x86/sev-es: Setup an early #VC handler

[mirror_ubuntu-jammy-kernel.git] / arch / x86 / kernel / head64.c

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

#define DISABLE_BRANCH_PROFILING

/* 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/mem_encrypt.h>
#include <linux/pgtable.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/desc.h>
#include <asm/extable.h>
#include <asm/trapnr.h>
#include <asm/sev-es.h>

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

#ifdef CONFIG_X86_5LEVEL
unsigned int __pgtable_l5_enabled __ro_after_init;
unsigned int pgdir_shift __ro_after_init = 39;
EXPORT_SYMBOL(pgdir_shift);
unsigned int ptrs_per_p4d __ro_after_init = 1;
EXPORT_SYMBOL(ptrs_per_p4d);
#endif

#ifdef CONFIG_DYNAMIC_MEMORY_LAYOUT
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);
#endif

/*
 * GDT used on the boot CPU before switching to virtual addresses.
 */
static struct desc_struct startup_gdt[GDT_ENTRIES] = {
        [GDT_ENTRY_KERNEL32_CS]         = GDT_ENTRY_INIT(0xc09b, 0, 0xfffff),
        [GDT_ENTRY_KERNEL_CS]           = GDT_ENTRY_INIT(0xa09b, 0, 0xfffff),
        [GDT_ENTRY_KERNEL_DS]           = GDT_ENTRY_INIT(0xc093, 0, 0xfffff),
};

/*
 * Address needs to be set at runtime because it references the startup_gdt
 * while the kernel still uses a direct mapping.
 */
static struct desc_ptr startup_gdt_descr = {
        .size = sizeof(startup_gdt),
        .address = 0,
};

#define __head  __section(.head.text)

static void __head *fixup_pointer(void *ptr, unsigned long physaddr)
{
        return ptr - (void *)_text + (void *)physaddr;
}

static unsigned long __head *fixup_long(void *ptr, unsigned long physaddr)
{
        return fixup_pointer(ptr, physaddr);
}

#ifdef CONFIG_X86_5LEVEL
static unsigned int __head *fixup_int(void *ptr, unsigned long physaddr)
{
        return fixup_pointer(ptr, physaddr);
}

static bool __head check_la57_support(unsigned long physaddr)
{
        /*
         * 5-level paging is detected and enabled at kernel decomression
         * stage. Only check if it has been enabled there.
         */
        if (!(native_read_cr4() & X86_CR4_LA57))
                return false;

        *fixup_int(&__pgtable_l5_enabled, physaddr) = 1;
        *fixup_int(&pgdir_shift, physaddr) = 48;
        *fixup_int(&ptrs_per_p4d, physaddr) = 512;
        *fixup_long(&page_offset_base, physaddr) = __PAGE_OFFSET_BASE_L5;
        *fixup_long(&vmalloc_base, physaddr) = __VMALLOC_BASE_L5;
        *fixup_long(&vmemmap_base, physaddr) = __VMEMMAP_BASE_L5;

        return true;
}
#else
static bool __head check_la57_support(unsigned long physaddr)
{
        return false;
}
#endif

/* Code in __startup_64() can be relocated during execution, but the compiler
 * doesn't have to generate PC-relative relocations when accessing globals from
 * that function. Clang actually does not generate them, which leads to
 * boot-time crashes. To work around this problem, every global pointer must
 * be adjusted using fixup_pointer().
 */
unsigned long __head __startup_64(unsigned long physaddr,
                                  struct boot_params *bp)
{
        unsigned long vaddr, vaddr_end;
        unsigned long load_delta, *p;
        unsigned long pgtable_flags;
        pgdval_t *pgd;
        p4dval_t *p4d;
        pudval_t *pud;
        pmdval_t *pmd, pmd_entry;
        pteval_t *mask_ptr;
        bool la57;
        int i;
        unsigned int *next_pgt_ptr;

        la57 = check_la57_support(physaddr);

        /* Is the address too large? */
        if (physaddr >> MAX_PHYSMEM_BITS)
                for (;;);

        /*
         * Compute the delta between the address I am compiled to run at
         * and the address I am actually running at.
         */
        load_delta = physaddr - (unsigned long)(_text - __START_KERNEL_map);

        /* Is the address not 2M aligned? */
        if (load_delta & ~PMD_PAGE_MASK)
                for (;;);

        /* Activate Secure Memory Encryption (SME) if supported and enabled */
        sme_enable(bp);

