mpu.h File Reference

Distinct Armv7-M and Armv8-M MPU encoding mechanisms. More...

#include "nexus/arch/features.h"
#include <stdbool.h>
#include <stdint.h>

Go to the source code of this file.

Data Structures
struct	nx_arch_mpu_v7_region_t
	Armv7-M region fields, without an implicit memory policy. More...
struct	nx_arch_mpu_v7_encoding_t
	Armv7-M words targeting the caller-selected RNR, not RBAR.VALID. More...
struct	nx_arch_mpu_v8_region_t
	Armv8-M fields; limit is the exact inclusive final byte. More...
struct	nx_arch_mpu_v8_encoding_t
	Armv8-M words retaining its separate MAIR indirection. More...

Functions
nx_arch_result_t	nx_arch_mpu_v7_encode (const nx_arch_mpu_v7_region_t *region, nx_arch_mpu_v7_encoding_t *encoding)
	Encode an exact Armv7-M region without accessing hardware.
nx_arch_result_t	nx_arch_mpu_v8_encode (const nx_arch_mpu_v8_region_t *region, nx_arch_mpu_v8_encoding_t *encoding)
	Encode an exact Armv8-M region without accessing hardware.
nx_arch_result_t	nx_arch_mpu_v7_program (uint32_t index, const nx_arch_mpu_v7_region_t *region)
	Program one disabled-MPU Armv7-M region in this world.
nx_arch_result_t	nx_arch_mpu_v8_program (uint32_t index, const nx_arch_mpu_v8_region_t *region)
	Program one disabled-MPU Armv8-M region in this world.
nx_arch_result_t	nx_arch_mpu_v8_attribute_set (uint32_t index, uint32_t attribute)
	Update one Armv8-M MAIR byte without changing its neighbors.

Detailed Description

Distinct Armv7-M and Armv8-M MPU encoding mechanisms.

Author

Nexus Team

Definition in file mpu.h.

Function Documentation

nx_arch_mpu_v7_encode()

nx_arch_result_t nx_arch_mpu_v7_encode	(	const nx_arch_mpu_v7_region_t *	region,
		nx_arch_mpu_v7_encoding_t *	encoding )

Encode an exact Armv7-M region without accessing hardware.

Parameters

[in]	region	Size exponent 5..32, aligned base, AP 0/1/2/3/5/6, TEX 0..7 and raw S/C/B bits. Subregion mask is at most 255 and must be zero for sizes below 256 bytes. A 4 GiB region has base zero. Reserved/implementation-defined TEX/C/B encodings are rejected, never truncated or rounded.
[out]	encoding	RBAR and enabled RASR; unchanged on failure.

Returns

NX_ARCH_OK or NX_ARCH_INVALID, independent of CPU profile.

Note

Pure bounded task/IRQ function. Inputs and output must not overlap. This encodes fields, not SoC memory reachability, cache ownership, DMA coherency or product protection policy.

nx_arch_mpu_v7_program()

nx_arch_result_t nx_arch_mpu_v7_program	(	uint32_t	index,
		const nx_arch_mpu_v7_region_t *	region )

Program one disabled-MPU Armv7-M region in this world.

Parameters

[in]	index	Region number below actual MPU_TYPE.DREGION.
[in]	region	Fields validated by nx_arch_mpu_v7_encode.

Returns

NX_ARCH_UNSUPPORTED before MMIO for a different/absent compiled MPU; NX_ARCH_INVALID for invalid fields or index; NX_ARCH_CONTEXT for an unprivileged, Handler, unmasked or enabled-MPU caller. Rejection performs no register writes.

Note

Privileged Thread only with PRIMASK set and exclusive caller ownership of this MPU. NMI/HardFault/another security world must not modify it. Disables only the selected region, writes its fields, restores incoming RNR and leaves CTRL unchanged. No allocation, OS calls, implicit MPU enable, bulk clear or Secure access to the Non-secure alias.

nx_arch_mpu_v8_attribute_set()

nx_arch_result_t nx_arch_mpu_v8_attribute_set	(	uint32_t	index,
		uint32_t	attribute )

Update one Armv8-M MAIR byte without changing its neighbors.

Parameters

[in]	index	Attribute slot 0..7.
[in]	attribute	Architectural MAIR byte, at most 255. Device encodings are 0x00/0x04/0x08/0x0c; Normal memory uses nonzero outer/inner nibbles other than reserved 0x8.

Returns

NX_ARCH_OK, NX_ARCH_UNSUPPORTED for absent/v7 MPU, NX_ARCH_INVALID for an out-of-range field, or NX_ARCH_CONTEXT under the programming context rules.

Note

Caller owns valid memory attributes and all regions using this slot. Privileged masked Thread, disabled MPU and exclusive local ownership required. No CTRL or RNR writes, no cache maintenance, and no cross-world register access.

nx_arch_mpu_v8_encode()

nx_arch_result_t nx_arch_mpu_v8_encode	(	const nx_arch_mpu_v8_region_t *	region,
		nx_arch_mpu_v8_encoding_t *	encoding )

Encode an exact Armv8-M region without accessing hardware.

Parameters

[in]	region	32-byte aligned base, inclusive limit ending in 0x1f, base not above limit, AP 0..3, SH 0/2/3 and MAIR index 0..7. The caller owns the corresponding MAIR policy.
[out]	encoding	RBAR and enabled RLAR; unchanged on failure.

Returns

NX_ARCH_OK or NX_ARCH_INVALID, independent of CPU profile.

Note

Pure bounded task/IRQ function. Inputs and output must not overlap. No address rounding or v7/v8 policy conversion.

nx_arch_mpu_v8_program()

nx_arch_result_t nx_arch_mpu_v8_program	(	uint32_t	index,
		const nx_arch_mpu_v8_region_t *	region )

Program one disabled-MPU Armv8-M region in this world.

Parameters

[in]	index	Region number below actual MPU_TYPE.DREGION.
[in]	region	Fields validated by nx_arch_mpu_v8_encode.

Returns

Same rejection and ownership rules as v7_program; the compiled MPU must specifically implement Armv8-M.

Note

Privileged masked Thread, disabled MPU and exclusive local ownership required. No MAIR updates or cross-world alias access. Incoming RNR and CTRL are preserved.