Bus fault and memory protection in ARM Architecture - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the type of fault caused by an invalid memory access.

ARM Architecture

if (fault_status == [1]) {
    // Handle bus fault
}

Drag options to blanks, or click blank then click option'

A0x05

B0x01

C0x0B

D0x0F

Attempts:

3 left

💡 Hint

Common Mistakes

Using a status code that corresponds to a different fault type.

The value 0x05 corresponds to a bus fault status indicating an invalid memory access on ARM processors.

2fill in blank

medium

Complete the code to enable memory protection unit (MPU) for a specific region.

ARM Architecture

MPU->RNR = [1]; // Select region number
MPU->RBAR = region_base_address;
MPU->RASR = region_attributes;

Drag options to blanks, or click blank then click option'

A3

B1

C2

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using a region number outside the valid range.

Region number 0 is often the first MPU region to configure.

3fill in blank

hard

Fix the error in the code that checks if a bus fault occurred by reading the correct fault status register.

ARM Architecture

if (SCB->[1] & (1 << 1)) {
    // Bus fault occurred
}

Drag options to blanks, or click blank then click option'

ADFSR

BHFSR

CCFSR

DMMFAR

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong fault status register leading to incorrect fault detection.

The CFSR (Configurable Fault Status Register) bit 1 indicates if a Bus Fault occurred.

4fill in blank

hard

Fill both blanks to configure an MPU region with read-only access and enable it.

ARM Architecture

MPU->RASR = ([1] << 2) | ([2] << 0);

Drag options to blanks, or click blank then click option'

A0x06

B0x03

C1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing access permission bits or forgetting to enable the region.

0x06 sets the access permission bits for read-only, and 1 enables the region.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps region numbers to their base addresses if the region is enabled.

ARM Architecture

region_map = { [1]: [2] for [1] in range(8) if is_region_enabled([1]) }

Drag options to blanks, or click blank then click option'

Ai

Bget_region_base(i)

Dregion_num

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent variable names or incorrect function calls.

Using i as the loop variable and key, and get_region_base(i) to get the base address for enabled regions.