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[87.94.132.183]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-539aff23307sm926237e87.197.2024.10.07.13.28.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Oct 2024 13:28:55 -0700 (PDT) From: Abdiel Janulgue To: rust-for-linux@vger.kernel.org, aliceryhl@google.com Cc: dakr@redhat.com, linux-kernel@vger.kernel.org, lyude@redhat.com, airlied@redhat.com, miguel.ojeda.sandonis@gmail.com, boqun.feng@gmail.com Subject: [PATCH 1/3] rust: page: replace the page pointer wrapper with Opaque Date: Mon, 7 Oct 2024 23:27:50 +0300 Message-Id: <20241007202752.3096472-2-abdiel.janulgue@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20241007202752.3096472-1-abdiel.janulgue@gmail.com> References: <20241007202752.3096472-1-abdiel.janulgue@gmail.com> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Replace NonNull with Opaque to make it possible to cast to a Page pointer from a raw struct page pointer. Signed-off-by: Abdiel Janulgue --- rust/kernel/page.rs | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs index 208a006d587c..08ff09a25223 100644 --- a/rust/kernel/page.rs +++ b/rust/kernel/page.rs @@ -8,8 +8,9 @@ error::code::*, error::Result, uaccess::UserSliceReader, + types::Opaque, }; -use core::ptr::{self, NonNull}; +use core::ptr::{self}; /// A bitwise shift for the page size. pub const PAGE_SHIFT: usize = bindings::PAGE_SHIFT as usize; @@ -25,8 +26,9 @@ /// # Invariants /// /// The pointer is valid, and has ownership over the page. +#[repr(transparent)] pub struct Page { - page: NonNull, + page: Opaque, } // SAFETY: Pages have no logic that relies on them staying on a given thread, so moving them across @@ -65,15 +67,20 @@ pub fn alloc_page(flags: Flags) -> Result { // SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it // is always safe to call this method. let page = unsafe { bindings::alloc_pages(flags.as_raw(), 0) }; - let page = NonNull::new(page).ok_or(AllocError)?; + if page.is_null() { + return Err(AllocError); + } + // CAST: Self` is a `repr(transparent)` wrapper around `bindings::page`. + let ptr = page.cast::(); // INVARIANT: We just successfully allocated a page, so we now have ownership of the newly // allocated page. We transfer that ownership to the new `Page` object. - Ok(Self { page }) + // SAFETY: According to invariant above ptr is valid. + Ok(unsafe { ptr::read(ptr) }) } /// Returns a raw pointer to the page. pub fn as_ptr(&self) -> *mut bindings::page { - self.page.as_ptr() + self.page.get() } /// Runs a piece of code with this page mapped to an address. @@ -245,6 +252,6 @@ pub unsafe fn copy_from_user_slice_raw( impl Drop for Page { fn drop(&mut self) { // SAFETY: By the type invariants, we have ownership of the page and can free it. - unsafe { bindings::__free_pages(self.page.as_ptr(), 0) }; + unsafe { bindings::__free_pages(self.page.get(), 0) }; } } -- 2.34.1