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

Some syntactical and whitespace fixes

Browse Source
This commit is contained in:
Philipp Oppermann
2015-10-24 15:55:30 +02:00
parent 710fa81c27
commit 01798b717f
1 changed files with 6 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
_posts/2015-08-25-entering-longmode.md
View File

@@ -410,8 +410,10 @@ We can't just use normal labels here, as we need the table offset. We calculate
Now there is just one last step left to enter the true 64-bit mode: We need to load `cs` with `gdt64.code`. But we can't do it through `mov`. The only way to reload the code selector is a _far jump_ or a _far return_. These instructions work like a normal jump/return but change the code selector. We use a far jump to a long mode label: Now there is just one last step left to enter the true 64-bit mode: We need to load `cs` with `gdt64.code`. But we can't do it through `mov`. The only way to reload the code selector is a _far jump_ or a _far return_. These instructions work like a normal jump/return but change the code selector. We use a far jump to a long mode label:
```nasm ```nasm
global start global start
extern long_mode_start extern long_mode_start
...
start:
... ...
lgdt [gdt64.pointer] lgdt [gdt64.pointer]
@@ -422,6 +424,7 @@ Now there is just one last step left to enter the true 64-bit mode: We need to l
mov es, ax mov es, ax
jmp gdt64.code:long_mode_start jmp gdt64.code:long_mode_start
...
``` ```
The actual `long_mode_start` label is defined as `extern`, so it's part of another file. The `jmp gdt64.code:long_mode_start` is the mentioned far jump. The actual `long_mode_start` label is defined as `extern`, so it's part of another file. The `jmp gdt64.code:long_mode_start` is the mentioned far jump.
@@ -437,9 +440,6 @@ long_mode_start:
mov rax, 0x2f592f412f4b2f4f mov rax, 0x2f592f412f4b2f4f
mov qword [0xb8000], rax mov qword [0xb8000], rax
hlt hlt
bits 32
...
``` ```
You should see a green `OKAY` on the screen. Some notes on this last step: You should see a green `OKAY` on the screen. Some notes on this last step:
@@ -449,7 +449,7 @@ You should see a green `OKAY` on the screen. Some notes on this last step:
_Congratulations_! You have successfully wrestled through this CPU configuration and compatibility mode mess :). _Congratulations_! You have successfully wrestled through this CPU configuration and compatibility mode mess :).
## Whats next? ## What's next?
It's time to finally leave assembly behind[^leave_assembly_behind] and switch to some higher level language. We won't use C or C++ (not even a single line). Instead we will use the relatively new [Rust] language. It's a systems language without garbage collections but with guaranteed memory safety. Through a real type system and many abstractions it feels like a high-level language but can still be low-level enough for OS development. The [next post] describes the Rust setup. It's time to finally leave assembly behind[^leave_assembly_behind] and switch to some higher level language. We won't use C or C++ (not even a single line). Instead we will use the relatively new [Rust] language. It's a systems language without garbage collections but with guaranteed memory safety. Through a real type system and many abstractions it feels like a high-level language but can still be low-level enough for OS development. The [next post] describes the Rust setup.
[^leave_assembly_behind]: Actually we will still need some assembly in the future, but I'll try to minimize it. [^leave_assembly_behind]: Actually we will still need some assembly in the future, but I'll try to minimize it.