bugGNU GRUB - Bugs: bug #63499, multiboot information structure...

 
 

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bug #63499: multiboot information structure has color_info offset by 2 bytes

Submitter:  Jason Youngberg <jasonyoungberg>
Submitted:  Sat 10 Dec 2022 01:19:58 AM UTC
   
 
Category:  Booting Severity:  Major
Priority:  5 - Normal Item Group:  Software Error
Status:  None Privacy:  Public
Assigned to:  None Originator Name: 
Open/Closed:  Open Release:  other
Release:  Reproducibility:  Every Time
Planned Release:  None

Sat 10 Dec 2022 01:19:58 AM UTC, original submission:  

Inside the multiboot information structure, the
color_type color_info bytes seem to be offset by 2 bytes.

I would expect values of {16,8,8,8,0,8}, but those bytes are found at 112 (0x70), instead of 110 (0x6E) as stated in the docs.

Here is a memory dump of the multiboot information structure:

00010000: 67 12 00 00  7f 02 00 00  80 fb 01 00  ff ff ff e0
00010010: 78 00 01 00  00 00 00 00  00 00 00 00  0a 00 00 00
00010020: 28 00 00 00  34 01 01 00  09 00 00 00  90 00 00 00
00010030: a4 00 01 00  00 00 00 00  00 00 00 00  00 00 00 00
00010040: 7c 00 01 00  00 00 00 00  00 00 00 00  00 00 00 00
00010050: 00 00 00 00  00 00 00 00  00 00 00 fd  00 00 00 00
00010060: 60 09 00 00  20 03 00 00  58 02 00 00  18 01 00 00
00010070: 10 08 08 08  00 08 00 00  00 66 89 43  47 52 55 42


I created my iso with the commmand 'grub-mkrescue -o os.iso .tmp'
I tested it using 'qemu-system-i386 -cdrom os.iso'

This is my multiboot header:

.set ALIGN,    1<<0 # align loaded modules on page boundaries
.set MEMINFO,  1<<1 # provide memory map
.set VIDINFO,  1<<2 # provide video information
.set FLAGS,    ALIGN | MEMINFO | VIDINFO
.set MAGIC,    0x1BADB002
.set CHECKSUM, -(MAGIC + FLAGS)

# Multiboot header
.section .multiboot
.align 4
.long MAGIC
.long FLAGS
.long CHECKSUM

.long 0, 0, 0, 0, 0
.long 0             # Set graphics mode
.long 0, 0, 0       # Width, height, depth

# ...


I'm using grub version 2.06-2, and qemu version 6.2.0.

Jason Youngberg <jasonyoungberg>

 

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