michaelkuc6/blog_os
1
0
Fork 0
mirror of https://github.com/phil-opp/blog_os.git synced 2025-12-16 22:37:49 +00:00
Code Issues Projects Releases Wiki Activity

Convert front matters to hugo's toml-based format

Browse Source
This commit is contained in:
Philipp Oppermann
2016-04-25 21:54:02 +02:00
parent 814fc5c3c0
commit cdc0b0748b
11 changed files with 68 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
blog/post/2015-08-25-entering-longmode.md
View File

@@ -1,9 +1,13 @@
---
layout: post
title: 'Entering Long Mode'
redirect_from: "/2015/08/25/entering-longmode/"
updated: 2015-10-29 00:00:00 +0000
---
+++
title = "Entering Long Mode"
slug = "entering-longmode"
date = "2015-08-25"
updated = "2015-10-29"
aliases = [
"/2015/08/25/entering-longmode/",
]
+++
In the [previous post] we created a minimal multiboot kernel. It just prints `OK` and hangs. The goal is to extend it and call 64-bit [Rust] code. But the CPU is currently in [protected mode] and allows only 32-bit instructions and up to 4GiB memory. So we need to set up _Paging_ and switch to the 64-bit [long mode] first.
I tried to explain everything in detail and to keep the code as simple as possible. If you have any questions, suggestions, or issues, please leave a comment or [create an issue] on Github. The source code is available in a [repository][source code], too.
@@ -155,7 +159,7 @@ check_long_mode:
cpuid ; get highest supported argument
cmp eax, 0x80000001 ; it needs to be at least 0x80000001
jb .no_long_mode ; if it's less, the CPU is too old for long mode
; use extended info to test if long mode is available
mov eax, 0x80000001 ; argument for extended processor info
cpuid ; returns various feature bits in ecx and edx