use syscall::flag::MapFlags;

mod offsets {
    extern "C" {
        // text (R-X)
        static __text_start: u8;
        static __text_end: u8;
        // rodata (R--)
        static __rodata_start: u8;
        static __rodata_end: u8;
        // data+bss (RW-)
        static __data_start: u8;
        static __bss_end: u8;

        static __end: u8;
    }
    pub fn text() -> (usize, usize) {
        unsafe { (&__text_start as *const u8 as usize, &__text_end as *const u8 as usize) }
    }
    pub fn rodata() -> (usize, usize) {
        unsafe { (&__rodata_start as *const u8 as usize, &__rodata_end as *const u8 as usize) }
    }
    pub fn data_and_bss() -> (usize, usize) {
        unsafe { (&__data_start as *const u8 as usize, &__bss_end as *const u8 as usize) }
    }
}

#[no_mangle]
pub unsafe extern "C" fn start() -> ! {
    // Remap self, from the previous RWX

    let (text_start, text_end) = offsets::text();
    let (rodata_start, rodata_end) = offsets::rodata();
    let (data_start, data_end) = offsets::data_and_bss();

    let _ = syscall::open("debug:", syscall::O_RDONLY); // stdin
    let _ = syscall::open("debug:", syscall::O_WRONLY); // stdout
    let _ = syscall::open("debug:", syscall::O_WRONLY); // stderr

    // TODO: PROT_NONE
    let _ = syscall::mprotect(0, 4096, MapFlags::PROT_READ | MapFlags::MAP_PRIVATE).expect("mprotect failed for NULL page");

    let _ = syscall::mprotect(text_start, text_end - text_start, MapFlags::PROT_READ | MapFlags::PROT_EXEC | MapFlags::MAP_PRIVATE).expect("mprotect failed for .text");
    let _ = syscall::mprotect(rodata_start, rodata_end - rodata_start, MapFlags::PROT_READ | MapFlags::MAP_PRIVATE).expect("mprotect failed for .rodata");
    let _ = syscall::mprotect(data_start, data_end - data_start, MapFlags::PROT_READ | MapFlags::PROT_WRITE | MapFlags::MAP_PRIVATE).expect("mprotect failed for .data/.bss");
    let _ = syscall::mprotect(data_end, crate::arch::STACK_START - data_end, MapFlags::PROT_READ | MapFlags::MAP_PRIVATE).expect("mprotect failed for rest of memory");

    crate::exec::main();
}