        /* Include the SME encryption mask in the fixup value */
        load_delta += sme_get_me_mask();

        /* Fixup the physical addresses in the page table */

        pgd = fixup_pointer(&early_top_pgt, physaddr);
        p = pgd + pgd_index(__START_KERNEL_map);
        if (la57)
                *p = (unsigned long)level4_kernel_pgt;
        else
                *p = (unsigned long)level3_kernel_pgt;
        *p += _PAGE_TABLE_NOENC - __START_KERNEL_map + load_delta;

        if (la57) {
                p4d = fixup_pointer(&level4_kernel_pgt, physaddr);
                p4d[511] += load_delta;
        }

        pud = fixup_pointer(&level3_kernel_pgt, physaddr);
        pud[510] += load_delta;
        pud[511] += load_delta;

        pmd = fixup_pointer(level2_fixmap_pgt, physaddr);
        for (i = FIXMAP_PMD_TOP; i > FIXMAP_PMD_TOP - FIXMAP_PMD_NUM; i--)
                pmd[i] += load_delta;

        /*
         * Set up the identity mapping for the switchover.  These
         * entries should *NOT* have the global bit set!  This also
         * creates a bunch of nonsense entries but that is fine --
         * it avoids problems around wraparound.
         */

        next_pgt_ptr = fixup_pointer(&next_early_pgt, physaddr);
        pud = fixup_pointer(early_dynamic_pgts[(*next_pgt_ptr)++], physaddr);
        pmd = fixup_pointer(early_dynamic_pgts[(*next_pgt_ptr)++], physaddr);

        pgtable_flags = _KERNPG_TABLE_NOENC + sme_get_me_mask();

        if (la57) {
                p4d = fixup_pointer(early_dynamic_pgts[(*next_pgt_ptr)++],
                                    physaddr);

                i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
                pgd[i + 0] = (pgdval_t)p4d + pgtable_flags;
                pgd[i + 1] = (pgdval_t)p4d + pgtable_flags;

                i = physaddr >> P4D_SHIFT;
                p4d[(i + 0) % PTRS_PER_P4D] = (pgdval_t)pud + pgtable_flags;
                p4d[(i + 1) % PTRS_PER_P4D] = (pgdval_t)pud + pgtable_flags;
        } else {
                i = (physaddr >> PGDIR_SHIFT) % PTRS_PER_PGD;
                pgd[i + 0] = (pgdval_t)pud + pgtable_flags;
                pgd[i + 1] = (pgdval_t)pud + pgtable_flags;
        }

        i = physaddr >> PUD_SHIFT;
        pud[(i + 0) % PTRS_PER_PUD] = (pudval_t)pmd + pgtable_flags;
        pud[(i + 1) % PTRS_PER_PUD] = (pudval_t)pmd + pgtable_flags;

        pmd_entry = __PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL;
        /* Filter out unsupported __PAGE_KERNEL_* bits: */
        mask_ptr = fixup_pointer(&__supported_pte_mask, physaddr);
        pmd_entry &= *mask_ptr;
        pmd_entry += sme_get_me_mask();
        pmd_entry +=  physaddr;

        for (i = 0; i < DIV_ROUND_UP(_end - _text, PMD_SIZE); i++) {
                int idx = i + (physaddr >> PMD_SHIFT);

                pmd[idx % PTRS_PER_PMD] = pmd_entry + i * PMD_SIZE;
        }

        /*
         * Fixup the kernel text+data virtual addresses. Note that
         * we might write invalid pmds, when the kernel is relocated
         * cleanup_highmap() fixes this up along with the mappings
         * beyond _end.
         *
         * Only the region occupied by the kernel image has so far
         * been checked against the table of usable memory regions
         * provided by the firmware, so invalidate pages outside that
         * region. A page table entry that maps to a reserved area of
         * memory would allow processor speculation into that area,
         * and on some hardware (particularly the UV platform) even
         * speculative access to some reserved areas is caught as an
         * error, causing the BIOS to halt the system.
         */

        pmd = fixup_pointer(level2_kernel_pgt, physaddr);

        /* invalidate pages before the kernel image */
        for (i = 0; i < pmd_index((unsigned long)_text); i++)
                pmd[i] &= ~_PAGE_PRESENT;

