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

// SPDX-License-Identifier: GPL-2.0-only
/*
 * AMD Memory Encryption Support
 *
 * Copyright (C) 2016 Advanced Micro Devices, Inc.
 *
 * Author: Tom Lendacky <thomas.lendacky@amd.com>
 */

#define DISABLE_BRANCH_PROFILING

/*
 * Since we're dealing with identity mappings, physical and virtual
 * addresses are the same, so override these defines which are ultimately
 * used by the headers in misc.h.
 */
#define __pa(x)  ((unsigned long)(x))
#define __va(x)  ((void *)((unsigned long)(x)))

/*
 * Special hack: we have to be careful, because no indirections are
 * allowed here, and paravirt_ops is a kind of one. As it will only run in
 * baremetal anyway, we just keep it from happening. (This list needs to
 * be extended when new paravirt and debugging variants are added.)
 */
#undef CONFIG_PARAVIRT
#undef CONFIG_PARAVIRT_XXL
#undef CONFIG_PARAVIRT_SPINLOCKS

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/mem_encrypt.h>

#include <asm/setup.h>
#include <asm/sections.h>
#include <asm/cmdline.h>

#include "mm_internal.h"

#define PGD_FLAGS               _KERNPG_TABLE_NOENC
#define P4D_FLAGS               _KERNPG_TABLE_NOENC
#define PUD_FLAGS               _KERNPG_TABLE_NOENC
#define PMD_FLAGS               _KERNPG_TABLE_NOENC

#define PMD_FLAGS_LARGE         (__PAGE_KERNEL_LARGE_EXEC & ~_PAGE_GLOBAL)

#define PMD_FLAGS_DEC           PMD_FLAGS_LARGE
#define PMD_FLAGS_DEC_WP        ((PMD_FLAGS_DEC & ~_PAGE_LARGE_CACHE_MASK) | \
                                 (_PAGE_PAT_LARGE | _PAGE_PWT))

#define PMD_FLAGS_ENC           (PMD_FLAGS_LARGE | _PAGE_ENC)

#define PTE_FLAGS               (__PAGE_KERNEL_EXEC & ~_PAGE_GLOBAL)

#define PTE_FLAGS_DEC           PTE_FLAGS
#define PTE_FLAGS_DEC_WP        ((PTE_FLAGS_DEC & ~_PAGE_CACHE_MASK) | \
                                 (_PAGE_PAT | _PAGE_PWT))

#define PTE_FLAGS_ENC           (PTE_FLAGS | _PAGE_ENC)

struct sme_populate_pgd_data {
        void    *pgtable_area;
        pgd_t   *pgd;

        pmdval_t pmd_flags;
        pteval_t pte_flags;
        unsigned long paddr;

        unsigned long vaddr;
        unsigned long vaddr_end;
};

/*
 * This work area lives in the .init.scratch section, which lives outside of
 * the kernel proper. It is sized to hold the intermediate copy buffer and
 * more than enough pagetable pages.
 *
 * By using this section, the kernel can be encrypted in place and it
 * avoids any possibility of boot parameters or initramfs images being
 * placed such that the in-place encryption logic overwrites them.  This
 * section is 2MB aligned to allow for simple pagetable setup using only
 * PMD entries (see vmlinux.lds.S).
 */
static char sme_workarea[2 * PMD_PAGE_SIZE] __section(".init.scratch");

static char sme_cmdline_arg[] __initdata = "mem_encrypt";
static char sme_cmdline_on[]  __initdata = "on";
static char sme_cmdline_off[] __initdata = "off";

static void __init sme_clear_pgd(struct sme_populate_pgd_data *ppd)
{
        unsigned long pgd_start, pgd_end, pgd_size;
        pgd_t *pgd_p;

        pgd_start = ppd->vaddr & PGDIR_MASK;
        pgd_end = ppd->vaddr_end & PGDIR_MASK;

        pgd_size = (((pgd_end - pgd_start) / PGDIR_SIZE) + 1) * sizeof(pgd_t);

        pgd_p = ppd->pgd + pgd_index(ppd->vaddr);

        memset(pgd_p, 0, pgd_size);
}

static pud_t __init *sme_prepare_pgd(struct sme_populate_pgd_data *ppd)
{
        pgd_t *pgd;
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;

        pgd = ppd->pgd + pgd_index(ppd->vaddr);
        if (pgd_none(*pgd)) {
                p4d = ppd->pgtable_area;
                memset(p4d, 0, sizeof(*p4d) * PTRS_PER_P4D);
                ppd->pgtable_area += sizeof(*p4d) * PTRS_PER_P4D;
                set_pgd(pgd, __pgd(PGD_FLAGS | __pa(p4d)));
        }

