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Test translate function

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Philipp Oppermann
2015-12-09 12:20:50 +01:00
parent d8c6b6f5b7
commit 786e1d5cab
2 changed files with 37 additions and 1 deletions
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31
posts/DRAFT-paging.md
View File

@@ -760,7 +760,36 @@ let mut frame_allocator = ...;
memory::test_paging(&mut frame_allocator);
```
TODO
### translate
First, we translate some addresses:
```rust
// address 0 is mapped
println!("Some = {:?}", page_table.translate(0));
// second P1 entry
println!("Some = {:?}", page_table.translate(4096));
// second P2 entry
println!("Some = {:?}", page_table.translate(512 * 4096));
// 300th P2 entry
println!("Some = {:?}", page_table.translate(300 * 512 * 4096));
// second P3 entry
println!("None = {:?}", page_table.translate(512 * 512 * 4096));
// last mapped byte
println!("Some = {:?}", page_table.translate(512 * 512 * 4096 - 1));
```
Currently, the first GiB of the address space is identity-mapped. Thus all addresses in this area should translate to `Some(x)`, where `x` is the virtual address. Only the second last address, `512 * 512 * 4096`, is not in that area and should resolve to `None`.
But the output shows two `None` lines:
```
Some = Some(0)
Some = Some(4096)
Some = Some(2097152)
Some = Some(629145600)
None = None
Some = None
```
The last line is wrong. But why?
## What's next?
In the next post we will extend this module and add a function to modify inactive page tables. Through that function, we will create a new page table hierarchy that maps the kernel correctly using 4KiB pages. Then we will switch to the new table to get a safer kernel environment.

7
src/memory/paging/mod.rs
View File

@@ -148,4 +148,11 @@ pub fn test_paging<A>(allocator: &mut A)
where A: FrameAllocator
{
let page_table = unsafe { RecursivePageTable::new() };
println!("Some = {:?}", page_table.translate(0));
println!("Some = {:?}", page_table.translate(4096)); // second P1 entry
println!("Some = {:?}", page_table.translate(512 * 4096)); // second P2 entry
println!("Some = {:?}", page_table.translate(300 * 512 * 4096)); // 300th P2 entry
println!("None = {:?}", page_table.translate(512 * 512 * 4096)); // second P3 entry
println!("Some = {:?}", page_table.translate(512 * 512 * 4096 - 1)); // last mapped byte
}