QEMU Bug in macOS 14: No "Hello, World" in `post-02` - just a black screen. #1249

nskobelevs · 2023-10-13T20:30:25Z

Having issue with "Hello, World!" now being displayed in QEMU.
Didn't work with my own code - tried the post-02 branch as a sanity check but it didn't work there either.

OS: MacOS Sonoma 14.0
rustc Version: rustc 1.75.0-nightly (475c71da0 2023-10-11)
QEMU Version: 8.1.1

Video:

Screen.Recording.2023-10-13.at.21.21.53.mp4

The text was updated successfully, but these errors were encountered:

nskobelevs · 2023-10-13T20:33:14Z

post-03 seems to work though:

AtomicGamer9523 · 2023-10-13T22:10:12Z

There seems to be a trend of MacBooks not being able to run post-02.
Lemme see...

Edit: See #1249 (comment)

phil-opp · 2023-10-25T12:49:44Z

Thanks for reporting this issue! Are these M1/M2 Macs or older ones?

post-03 seems to work though:

That's surprising.. Both branches are writing to the VGA text buffer at 0xb8000, so I don't really understand how one of them works but the other doesn't...

nskobelevs · 2023-10-25T12:56:04Z

Are these M1/M2 Macs oder older ones?

These are the newer ones that started releasing in 2020 with Apple's new series of ARM chips ("Apple Silicon")

phil-opp · 2023-10-25T13:32:38Z

I just tried to reproduce this issue on an M2 MacBook Air, but the post-02 branch worked as expected for me.

nskobelevs · 2023-10-25T16:14:43Z

It's unlikely to be an issue specifically with M1 vs M2 given architecture is the same as far as I know.

What was the OS, QEMU & rustc versions on the M2 you used? - perhaps something is different there

qwerzl · 2023-10-31T13:40:48Z

Same here - the post-02 branch only outputs a blank screen. I'm with an M1Pro Macbook Pro.

Here are the versions that I'm using:
rustc: rustc 1.75.0-nightly (31bc7e2c4 2023-10-30)
QEMU: 8.1.2
OS: macOS Sonoma Version 14.0 Beta (23A5312d)

rprovodenko · 2023-11-19T20:47:49Z

The line width is different (160, not 80 as the code in post 3 assumes), and the first line is invisible. If you change the function to

#[no_mangle]
pub extern "C" fn _start() -> ! {
    let vga_buffer = 0xb8000 as *mut u8;

    for (i, &byte) in HELLO.iter().enumerate() {
        unsafe {
            let line_offset: isize = 160 * 2;
            let char_offset_within_line: isize = i as isize * 2;
            let color_offset_within_line: isize = i as isize * 2 + 1;
            let char_offset = char_offset_within_line + line_offset;
            let color_offset = color_offset_within_line + line_offset;


            *vga_buffer.offset(char_offset) = byte;
            *vga_buffer.offset(color_offset) = 0xb;
        }
    }

    loop {}
}

You get the first fully visible line

And:

let line_offset: isize = 160 * 24;

gives

Looking at the code of post 3 I see that it starts writing from column 23. So yeah, that's the problem. Maybe qemu has an ability to specify different settings for VGA, but it seems that it just doesn't display the 0 line with in the current setup

rprovodenko · 2023-11-19T21:09:09Z

#1252 is the fix

AtomicGamer9523 · 2023-11-20T00:26:34Z

This seems to be related to an issue on how Qemu works on MacOS. Specifically some bug, only visible in certain versions of Qemu...

Qemu Versions affected (going from comments): 8.1.1 and 8.1.2. Both of these are obtainable from Homebrew. MacPorts seems to be outdated and only hold the 8.0.5 version... could anybody test to see if that one is affected ?

vladimir-kazan · 2023-11-20T13:59:54Z

I've got the same problem, just figured out that the first line with "Hello world" is visible in full screen mode.

phil-opp · 2023-11-21T15:29:53Z

What was the OS, QEMU & rustc versions on the M2 you used? - perhaps something is different there

I'm also using 8.1.2 installed through homebrew. I just tried it again with the latest rustc nightly (2023-11-20), but I still see the expected output on the post-02 branch. I'm on macOS 13.5.2.

I've got the same problem, just figured out that the first line with "Hello world" is visible in full screen mode.

