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Update posts for x86_64 version 0.7.0 (#607)

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Philipp Oppermann
2019-05-09 15:00:49 +02:00
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parent e2f0881701
commit 0632a0de80
6 changed files with 42 additions and 42 deletions
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blog/content/second-edition/posts/09-paging-implementation/index.md
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@@ -247,7 +247,7 @@ The above code assumes that the last level 4 entry with index `0o777` (511) is r
Alternatively to performing the bitwise operations by hand, you can use the [`RecursivePageTable`] type of the `x86_64` crate, which provides safe abstractions for various page table operations. For example, the code below shows how to translate a virtual address to its mapped physical address:
[`RecursivePageTable`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/struct.RecursivePageTable.html
[`RecursivePageTable`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/struct.RecursivePageTable.html
```rust
// in src/memory.rs
@@ -573,7 +573,7 @@ The `VirtAddr` struct already provides methods to compute the indexes into the p
Inside the loop, we again use the `physical_memory_offset` to convert the frame into a page table reference. We then read the entry of the current page table and use the [`PageTableEntry::frame`] function to retrieve the mapped frame. If the entry is not mapped to a frame we return `None`. If the entry maps a huge 2MiB or 1GiB page we panic for now.
[`PageTableEntry::frame`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/page_table/struct.PageTableEntry.html#method.frame
[`PageTableEntry::frame`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/page_table/struct.PageTableEntry.html#method.frame
Let's test our translation function by translating some addresses:
@@ -624,17 +624,17 @@ The base of the abstraction are two traits that define various page table mappin
- The [`Mapper`] trait is generic over the page size and provides functions that operate on pages. Examples are [`translate_page`], which translates a given page to a frame of the same size, and [`map_to`], which creates a new mapping in the page table.
- The [`MapperAllSizes`] trait implies that the implementor implements `Mapper` for all pages sizes. In addition, it provides functions that work with multiple page sizes such as [`translate_addr`] or the general [`translate`].
[`Mapper`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/mapper/trait.Mapper.html
[`translate_page`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/mapper/trait.Mapper.html#tymethod.translate_page
[`map_to`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/mapper/trait.Mapper.html#tymethod.map_to
[`MapperAllSizes`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/mapper/trait.MapperAllSizes.html
[`translate_addr`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/mapper/trait.MapperAllSizes.html#method.translate_addr
[`translate`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/mapper/trait.MapperAllSizes.html#tymethod.translate
[`Mapper`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/mapper/trait.Mapper.html
[`translate_page`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/mapper/trait.Mapper.html#tymethod.translate_page
[`map_to`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/mapper/trait.Mapper.html#tymethod.map_to
[`MapperAllSizes`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/mapper/trait.MapperAllSizes.html
[`translate_addr`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/mapper/trait.MapperAllSizes.html#method.translate_addr
[`translate`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/mapper/trait.MapperAllSizes.html#tymethod.translate
The traits only define the interface, they don't provide any implementation. The `x86_64` crate currently provides two types that implement the traits: [`MappedPageTable`] and [`RecursivePageTable`]. The former type requires that each page table frame is mapped somewhere (e.g. at an offset). The latter type can be used when the level 4 table is [mapped recursively](#recursive-page-tables).
[`MappedPageTable`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/struct.MappedPageTable.html
[`RecursivePageTable`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/struct.RecursivePageTable.html
[`MappedPageTable`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/struct.MappedPageTable.html
[`RecursivePageTable`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/struct.RecursivePageTable.html
We have the complete physical memory mapped at `physical_memory_offset`, so we can use the `MappedPageTable` type. To initialize it, we create a new `init` function in our `memory` module:
@@ -670,7 +670,7 @@ We can't directly return a `MappedPageTable` from the function because it is gen
The [`MappedPageTable::new`] function expects two parameters: a mutable reference to the level 4 page table and a `phys_to_virt` closure that converts a physical frame to a page table pointer `*mut PageTable`. For the first parameter we can reuse our `active_level_4_table` function. For the second parameter, we create a closure that uses the `physical_memory_offset` to perform the conversion.
[`MappedPageTable::new`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/struct.MappedPageTable.html#method.new
[`MappedPageTable::new`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/struct.MappedPageTable.html#method.new
We also make the `active_level_4_table` private because it should only be called from the `init` function from now on.
@@ -714,8 +714,8 @@ Until now we only looked at the page tables without modifying anything. Let's ch
We will use the [`map_to`] function of the [`Mapper`] trait for our implementation, so let's take a look at that function first. The documentation tells us that it takes four arguments: the page that we want to map, the frame that the page should be mapped to, a set of flags for the page table entry, and a `frame_allocator`. The frame allocator is needed because mapping the given page might require creating additional page tables, which need unused frames as backing storage.
[`map_to`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/trait.Mapper.html#tymethod.map_to
[`Mapper`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/trait.Mapper.html
[`map_to`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/trait.Mapper.html#tymethod.map_to
[`Mapper`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/trait.Mapper.html
#### A `create_example_mapping` Function
@@ -749,7 +749,7 @@ pub fn create_example_mapping(
In addition to the `page` that should be mapped, the function expects a `mapper` instance and a `frame_allocator`. The `mapper` is a type that implements the `Mapper<Size4KiB>` trait, which provides the `map_to` method. The generic `Size4KiB` parameter is needed because the [`Mapper`] trait is [generic] over the [`PageSize`] trait to work with both standard 4KiB pages and huge 2MiB/1GiB pages. We only want to create 4KiB pages, so we can use `Mapper<Size4KiB>` instead of requiring `MapperAllSizes`.
[generic]: https://doc.rust-lang.org/book/ch10-00-generics.html
[`PageSize`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/trait.PageSize.html
[`PageSize`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/trait.PageSize.html
For the mapping, we set the `PRESENT` flag because it is required for all valid entries and the `WRITABLE` flag to make the mapped page writable. Calling `map_to` is unsafe because it's possible to break memory safety with invalid arguments, so we need to use an `unsafe` block. For a list of all possible flags, see the [_Page Table Format_] section of the previous post.
@@ -759,8 +759,8 @@ The `map_to` function can fail, so it returns a [`Result`]. Since this is just s
[`Result`]: https://doc.rust-lang.org/core/result/enum.Result.html
[`expect`]: https://doc.rust-lang.org/core/result/enum.Result.html#method.expect
[`MapperFlush`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/struct.MapperFlush.html
[`flush`]: https://docs.rs/x86_64/0.6.0/x86_64/structures/paging/struct.MapperFlush.html#method.flush
[`MapperFlush`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/struct.MapperFlush.html
[`flush`]: https://docs.rs/x86_64/0.7.0/x86_64/structures/paging/struct.MapperFlush.html#method.flush
[`#[must_use]`]: https://doc.rust-lang.org/std/result/#results-must-be-used
#### A dummy `FrameAllocator`