigned long)params->hdr.ramdisk_image) & ~PAGE_MASK;

        /* Save PLP2 for cleanup */
        ptr = (unsigned long *)__pa_nodebug(&initrd_pl2p_start);
        *ptr = (unsigned long)pl2p + PAGE_OFFSET;

        limit = (unsigned long)params->hdr.ramdisk_image;
        pte.pte = PTE_IDENT_ATTR | PFN_ALIGN(limit);
        limit = (unsigned long)params->hdr.ramdisk_image + params->hdr.ramdisk_size;

        init_map(pte, &ptep, &pl2p, limit);

        ptr = (unsigned long *)__pa_nodebug(&initrd_pl2p_end);
        *ptr = (unsigned long)pl2p + PAGE_OFFSET;
#endif
}