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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. Our new kernel will be able to run the following Hello World program.
```s ```s
global _start .global _start # entry point
.section .text # code section
section .text
_start: _start:
mov rax, 1 ; syswrite mov $1, %rax # syscall number of write
mov rdi, 1 ; fd mov $1, %rdi # stdout
mov rsi, msg ; "Hello, world!\n", mov $message, %rsi # address of message
mov rdx, msglen ; sizeof("Hello, world!\n") mov $message_end, %rdx
sub %rsi, %rdx # calculate message len
syscall 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 .section .rodata # read only data section
mov rdi, 0 ; exit_code message:
syscall .ascii "Hello, world\n"
message_end:
```
section .rodata The assembly program above can be compiled with the following command.
msg: db "Hello, world!", 10
```bash
gcc -static -nostdlib hello.S -o hello
``` ```
The user program above requires our kernel to support three main features: 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; extern crate alloc;
use alloc::boxed::Box; use align_ext::AlignExt;
use alloc::collections::VecDeque; use core::str;
use alloc::sync::Arc; use alloc::sync::Arc;
use alloc::vec; use alloc::vec;
@ -49,7 +56,7 @@ use aster_frame::cpu::UserContext;
use aster_frame::prelude::*; use aster_frame::prelude::*;
use aster_frame::task::{Task, TaskOptions}; use aster_frame::task::{Task, TaskOptions};
use aster_frame::user::{UserEvent, UserMode, UserSpace}; 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. /// The kernel's boot and initialization process is managed by Asterinas Framework.
/// After the process is done, the kernel's execution environment /// 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() { pub fn main() {
let program_binary = include_bytes!("../hello_world"); let program_binary = include_bytes!("../hello_world");
let user_space = create_user_space(program_binary); 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(); user_task.run();
} }
fn create_user_space(program: &[u8]) -> UserSpace { fn create_user_space(program: &[u8]) -> UserSpace {
let user_pages = { 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(); let vm_frames = VmAllocOptions::new(nframes).alloc().unwrap();
// Phyiscal memory pages can be only accessed // Phyiscal memory pages can be only accessed
// via the VmFrame abstraction. // via the VmFrame abstraction.
frames.write_bytes(0, program).unwrap() vm_frames.write_bytes(0, program).unwrap();
vm_frames
}; };
let user_address_space = { let user_address_space = {
const MAP_ADDR: Vaddr = 0x0040_0000; // The map addr for statically-linked executable 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. // abstraction.
let mut user_cpu_state = UserContext::default(); let mut user_cpu_state = UserContext::default();
user_cpu_state.set_rip(ENTRY_POINT); user_cpu_state.set_rip(ENTRY_POINT);
user_cpu_state
}; };
UserSpace::new(user_address_space, 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. // the `UserContext` abstraction.
let user_context = user_mode.context_mut(); let user_context = user_mode.context_mut();
if UserEvent::Syscall == user_event { 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() { match user_context.rax() {
SYS_WRITE => { SYS_WRITE => {
// Access the user-space CPU registers safely. // 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()); (user_context.rdi(), user_context.rsi(), user_context.rdx());
let buf = { let buf = {
let mut buf = vec![0u8; buf_len]; let mut buf = vec![0u8; buf_len];
@ -146,6 +155,7 @@ fn handle_syscall(user_context: &mut UserContext, user_space: &UserSpace) {
.vm_space() .vm_space()
.read_bytes(buf_addr, &mut buf) .read_bytes(buf_addr, &mut buf)
.unwrap(); .unwrap();
buf
}; };
// Use the console for output safely. // Use the console for output safely.
println!("{}", str::from_utf8(&buf).unwrap()); println!("{}", str::from_utf8(&buf).unwrap());