michaelkuc6/blog_os
1
0
Fork 0
mirror of https://github.com/phil-opp/blog_os.git synced 2025-12-17 06:47:49 +00:00
Code Issues Projects Releases Wiki Activity

Move footnotes to the bottom

Browse Source
This commit is contained in:
Philipp Oppermann
2017-05-03 19:02:47 +02:00
parent 7e63bf08ff
commit 7744a08212
7 changed files with 26 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
blog/content/posts/02-entering-longmode/index.md
View File

@@ -215,10 +215,6 @@ As I don't like these names, I will call them P4, P3, P2, and P1 from now on.
Each page table contains 512 entries and one entry is 8 bytes, so they fit exactly in one page (`512*8 = 4096`). To translate a virtual address to a physical address the CPU[^hardware_lookup] will do the following[^virtual_physical_translation_source]:
[^hardware_lookup]: In the x86 architecture, the page tables are _hardware walked_, so the CPU will look at the table on its own when it needs a translation. Other architectures, for example MIPS, just throw an exception and let the OS translate the virtual address.
[^virtual_physical_translation_source]: Image source: [Wikipedia](https://commons.wikimedia.org/wiki/File:X86_Paging_64bit.svg), with modified font size, page table naming, and removed sign extended bits. The modified file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
![translation of virtual to physical addresses in 64 bit mode](/images/X86_Paging_64bit.svg)
1. Get the address of the P4 table from the CR3 register
@@ -259,8 +255,6 @@ To identity map the first gigabyte of our kernel with 512 2MiB pages, we need on
We can add these two tables at the beginning[^page_table_alignment] of the `.bss` section:
[^page_table_alignment]: Page tables need to be page-aligned as the bits 0-11 are used for flags. By putting these tables at the beginning of `.bss`, the linker can just page align the whole section and we don't have unused padding bytes in between.
```nasm
...
@@ -524,3 +518,10 @@ It's time to finally leave assembly behind and switch to [Rust]. Rust is a syste
[Rust]: https://www.rust-lang.org/
[next post]: {{% relref "03-set-up-rust.md" %}}
## Footnotes
[^hardware_lookup]: In the x86 architecture, the page tables are _hardware walked_, so the CPU will look at the table on its own when it needs a translation. Other architectures, for example MIPS, just throw an exception and let the OS translate the virtual address.
[^virtual_physical_translation_source]: Image source: [Wikipedia](https://commons.wikimedia.org/wiki/File:X86_Paging_64bit.svg), with modified font size, page table naming, and removed sign extended bits. The modified file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
[^page_table_alignment]: Page tables need to be page-aligned as the bits 0-11 are used for flags. By putting these tables at the beginning of `.bss`, the linker can just page align the whole section and we don't have unused padding bytes in between.