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99 lines
2.8 KiB
99 lines
2.8 KiB
//! Loading user applications into memory
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//!
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//! For chapter 3, user applications are simply part of the data included in the
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//! kernel binary, so we only need to copy them to the space allocated for each
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//! app to load them. We also allocate fixed spaces for each task's
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//! [`KernelStack`] and [`UserStack`].
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use crate::config::*;
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use crate::trap::TrapContext;
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use core::arch::asm;
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#[repr(align(4096))]
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#[derive(Copy, Clone)]
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struct KernelStack {
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data: [u8; KERNEL_STACK_SIZE],
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}
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#[repr(align(4096))]
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#[derive(Copy, Clone)]
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struct UserStack {
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data: [u8; USER_STACK_SIZE],
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}
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static KERNEL_STACK: [KernelStack; MAX_APP_NUM] = [KernelStack {
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data: [0; KERNEL_STACK_SIZE],
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}; MAX_APP_NUM];
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static USER_STACK: [UserStack; MAX_APP_NUM] = [UserStack {
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data: [0; USER_STACK_SIZE],
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}; MAX_APP_NUM];
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impl KernelStack {
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fn get_sp(&self) -> usize {
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self.data.as_ptr() as usize + KERNEL_STACK_SIZE
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}
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pub fn push_context(&self, trap_cx: TrapContext) -> usize {
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let trap_cx_ptr = (self.get_sp() - core::mem::size_of::<TrapContext>()) as *mut TrapContext;
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unsafe {
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*trap_cx_ptr = trap_cx;
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}
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trap_cx_ptr as usize
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}
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}
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impl UserStack {
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fn get_sp(&self) -> usize {
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self.data.as_ptr() as usize + USER_STACK_SIZE
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}
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}
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/// Get base address of app i.
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fn get_base_i(app_id: usize) -> usize {
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APP_BASE_ADDRESS + app_id * APP_SIZE_LIMIT
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}
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/// Get the total number of applications.
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pub fn get_num_app() -> usize {
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extern "C" {
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fn _num_app();
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}
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unsafe { (_num_app as usize as *const usize).read_volatile() }
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}
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/// Load nth user app at
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/// [APP_BASE_ADDRESS + n * APP_SIZE_LIMIT, APP_BASE_ADDRESS + (n+1) * APP_SIZE_LIMIT).
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pub fn load_apps() {
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extern "C" {
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fn _num_app();
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}
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let num_app_ptr = _num_app as usize as *const usize;
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let num_app = get_num_app();
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let app_start = unsafe { core::slice::from_raw_parts(num_app_ptr.add(1), num_app + 1) };
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// clear i-cache first
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unsafe {
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asm!("fence.i");
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}
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// load apps
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for i in 0..num_app {
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let base_i = get_base_i(i);
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// clear region
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(base_i..base_i + APP_SIZE_LIMIT)
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.for_each(|addr| unsafe { (addr as *mut u8).write_volatile(0) });
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// load app from data section to memory
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let src = unsafe {
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core::slice::from_raw_parts(app_start[i] as *const u8, app_start[i + 1] - app_start[i])
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};
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let dst = unsafe { core::slice::from_raw_parts_mut(base_i as *mut u8, src.len()) };
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dst.copy_from_slice(src);
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}
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}
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/// get app info with entry and sp and save `TrapContext` in kernel stack
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pub fn init_app_cx(app_id: usize) -> usize {
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KERNEL_STACK[app_id].push_context(TrapContext::app_init_context(
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get_base_i(app_id),
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USER_STACK[app_id].get_sp(),
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))
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}
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