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Update a-100-line-kernel.md

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Wang Taojie
2024-04-11 15:11:31 +08:00
committed by Tate, Hongliang Tian
parent c3c6b0c19d
commit 726632ad70
1 changed files with 31 additions and 21 deletions
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52
docs/src/framework/a-100-line-kernel.md
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@ -7,23 +7,29 @@ we will show a new kernel in about 100 lines of safe Rust.
Our new kernel will be able to run the following Hello World program.
```s
global _start
section .text
.global _start # entry point
.section .text # code section
_start:
mov rax, 1 ; syswrite
mov rdi, 1 ; fd
mov rsi, msg ; "Hello, world!\n",
mov rdx, msglen ; sizeof("Hello, world!\n")
mov $1, %rax # syscall number of write
mov $1, %rdi # stdout
mov $message, %rsi # address of message
mov $message_end, %rdx
sub %rsi, %rdx # calculate message len
syscall
mov $60, %rax # syscall number of exit, move it to rax
mov $0, %rdi # exit code, move it to rdi
syscall
mov rax, 60 ; sys_exit
mov rdi, 0 ; exit_code
syscall
.section .rodata # read only data section
message:
.ascii "Hello, world\n"
message_end:
```
section .rodata
msg: db "Hello, world!", 10
The assembly program above can be compiled with the following command.
```bash
gcc -static -nostdlib hello.S -o hello
```
The user program above requires our kernel to support three main features:
@ -40,8 +46,9 @@ to highlight how the APIs of Asterinas Framework enable safe kernel development.
extern crate alloc;
use alloc::boxed::Box;
use alloc::collections::VecDeque;
use align_ext::AlignExt;
use core::str;
use alloc::sync::Arc;
use alloc::vec;
@ -49,7 +56,7 @@ use aster_frame::cpu::UserContext;
use aster_frame::prelude::*;
use aster_frame::task::{Task, TaskOptions};
use aster_frame::user::{UserEvent, UserMode, UserSpace};
use aster_frame::vm::{Vaddr, VmAllocOptions, VmIo, VmMapOptions, VmPerm, VmSpace};
use aster_frame::vm::{Vaddr, VmAllocOptions, VmIo, VmMapOptions, VmPerm, VmSpace, PAGE_SIZE};
/// The kernel's boot and initialization process is managed by Asterinas Framework.
/// After the process is done, the kernel's execution environment
@ -59,17 +66,18 @@ use aster_frame::vm::{Vaddr, VmAllocOptions, VmIo, VmMapOptions, VmPerm, VmSpace
pub fn main() {
let program_binary = include_bytes!("../hello_world");
let user_space = create_user_space(program_binary);
let user_task = create_user_task(user_space);
let user_task = create_user_task(Arc::new(user_space));
user_task.run();
}
fn create_user_space(program: &[u8]) -> UserSpace {
let user_pages = {
let nframes = content.len().align_up(PAGE_SIZE) / PAGE_SIZE;
let nframes = program.len().align_up(PAGE_SIZE) / PAGE_SIZE;
let vm_frames = VmAllocOptions::new(nframes).alloc().unwrap();
// Phyiscal memory pages can be only accessed
// via the VmFrame abstraction.
frames.write_bytes(0, program).unwrap()
vm_frames.write_bytes(0, program).unwrap();
vm_frames
};
let user_address_space = {
const MAP_ADDR: Vaddr = 0x0040_0000; // The map addr for statically-linked executable
@ -91,6 +99,7 @@ fn create_user_space(program: &[u8]) -> UserSpace {
// abstraction.
let mut user_cpu_state = UserContext::default();
user_cpu_state.set_rip(ENTRY_POINT);
user_cpu_state
};
UserSpace::new(user_address_space, user_cpu_state)
}
@ -114,7 +123,7 @@ fn create_user_task(user_space: Arc<UserSpace>) -> Arc<Task> {
// the `UserContext` abstraction.
let user_context = user_mode.context_mut();
if UserEvent::Syscall == user_event {
handle_syscall(user_context, user_space);
handle_syscall(user_context, current.user_space().unwrap());
}
}
}
@ -136,7 +145,7 @@ fn handle_syscall(user_context: &mut UserContext, user_space: &UserSpace) {
match user_context.rax() {
SYS_WRITE => {
// Access the user-space CPU registers safely.
let (fd, buf_addr, buf_len) =
let (_, buf_addr, buf_len) =
(user_context.rdi(), user_context.rsi(), user_context.rdx());
let buf = {
let mut buf = vec![0u8; buf_len];
@ -146,6 +155,7 @@ fn handle_syscall(user_context: &mut UserContext, user_space: &UserSpace) {
.vm_space()
.read_bytes(buf_addr, &mut buf)
.unwrap();
buf
};
// Use the console for output safely.
println!("{}", str::from_utf8(&buf).unwrap());