alistair23-linux/include/asm-generic/pgalloc.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __ASM_GENERIC_PGALLOC_H
#define __ASM_GENERIC_PGALLOC_H

#ifdef CONFIG_MMU

#define GFP_PGTABLE_KERNEL	(GFP_KERNEL | __GFP_ZERO)
#define GFP_PGTABLE_USER	(GFP_PGTABLE_KERNEL | __GFP_ACCOUNT)

/**
 * __pte_alloc_one_kernel - allocate a page for PTE-level kernel page table
 * @mm: the mm_struct of the current context
 *
 * This function is intended for architectures that need
 * anything beyond simple page allocation.
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
static inline pte_t *__pte_alloc_one_kernel(struct mm_struct *mm)
{
	return (pte_t *)__get_free_page(GFP_PGTABLE_KERNEL);
}

#ifndef __HAVE_ARCH_PTE_ALLOC_ONE_KERNEL
/**
 * pte_alloc_one_kernel - allocate a page for PTE-level kernel page table
 * @mm: the mm_struct of the current context
 *
 * Return: pointer to the allocated memory or %NULL on error
 */
static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
{
	return __pte_alloc_one_kernel(mm);
}
#endif

/**
 * pte_free_kernel - free PTE-level kernel page table page
 * @mm: the mm_struct of the current context
 * @pte: pointer to the memory containing the page table
 */
static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
{
	free_page((unsigned long)pte);
}

/**
 * __pte_alloc_one - allocate a page for PTE-level user page table
 * @mm: the mm_struct of the current context
 * @gfp: GFP flags to use for the allocation
 *
 * Allocates a page and runs the pgtable_page_ctor().
 *
 * This function is intended for architectures that need
 * anything beyond simple page allocation or must have custom GFP flags.
 *
 * Return: `struct page` initialized as page table or %NULL on error
 */
static inline pgtable_t __pte_alloc_one(struct mm_struct *mm, gfp_t gfp)
{
	struct page *pte;

	pte = alloc_page(gfp);
	if (!pte)
		return NULL;
	if (!pgtable_page_ctor(pte)) {
		__free_page(pte);
		return NULL;
	}

	return pte;
}

#ifndef __HAVE_ARCH_PTE_ALLOC_ONE
/**
 * pte_alloc_one - allocate a page for PTE-level user page table
 * @mm: the mm_struct of the current context
 *
 * Allocates a page and runs the pgtable_page_ctor().
 *
 * Return: `struct page` initialized as page table or %NULL on error
 */
static inline pgtable_t pte_alloc_one(struct mm_struct *mm)
{
	return __pte_alloc_one(mm, GFP_PGTABLE_USER);
}
#endif

/*
 * Should really implement gc for free page table pages. This could be
 * done with a reference count in struct page.
 */

/**
 * pte_free - free PTE-level user page table page
 * @mm: the mm_struct of the current context
 * @pte_page: the `struct page` representing the page table
 */
static inline void pte_free(struct mm_struct *mm, struct page *pte_page)
{
	pgtable_page_dtor(pte_page);
	__free_page(pte_page);
}

#endif /* CONFIG_MMU */

#endif /* __ASM_GENERIC_PGALLOC_H */