        p4d = p4d_offset(pgd, ppd->vaddr);
        if (p4d_none(*p4d)) {
                pud = ppd->pgtable_area;
                memset(pud, 0, sizeof(*pud) * PTRS_PER_PUD);
                ppd->pgtable_area += sizeof(*pud) * PTRS_PER_PUD;
                set_p4d(p4d, __p4d(P4D_FLAGS | __pa(pud)));
        }

        pud = pud_offset(p4d, ppd->vaddr);
        if (pud_none(*pud)) {
                pmd = ppd->pgtable_area;
                memset(pmd, 0, sizeof(*pmd) * PTRS_PER_PMD);
                ppd->pgtable_area += sizeof(*pmd) * PTRS_PER_PMD;
                set_pud(pud, __pud(PUD_FLAGS | __pa(pmd)));
        }

        if (pud_large(*pud))
                return NULL;

        return pud;
}

static void __init sme_populate_pgd_large(struct sme_populate_pgd_data *ppd)
{
        pud_t *pud;
        pmd_t *pmd;

        pud = sme_prepare_pgd(ppd);
        if (!pud)
                return;

        pmd = pmd_offset(pud, ppd->vaddr);
        if (pmd_large(*pmd))
                return;

        set_pmd(pmd, __pmd(ppd->paddr | ppd->pmd_flags));
}

static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd)
{
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;

        pud = sme_prepare_pgd(ppd);
        if (!pud)
                return;

        pmd = pmd_offset(pud, ppd->vaddr);
        if (pmd_none(*pmd)) {
                pte = ppd->pgtable_area;
                memset(pte, 0, sizeof(*pte) * PTRS_PER_PTE);
                ppd->pgtable_area += sizeof(*pte) * PTRS_PER_PTE;
                set_pmd(pmd, __pmd(PMD_FLAGS | __pa(pte)));
        }

        if (pmd_large(*pmd))
                return;

        pte = pte_offset_map(pmd, ppd->vaddr);
        if (pte_none(*pte))
                set_pte(pte, __pte(ppd->paddr | ppd->pte_flags));
}

static void __init __sme_map_range_pmd(struct sme_populate_pgd_data *ppd)
{
        while (ppd->vaddr < ppd->vaddr_end) {
                sme_populate_pgd_large(ppd);

                ppd->vaddr += PMD_PAGE_SIZE;
                ppd->paddr += PMD_PAGE_SIZE;
        }
}

static void __init __sme_map_range_pte(struct sme_populate_pgd_data *ppd)
{
        while (ppd->vaddr < ppd->vaddr_end) {
                sme_populate_pgd(ppd);

                ppd->vaddr += PAGE_SIZE;
                ppd->paddr += PAGE_SIZE;
        }
}

static void __init __sme_map_range(struct sme_populate_pgd_data *ppd,
                                   pmdval_t pmd_flags, pteval_t pte_flags)
{
        unsigned long vaddr_end;

        ppd->pmd_flags = pmd_flags;
        ppd->pte_flags = pte_flags;

        /* Save original end value since we modify the struct value */
        vaddr_end = ppd->vaddr_end;

        /* If start is not 2MB aligned, create PTE entries */
        ppd->vaddr_end = ALIGN(ppd->vaddr, PMD_PAGE_SIZE);
        __sme_map_range_pte(ppd);

        /* Create PMD entries */
        ppd->vaddr_end = vaddr_end & PMD_PAGE_MASK;
        __sme_map_range_pmd(ppd);

        /* If end is not 2MB aligned, create PTE entries */
        ppd->vaddr_end = vaddr_end;
        __sme_map_range_pte(ppd);
}

static void __init sme_map_range_encrypted(struct sme_populate_pgd_data *ppd)
{
        __sme_map_range(ppd, PMD_FLAGS_ENC, PTE_FLAGS_ENC);
}

static void __init sme_map_range_decrypted(struct sme_populate_pgd_data *ppd)
{
        __sme_map_range(ppd, PMD_FLAGS_DEC, PTE_FLAGS_DEC);
}

static void __init sme_map_range_decrypted_wp(struct sme_populate_pgd_data *ppd)
{
        __sme_map_range(ppd, PMD_FLAGS_DEC_WP, PTE_FLAGS_DEC_WP);
}

static unsigned long __init sme_pgtable_calc(unsigned long len)
{
        unsigned long entries = 0, tables = 0;