Interesting! Maybe it's just a window sizing bug then. Are you all on MacOS 14?

AtomicGamer9523 · 2023-11-21T16:27:04Z

What was the OS, QEMU & rustc versions on the M2 you used? - perhaps something is different there

I'm also using 8.1.2 installed through homebrew. I just tried it again with the latest rustc nightly (2023-11-20), but I still see the expected output on the post-02 branch. I'm on macOS 13.5.2.

I've got the same problem, just figured out that the first line with "Hello world" is visible in full screen mode.

Interesting! Maybe it's just a window sizing bug then. Are you all on MacOS 14?

Quite interesting... so this verifies that it is not the os code. It is an issue related to Qemu on MacOS.

that-ben · 2023-11-24T17:14:18Z

macOS Sonoma 14.1.1

Latest stable QEMU build also has the first 20-ish pixels at the top of the output window hidden by the window's title bar:

wzslr321 · 2023-12-21T00:34:21Z

The line width is different (160, not 80 as the code in post 3 assumes), and the first line is invisible. If you change the function to
#[no_mangle]
pub extern "C" fn _start() -> ! {
    let vga_buffer = 0xb8000 as *mut u8;

    for (i, &byte) in HELLO.iter().enumerate() {
        unsafe {
            let line_offset: isize = 160 * 2;
            let char_offset_within_line: isize = i as isize * 2;
            let color_offset_within_line: isize = i as isize * 2 + 1;
            let char_offset = char_offset_within_line + line_offset;
            let color_offset = color_offset_within_line + line_offset;


            *vga_buffer.offset(char_offset) = byte;
            *vga_buffer.offset(color_offset) = 0xb;
        }
    }

    loop {}
}
You get the first fully visible line
And:
let line_offset: isize = 160 * 24;
gives
Looking at the code of `post 3` I see that it starts writing from column `23`. So yeah, that's the problem. Maybe qemu has an ability to specify different settings for VGA, but it seems that it just doesn't display the `0` line with in the current setup

Works for me, thanks!

yasinldev · 2024-01-20T12:39:48Z

The line width is different (160, not 80 as the code in post 3 assumes), and the first line is invisible. If you change the function to
#[no_mangle]
pub extern "C" fn _start() -> ! {
    let vga_buffer = 0xb8000 as *mut u8;

    for (i, &byte) in HELLO.iter().enumerate() {
        unsafe {
            let line_offset: isize = 160 * 2;
            let char_offset_within_line: isize = i as isize * 2;
            let color_offset_within_line: isize = i as isize * 2 + 1;
            let char_offset = char_offset_within_line + line_offset;
            let color_offset = color_offset_within_line + line_offset;


            *vga_buffer.offset(char_offset) = byte;
            *vga_buffer.offset(color_offset) = 0xb;
        }
    }

    loop {}
}
You get the first fully visible line

And:
let line_offset: isize = 160 * 24;
gives

Looking at the code of post 3 I see that it starts writing from column 23. So yeah, that's the problem. Maybe qemu has an ability to specify different settings for VGA, but it seems that it just doesn't display the 0 line with in the current setup
Works for me, thanks!

thanks for the solution

NightProg · 2024-01-28T08:49:25Z

The line width is different (160, not 80 as the code in post 3 assumes), and the first line is invisible. If you change the function to
#[no_mangle]
pub extern "C" fn _start() -> ! {
    let vga_buffer = 0xb8000 as *mut u8;

    for (i, &byte) in HELLO.iter().enumerate() {
        unsafe {
            let line_offset: isize = 160 * 2;
            let char_offset_within_line: isize = i as isize * 2;
            let color_offset_within_line: isize = i as isize * 2 + 1;
            let char_offset = char_offset_within_line + line_offset;
            let color_offset = color_offset_within_line + line_offset;


            *vga_buffer.offset(char_offset) = byte;
            *vga_buffer.offset(color_offset) = 0xb;
        }
    }

    loop {}
}
You get the first fully visible line

And:
let line_offset: isize = 160 * 24;
gives

Looking at the code of post 3 I see that it starts writing from column 23. So yeah, that's the problem. Maybe qemu has an ability to specify different settings for VGA, but it seems that it just doesn't display the 0 line with in the current setup

Thanks that work for me

AtomicGamer9523 · 2024-02-27T00:00:17Z

I have opened this issue: https://gitlab.com/qemu-project/qemu/-/issues/1994

It's an API difference between Sonoma and earlier macOS versions NSView documented in https://developer.apple.com/documentation/macos-release-notes/appkit-release-notes-for-macos-14.

