Doom

and pixel format before it can render anything — this is the discovery mechanism. Why it matters: Userspace needs the framebuffer dimensions, pitch, bytes-per-pixel,. Focus on `sys_framebuffer_info` and `0x1002` in `kernel/src/arch/x86_64/syscall.rs` while you trace the snippet.

fn sys_framebuffer_info(buf_addr: u64, buf_len: u64) -> u64 {
    const USER_LIMIT: u64 = 0x0000_8000_0000_0000;
    const FB_INFO_SIZE: u64 = core::mem::size_of::<FbInfo>() as u64;

    if buf_addr == 0 || buf_addr >= USER_LIMIT || buf_len < FB_INFO_SIZE {
        return NEG_EINVAL;
    }

    let (width, height, stride, bpp, pixel_format) = match crate::fb::framebuffer_raw_info() {
        Some(info) => info,
        None => return NEG_EINVAL,
    };

    let pixel_format_val: u32 = match pixel_format {
        bootloader_api::info::PixelFormat::Rgb => 0,
        bootloader_api::info::PixelFormat::Bgr => 1,
        _ => return NEG_EINVAL,
    };

    let info = FbInfo {
        width: width as u32,
        height: height as u32,
        stride: stride as u32,
        bpp: bpp as u32,

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assembly or direct syscall invocation) need named constants for the new syscall. Why it matters: Rust userspace programs (and the C platform layer via inline. Focus on `syscall-lib` and `SYS_FRAMEBUFFER_INFO` in `userspace/syscall-lib/src/lib.rs` while you trace the snippet.

/// Phase 47: framebuffer info syscall.
pub const SYS_FRAMEBUFFER_INFO: u64 = 0x1005;

/// Phase 47: framebuffer mmap syscall.
pub const SYS_FRAMEBUFFER_MMAP: u64 = 0x1006;

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same framebuffer memory, causing garbled output. Why it matters: Without this, the kernel text console and DOOM would race on the. Focus on `yield_console` and `write_str` in `kernel/src/fb/mod.rs` while you trace the snippet.

/// Suppresses all framebuffer console output.
///
/// For internal use only.  External callers that need to claim the
/// framebuffer should use [`try_yield_console`] which performs an
/// atomic compare-and-swap ownership check.
fn yield_console(owner_pid: u32) {
    FB_OWNER_PID.store(owner_pid, Ordering::Release);
    crate::arch::x86_64::interrupts::reset_raw_input_state();
    let _guard = CONSOLE.lock();
    CONSOLE_YIELDED.store(true, Ordering::Release);
}

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