Exit BootServices fails on real machine if custom memory type is used.

[hannahfluch]

When allocating memory for a UEFI application using BootServices with a custom memory type, the ExitBootServices call later freezes on a real machine, but it works fine in QEMU.

Everything works as expected on the real machine as well, if MemoryType::LOADER_DATA is used.

System Information:

Tested on: Lenovo V15 G3 IAP
CPU: 12th Gen Intel(R) Core(TM) i5-1235U
Rust Toolchain: nightly

Dependencies Used:

log = "0.4.22"
uefi = { version = "0.31.0", features = ["logger", "alloc", "global_allocator", "panic_handler"] }

Source Code:

config.toml

[unstable]
build-std = ["core", "compiler_builtins", "alloc"]
build-std-features = ["compiler-builtins-mem"]

[build]
target = "x86_64-unknown-uefi"

main.rs

#![no_std]
#![no_main]
extern crate alloc;

use alloc::format;
use alloc::string::String;

use log::info;
use uefi::{
    entry,
    Handle,
    Status, table::{Boot, SystemTable},
};
use uefi::prelude::BootServices;
use uefi::proto::console::gop::{GraphicsOutput, PixelFormat};
use uefi::table::boot::{AllocateType, MemoryType};

use crate::framebuffer::{Color, FrameBufferMetadata, RawFrameBuffer};

mod framebuffer;

const MY_MEMORY_TYPE: MemoryType = MemoryType::custom(0x80000001);
#[entry]
fn main(_image_handle: Handle, system_table: SystemTable<Boot>) -> Status {
    uefi::helpers::init().unwrap();

    info!("Hello, uefi world!");

    // some boilerplate to get a working framebuffer using Graphics Output Protocol
    let fb_meta = initialize_framebuffer(system_table.boot_services()).unwrap();
    let fb = RawFrameBuffer::from(fb_meta);

    // color white indicates framebuffer initialization was successful
    fb.fill(Color::white());

    // allocate some memory using the custom memory type
    let x = system_table.boot_services().allocate_pages(AllocateType::AnyPages, MY_MEMORY_TYPE, 5).unwrap();
    // "use" the newly allocated memory
    let _y = unsafe { *(x as *const u8) };

    // color blue indicates allocation was successful
    fb.fill(Color::blue());

    // exit boot services
    let (_, _) = unsafe { system_table.exit_boot_services(MemoryType::LOADER_DATA) };

    // color green indicates exit was successful
    fb.fill(Color::green());

    loop {}
}


/// Initialize framebuffer (GOP)
fn initialize_framebuffer(
    boot_services: &BootServices,
) -> Result<FrameBufferMetadata, String> {
    let gop_handle = boot_services
        .get_handle_for_protocol::<GraphicsOutput>()
        .map_err(|error| format!("Could not get handle for GOP: {error}."))?;

    let mut gop = boot_services
        .open_protocol_exclusive::<GraphicsOutput>(gop_handle)
        .map_err(|error| format!("Could not open GOP: {error}."))?;
    let mut raw_frame_buffer = gop.frame_buffer();
    let base = raw_frame_buffer.as_mut_ptr() as u64;
    let size = raw_frame_buffer.size();
    let info = gop.current_mode_info();

    let is_rgb = match info.pixel_format() {
        PixelFormat::Rgb => Ok(true),
        PixelFormat::Bgr => Ok(false),
        PixelFormat::Bitmask | PixelFormat::BltOnly => {
            Err("Not supported")
        }
    }?;
    let (width, height) = info.resolution();
    let stride = info.stride();

    Ok(FrameBufferMetadata {
        base,
        size,
        width,
        height,
        stride,
        is_rgb,
    })
}

framebuffer.rs

use core::{
    fmt,
    fmt::{Debug, Formatter},
};
use core::ptr::write_volatile;

pub(crate) const BPP: usize = 4;

#[derive(Copy, Clone)]
pub(crate) struct FrameBufferMetadata {
    pub(crate) base: u64,
    pub(crate) size: usize,
    pub(crate) width: usize,
    pub(crate) height: usize,
    pub(crate) stride: usize, // pixels per scanline
    pub(crate) is_rgb: bool,
}

impl Debug for FrameBufferMetadata {
    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
        f.write_fmt(format_args!(
            "FrameBufferMetadata {{\n\tbase: {:#x},\n\tsize: {:#x},\n\twidth: {},\n\theight: {},\n\tstride: {},\n}}",
            self.base, self.size, self.width, self.height, self.stride
        ))
    }
}
#[derive(Copy, Clone, Debug, Default)]
pub(crate) struct Color {
    pub(crate) red: u8,
    pub(crate) green: u8,
    pub(crate) blue: u8,
}
macro_rules! color {
    ($color:ident, $red:expr, $green:expr, $blue:expr) => {
        impl Color {
            pub(crate) const fn $color() -> Color {
                Color {
                    red: $red,
                    green: $green,
                    blue: $blue,
                }
            }
        }
    };
}

color!(green, 0x00, 0xFF, 0x00);
color!(blue, 0x00, 0x00, 0xFF);
color!(white, 0xFF, 0xFF, 0xFF);

/// Directly accesses video memory in order to display graphics
#[derive(Clone, Debug)]
pub(crate) struct RawFrameBuffer {
    pub(crate) meta_data: FrameBufferMetadata,
}

impl RawFrameBuffer {
    /// Draws a pixel onto the screen at coordinates x,y and with the specified color. Returns, whether the action succeeds or the coordinates are invalid.
    pub(crate) fn draw_pixel(
        &self,
        x: usize,
        y: usize,
        color: Color,
    ) -> Result<(), (usize, usize)> {
        if !self.in_bounds(x, y) {
            return Err((x, y));
        }

        let pitch = self.meta_data.stride * BPP;

        unsafe {
            let pixel = (self.meta_data.base as *mut u8).add(pitch * y + BPP * x);

            if self.meta_data.is_rgb {
                write_volatile(pixel, color.red);
                write_volatile(pixel.add(1), color.green);
                write_volatile(pixel.add(2), color.blue);
            } else {
                write_volatile(pixel, color.blue);
                write_volatile(pixel.add(1), color.green);
                write_volatile(pixel.add(2), color.red);
            }
        }

        Ok(())
    }
    /// Fills entire display with certain color
    pub(crate) fn fill(&self, color: Color) {
        for x in 0..self.meta_data.width {
            for y in 0..self.meta_data.height {
                self.draw_pixel(x, y, color).unwrap();
            }
        }
    }
}

impl RawFrameBuffer {
    /// Whether a point is within the framebuffer vram
    fn in_bounds(&self, x: usize, y: usize) -> bool {
        x < self.meta_data.width && y < self.meta_data.height
    }
}

impl From<FrameBufferMetadata> for RawFrameBuffer {
    fn from(value: FrameBufferMetadata) -> Self {
        Self { meta_data: value }
    }
}

Note: I'm relatively new to the UEFI and OSDev community so there might be an issue with my code itself. Please feel free to correct me if the mistake is mine.

[phip1611]

Do you have the option to get the serial output from the real hardware? This would help to get a specific panic message.

[hannahfluch]

Unfortuantely not. I also set up a more comprehensive loader where the panic handler uses my own screen writing protocol utilizing the framebuffer I got from the GOP. It still hangs nevertheless.

I did find someone facing the same issue though: StackOverflow

[hannahfluch]

The issue seems to be platform-specific and independent of the rust implementation, thus I will close it.
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