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arm: implement API to validate user buffer

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Implement API to validate user buffer. This API will iterate
all MPU regions to check if the given buffer is user accessible
or not. For #3832.

Signed-off-by: Chunlin Han <chunlin.han@linaro.org>
This commit is contained in:
Chunlin Han 2017-11-14 19:06:19 +08:00 • committed by Anas Nashif
commit d051740ee0
5 changed files with 174 additions and 0 deletions
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8
arch/arm/core/cortex_m/mpu/arm_core_mpu.c
View file

@ -79,4 +79,12 @@ void _arch_mem_domain_destroy(struct k_mem_domain *domain)
arm_core_mpu_enable();
}
/*
* Validate the given buffer is user accessible or not
*/
int _arch_buffer_validate(void *addr, size_t size, int write)
{
return arm_core_mpu_buffer_validate(addr, size, write);
}
#endif

79
arch/arm/core/cortex_m/mpu/arm_mpu.c
View file

@ -140,6 +140,56 @@ static inline u32_t _size_to_mpu_rasr_size(u32_t size)
return (find_msb_set(size) - 2) << 1;
}
/**
* This internal function check if region is enabled or not
*/
static inline int _is_enabled_region(u32_t r_index)
{
ARM_MPU_DEV->rnr = r_index;
return ARM_MPU_DEV->rasr & REGION_ENABLE_MASK;
}
/**
* This internal function check if the given buffer in in the region
*/
static inline int _is_in_region(u32_t r_index, u32_t start, u32_t size)
{
u32_t r_addr_start;
u32_t r_size_lshift;
u32_t r_addr_end;
ARM_MPU_DEV->rnr = r_index;
r_addr_start = ARM_MPU_DEV->rbar & REGION_BASE_ADDR_MASK;
r_size_lshift = ((ARM_MPU_DEV->rasr & REGION_SIZE_MASK) >>
REGION_SIZE_OFFSET) + 1;
r_addr_end = r_addr_start + (1 << r_size_lshift) - 1;
if (start >= r_addr_start && (start + size - 1) <= r_addr_end) {
return 1;
}
return 0;
}
/**
* This internal function check if the region is user accessible or not
*/
static inline int _is_user_accessible_region(u32_t r_index, int write)
{
u32_t r_ap;
ARM_MPU_DEV->rnr = r_index;
r_ap = ARM_MPU_DEV->rasr & ACCESS_PERMS_MASK;
if (write) {
return r_ap == P_RW_U_RW;
}
/* For all user accessible permissions, their AP[1] bit is l */
return r_ap & (0x2 << ACCESS_PERMS_OFFSET);
}
/* ARM Core MPU Driver API Implementation for ARM MPU */
/**
@ -292,6 +342,35 @@ int arm_core_mpu_get_max_domain_partition_regions(void)
return _get_num_regions() -
_get_region_index_by_type(THREAD_DOMAIN_PARTITION_REGION);
}
/**
* @brief validate the given buffer is user accessible or not
*/
int arm_core_mpu_buffer_validate(void *addr, size_t size, int write)
{
u32_t r_index;
/* Iterate all mpu regions in reversed order */
for (r_index = _get_num_regions() + 1; r_index-- > 0;) {
if (!_is_enabled_region(r_index) ||
!_is_in_region(r_index, (u32_t)addr, size)) {
continue;
}
/* For ARM MPU, higher region number takes priority.
* Since we iterate all mpu regions in reversed order, so
* we can stop the iteration immediately once we find the
* matched region that grants permission or denies access.
*/
if (_is_user_accessible_region(r_index, write)) {
return 0;
} else {
return -EPERM;
}
}
return -EPERM;
}
#endif /* CONFIG_USERSPACE */
/* ARM MPU Driver Initial Setup */

67
arch/arm/core/cortex_m/mpu/nxp_mpu.c
View file

@ -112,6 +112,46 @@ static inline u32_t _get_region_index_by_type(u32_t type)
}
}
/**
* This internal function check if region is enabled or not
*/
static inline int _is_enabled_region(u32_t r_index)
{
return SYSMPU->WORD[r_index][3] & SYSMPU_WORD_VLD_MASK;
}
/**
* This internal function check if the given buffer in in the region
*/
static inline int _is_in_region(u32_t r_index, u32_t start, u32_t size)
{
u32_t r_addr_start;
u32_t r_addr_end;
r_addr_start = SYSMPU->WORD[r_index][0];
r_addr_end = SYSMPU->WORD[r_index][1];
if (start >= r_addr_start && (start + size - 1) <= r_addr_end) {
return 1;
}
return 0;
}
/**
* This internal function check if the region is user accessible or not
*/
static inline int _is_user_accessible_region(u32_t r_index, int write)
{
u32_t r_ap = SYSMPU->WORD[r_index][2];
if (write) {
return (r_ap & MPU_REGION_WRITE) == MPU_REGION_WRITE;
}
return (r_ap & MPU_REGION_READ) == MPU_REGION_READ;
}
/* ARM Core MPU Driver API Implementation for NXP MPU */
/**
@ -322,6 +362,33 @@ int arm_core_mpu_get_max_domain_partition_regions(void)
return _get_num_regions() -
_get_region_index_by_type(THREAD_DOMAIN_PARTITION_REGION) - 1;
}
/**
* @brief validate the given buffer is user accessible or not
*/
int arm_core_mpu_buffer_validate(void *addr, size_t size, int write)
{
u32_t r_index;
/* Iterate all mpu regions */
for (r_index = 0; r_index < _get_num_regions(); r_index++) {
if (!_is_enabled_region(r_index) ||
!_is_in_region(r_index, (u32_t)addr, size)) {
continue;
}
/* For NXP MPU, priority given to granting permission over
* denying access for overlapping region.
* So we can stop the iteration immediately once we find the
* matched region that grants permission.
*/
if (_is_user_accessible_region(r_index, write)) {
return 0;
}
}
return -EPERM;
}
#endif /* CONFIG_USERSPACE */
/* NXP MPU Driver Initial Setup */

5
include/arch/arm/cortex_m/mpu/arm_core_mpu_dev.h
View file

@ -92,6 +92,11 @@ void arm_core_mpu_mem_partition_remove(u32_t part_index);
*/
int arm_core_mpu_get_max_domain_partition_regions(void);
/**
* @brief validate the given buffer is user accessible or not
*/
int arm_core_mpu_buffer_validate(void *addr, size_t size, int write);
#endif /* CONFIG_ARM_CORE_MPU */
#ifdef __cplusplus

15
include/arch/arm/cortex_m/mpu/arm_mpu.h
View file

@ -48,6 +48,21 @@ struct arm_mpu {
/* Region base address mask */
#define REGION_BASE_ADDR_MASK 0xFFFFFFE0
/* ARM MPU RASR Register */
/* Region enable bit offset */
#define REGION_ENABLE_OFFSET (0)
/* Region enable bit mask */
#define REGION_ENABLE_MASK (0x1 << REGION_ENABLE_OFFSET)
/* Region size bit offset */
#define REGION_SIZE_OFFSET (1)
/* Region size bit mask */
#define REGION_SIZE_MASK (0x1F << REGION_SIZE_OFFSET)
/* Access permissions bit offset */
#define ACCESS_PERMS_OFFSET (24)
/* Access permissions bit mask */
#define ACCESS_PERMS_MASK (0x7 << ACCESS_PERMS_OFFSET)
/* eXecute Never */
#define NOT_EXEC (0x1 << 28)