The Comprehensive Guide to Using 'flashrom' (with examples)

Flashrom is an open-source utility designed to efficiently read, write, verify, and erase flash chips. It is a crucial tool for anyone dealing with firmware updates or backup processes, such as BIOS manipulation, embedded systems programming, or hardware hacking. The utility supports a wide range of flash ROM chips and offers a flexible set of commands to perform various operations, ensuring the correct functioning of hardware components.

Use case 1: Probe the chip, ensuring the wiring is correct

Code:

flashrom --programmer programmer

Motivation for using the example:

Before any data operations can commence on a flash chip, it’s imperative to ensure the wiring between the programmer and the flash chip is correctly set up. This probing step is vital because it can prevent any potential damage to the hardware or incorrect data manipulation that might occur due to faulty connections. Correct wiring ensures reliable communication between the programmer and the chip, providing an essential validation step in the flashing process.

Explanation for every argument given in the command:

• --programmer programmer: This part of the command specifies the programmer’s driver being used to interface with the flash chip. Replacing “programmer” with your actual programmer’s name is crucial for establishing the correct connection. The utility supports various programmers and requires you to specify one for the operations.

Example output:

Found chip <CHIP NAME> on <PROGRAMMER NAME>.
Action sequence successful.

Use case 2: Read flash and save it to a file

Code:

flashrom -p programmer --read path/to/file

Motivation for using the example:

Reading the flash and saving its content to a file is a fundamental step, especially for creating backups before making any changes to the firmware. By doing so, users ensure they have a recovery point to restore the original state should anything go awry during further operations like writing new data to the chip.

Explanation for every argument given in the command:

• -p programmer: Short for --programmer, this flag specifies the programmer’s driver, facilitating data exchange between the flash chip and the tool.
• --read path/to/file: This argument instructs flashrom to read the current contents of the flash chip and write it to the specified file path. It ensures the data is securely stored for future reference or restoration.

Example output:

Reading flash... Done.
Contents have been saved to path/to/file.

Use case 3: Write a file to the flash

Code:

flashrom -p programmer --write path/to/file

Motivation for using the example:

Writing a file to flash is often used when updating the firmware or applying custom configurations to a device. This could be necessary for performance enhancements, security patches, or enabling new hardware features. It is a delicate operation requiring accuracy and a reliable connection to prevent device bricking or incomplete updates.

Explanation for every argument given in the command:

• -p programmer: Again, this refers to the programmer interfacing with the flash chip.
• --write path/to/file: This directive tells flashrom to write the data from the specified file onto the flash chip, effectively overwriting its current contents.

Example output:

Erasing flash... Done.
Writing flash... Done.
Verifying flash... Done.
Flash operation successful.

Use case 4: Verify the flash against a file

Code:

flashrom -p programmer --verify path/to/file

Motivation for using the example:

Verification is a crucial step in the flashing process, acting as a safeguard to ensure that the data intended for the flash matches precisely with what’s actually written. It minimizes risks of data corruption and inconsistencies which might lead to faulty device behavior or failures after the flash operation.

Explanation for every argument given in the command:

• -p programmer: Specifies the programmer driver, ensuring the tool can communicate with the chip needed for verification processes.
• --verify path/to/file: This command checks if the current contents of the flash chip match the provided file, offering an additional layer of validation.

Example output:

Verifying against path/to/file... Done.
Contents are identical. Verification successful.

Use case 5: Probe the chip using Raspberry Pi

Code:

flashrom -p linux_spi:dev=/dev/spidev0.0

Motivation for using the example:

Utilizing a Raspberry Pi as a programmer can be a cost-effective and convenient option for many small-scale projects and educational purposes. Raspberry Pi’s GPIO pins provide accessible interfacing options with flash chips, making it an excellent choice for hobbyists and professionals alike who wish to perform flash operations without investing in dedicated hardware tools.

Explanation for every argument given in the command:

• -p linux_spi:dev=/dev/spidev0.0: This argument sets up the Raspberry Pi to act as the programmer by specifying the SPI (Serial Peripheral Interface) device. This setting for the dev path (/dev/spidev0.0) is typically configured to match the Pi’s SPI hardware interface.

Example output:

Found chip <CHIP NAME> on SPI bus connected to Raspberry Pi.
Action sequence successful.

Conclusion

Flashrom provides a robust suite of tools for interacting with flash chips, ranging from initial probing to ensure connectivity, all the way to complex operations like reading, writing, and verifying data. Whether working on a personal hobby project with a Raspberry Pi or handling critical firmware updates in an industrial setting, flashrom’s flexibility and broad support for different chips and programming interfaces make it an indispensable tool in any hardware engineer’s toolkit. Through the use of these detailed examples, users can navigate flashrom’s functionalities with greater confidence and precision.