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Minor fixes in code examples

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Philipp Oppermann
2017-04-18 12:36:04 +02:00
parent 1ad30d488c
commit f2c8b792d6
1 changed files with 10 additions and 7 deletions
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17
blog/content/post/07-remap-the-kernel.md
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@@ -482,11 +482,11 @@ pub fn with<F>(&mut self,
where F: FnOnce(&mut Mapper) where F: FnOnce(&mut Mapper)
{ {
use x86_64::instructions::tlb; use x86_64::instructions::tlb;
use x86_64::registers::{control_regs, tlb}; use x86_64::registers::control_regs;
{ {
let backup = Frame::containing_address( let backup = Frame::containing_address(
control_regs::cr3() as usize); control_regs::cr3().0 as usize);
// map temporary_page to current p4 table // map temporary_page to current p4 table
let p4_table = temporary_page.map_table_frame(backup.clone(), self); let p4_table = temporary_page.map_table_frame(backup.clone(), self);
@@ -554,7 +554,7 @@ for section in elf_sections_tag.sections() {
// section is not loaded to memory // section is not loaded to memory
continue; continue;
} }
assert!(address % PAGE_SIZE == 0, assert!(section.start_address() % PAGE_SIZE == 0,
"sections need to be page aligned"); "sections need to be page aligned");
println!("mapping section at addr: {:#x}, size: {:#x}", println!("mapping section at addr: {:#x}, size: {:#x}",
@@ -754,15 +754,17 @@ We do this in a new `ActivePageTable::switch` method:
// in `impl ActivePageTable` in src/memory/paging/mod.rs // in `impl ActivePageTable` in src/memory/paging/mod.rs
pub fn switch(&mut self, new_table: InactivePageTable) -> InactivePageTable { pub fn switch(&mut self, new_table: InactivePageTable) -> InactivePageTable {
use x86_64::PhysicalAddress;
use x86_64::registers::control_regs; use x86_64::registers::control_regs;
let old_table = InactivePageTable { let old_table = InactivePageTable {
p4_frame: Frame::containing_address( p4_frame: Frame::containing_address(
control_regs::cr3() as usize control_regs::cr3().0 as usize
), ),
}; };
unsafe { unsafe {
control_regs::cr3_write(new_table.p4_frame.start_address()); control_regs::cr3_write(PhysicalAddress(
new_table.p4_frame.start_address() as u64));
} }
old_table old_table
} }
@@ -968,8 +970,9 @@ This time the responsible function is `control_regs::cr3_write()` itself. From t
The reason is that the `NO_EXECUTE` bit must only be used when the `NXE` bit in the [Extended Feature Enable Register] \(EFER) is set. That register is similar to Rust's feature gating and can be used to enable all sorts of advanced CPU features. Since the `NXE` bit is off by default, we caused a page fault when we added the `NO_EXECUTE` bit to the page table. The reason is that the `NO_EXECUTE` bit must only be used when the `NXE` bit in the [Extended Feature Enable Register] \(EFER) is set. That register is similar to Rust's feature gating and can be used to enable all sorts of advanced CPU features. Since the `NXE` bit is off by default, we caused a page fault when we added the `NO_EXECUTE` bit to the page table.
[Extended Feature Enable Register]: https://en.wikipedia.org/wiki/Control_register#EFER [Extended Feature Enable Register]: https://en.wikipedia.org/wiki/Control_register#EFER
So we need to enable the `NXE` bit. For that we use the awesome [x86][rust-x86] crate again: So we need to enable the `NXE` bit. For that we use the [x86_64 crate] again:
[rust-x86]: https://github.com/gz/rust-x86
[x86_64 crate]: https://docs.rs/x86_64
```rust ```rust
// in lib.rs // in lib.rs