path: root/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_CACHE_MASK) | \
				 (_PAGE_PAT | _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