arch/arm64/mm/pgd.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * PGD allocation/freeing
 *
 * Copyright (C) 2012 ARM Ltd.
 * Author: Catalin Marinas <catalin.marinas@arm.com>
 */

#include <linux/mm.h>
#include <linux/gfp.h>
#include <linux/highmem.h>
#include <linux/set_memory.h>
#include <linux/slab.h>

#include <asm/mmu_context.h>
#include <asm/pgalloc.h>
#include <asm/page.h>
#include <asm/tlbflush.h>

static struct kmem_cache *pgd_cache __ro_after_init;

pgd_t *pgd_alloc(struct mm_struct *mm)
{
	gfp_t gfp = GFP_PGTABLE_USER;
	pgd_t *pgd;

	if (PGD_SIZE < PAGE_SIZE && !page_tables_are_ro())
		return kmem_cache_alloc(pgd_cache, gfp);

	pgd = (pgd_t *)__get_free_page(gfp);
	if (!pgd)
		return NULL;
	if (page_tables_are_ro())
		set_pgtable_ro(pgd);
	return pgd;
}

void pgd_free(struct mm_struct *mm, pgd_t *pgd)
{
	if (PGD_SIZE < PAGE_SIZE && !page_tables_are_ro()) {
		kmem_cache_free(pgd_cache, pgd);
	} else {
		if (page_tables_are_ro())
			set_pgtable_rw(pgd);
		free_page((unsigned long)pgd);
	}
}

void __init pgtable_cache_init(void)
{
	if (PGD_SIZE == PAGE_SIZE || page_tables_are_ro())
		return;

#ifdef CONFIG_ARM64_PA_BITS_52
	/*
	 * With 52-bit physical addresses, the architecture requires the
	 * top-level table to be aligned to at least 64 bytes.
	 */
	BUILD_BUG_ON(PGD_SIZE < 64);
#endif

	/*
	 * Naturally aligned pgds required by the architecture.
	 */
	pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_SIZE,
				      SLAB_PANIC, NULL);
}