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Provide more context in code example

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Philipp Oppermann
2019-03-13 13:57:13 +01:00
parent b8a3bb44df
commit 1041754c71
1 changed files with 17 additions and 9 deletions
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10
blog/content/second-edition/posts/10-paging-implementation/index.md
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@@ -445,10 +445,17 @@ We see that there are various non-empty entries, which all map to different leve
To traverse the page tables further and take a look at a level 3 table, we can take the mapped frame of an entry convert it to a virtual address again: To traverse the page tables further and take a look at a level 3 table, we can take the mapped frame of an entry convert it to a virtual address again:
```rust ```rust
// in the for loop in src/main.rs
use x86_64::{structures::paging::PageTable, VirtAddr};
if !entry.is_unused() {
println!("L4 Entry {}: {:?}", i, entry);
// get the physical address from the entry and convert it // get the physical address from the entry and convert it
let phys = entry.frame().unwrap().start_address(); let phys = entry.frame().unwrap().start_address();
let virt = phys.as_u64() + boot_info.physical_memory_offset; let virt = phys.as_u64() + boot_info.physical_memory_offset;
let ptr = VirtAddr::new(virt).as_mut_ptr() let ptr = VirtAddr::new(virt).as_mut_ptr();
let l3_table: &PageTable = unsafe { &*ptr }; let l3_table: &PageTable = unsafe { &*ptr };
// print non-empty entries of the level 3 table // print non-empty entries of the level 3 table
@@ -457,6 +464,7 @@ for (i, entry) in l3_table.iter().enumerate() {
println!(" L3 Entry {}: {:?}", i, entry); println!(" L3 Entry {}: {:?}", i, entry);
} }
} }
}
``` ```
For looking at the level 2 and level 1 tables, we repeat that process for the level 3 and level 2 entries. As you can imagine, this gets very verbose quickly, so we don't show the full code here. For looking at the level 2 and level 1 tables, we repeat that process for the level 3 and level 2 entries. As you can imagine, this gets very verbose quickly, so we don't show the full code here.