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| 1 | +//! Loading user applications into memory |
| 2 | +//! |
| 3 | +//! For chapter 3, user applications are simply part of the data included in the |
| 4 | +//! kernel binary, so we only need to copy them to the space allocated for each |
| 5 | +//! app to load them. We also allocate fixed spaces for each task's |
| 6 | +//! [`KernelStack`] and [`UserStack`]. |
| 7 | +
|
| 8 | +use crate::config::*; |
| 9 | +use crate::trap::TrapContext; |
| 10 | +use core::arch::asm; |
| 11 | + |
| 12 | +#[repr(align(4096))] |
| 13 | +#[derive(Copy, Clone)] |
| 14 | +struct KernelStack { |
| 15 | + data: [u8; KERNEL_STACK_SIZE], |
| 16 | +} |
| 17 | + |
| 18 | +#[repr(align(4096))] |
| 19 | +#[derive(Copy, Clone)] |
| 20 | +struct UserStack { |
| 21 | + data: [u8; USER_STACK_SIZE], |
| 22 | +} |
| 23 | + |
| 24 | +static KERNEL_STACK: [KernelStack; MAX_APP_NUM] = [KernelStack { |
| 25 | + data: [0; KERNEL_STACK_SIZE], |
| 26 | +}; MAX_APP_NUM]; |
| 27 | + |
| 28 | +static USER_STACK: [UserStack; MAX_APP_NUM] = [UserStack { |
| 29 | + data: [0; USER_STACK_SIZE], |
| 30 | +}; MAX_APP_NUM]; |
| 31 | + |
| 32 | +impl KernelStack { |
| 33 | + fn get_sp(&self) -> usize { |
| 34 | + self.data.as_ptr() as usize + KERNEL_STACK_SIZE |
| 35 | + } |
| 36 | + pub fn push_context(&self, trap_cx: TrapContext) -> usize { |
| 37 | + let trap_cx_ptr = (self.get_sp() - core::mem::size_of::<TrapContext>()) as *mut TrapContext; |
| 38 | + unsafe { |
| 39 | + *trap_cx_ptr = trap_cx; |
| 40 | + } |
| 41 | + trap_cx_ptr as usize |
| 42 | + } |
| 43 | +} |
| 44 | + |
| 45 | +impl UserStack { |
| 46 | + fn get_sp(&self) -> usize { |
| 47 | + self.data.as_ptr() as usize + USER_STACK_SIZE |
| 48 | + } |
| 49 | +} |
| 50 | + |
| 51 | +/// Get base address of app i. |
| 52 | +fn get_base_i(app_id: usize) -> usize { |
| 53 | + APP_BASE_ADDRESS + app_id * APP_SIZE_LIMIT |
| 54 | +} |
| 55 | + |
| 56 | +/// Get the total number of applications. |
| 57 | +pub fn get_num_app() -> usize { |
| 58 | + extern "C" { |
| 59 | + fn _num_app(); |
| 60 | + } |
| 61 | + unsafe { (_num_app as usize as *const usize).read_volatile() } |
| 62 | +} |
| 63 | + |
| 64 | +/// Load nth user app at |
| 65 | +/// [APP_BASE_ADDRESS + n * APP_SIZE_LIMIT, APP_BASE_ADDRESS + (n+1) * APP_SIZE_LIMIT). |
| 66 | +pub fn load_apps() { |
| 67 | + extern "C" { |
| 68 | + fn _num_app(); |
| 69 | + } |
| 70 | + let num_app_ptr = _num_app as usize as *const usize; |
| 71 | + let num_app = get_num_app(); |
| 72 | + let app_start = unsafe { core::slice::from_raw_parts(num_app_ptr.add(1), num_app + 1) }; |
| 73 | + // load apps |
| 74 | + for i in 0..num_app { |
| 75 | + let base_i = get_base_i(i); |
| 76 | + // clear region |
| 77 | + (base_i..base_i + APP_SIZE_LIMIT) |
| 78 | + .for_each(|addr| unsafe { (addr as *mut u8).write_volatile(0) }); |
| 79 | + // load app from data section to memory |
| 80 | + let src = unsafe { |
| 81 | + core::slice::from_raw_parts(app_start[i] as *const u8, app_start[i + 1] - app_start[i]) |
| 82 | + }; |
| 83 | + let dst = unsafe { core::slice::from_raw_parts_mut(base_i as *mut u8, src.len()) }; |
| 84 | + dst.copy_from_slice(src); |
| 85 | + } |
| 86 | + // Memory fence about fetching the instruction memory |
| 87 | + // It is guaranteed that a subsequent instruction fetch must |
| 88 | + // observes all previous writes to the instruction memory. |
| 89 | + // Therefore, fence.i must be executed after we have loaded |
| 90 | + // the code of the next app into the instruction memory. |
| 91 | + // See also: riscv non-priv spec chapter 3, 'Zifencei' extension. |
| 92 | + unsafe { |
| 93 | + asm!("fence.i"); |
| 94 | + } |
| 95 | +} |
| 96 | + |
| 97 | +/// get app info with entry and sp and save `TrapContext` in kernel stack |
| 98 | +pub fn init_app_cx(app_id: usize) -> usize { |
| 99 | + KERNEL_STACK[app_id].push_context(TrapContext::app_init_context( |
| 100 | + get_base_i(app_id), |
| 101 | + USER_STACK[app_id].get_sp(), |
| 102 | + )) |
| 103 | +} |
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