// SPDX-License-Identifier: GPL-2.0
/*
 *  prepare to run common code
 *
 *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
 */

/* cpu_feature_enabled() cannot be used this early */
#define USE_EARLY_PGTABLE_L5

#include <linux/init.h>
#include <linux/linkage.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/percpu.h>
#include <linux/start_kernel.h>
#include <linux/io.h>
#include <linux/memblock.h>
#include <linux/cc_platform.h>
#include <linux/pgtable.h>

#include <asm/asm.h>
#include <asm/page_64.h>
#include <asm/processor.h>
#include <asm/proto.h>
#include <asm/smp.h>
#include <asm/setup.h>
#include <asm/desc.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>
#include <asm/kdebug.h>
#include <asm/e820/api.h>
#include <asm/bios_ebda.h>
#include <asm/bootparam_utils.h>
#include <asm/microcode.h>
#include <asm/kasan.h>
#include <asm/fixmap.h>
#include <asm/realmode.h>
#include <asm/extable.h>
#include <asm/trapnr.h>
#include <asm/sev.h>
#include <asm/tdx.h>
#include <asm/init.h>

/*
 * Manage page tables very early on.
 */
extern pmd_t early_dynamic_pgts[EARLY_DYNAMIC_PAGE_TABLES][PTRS_PER_PMD];
unsigned int __initdata next_early_pgt;
SYM_PIC_ALIAS(next_early_pgt);
pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);

unsigned int __pgtable_l5_enabled __ro_after_init;
SYM_PIC_ALIAS(__pgtable_l5_enabled);
unsigned int pgdir_shift __ro_after_init = 39;
EXPORT_SYMBOL(pgdir_shift);
SYM_PIC_ALIAS(pgdir_shift);
unsigned int ptrs_per_p4d __ro_after_init = 1;
EXPORT_SYMBOL(ptrs_per_p4d);
SYM_PIC_ALIAS(ptrs_per_p4d);

unsigned long page_offset_base __ro_after_init = __PAGE_OFFSET_BASE_L4;
EXPORT_SYMBOL(page_offset_base);
unsigned long vmalloc_base __ro_after_init = __VMALLOC_BASE_L4;
EXPORT_SYMBOL(vmalloc_base);
unsigned long vmemmap_base __ro_after_init = __VMEMMAP_BASE_L4;
EXPORT_SYMBOL(vmemmap_base);

/* Wipe all early page tables except for the kernel symbol map */
static void __init reset_early_page_tables(void)
{
        memset(early_top_pgt, 0, sizeof(pgd_t)*(PTRS_PER_PGD-1));
        next_early_pgt = 0;
        write_cr3(__sme_pa_nodebug(early_top_pgt));
}

/* Create a new PMD entry */
bool __init __early_make_pgtable(unsigned long address, pmdval_t pmd)
{
        unsigned long physaddr = address - __PAGE_OFFSET;
        pgdval_t pgd, *pgd_p;
        p4dval_t p4d, *p4d_p;
        pudval_t pud, *pud_p;
        pmdval_t *pmd_p;

        /* Invalid address or early pgt is done ?  */
        if (physaddr >= MAXMEM || read_cr3_pa() != __pa_nodebug(early_top_pgt))
                return false;

again:
        pgd_p = &early_top_pgt[pgd_index(address)].pgd;
        pgd = *pgd_p;

        /*
         * The use of __START_KERNEL_map rather than __PAGE_OFFSET here is
         * critical -- __PAGE_OFFSET would point us back into the dynamic
         * range and we might end up looping forever...
         */
        if (!pgtable_l5_enabled())
                p4d_p = pgd_p;
        else if (pgd)
                p4d_p = (p4dval_t *)((pgd & PTE_PFN_MASK) + __START_KERNEL_map - phys_base);
        else {
                if (next_early_pgt >= EARLY_DYNAMIC_PAGE_TABLES) {
                        reset_early_page_tables();
                        goto again;
                }

                p4d_p = (p4dval_t *)early_dynamic_pgts[next_early_pgt++];
                memset(p4d_p, 0, sizeof(*p4d_p) * PTRS_PER_P4D);
                *pgd_p = (pgdval_t)p4d_p - __START_KERNEL_map + phys_base + _KERNPG_TABLE;
        }
        p4d_p += p4d_index(address);
        p4d = *p4d_p;

        if (p4d)
                pud_p = (pudval_t *)((p4d & PTE_PFN_MASK) + __START_KERNEL_map - phys_base);
        else {
                if (next_early_pgt >= EARLY_DYNAMIC_PAGE_TABLES) {
                        reset_early_page_tables();
                        goto again;
                }

                pud_p = (pudval_t *)early_dynamic_pgts[next_early_pgt++];
                memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);
                *p4d_p = (p4dval_t)pud_p - __START_KERNEL_map + phys_base + _KERNPG_TABLE;
        }
        pud_p += pud_index(address);
        pud = *pud_p;

        if (pud)
                pmd_p = (pmdval_t *)((pud & PTE_PFN_MASK) + __START_KERNEL_map - phys_base);
        else {
                if (next_early_pgt >= EARLY_DYNAMIC_PAGE_TABLES) {
                        reset_early_page_tables();
                        goto again;
                }

                pmd_p = (pmdval_t *)early_dynamic_pgts[next_early_pgt++];
                memset(pmd_p, 0, sizeof(*pmd_p) * PTRS_PER_PMD);
                *pud_p = (pudval_t)pmd_p - __START_KERNEL_map + phys_base + _KERNPG_TABLE;
        }
        pmd_p[pmd_index(address)] = pmd;

