From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f74.google.com (mail-wm1-f74.google.com [209.85.128.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F0C69211A08 for ; Wed, 11 Dec 2024 10:37:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733913469; cv=none; b=GLD3pKrXTNjmifE6YZWiU546/gpsBdg+KKw8b7HdYBIcdfPleysbEZRHw3EXIP/WiFkKPKMY0vZaBJvv0tqgij+fONs4lQ0XYExCAqVVNQ9eYMV/pKCqy02eLWQ4Wphg3DPppO3KqizK3L3SdsbX9sEWwcsR5qFFTdoxip03Pgo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733913469; c=relaxed/simple; bh=seaPzXRr+ND8q/GQYnUjLUdeX+eDlOtmUd9qc8R35Uw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=bVJFS/xju/YMf5XQv/pdxq/pjT11fhj5oxhipcfxOHX6P0pcC2hf2QOUqr5FK1FVsXYFSRtwGI8JNlJlbox4mfezX4pM9nv1YDA7fVmMMAgKB10EE/0WHP4bnS3wPHoNncOarLja2x3gZ/TyuDGQ7RREyGUDxdQKzHKzEtGoaHo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=r4zwL1Sl; arc=none smtp.client-ip=209.85.128.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="r4zwL1Sl" Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-434f852cb35so2245985e9.0 for ; Wed, 11 Dec 2024 02:37:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1733913465; x=1734518265; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=H9J7APDOlzo7bms4ez8DHMnNHWyqhL35jyR1kYpr9QI=; b=r4zwL1SlABpgTLct/fbhgNey/m5H+/wHBmv4fAoNu761+s6Bb5bMSvehYbvoBpUa8X rjP88O0OohFmW8QThTlXG92uc/A+iJeBhXBH3vX7uljjchcaPXTIkOXbJHQMFrqWjGg5 aEFCRC5ji5wzjtvR3Lk1I4v8WJB6DKOJZ2UVv1zBmx5ekIXHSqXN3MWw2VB6/FDzqUQP ULkhd+lETKksuttnkYln970qzJ1akFKquDIujrPjKt39X7t6sF/6uLoKkGdk+t/wKZtA vgGBR7pS2SqL/J9Q+bEW1aT7W8ZxZIFBgWhYZTgHTogWH+isnc1FLQWwCZnGRsEg9T5i FDWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1733913465; x=1734518265; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=H9J7APDOlzo7bms4ez8DHMnNHWyqhL35jyR1kYpr9QI=; b=S7of81O4eXwEYedQEIpl+07s2ZoxkGKbZ3zGirwiHRl1T+olsOVHHs3YiMDo+bWIRS 4MnrJ2wpzJ9ZPSGWM9a7VvbY4CDkfVxEqinhlVe+SWf+oZ0K+CKisuGxU77eeAt0sfL4 /aM6xJAHBZRjgU4DwIcnx9JXpk1UBTEehASQ7WctCjiE4v7T2TyOc9GrtUR/5iqNy6O5 jwNu01kSz1P81eFuSgehmtptLC/9iIuPfXRERBcPXVTbX+u8Z01iHyNti0DTamN7RKnx 8gThTwTk5oLRNVmziSW9frTPAPRIXvTIN5qgWU2GJ5fBDo7cnfsSz/LXdn/GSp1Q23mK oI0g== X-Forwarded-Encrypted: i=1; AJvYcCUgA0aG/o+sNXEnYpR4+UceCy822Gyh2bVeOyT4TiAs41FNhjhKuwLy7hDV9/1DwzBIg1IOXKq/H/DcZEtv9w==@vger.kernel.org X-Gm-Message-State: AOJu0Yx7g7HQina8RQMcb7COnm5ZsXZddF6ibTzO8iCla0FfAlEttR60 prFSow+2yHyZgcYLXONEU9eBZhMKkcP0dmwTPBWm/z0MaWRiNU4rnlky9WJ72BZh9ICrfo99E11 fu02qr3BodV4b0Q== X-Google-Smtp-Source: AGHT+IEHXGYW3IxnBDufE3uW2/yO/pfGqLpiPsVXzHTtpypegQgEznYG6piRm0MwSTPxkbuG6wjEylcUkB+RemI= X-Received: from wmlu15.prod.google.com ([2002:a05:600c:210f:b0:434:f0d4:cbaf]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:3b94:b0:434:f0df:9f6 with SMTP id 5b1f17b1804b1-4361c346814mr18704535e9.3.1733913465503; Wed, 11 Dec 2024 02:37:45 -0800 (PST) Date: Wed, 11 Dec 2024 10:37:10 +0000 In-Reply-To: <20241211-vma-v11-0-466640428fc3@google.com> Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241211-vma-v11-0-466640428fc3@google.com> X-Developer-Key: