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Improve naming and wording

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Philipp Oppermann
2015-07-31 19:18:52 +02:00
parent 9588bbe5ff
commit 0e73acda14
1 changed files with 6 additions and 5 deletions
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11
_posts/2015-07-22-rust-os-boot.md
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@@ -17,9 +17,10 @@ checksum | u32 | -(magic + architecture + header length)
tags | variable |
end tag | (u16, u16, u32) | (0, 0, 8)
Converted to x86 assembly it looks like this (Intel syntax):
Converted to a x86 assembly file it looks like this (Intel syntax):
```nasm
section .multiboot_header
header_start:
dd 0xe85250d6 ; magic number (multiboot 2)
dd 0 ; architecture 0 (protected mode i386)
@@ -35,18 +36,18 @@ header_start:
dd 8 ; size
header_end:
```
If you don't know x86 assembly, here is some quick guide:
- the header will be written to a section named `.multiboot_header` (we need this later)
- `header_start` and `header_end` are _labels_ that mark a memory location. We use them to calculate the header length easily
- `dd` stands for `define double` (32bit) and `dw` stands for `define word` (16bit)
- the additional `0x100000000` in the checksum calculation is a small hack[^fn-checksum_hack] to avoid a compiler warning
We can already compile it using `nasm`. As it produces a flat binary by default, the resulting file contains just our 24 bytes (in little endian if you work on a x86 machine):
We can already _assemble_ this file (which I called `multiboot_header.asm`) using `nasm`. As it produces a flat binary by default, the resulting file just contains our 24 bytes (in little endian if you work on a x86 machine):
```
> nasm boot.asm
> hexdump -x boot
> nasm multiboot_header.asm
> hexdump -x multiboot_header
0000000 50d6 e852 0000 0000 0018 0000 af12 17ad
0000010 0000 0000 0008 0000
0000018