        return true;
}

static bool __init early_make_pgtable(unsigned long address)
{
        unsigned long physaddr = address - __PAGE_OFFSET;
        pmdval_t pmd;

        pmd = (physaddr & PMD_MASK) + early_pmd_flags;

        return __early_make_pgtable(address, pmd);
}

void __init do_early_exception(struct pt_regs *regs, int trapnr)
{
        if (trapnr == X86_TRAP_PF &&
            early_make_pgtable(native_read_cr2()))
                return;

        if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT) &&
            trapnr == X86_TRAP_VC && handle_vc_boot_ghcb(regs))
                return;

        if (trapnr == X86_TRAP_VE && tdx_early_handle_ve(regs))
                return;

        early_fixup_exception(regs, trapnr);
}

/* Don't add a printk in there. printk relies on the PDA which is not initialized 
   yet. */
void __init clear_bss(void)
{
        memset(__bss_start, 0,
               (unsigned long) __bss_stop - (unsigned long) __bss_start);
        memset(__brk_base, 0,
               (unsigned long) __brk_limit - (unsigned long) __brk_base);
}

static unsigned long get_cmd_line_ptr(void)
{
        unsigned long cmd_line_ptr = boot_params.hdr.cmd_line_ptr;

        cmd_line_ptr |= (u64)boot_params.ext_cmd_line_ptr << 32;

        return cmd_line_ptr;
}

static void __init copy_bootdata(char *real_mode_data)
{
        char * command_line;
        unsigned long cmd_line_ptr;

        /*
         * If SME is active, this will create decrypted mappings of the
         * boot data in advance of the copy operations.
         */
        sme_map_bootdata(real_mode_data);

        memcpy(&boot_params, real_mode_data, sizeof(boot_params));
        sanitize_boot_params(&boot_params);
        cmd_line_ptr = get_cmd_line_ptr();
        if (cmd_line_ptr) {
                command_line = __va(cmd_line_ptr);
                memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
        }

        /*
         * The old boot data is no longer needed and won't be reserved,
         * freeing up that memory for use by the system. If SME is active,
         * we need to remove the mappings that were created so that the
         * memory doesn't remain mapped as decrypted.
         */
        sme_unmap_bootdata(real_mode_data);
}

asmlinkage __visible void __init __noreturn x86_64_start_kernel(char * real_mode_data)
{
        /*
         * Build-time sanity checks on the kernel image and module
         * area mappings. (these are purely build-time and produce no code)
         */
        BUILD_BUG_ON(MODULES_VADDR < __START_KERNEL_map);
        BUILD_BUG_ON(MODULES_VADDR - __START_KERNEL_map < KERNEL_IMAGE_SIZE);
        BUILD_BUG_ON(MODULES_LEN + KERNEL_IMAGE_SIZE > 2*PUD_SIZE);
        BUILD_BUG_ON((__START_KERNEL_map & ~PMD_MASK) != 0);
        BUILD_BUG_ON((MODULES_VADDR & ~PMD_MASK) != 0);
        BUILD_BUG_ON(!(MODULES_VADDR > __START_KERNEL));
        MAYBE_BUILD_BUG_ON(!(((MODULES_END - 1) & PGDIR_MASK) ==
                                (__START_KERNEL & PGDIR_MASK)));
        BUILD_BUG_ON(__fix_to_virt(__end_of_fixed_addresses) <= MODULES_END);

        cr4_init_shadow();

        /* Kill off the identity-map trampoline */
        reset_early_page_tables();

        if (pgtable_l5_enabled()) {
                page_offset_base        = __PAGE_OFFSET_BASE_L5;
                vmalloc_base            = __VMALLOC_BASE_L5;
                vmemmap_base            = __VMEMMAP_BASE_L5;
        }

        clear_bss();

        /*
         * This needs to happen *before* kasan_early_init() because latter maps stuff
         * into that page.
         */
        clear_page(init_top_pgt);

        /*
         * SME support may update early_pmd_flags to include the memory
         * encryption mask, so it needs to be called before anything
         * that may generate a page fault.
         */
        sme_early_init();

        kasan_early_init();

        /*
         * Flush global TLB entries which could be left over from the trampoline page
         * table.
         *
         * This needs to happen *after* kasan_early_init() as KASAN-enabled .configs
         * instrument native_write_cr4() so KASAN must be initialized for that
         * instrumentation to work.
         */
        __native_tlb_flush_global(this_cpu_read(cpu_tlbstate.cr4));

        idt_setup_early_handler();

        /* Needed before cc_platform_has() can be used for TDX */
        tdx_early_init();

        copy_bootdata(__va(real_mode_data));

        /*
         * Load microcode early on BSP.
         */
        load_ucode_bsp();

        /* set init_top_pgt kernel high mapping*/
        init_top_pgt[511] = early_top_pgt[511];

        x86_64_start_reservations(real_mode_data);
}

void __init __noreturn x86_64_start_reservations(char *real_mode_data)
{
        /* version is always not zero if it is copied */
        if (!boot_params.hdr.version)
                copy_bootdata(__va(real_mode_data));

        x86_early_init_platform_quirks();

        switch (boot_params.hdr.hardware_subarch) {
        case X86_SUBARCH_INTEL_MID:
                x86_intel_mid_early_setup();
                break;
        default:
                break;
        }

        start_kernel();
}

void early_setup_idt(void)
{
        void *handler = NULL;

        if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
                setup_ghcb();
                handler = vc_boot_ghcb;
        }

        __pi_startup_64_load_idt(handler);
}