        /*
         * Perform a relatively simplistic calculation of the pagetable
         * entries that are needed. Those mappings will be covered mostly
         * by 2MB PMD entries so we can conservatively calculate the required
         * number of P4D, PUD and PMD structures needed to perform the
         * mappings.  For mappings that are not 2MB aligned, PTE mappings
         * would be needed for the start and end portion of the address range
         * that fall outside of the 2MB alignment.  This results in, at most,
         * two extra pages to hold PTE entries for each range that is mapped.
         * Incrementing the count for each covers the case where the addresses
         * cross entries.
         */

        /* PGDIR_SIZE is equal to P4D_SIZE on 4-level machine. */
        if (PTRS_PER_P4D > 1)
                entries += (DIV_ROUND_UP(len, PGDIR_SIZE) + 1) * sizeof(p4d_t) * PTRS_PER_P4D;
        entries += (DIV_ROUND_UP(len, P4D_SIZE) + 1) * sizeof(pud_t) * PTRS_PER_PUD;
        entries += (DIV_ROUND_UP(len, PUD_SIZE) + 1) * sizeof(pmd_t) * PTRS_PER_PMD;
        entries += 2 * sizeof(pte_t) * PTRS_PER_PTE;

        /*
         * Now calculate the added pagetable structures needed to populate
         * the new pagetables.
         */

        if (PTRS_PER_P4D > 1)
                tables += DIV_ROUND_UP(entries, PGDIR_SIZE) * sizeof(p4d_t) * PTRS_PER_P4D;
        tables += DIV_ROUND_UP(entries, P4D_SIZE) * sizeof(pud_t) * PTRS_PER_PUD;
        tables += DIV_ROUND_UP(entries, PUD_SIZE) * sizeof(pmd_t) * PTRS_PER_PMD;

        return entries + tables;
}

void __init sme_encrypt_kernel(struct boot_params *bp)
{
        unsigned long workarea_start, workarea_end, workarea_len;
        unsigned long execute_start, execute_end, execute_len;
        unsigned long kernel_start, kernel_end, kernel_len;
        unsigned long initrd_start, initrd_end, initrd_len;
        struct sme_populate_pgd_data ppd;
        unsigned long pgtable_area_len;
        unsigned long decrypted_base;

        if (!sme_active())
                return;

        /*
         * Prepare for encrypting the kernel and initrd by building new
         * pagetables with the necessary attributes needed to encrypt the
         * kernel in place.
         *
         *   One range of virtual addresses will map the memory occupied
         *   by the kernel and initrd as encrypted.
         *
         *   Another range of virtual addresses will map the memory occupied
         *   by the kernel and initrd as decrypted and write-protected.
         *
         *     The use of write-protect attribute will prevent any of the
         *     memory from being cached.
         */

        /* Physical addresses gives us the identity mapped virtual addresses */
        kernel_start = __pa_symbol(_text);
        kernel_end = ALIGN(__pa_symbol(_end), PMD_PAGE_SIZE);
        kernel_len = kernel_end - kernel_start;

        initrd_start = 0;
        initrd_end = 0;
        initrd_len = 0;
#ifdef CONFIG_BLK_DEV_INITRD
        initrd_len = (unsigned long)bp->hdr.ramdisk_size |
                     ((unsigned long)bp->ext_ramdisk_size << 32);
        if (initrd_len) {
                initrd_start = (unsigned long)bp->hdr.ramdisk_image |
                               ((unsigned long)bp->ext_ramdisk_image << 32);
                initrd_end = PAGE_ALIGN(initrd_start + initrd_len);
                initrd_len = initrd_end - initrd_start;
        }
#endif

        /*
         * We're running identity mapped, so we must obtain the address to the
         * SME encryption workarea using rip-relative addressing.
         */
        asm ("lea sme_workarea(%%rip), %0"
             : "=r" (workarea_start)
             : "p" (sme_workarea));

        /*
         * Calculate required number of workarea bytes needed:
         *   executable encryption area size:
         *     stack page (PAGE_SIZE)
         *     encryption routine page (PAGE_SIZE)
         *     intermediate copy buffer (PMD_PAGE_SIZE)
         *   pagetable structures for the encryption of the kernel
         *   pagetable structures for workarea (in case not currently mapped)
         */
        execute_start = workarea_start;
        execute_end = execute_start + (PAGE_SIZE * 2) + PMD_PAGE_SIZE;
        execute_len = execute_end - execute_start;

        /*
         * One PGD for both encrypted and decrypted mappings and a set of
         * PUDs and PMDs for each of the encrypted and decrypted mappings.
         */
        pgtable_area_len = sizeof(pgd_t) * PTRS_PER_PGD;
        pgtable_area_len += sme_pgtable_calc(execute_end - kernel_start) * 2;
        if (initrd_len)
                pgtable_area_len += sme_pgtable_calc(initrd_len) * 2;