i=aliceryhl@google.com; a=openpgp; fpr=49F6C1FAA74960F43A5B86A1EE7A392FDE96209F X-Developer-Signature: v=1; a=openpgp-sha256; l=8235; i=aliceryhl@google.com; h=from:subject:message-id; bh=seaPzXRr+ND8q/GQYnUjLUdeX+eDlOtmUd9qc8R35Uw=; b=owEBbQKS/ZANAwAKAQRYvu5YxjlGAcsmYgBnWWtph/aiDjcWSnagWFqg3c8CayEabkssTHofo IIZe48WPGWJAjMEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCZ1lraQAKCRAEWL7uWMY5 RhAmD/48pALXpz/NRk7/Fwz/9MCuo0u66DfT05kQmm6LINIciACvTECWnSEQ0tqAKRNpsp/3Fex M4Jpu48j5eDcPWEe/l1C35rsiOmHX4W4JVrnnbQZp+/CjgyqyKCcGdDeeAsbF9Fup1VX8msId3D /03PP6NhmDZYipxZdlby2oUlmR34VgBi5vhQUaLndkfR7m4sEFY9dttHnlypa8gl+V0gKxmY79U 9JhN1ZFWyvUIYXm8lClnAsbDLy08fgFrDbEUeFzSMhVR1kTYVdrrhv5dekv/RSP83A632PXlet0 PYeKGYna7WKapvDmtx8K7d0S/9kzlS2ohG7IDbWe5ZGerwfda1ceER8EtUwLQcpx6Lodt9LYOWU 0WrCa6ARlGG4I/YVU2U6dzSxkYI3Kozqnl6EzH58UkK9BXMGdSGAL+HX19s8k94rmcbVe5P7PHi W+05YwL+uuVwdmWJJ3JWrwvQTW1iF2nFdQXtgZ2iGluLiOIQYSiG9J8og/1HIcZ0hzT7VTzDTL7 8A3/CIHP3KV5PwM6wFMQXsbOnuL1jQF2ZQmrxOfLskPlDXn3meCorLLNaO9pkEG5rjCOyNHwD6p 7r6CLbjSBFYOiYh8+hJVc36KbYuQafNb+ARWM1sWBLGLoe0W8HWuM103Eetus0orFCyJ79zlJFI VIEfxrJdZ6KH4lQ== X-Mailer: b4 0.13.0 Message-ID: <20241211-vma-v11-6-466640428fc3@google.com> Subject: [PATCH v11 6/8] mm: rust: add VmAreaNew for f_ops->mmap() From: Alice Ryhl To: Miguel Ojeda , Matthew Wilcox , Lorenzo Stoakes , Vlastimil Babka , John Hubbard , "Liam R. Howlett" , Andrew Morton , Greg Kroah-Hartman , Arnd Bergmann , Christian Brauner , Jann Horn , Suren Baghdasaryan Cc: Alex Gaynor , Boqun Feng , Gary Guo , "=?utf-8?q?Bj=C3=B6rn_Roy_Baron?=" , Benno Lossin , Andreas Hindborg , Trevor Gross , linux-kernel@vger.kernel.org, linux-mm@kvack.org, rust-for-linux@vger.kernel.org, Alice Ryhl Content-Type: text/plain; charset="utf-8" This type will be used when setting up a new vma in an f_ops->mmap() hook. Using a separate type from VmAreaRef allows us to have a separate set of operations that you are only able to use during the mmap() hook. For example, the VM_MIXEDMAP flag must not be changed after the initial setup that happens during the f_ops->mmap() hook. To avoid setting invalid flag values, the methods for clearing VM_MAYWRITE and similar involve a check of VM_WRITE, and return an error if VM_WRITE is set. Trying to use `try_clear_maywrite` without checking the return value results in a compilation error because the `Result` type is marked #[must_use]. For now, there's only a method for VM_MIXEDMAP and not VM_PFNMAP. When we add a VM_PFNMAP method, we will need some way to prevent you from setting both VM_MIXEDMAP and VM_PFNMAP on the same vma. Acked-by: Lorenzo Stoakes (for mm bits) Reviewed-by: Jann Horn Signed-off-by: Alice Ryhl --- rust/kernel/mm/virt.rs | 181 ++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 180 insertions(+), 1 deletion(-) diff --git a/rust/kernel/mm/virt.rs b/rust/kernel/mm/virt.rs index 3a23854e14f4..6d9ba56d4f95 100644 --- a/rust/kernel/mm/virt.rs +++ b/rust/kernel/mm/virt.rs @@ -6,7 +6,7 @@ use crate::{ bindings, - error::{to_result, Result}, + error::{code::EINVAL, to_result, Result}, mm::MmWithUser, page::Page, types::Opaque, @@ -171,6 +171,185 @@ pub fn vm_insert_page(&self, address: usize, page: &Page) -> Result { } } +/// A builder for setting up a vma in an `f_ops->mmap()` hook. +/// +/// # Invariants +/// +/// For the duration of 'a, the referenced vma must be undergoing initialization in an +/// `f_ops->mmap()` hook. +pub struct VmAreaNew { + vma: VmAreaRef, +} + +// Make all `VmAreaRef` methods available on `VmAreaNew`. +impl Deref for VmAreaNew { + type Target = VmAreaRef; + + #[inline] + fn deref(&self) -> &VmAreaRef { + &self.vma + } +} + +impl VmAreaNew { + /// Access a virtual memory area given a raw pointer. + /// + /// # Safety + /// + /// Callers must ensure that `vma` is undergoing initial vma setup for the duration of 'a. + #[inline] + pub unsafe fn from_raw<'a>(vma: *const bindings::vm_area_struct) -> &'a Self { + // SAFETY: The caller ensures that the invariants are satisfied for the duration of 'a. + unsafe { &*vma.cast() } + } + + /// Internal method for updating the vma flags. + /// + /// # Safety + /// + /// This must not be used to set the flags to an invalid value. + #[inline] + unsafe fn update_flags(&self, set: vm_flags_t, unset: vm_flags_t) { + let mut flags = self.flags(); + flags |= set; + flags &= !unset; + + // SAFETY: This is not a data race: the vma is undergoing initial setup, so it's not yet + // shared. Additionally, `VmAreaNew` is `!Sync`, so it cannot be used to write in parallel. + // The caller promises that this does not set the flags to an invalid value. + unsafe { (*self.as_ptr()).__bindgen_anon_2.__vm_flags = flags }; + } + + /// Set the `VM_MIXEDMAP` flag on this vma. + /// + /// This enables the vma to contain both `struct page` and pure PFN pages. Returns a reference + /// that can be used to call `vm_insert_page` on the vma. + #[inline] + pub fn set_mixedmap(&self) -> &VmAreaMixedMap { + // SAFETY: We don't yet provide a way to set VM_PFNMAP, so this cannot put the flags in an + // invalid state. + unsafe { self.update_flags(flags::MIXEDMAP, 0) }; + + // SAFETY: We just set `VM_MIXEDMAP` on the vma. + unsafe { VmAreaMixedMap::from_raw(self.vma.as_ptr()) } + } + + /// Set the `VM_IO` flag on this vma. + /// + /// This is used for memory mapped IO and similar. The flag tells other parts of the kernel to + /// avoid looking at the pages. For memory mapped IO this is useful as accesses to the pages + /// could have side effects. + #[inline] + pub fn set_io(&self) { + // SAFETY: Setting the VM_IO flag is always okay. + unsafe { self.update_flags(flags::IO, 0) }; + } + + /// Set the `VM_DONTEXPAND` flag on this vma. + /// + /// This prevents the vma from being expanded with `mremap()`. + #[inline] + pub fn set_dontexpand(&self) { + // SAFETY: Setting the VM_DONTEXPAND flag is always okay. + unsafe { self.update_flags(flags::DONTEXPAND, 0) }; + } + + /// Set the `VM_DONTCOPY` flag on this vma. + /// + /// This