Alice Ryhl <aliceryhl@xxxxxxxxxx> writes: > Adds a new struct called `Page` that wraps a pointer to `struct page`. > This struct is assumed to hold ownership over the page, so that Rust > code can allocate and manage pages directly. > > The page type has various methods for reading and writing into the page. > These methods will temporarily map the page to allow the operation. All > of these methods use a helper that takes an offset and length, performs > bounds checks, and returns a pointer to the given offset in the page. > > This patch only adds support for pages of order zero, as that is all > Rust Binder needs. However, it is written to make it easy to add support > for higher-order pages in the future. To do that, you would add a const > generic parameter to `Page` that specifies the order. Most of the > methods do not need to be adjusted, as the logic for dealing with > mapping multiple pages at once can be isolated to just the > `with_pointer_into_page` method. > > Rust Binder needs to manage pages directly as that is how transactions > are delivered: Each process has an mmap'd region for incoming > transactions. When an incoming transaction arrives, the Binder driver > will choose a region in the mmap, allocate and map the relevant pages > manually, and copy the incoming transaction directly into the page. This > architecture allows the driver to copy transactions directly from the > address space of one process to another, without an intermediate copy > to a kernel buffer. > > This code is based on Wedson's page abstractions from the old rust > branch, but it has been modified by Alice by removing the incomplete > support for higher-order pages, by introducing the `with_*` helpers > to consolidate the bounds checking logic into a single place, and by > introducing gfp flags. > > Co-developed-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxx> > Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxx> > Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> > --- Reviewed-by: Andreas Hindborg <a.hindborg@xxxxxxxxxxx>