        /* fixup pages that are part of the kernel image */
        for (; i <= pmd_index((unsigned long)_end); i++)
                if (pmd[i] & _PAGE_PRESENT)
                        pmd[i] += load_delta;

        /* invalidate pages after the kernel image */
        for (; i < PTRS_PER_PMD; i++)
                pmd[i] &= ~_PAGE_PRESENT;

        /*
         * Fixup phys_base - remove the memory encryption mask to obtain
         * the true physical address.
         */
        *fixup_long(&phys_base, physaddr) += load_delta - sme_get_me_mask();

        /* Encrypt the kernel and related (if SME is active) */
        sme_encrypt_kernel(bp);

        /*
         * Clear the memory encryption mask from the .bss..decrypted section.
         * The bss section will be memset to zero later in the initialization so
         * there is no need to zero it after changing the memory encryption
         * attribute.
         */
        if (mem_encrypt_active()) {
                vaddr = (unsigned long)__start_bss_decrypted;
                vaddr_end = (unsigned long)__end_bss_decrypted;
                for (; vaddr < vaddr_end; vaddr += PMD_SIZE) {
                        i = pmd_index(vaddr);
                        pmd[i] -= sme_get_me_mask();
                }
        }

        /*
         * Return the SME encryption mask (if SME is active) to be used as a
         * modifier for the initial pgdir entry programmed into CR3.
         */
        return sme_get_me_mask();
}

unsigned long __startup_secondary_64(void)
{
        /*
         * Return the SME encryption mask (if SME is active) to be used as a
         * modifier for the initial pgdir entry programmed into CR3.
         */
        return sme_get_me_mask();
}

/* 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;

        early_fixup_exception(regs, trapnr);
}

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

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 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();

        clear_bss();

        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();

        idt_setup_early_handler();

        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 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();
}

/*
 * Data structures and code used for IDT setup in head_64.S. The bringup-IDT is
 * used until the idt_table takes over. On the boot CPU this happens in
 * x86_64_start_kernel(), on secondary CPUs in start_secondary(). In both cases
 * this happens in the functions called from head_64.S.
 *
 * The idt_table can't be used that early because all the code modifying it is
 * in idt.c and can be instrumented by tracing or KASAN, which both don't work
 * during early CPU bringup. Also the idt_table has the runtime vectors
 * configured which require certain CPU state to be setup already (like TSS),
 * which also hasn't happened yet in early CPU bringup.
 */
static gate_desc bringup_idt_table[NUM_EXCEPTION_VECTORS] __page_aligned_data;

static struct desc_ptr bringup_idt_descr = {
        .size           = (NUM_EXCEPTION_VECTORS * sizeof(gate_desc)) - 1,
        .address        = 0, /* Set at runtime */
};

static void set_bringup_idt_handler(gate_desc *idt, int n, void *handler)
{
#ifdef CONFIG_AMD_MEM_ENCRYPT
        struct idt_data data;
        gate_desc desc;

        init_idt_data(&data, n, handler);
        idt_init_desc(&desc, &data);
        native_write_idt_entry(idt, n, &desc);
#endif
}

/* This runs while still in the direct mapping */
static void startup_64_load_idt(unsigned long physbase)
{
        struct desc_ptr *desc = fixup_pointer(&bringup_idt_descr, physbase);
        gate_desc *idt = fixup_pointer(bringup_idt_table, physbase);


        if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
                void *handler;

                /* VMM Communication Exception */
                handler = fixup_pointer(vc_no_ghcb, physbase);
                set_bringup_idt_handler(idt, X86_TRAP_VC, handler);
        }

        desc->address = (unsigned long)idt;
        native_load_idt(desc);
}

/* This is used when running on kernel addresses */
void early_setup_idt(void)
{
        bringup_idt_descr.address = (unsigned long)bringup_idt_table;
        native_load_idt(&bringup_idt_descr);
}

/*
 * Setup boot CPU state needed before kernel switches to virtual addresses.
 */
void __head startup_64_setup_env(unsigned long physbase)
{
        /* Load GDT */
        startup_gdt_descr.address = (unsigned long)fixup_pointer(startup_gdt, physbase);
        native_load_gdt(&startup_gdt_descr);

        /* New GDT is live - reload data segment registers */
        asm volatile("movl %%eax, %%ds\n"
                     "movl %%eax, %%ss\n"
                     "movl %%eax, %%es\n" : : "a"(__KERNEL_DS) : "memory");

        startup_64_load_idt(physbase);
}