Sonoma set NSView.clipsToBounds to false by default and it was true in earlier versions.

DrDonk seems to he working on it, it will hopefully be in the upstream Qemu soon...

phil-opp · 2024-02-27T06:35:44Z

@AtomicGamer9523 Thanks a lot, that is great news!

AtomicGamer9523 · 2024-03-18T22:29:11Z

To anybody that stumbled upon this via a google search or because of a pinned comment, here's a quick rundown:

If you are not on MacOS, this should not affect you
If you are not using Qemu, this should not affect you
If you are on MacOS version 13 and bellow, this should not affect you

Now, if you are on MacOS newer than than version 14, and you are using Qemu, listen up.
There is a window-sizing bug in Qemu that will shift text up, preventing you from being able to see some of it.
It is fixed in Qemu 9.0. Bellow are package managers and latest version of Qemu available:

Homebrew (9.0.0)
MacPorts (9.0.0)

Edit: The package managers have updated their packages. Both of them are now up to date. To fix the big, just update Qemu!

phil-opp · 2024-04-30T14:48:32Z

Looks like both homebrew and macPorts provide v0.9 now, do I see that right?

AtomicGamer9523 · 2024-04-30T18:59:30Z

Looks like both homebrew and macPorts provide v0.9 now, do I see that right?

Correct, updating my comment.

Edit: Is it safe to close this issue as completed ?

phil-opp · 2024-04-30T20:20:05Z

Great! Yes, I think we can close this then. I'll keep it pinned for a while, so it should still be visible enough.

rprovodenko mentioned this issue Nov 19, 2023

Fix for "hello world" not getting displayed #1252

Closed

phil-opp changed the title ~~No "Hello, World" in post-02 - just a black screen.~~ QEMU Bug in macOS 14: No "Hello, World" in post-02 - just a black screen. Feb 27, 2024

phil-opp pinned this issue Feb 27, 2024

phil-opp closed this as completed Apr 30, 2024

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QEMU Bug in macOS 14: No "Hello, World" in `post-02` - just a black screen. #1249

QEMU Bug in macOS 14: No "Hello, World" in `post-02` - just a black screen. #1249

nskobelevs commented Oct 13, 2023 •

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nskobelevs commented Oct 25, 2023

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rprovodenko commented Nov 19, 2023

AtomicGamer9523 commented Nov 20, 2023

vladimir-kazan commented Nov 20, 2023

phil-opp commented Nov 21, 2023

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wzslr321 commented Dec 21, 2023

yasinldev commented Jan 20, 2024

NightProg commented Jan 28, 2024

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phil-opp commented Feb 27, 2024

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phil-opp commented Apr 30, 2024

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phil-opp commented Apr 30, 2024

QEMU Bug in macOS 14: No "Hello, World" in post-02 - just a black screen. #1249

QEMU Bug in macOS 14: No "Hello, World" in post-02 - just a black screen. #1249

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nskobelevs commented Oct 13, 2023 • edited Loading

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nskobelevs commented Oct 25, 2023

phil-opp commented Oct 25, 2023

nskobelevs commented Oct 25, 2023

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rprovodenko commented Nov 19, 2023 • edited Loading

rprovodenko commented Nov 19, 2023

AtomicGamer9523 commented Nov 20, 2023

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phil-opp commented Nov 21, 2023

AtomicGamer9523 commented Nov 21, 2023

that-ben commented Nov 24, 2023 • edited Loading

wzslr321 commented Dec 21, 2023

yasinldev commented Jan 20, 2024

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phil-opp commented Feb 27, 2024

AtomicGamer9523 commented Mar 18, 2024 • edited Loading

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phil-opp commented Apr 30, 2024

QEMU Bug in macOS 14: No "Hello, World" in `post-02` - just a black screen. #1249

QEMU Bug in macOS 14: No "Hello, World" in `post-02` - just a black screen. #1249

nskobelevs commented Oct 13, 2023 •

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AtomicGamer9523 commented Oct 13, 2023 •

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phil-opp commented Oct 25, 2023 •

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rprovodenko commented Nov 19, 2023 •

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