prevents the vma from being copied on fork. This option is only permanent if `VM_IO` + /// is set. + #[inline] + pub fn set_dontcopy(&self) { + // SAFETY: Setting the VM_DONTCOPY flag is always okay. + unsafe { self.update_flags(flags::DONTCOPY, 0) }; + } + + /// Set the `VM_DONTDUMP` flag on this vma. + /// + /// This prevents the vma from being included in core dumps. This option is only permanent if + /// `VM_IO` is set. + #[inline] + pub fn set_dontdump(&self) { + // SAFETY: Setting the VM_DONTDUMP flag is always okay. + unsafe { self.update_flags(flags::DONTDUMP, 0) }; + } + + /// Returns whether `VM_READ` is set. + /// + /// This flag indicates whether userspace is mapping this vma as readable. + #[inline] + pub fn get_read(&self) -> bool { + (self.flags() & flags::READ) != 0 + } + + /// Try to clear the `VM_MAYREAD` flag, failing if `VM_READ` is set. + /// + /// This flag indicates whether userspace is allowed to make this vma readable with + /// `mprotect()`. + /// + /// Note that this operation is irreversible. Once `VM_MAYREAD` has been cleared, it can never + /// be set again. + #[inline] + pub fn try_clear_mayread(&self) -> Result { + if self.get_read() { + return Err(EINVAL); + } + // SAFETY: Clearing `VM_MAYREAD` is okay when `VM_READ` is not set. + unsafe { self.update_flags(0, flags::MAYREAD) }; + Ok(()) + } + + /// Returns whether `VM_WRITE` is set. + /// + /// This flag indicates whether userspace is mapping this vma as writable. + #[inline] + pub fn get_write(&self) -> bool { + (self.flags() & flags::WRITE) != 0 + } + + /// Try to clear the `VM_MAYWRITE` flag, failing if `VM_WRITE` is set. + /// + /// This flag indicates whether userspace is allowed to make this vma writable with + /// `mprotect()`. + /// + /// Note that this operation is irreversible. Once `VM_MAYWRITE` has been cleared, it can never + /// be set again. + #[inline] + pub fn try_clear_maywrite(&self) -> Result { + if self.get_write() { + return Err(EINVAL); + } + // SAFETY: Clearing `VM_MAYWRITE` is okay when `VM_WRITE` is not set. + unsafe { self.update_flags(0, flags::MAYWRITE) }; + Ok(()) + } + + /// Returns whether `VM_EXEC` is set. + /// + /// This flag indicates whether userspace is mapping this vma as executable. + #[inline] + pub fn get_exec(&self) -> bool { + (self.flags() & flags::EXEC) != 0 + } + + /// Try to clear the `VM_MAYEXEC` flag, failing if `VM_EXEC` is set. + /// + /// This flag indicates whether userspace is allowed to make this vma executable with + /// `mprotect()`. + /// + /// Note that this operation is irreversible. Once `VM_MAYEXEC` has been cleared, it can never + /// be set again. + #[inline] + pub fn try_clear_mayexec(&self) -> Result { + if self.get_exec() { + return Err(EINVAL); + } + // SAFETY: Clearing `VM_MAYEXEC` is okay when `VM_EXEC` is not set. + unsafe { self.update_flags(0, flags::MAYEXEC) }; + Ok(()) + } +} + /// The integer type used for vma flags. #[doc(inline)] pub use bindings::vm_flags_t; -- 2.47.1.613.gc27f4b7a9f-goog