Boot

In this section, we explain how Awkernel boots.

x86_64

Primary Core

The primary core calls kernel_main of x86_64 first, which is called by UEFI.

1. kernel_main:kernel/src/arch/x86_64/kernel_main.rs
2. kernel_main2:kernel/src/arch/x86_64/kernel_main.rs
3. main:kernel/src/main.rs

graph TD;
    kernel_main:kernel_main.rs-->kernel_main2:kernel_main.rs;
    kernel_main2:kernel_main.rs-->main:main.rs;

During the primary core is booting, it wakes up non-primary cores by sending ACPI's IPIs.

Non-primary Cores

Non-primary cores calls _start_cpu defined in mpboot.S first, and it then calls non_primary_kernel_main. It eventually calls main like the primary core.

1. _start_cpu:kernel/asm/x86/mpboot.S
2. non_primary_kernel_main:kernel/src/arch/x86_64/kernel_main.rs
3. main:kernel/src/main.rs

graph TD;
    _start_cpu:mpboot.S-->non_primary_kernel_main:kernel_main.rs;
    non_primary_kernel_main:kernel_main.rs-->main:main.rs;

AArch64

Primary and Non-primary Cores

_start defined in boot.S is the entry point for both the primary and non-primary cores. _start eventually calls kernel_main in kernel_main.rs. After that, the primary core calls primary_cpu and non-primary cores call non_primary_cpu. Eventually, main is called.

1. _start:kernel/asm/aarch64/boot.S
2. kernel_main:kernel/src/arch/aarch64/kernel_main.rs
3. The primary core calls primary_cpu and non-primary cores call non_primary_cpu.
   1. primary_cpu:kernel/src/arch/aarch64/kernel_main.rs
   2. non_primary_cpu:kernel/src/arch/aarch64/kernel_main.rs
4. main:kernel/src/main.rs

graph TD;
    _start:boot.S-->kernel_main:kernel_main.rs;
    kernel_main:kernel_main.rs-->primary_cpu:kernel_main.rs;
    kernel_main:kernel_main.rs-->non_primary_cpu:kernel_main.rs;
    primary_cpu:kernel_main.rs-->main:main.rs;
    non_primary_cpu:kernel_main.rs-->main:main.rs;

Main Function

After booting, in the main function, the primary core wakes async/await tasks, and non-primary cores execute async/await tasks.

Primary Core

In main function, the primary core periodically calls wake_task and poll functions defined in awkernel_async_lib and awkernel_lib,

1. main:kernel/src/main.rs
2. wake_task:awkernel_async_lib/src/scheduler.rs
3. poll:awkernel_lib/src/net.rs

graph TD;
    main:kernel/src/main.rs-->wake_task:awkernel_async_lib/src/scheduler.rs;
    main:kernel/src/main.rs-->poll:awkernel_lib/src/net.rs;

wake_task is a function to wake sleeping async/await tasks up, and it will be explained in Sec. Scheduler. poll is a function to poll network interface controllers. If some events arrives, poll wakes async/await tasks related to the controllers.

Non-primary Cores

In main function, non-primary core periodically call run defined in awkernel_async_lib. run initializes variables regarding preemption by calling preempt::init. After that, it calls run_main to execute async/await tasks.

1. main:kernel/src/main.rs
2. run:awkernel_async_lib/src/task.rs
3. init:awkernel_async_lib/src/task/preempt.rs
4. run_main:awkernel_async_lib/src/task.rs

graph TD;
    main:kernel/src/main.rs-->run:awkernel_async_lib/src/task.rs;
    run:awkernel_async_lib/src/task.rs-->init:awkernel_async_lib/src/task/preempt.rs;
    run:awkernel_async_lib/src/task.rs-->run_main:awkernel_async_lib/src/task.rs;

run_main executes async/await tasks, and it will be explained in Sec. Scheduler.