Passing data from a bootloader to a kernel is a crucial step in the boot process. This data can include boot parameters, memory maps, kernel command-line arguments, and other necessary information. There are several methods to achieve this, each with its advantages and use cases. In this article, we'll explore different ways to pass data from a bootloader to a kernel.
1 Using a Predefined Memory Location
This method involves storing the data at a specific, predefined memory address that both the bootloader and the kernel agree upon. The kernel then reads the data from this location during its initialization phase.
2 Using CPU Registers
Another method is to use CPU registers to pass small amounts of data. This is often used for passing pointers to data structures or simple flags.
3 Using BIOS Data Area
The BIOS data area (BDA) is a memory area used by the BIOS to store information about the system. A bootloader can use this area to pass information to the kernel.
4 Using a Boot Information Structure
You can define a custom boot information structure that the bootloader populates and the kernel reads. This structure is placed in a known memory location or passed via a register.