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

[Jason Youngberg]

URL:
  <https://savannah.gnu.org/bugs/?63499>

                 Summary: multiboot information structure has color_info
offset by 2 bytes
                 Project: GNU GRUB
               Submitter: 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: 
        Originator Email: 
             Open/Closed: Open
                 Release: other
                 Release: 
         Discussion Lock: Any
         Reproducibility: Every Time
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Sat 10 Dec 2022 01:19:58 AM UTC By: Jason Youngberg <jasonyoungberg>
Inside the multiboot information structure
<https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Boot-information-format>,
the 
color_type color_info
<https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Boot-modules:~:text=color_type%20is%20defined%20as%20follows>
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.







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