Efiloader
efiloader is the bootloader for Poplar on x86_64. It utilities UEFI boot-services to load the kernel and any
extra images needed into memory, allocate memory for the heap, configure a basic framebuffer, and enter the kernel.
Description of booting process
A rough order of the steps that efiloader performs is:
- Parses a set of load options passed to the loader, allowing the user to instruct it on how to load the kernel
- Finds the physical address of the RSDP, so the kernel can find the ACPI tables
- Creates a basic framebuffer using the UEFI GOP (Graphics Output Protocol), if requested
- Allocate and map a heap for the kernel to use
- Load any additional images needed from the filesystem
- Constructs some "boot info", including a map of physical memory, telling the kernel about the hardware
- Jumps into the kernel
Load options
A series of load options may be supplied to efiloader to tell it how Poplar should be booted. These options
consist of a string of space separated key-value pairs, of the form a.dot.separated.key=value. Supported keys,
plus descriptions of their values, are:
| Key | Example value | Description |
|---|---|---|
kernel | kernel.elf | The path within the ESP that the kernel should be loaded from. |
fb.none | No value | Specify that a GOP framebuffer should not be created. |
fb.width | 1920 | Specify that a GOP framebuffer should be created, and its width. |
fb.height | 1080 | Specify that a GOP framebuffer should be created, and its height. |
image.{name} | my_task.elf | Specifies a path that an additional image should be loaded from. The key is the name that is passed in the boot info. |
If no load options are supplied, a kernel will be loaded from \kernel.elf, no additional images will be loaded,
and a GOP framebuffer with a width of 800 and a height of 600 will be created.