        /* PUDs and PMDs needed in the current pagetables for the workarea */
        pgtable_area_len += sme_pgtable_calc(execute_len + pgtable_area_len);

        /*
         * The total workarea includes the executable encryption area and
         * the pagetable area. The start of the workarea is already 2MB
         * aligned, align the end of the workarea on a 2MB boundary so that
         * we don't try to create/allocate PTE entries from the workarea
         * before it is mapped.
         */
        workarea_len = execute_len + pgtable_area_len;
        workarea_end = ALIGN(workarea_start + workarea_len, PMD_PAGE_SIZE);

        /*
         * Set the address to the start of where newly created pagetable
         * structures (PGDs, PUDs and PMDs) will be allocated. New pagetable
         * structures are created when the workarea is added to the current
         * pagetables and when the new encrypted and decrypted kernel
         * mappings are populated.
         */
        ppd.pgtable_area = (void *)execute_end;

        /*
         * Make sure the current pagetable structure has entries for
         * addressing the workarea.
         */
        ppd.pgd = (pgd_t *)native_read_cr3_pa();
        ppd.paddr = workarea_start;
        ppd.vaddr = workarea_start;
        ppd.vaddr_end = workarea_end;
        sme_map_range_decrypted(&ppd);

        /* Flush the TLB - no globals so cr3 is enough */
        native_write_cr3(__native_read_cr3());

        /*
         * A new pagetable structure is being built to allow for the kernel
         * and initrd to be encrypted. It starts with an empty PGD that will
         * then be populated with new PUDs and PMDs as the encrypted and
         * decrypted kernel mappings are created.
         */
        ppd.pgd = ppd.pgtable_area;
        memset(ppd.pgd, 0, sizeof(pgd_t) * PTRS_PER_PGD);
        ppd.pgtable_area += sizeof(pgd_t) * PTRS_PER_PGD;

        /*
         * A different PGD index/entry must be used to get different
         * pagetable entries for the decrypted mapping. Choose the next
         * PGD index and convert it to a virtual address to be used as
         * the base of the mapping.
         */
        decrypted_base = (pgd_index(workarea_end) + 1) & (PTRS_PER_PGD - 1);
        if (initrd_len) {
                unsigned long check_base;

                check_base = (pgd_index(initrd_end) + 1) & (PTRS_PER_PGD - 1);
                decrypted_base = max(decrypted_base, check_base);
        }
        decrypted_base <<= PGDIR_SHIFT;

        /* Add encrypted kernel (identity) mappings */
        ppd.paddr = kernel_start;
        ppd.vaddr = kernel_start;
        ppd.vaddr_end = kernel_end;
        sme_map_range_encrypted(&ppd);

        /* Add decrypted, write-protected kernel (non-identity) mappings */
        ppd.paddr = kernel_start;
        ppd.vaddr = kernel_start + decrypted_base;
        ppd.vaddr_end = kernel_end + decrypted_base;
        sme_map_range_decrypted_wp(&ppd);

        if (initrd_len) {
                /* Add encrypted initrd (identity) mappings */
                ppd.paddr = initrd_start;
                ppd.vaddr = initrd_start;
                ppd.vaddr_end = initrd_end;
                sme_map_range_encrypted(&ppd);
                /*
                 * Add decrypted, write-protected initrd (non-identity) mappings
                 */
                ppd.paddr = initrd_start;
                ppd.vaddr = initrd_start + decrypted_base;
                ppd.vaddr_end = initrd_end + decrypted_base;
                sme_map_range_decrypted_wp(&ppd);
        }

        /* Add decrypted workarea mappings to both kernel mappings */
        ppd.paddr = workarea_start;
        ppd.vaddr = workarea_start;
        ppd.vaddr_end = workarea_end;
        sme_map_range_decrypted(&ppd);

        ppd.paddr = workarea_start;
        ppd.vaddr = workarea_start + decrypted_base;
        ppd.vaddr_end = workarea_end + decrypted_base;
        sme_map_range_decrypted(&ppd);

        /* Perform the encryption */
        sme_encrypt_execute(kernel_start, kernel_start + decrypted_base,
                            kernel_len, workarea_start, (unsigned long)ppd.pgd);

        if (initrd_len)
                sme_encrypt_execute(initrd_start, initrd_start + decrypted_base,
                                    initrd_len, workarea_start,
                                    (unsigned long)ppd.pgd);

