arm: nxp: mpu: Fix off-by-1 error in region index calculation

Both the ARM and NXP MPU drivers incorrectly calculated the region index by assuming the region type (e.g., THREAD_STACK_GUARD_REGION) was zero-indexed, when in reality it is one-indexed. This had the effect of wasting one region. Signed-off-by: Maureen Helm <[email protected]>
zephyrproject-rtos · Jun 9, 2017 · 0a8ad73 · 0a8ad73
1 parent 07e0a78
commit 0a8ad73
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Showing 2 changed files with 10 additions and 6 deletions.
diff --git a/arch/arm/core/cortex_m/mpu/arm_mpu.c b/arch/arm/core/cortex_m/mpu/arm_mpu.c
@@ -108,10 +108,12 @@ void arm_core_mpu_configure(u8_t type, u32_t base, u32_t size)
 {
  SYS_LOG_DBG("Region info: 0x%x 0x%x", base, size);
  /*
- * The new MPU regions are are allocated per type after the statically
- * configured regions.
+ * The new MPU regions are allocated per type after the statically
+ * configured regions. The type is one-indexed rather than
+ * zero-indexed, therefore we need to subtract by one to get the region
+ * index.
  */
- u32_t region_index = mpu_config.num_regions + type;
+ u32_t region_index = mpu_config.num_regions + type - 1;
  u32_t region_attr = _get_region_attr_by_type(type, size);
 
  /* ARM MPU supports up to 16 Regions */

diff --git a/arch/arm/core/cortex_m/mpu/nxp_mpu.c b/arch/arm/core/cortex_m/mpu/nxp_mpu.c
@@ -120,10 +120,12 @@ void arm_core_mpu_configure(u8_t type, u32_t base, u32_t size)
 {
  SYS_LOG_DBG("Region info: 0x%x 0x%x", base, size);
  /*
- * The new MPU regions are are allocated per type after the statically
- * configured regions.
+ * The new MPU regions are allocated per type after the statically
+ * configured regions. The type is one-indexed rather than
+ * zero-indexed, therefore we need to subtract by one to get the region
+ * index.
  */
- u32_t region_index = mpu_config.num_regions + type;
+ u32_t region_index = mpu_config.num_regions + type - 1;
  u32_t region_attr = _get_region_attr_by_type(type);
  u32_t last_region = _get_num_regions() - 1;