zephyr/kernel/mm.h

/*
 * Copyright (c) 2020 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#ifndef ZEPHYR_INCLUDE_KERNEL_MM_H
#define ZEPHYR_INCLUDE_KERNEL_MM_H

#include <zephyr/sys/util.h>
#include <zephyr/toolchain.h>
#if defined(CONFIG_ARM_MMU) && defined(CONFIG_ARM64)
#include <zephyr/arch/arm64/arm_mem.h>
#elif defined(CONFIG_ARM_AARCH32_MMU)
#include <zephyr/arch/arm/mmu/arm_mem.h>
#endif /* CONFIG_ARM_MMU && CONFIG_ARM64 */

#include <zephyr/kernel/internal/mm.h>

/**
 * @brief Kernel Memory Management
 * @defgroup kernel_memory_management Kernel Memory Management
 * @ingroup kernel_apis
 * @{
 */

/**
 * @name Caching mode definitions.
 *
 * These are mutually exclusive.
 *
 * @{
 */

/** No caching. Most drivers want this. */
#define K_MEM_CACHE_NONE	2

/** Write-through caching. Used by certain drivers. */
#define K_MEM_CACHE_WT		1

/** Full write-back caching. Any RAM mapped wants this. */
#define K_MEM_CACHE_WB		0

/*
 * ARM64 Specific flags are defined in arch/arm64/arm_mem.h,
 * pay attention to be not conflicted when updating these flags.
 */

/** Reserved bits for cache modes in k_map() flags argument */
#define K_MEM_CACHE_MASK	(BIT(3) - 1)

/** @} */

/**
 * @name Region permission attributes.
 *
 * Default is read-only, no user, no exec
 *
 * @{
 */

/** Region will have read/write access (and not read-only) */
#define K_MEM_PERM_RW		BIT(3)

/** Region will be executable (normally forbidden) */
#define K_MEM_PERM_EXEC		BIT(4)

/** Region will be accessible to user mode (normally supervisor-only) */
#define K_MEM_PERM_USER		BIT(5)

/** @} */

/**
 * @name Region mapping behaviour attributes
 *
 * @{
 */

/** Region will be mapped to 1:1 virtual and physical address */
#define K_MEM_DIRECT_MAP	BIT(6)

/** @} */

#ifndef _ASMLANGUAGE
#include <stdint.h>
#include <stddef.h>
#include <inttypes.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @name k_mem_map() control flags
 *
 * @{
 */

/**
 * @brief The mapped region is not guaranteed to be zeroed.
 *
 * This may improve performance. The associated page frames may contain
 * indeterminate data, zeroes, or even sensitive information.
 *
 * This may not be used with K_MEM_PERM_USER as there are no circumstances
 * where this is safe.
 */
#define K_MEM_MAP_UNINIT	BIT(16)

/**
 * Region will be pinned in memory and never paged
 *
 * Such memory is guaranteed to never produce a page fault due to page-outs
 * or copy-on-write once the mapping call has returned. Physical page frames
 * will be pre-fetched as necessary and pinned.
 */
#define K_MEM_MAP_LOCK		BIT(17)

/**
 * Region will be unpaged i.e. not mapped into memory
 *
 * This is meant to be used by kernel code and not by application code.
 *
 * Corresponding memory address range will be set so no actual memory will
 * be allocated initially. Allocation will happen through demand paging when
 * addresses in that range are accessed. This is incompatible with
 * K_MEM_MAP_LOCK.
 *
 * When this flag is specified, the phys argument to arch_mem_map()
 * is interpreted as a backing store location value not a physical address.
 * This is very similar to arch_mem_page_out() in that regard.
 * Two special location values are defined: ARCH_UNPAGED_ANON_ZERO and
 * ARCH_UNPAGED_ANON_UNINIT. Those are to be used with anonymous memory
 * mappings for zeroed and uninitialized pages respectively.
 */
#define K_MEM_MAP_UNPAGED	BIT(18)

/** @} */

/**
 * Return the amount of free memory available
 *
 * The returned value will reflect how many free RAM page frames are available.
 * If demand paging is enabled, it may still be possible to allocate more.
 *
 * The information reported by this function may go stale immediately if
 * concurrent memory mappings or page-ins take place.
 *
 * @return Free physical RAM, in bytes
 */
size_t k_mem_free_get(void);