        /*
         * At this point we are running encrypted.  Remove the mappings for
         * the decrypted areas - all that is needed for this is to remove
         * the PGD entry/entries.
         */
        ppd.vaddr = kernel_start + decrypted_base;
        ppd.vaddr_end = kernel_end + decrypted_base;
        sme_clear_pgd(&ppd);

        if (initrd_len) {
                ppd.vaddr = initrd_start + decrypted_base;
                ppd.vaddr_end = initrd_end + decrypted_base;
                sme_clear_pgd(&ppd);
        }

        ppd.vaddr = workarea_start + decrypted_base;
        ppd.vaddr_end = workarea_end + decrypted_base;
        sme_clear_pgd(&ppd);

        /* Flush the TLB - no globals so cr3 is enough */
        native_write_cr3(__native_read_cr3());
}

void __init sme_enable(struct boot_params *bp)
{
        const char *cmdline_ptr, *cmdline_arg, *cmdline_on, *cmdline_off;
        unsigned int eax, ebx, ecx, edx;
        unsigned long feature_mask;
        bool active_by_default;
        unsigned long me_mask;
        char buffer[16];
        u64 msr;

        /* Check for the SME/SEV support leaf */
        eax = 0x80000000;
        ecx = 0;
        native_cpuid(&eax, &ebx, &ecx, &edx);
        if (eax < 0x8000001f)
                return;

#define AMD_SME_BIT     BIT(0)
#define AMD_SEV_BIT     BIT(1)

        /* Check the SEV MSR whether SEV or SME is enabled */
        sev_status   = __rdmsr(MSR_AMD64_SEV);
        feature_mask = (sev_status & MSR_AMD64_SEV_ENABLED) ? AMD_SEV_BIT : AMD_SME_BIT;

        /*
         * Check for the SME/SEV feature:
         *   CPUID Fn8000_001F[EAX]
         *   - Bit 0 - Secure Memory Encryption support
         *   - Bit 1 - Secure Encrypted Virtualization support
         *   CPUID Fn8000_001F[EBX]
         *   - Bits 5:0 - Pagetable bit position used to indicate encryption
         */
        eax = 0x8000001f;
        ecx = 0;
        native_cpuid(&eax, &ebx, &ecx, &edx);
        if (!(eax & feature_mask))
                return;

        me_mask = 1UL << (ebx & 0x3f);

        /* Check if memory encryption is enabled */
        if (feature_mask == AMD_SME_BIT) {
                /*
                 * No SME if Hypervisor bit is set. This check is here to
                 * prevent a guest from trying to enable SME. For running as a
                 * KVM guest the MSR_K8_SYSCFG will be sufficient, but there
                 * might be other hypervisors which emulate that MSR as non-zero
                 * or even pass it through to the guest.
                 * A malicious hypervisor can still trick a guest into this
                 * path, but there is no way to protect against that.
                 */
                eax = 1;
                ecx = 0;
                native_cpuid(&eax, &ebx, &ecx, &edx);
                if (ecx & BIT(31))
                        return;

                /* For SME, check the SYSCFG MSR */
                msr = __rdmsr(MSR_K8_SYSCFG);
                if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT))
                        return;
        } else {
                /* SEV state cannot be controlled by a command line option */
                sme_me_mask = me_mask;
                physical_mask &= ~sme_me_mask;
                return;
        }

        /*
         * Fixups have not been applied to phys_base yet and we're running
         * identity mapped, so we must obtain the address to the SME command
         * line argument data using rip-relative addressing.
         */
        asm ("lea sme_cmdline_arg(%%rip), %0"
             : "=r" (cmdline_arg)
             : "p" (sme_cmdline_arg));
        asm ("lea sme_cmdline_on(%%rip), %0"
             : "=r" (cmdline_on)
             : "p" (sme_cmdline_on));
        asm ("lea sme_cmdline_off(%%rip), %0"
             : "=r" (cmdline_off)
             : "p" (sme_cmdline_off));

        if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT))
                active_by_default = true;
        else
                active_by_default = false;

        cmdline_ptr = (const char *)((u64)bp->hdr.cmd_line_ptr |
                                     ((u64)bp->ext_cmd_line_ptr << 32));

        cmdline_find_option(cmdline_ptr, cmdline_arg, buffer, sizeof(buffer));

        if (!strncmp(buffer, cmdline_on, sizeof(buffer)))
                sme_me_mask = me_mask;
        else if (!strncmp(buffer, cmdline_off, sizeof(buffer)))
                sme_me_mask = 0;
        else
                sme_me_mask = active_by_default ? me_mask : 0;

        physical_mask &= ~sme_me_mask;
}