1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154

//! batch subsystem

use crate::sync::UPSafeCell;
use crate::trap::TrapContext;
use core::arch::asm;
use lazy_static::*;

const USER_STACK_SIZE: usize = 4096 * 2;
const KERNEL_STACK_SIZE: usize = 4096 * 2;
const MAX_APP_NUM: usize = 16;
const APP_BASE_ADDRESS: usize = 0x80400000;
const APP_SIZE_LIMIT: usize = 0x20000;

#[repr(align(4096))]
struct KernelStack {
    data: [u8; KERNEL_STACK_SIZE],
}

#[repr(align(4096))]
struct UserStack {
    data: [u8; USER_STACK_SIZE],
}

static KERNEL_STACK: KernelStack = KernelStack {
    data: [0; KERNEL_STACK_SIZE],
};
static USER_STACK: UserStack = UserStack {
    data: [0; USER_STACK_SIZE],
};

impl KernelStack {
    fn get_sp(&self) -> usize {
        self.data.as_ptr() as usize + KERNEL_STACK_SIZE
    }
    pub fn push_context(&self, cx: TrapContext) -> &'static mut TrapContext {
        let cx_ptr = (self.get_sp() - core::mem::size_of::<TrapContext>()) as *mut TrapContext;
        unsafe {
            *cx_ptr = cx;
        }
        unsafe { cx_ptr.as_mut().unwrap() }
    }
}

impl UserStack {
    fn get_sp(&self) -> usize {
        self.data.as_ptr() as usize + USER_STACK_SIZE
    }
}

struct AppManager {
    num_app: usize,
    current_app: usize,
    app_start: [usize; MAX_APP_NUM + 1],
}

impl AppManager {
    pub fn print_app_info(&self) {
        println!("[kernel] num_app = {}", self.num_app);
        for i in 0..self.num_app {
            println!(
                "[kernel] app_{} [{:#x}, {:#x})",
                i,
                self.app_start[i],
                self.app_start[i + 1]
            );
        }
    }

    unsafe fn load_app(&self, app_id: usize) {
        if app_id >= self.num_app {
            println!("All applications completed!");
            use crate::board::QEMUExit;
            crate::board::QEMU_EXIT_HANDLE.exit_success();
        }
        println!("[kernel] Loading app_{}", app_id);
        // clear app area
        core::slice::from_raw_parts_mut(APP_BASE_ADDRESS as *mut u8, APP_SIZE_LIMIT).fill(0);
        let app_src = core::slice::from_raw_parts(
            self.app_start[app_id] as *const u8,
            self.app_start[app_id + 1] - self.app_start[app_id],
        );
        let app_dst = core::slice::from_raw_parts_mut(APP_BASE_ADDRESS as *mut u8, app_src.len());
        app_dst.copy_from_slice(app_src);
        // Memory fence about fetching the instruction memory
        // It is guaranteed that a subsequent instruction fetch must
        // observes all previous writes to the instruction memory.
        // Therefore, fence.i must be executed after we have loaded
        // the code of the next app into the instruction memory.
        // See also: riscv non-priv spec chapter 3, 'Zifencei' extension.
        asm!("fence.i");
    }

    pub fn get_current_app(&self) -> usize {
        self.current_app
    }

    pub fn move_to_next_app(&mut self) {
        self.current_app += 1;
    }
}

lazy_static! {
    static ref APP_MANAGER: UPSafeCell<AppManager> = unsafe {
        UPSafeCell::new({
            extern "C" {
                fn _num_app();
            }
            let num_app_ptr = _num_app as usize as *const usize;
            let num_app = num_app_ptr.read_volatile();
            let mut app_start: [usize; MAX_APP_NUM + 1] = [0; MAX_APP_NUM + 1];
            let app_start_raw: &[usize] =
                core::slice::from_raw_parts(num_app_ptr.add(1), num_app + 1);
            app_start[..=num_app].copy_from_slice(app_start_raw);
            AppManager {
                num_app,
                current_app: 0,
                app_start,
            }
        })
    };
}

/// init batch subsystem
pub fn init() {
    print_app_info();
}

/// print apps info
pub fn print_app_info() {
    APP_MANAGER.exclusive_access().print_app_info();
}

/// run next app
pub fn run_next_app() -> ! {
    let mut app_manager = APP_MANAGER.exclusive_access();
    let current_app = app_manager.get_current_app();
    unsafe {
        app_manager.load_app(current_app);
    }
    app_manager.move_to_next_app();
    drop(app_manager);
    // before this we have to drop local variables related to resources manually
    // and release the resources
    extern "C" {
        fn __restore(cx_addr: usize);
    }
    unsafe {
        __restore(KERNEL_STACK.push_context(TrapContext::app_init_context(
            APP_BASE_ADDRESS,
            USER_STACK.get_sp(),
        )) as *const _ as usize);
    }
    panic!("Unreachable in batch::run_current_app!");
}