/**
 * Map anonymous memory into Zephyr's address space
 *
 * This function effectively increases the data space available to Zephyr.
 * The kernel will choose a base virtual address and return it to the caller.
 * The memory will have access permissions for all contexts set per the
 * provided flags argument.
 *
 * If user thread access control needs to be managed in any way, do not enable
 * K_MEM_PERM_USER flags here; instead manage the region's permissions
 * with memory domain APIs after the mapping has been established. Setting
 * K_MEM_PERM_USER here will allow all user threads to access this memory
 * which is usually undesirable.
 *
 * Unless K_MEM_MAP_UNINIT is used, the returned memory will be zeroed.
 *
 * The mapped region is not guaranteed to be physically contiguous in memory.
 * Physically contiguous buffers should be allocated statically and pinned
 * at build time.
 *
 * Pages mapped in this way have write-back cache settings.
 *
 * The returned virtual memory pointer will be page-aligned. The size
 * parameter, and any base address for re-mapping purposes must be page-
 * aligned.
 *
 * Note that the allocation includes two guard pages immediately before
 * and after the requested region. The total size of the allocation will be
 * the requested size plus the size of these two guard pages.
 *
 * Many K_MEM_MAP_* flags have been implemented to alter the behavior of this
 * function, with details in the documentation for these flags.
 *
 * @param size Size of the memory mapping. This must be page-aligned.
 * @param flags K_MEM_PERM_*, K_MEM_MAP_* control flags.
 * @return The mapped memory location, or NULL if insufficient virtual address
 *         space, insufficient physical memory to establish the mapping,
 *         or insufficient memory for paging structures.
 */
static inline void *k_mem_map(size_t size, uint32_t flags)
{
	return k_mem_map_phys_guard((uintptr_t)NULL, size, flags, true);
}

#ifdef CONFIG_DEMAND_MAPPING
/**
 * Create an unpaged mapping
 *
 * This maps backing-store "location" tokens into Zephyr's address space.
 * Corresponding memory address range will be set so no actual memory will
 * be allocated initially. Allocation will happen through demand paging when
 * addresses in the mapped range are accessed.
 *
 * The kernel will choose a base virtual address and return it to the caller.
 * The memory access permissions for all contexts will be set per the
 * provided flags argument.
 *
 * If user thread access control needs to be managed in any way, do not enable
 * K_MEM_PERM_USER flags here; instead manage the region's permissions
 * with memory domain APIs after the mapping has been established. Setting
 * K_MEM_PERM_USER here will allow all user threads to access this memory
 * which is usually undesirable.
 *
 * This is incompatible with K_MEM_MAP_LOCK.
 *
 * The provided backing-store "location" token must be linearly incrementable
 * by a page size across the entire mapping.
 *
 * Allocated pages will have write-back cache settings.
 *
 * The returned virtual memory pointer will be page-aligned. The size
 * parameter, and any base address for re-mapping purposes must be page-
 * aligned.
 *
 * Note that the allocation includes two guard pages immediately before
 * and after the requested region. The total size of the allocation will be
 * the requested size plus the size of these two guard pages.
 *
 * @param location Backing store initial location token
 * @param size Size of the memory mapping. This must be page-aligned.
 * @param flags K_MEM_PERM_*, K_MEM_MAP_* control flags.
 * @return The mapping location, or NULL if insufficient virtual address
 *         space to establish the mapping, or insufficient memory for paging
 *         structures.
 */
static inline void *k_mem_map_unpaged(uintptr_t location, size_t size, uint32_t flags)
{
	flags |= K_MEM_MAP_UNPAGED;
	return k_mem_map_phys_guard(location, size, flags, false);
}
#endif

/**
 * Un-map mapped memory
 *
 * This removes a memory mapping for the provided page-aligned region.
 * Associated page frames will be free and the kernel may re-use the associated
 * virtual address region. Any paged out data pages may be discarded.
 *
 * Calling this function on a region which was not mapped to begin with is
 * undefined behavior.
 *
 * @param addr Page-aligned memory region base virtual address
 * @param size Page-aligned memory region size
 */
static inline void k_mem_unmap(void *addr, size_t size)
{
	k_mem_unmap_phys_guard(addr, size, true);
}

/**
 * Modify memory mapping attribute flags
 *
 * This updates caching, access and control flags for the provided
 * page-aligned memory region.
 *
 * Calling this function on a region which was not mapped to begin with is
 * undefined behavior. However system memory implicitly mapped at boot time
 * is supported.
 *
 * @param addr Page-aligned memory region base virtual address
 * @param size Page-aligned memory region size
 * @param flags K_MEM_PERM_*, K_MEM_MAP_* control flags.
 * @return 0 for success, negative error code otherwise.
 */
int k_mem_update_flags(void *addr, size_t size, uint32_t flags);

/**
 * Given an arbitrary region, provide a aligned region that covers it
 *
 * The returned region will have both its base address and size aligned
 * to the provided alignment value.
 *
 * @param[out] aligned_addr Aligned address
 * @param[out] aligned_size Aligned region size
 * @param[in]  addr Region base address
 * @param[in]  size Region size
 * @param[in]  align What to align the address and size to
 * @return offset between aligned_addr and addr
 */
size_t k_mem_region_align(uintptr_t *aligned_addr, size_t *aligned_size,
			  uintptr_t addr, size_t size, size_t align);

#ifdef __cplusplus
}
#endif

/** @} */

#endif /* !_ASMLANGUAGE */
#endif /* ZEPHYR_INCLUDE_KERNEL_MM_H */