From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.90_1) id 1tneoB-0006jj-9T for mharc-qemu-rust@gnu.org; Thu, 27 Feb 2025 09:24:20 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tnemg-0003pz-78 for qemu-rust@nongnu.org; Thu, 27 Feb 2025 09:22:43 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tnemT-00044N-Cd for qemu-rust@nongnu.org; Thu, 27 Feb 2025 09:22:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740666148; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=DU8RnwXUCUOFmlQq7LelOhzzqajTuinw3yOxvFn4Jv4=; b=Bfx+HE4Ki4yH2d7wE9hbjWjVARpSbeLNZlezVIBX4dA4gmwHdHlqN0wCMjpxNuEr8mdnvZ 6r5Bl8oLsLYRaEhL3t833hC5QRNQm3G7PTCR995eTCYWs7qbPPIHIGtsUPUNN1a4ccMZQV 8CagOUe9afG59jxCSayUeOP1kc3EueY= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-206-bNn1jzTSNPqUkn2VBWmiYQ-1; Thu, 27 Feb 2025 09:22:27 -0500 X-MC-Unique: bNn1jzTSNPqUkn2VBWmiYQ-1 X-Mimecast-MFC-AGG-ID: bNn1jzTSNPqUkn2VBWmiYQ_1740666146 Received: by mail-ed1-f72.google.com with SMTP id 4fb4d7f45d1cf-5e04de6583bso1482239a12.1 for ; Thu, 27 Feb 2025 06:22:26 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740666146; x=1741270946; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=DU8RnwXUCUOFmlQq7LelOhzzqajTuinw3yOxvFn4Jv4=; b=bTZFQgcFAUMSCdeIA05pYJtWGIjvvwVJWjamxAn4yg4uDB9as15kYX78bULZF1dYK/ bHreSDGaLS2K++6CFyUB2WUuxRiYI5w/31KC8rc1r2ZlgF/gpPwj5MfQsV0xny05Mpgy 6KVHrGESCC5hYDDOfopL7rObiOMr3KtLCcT8Eq4LL/rPxMD/V7YgbDJ8K9UPY3/mjENO QVdCXNh9s5KvNUW2zT0rKbCzaV2wEWNr4mupjEF+qZ2vmWfquSmGp8U4iNTw4Tf0fd1F BiAWaK8+I3GuC6JiyslXD8BrA4P/TwWKyanYvk3gj2HBaLyiV+oU/muqzdxXyDnnlWRe /0Mw== X-Gm-Message-State: AOJu0Yxa/H+oHIRLa2mXBNODVEATFFoGF4a54kEyatcUtZ6fqDDyjvOr ZEnA/poJGm8wotKcqKHtgCDaZEf3Kiivv/zSpblCNNrAPv6r4e62gfZInYjRoZ+x6dZY/W/B3nH ynQPRCsPv7ReDOWydYvajmrIKZIS6FtndwT24zdcv/rWiu424BhE= X-Gm-Gg: ASbGncvFPDkZKRRZ9Qsztt4msOg6vnVCQJx8yDPWA11FDXEbihAEUe9RW2mO99LXybi NJtMhZlRLlaE6uJhl+8R0L9FxNDngQGC/HgIPtH2BFp/4ERZdPr9Fdt5nmTIR7pgmTtwrXxek33 6inogZTcVzEmFefuQf9ZACZvMvsIvTXZH4VSYeD70npO8TajOdXJy6Bj/dVfysnS5IxXW4NhEpR W0mtdPMy8ppRMZFWoBWBWcjVQhIkcMS6r6py9EiHpyw4QryPVrhCm6aNES0QmOYgPmwnD8SQWan 8+Vh7a3BtbxaBMBdgXFO X-Received: by 2002:a05:6402:3595:b0:5e0:8c55:536 with SMTP id 4fb4d7f45d1cf-5e444481531mr13914555a12.4.1740666145461; Thu, 27 Feb 2025 06:22:25 -0800 (PST) X-Google-Smtp-Source: AGHT+IHQEvRXKFNO8uqehyPrMvfwzyUwe/T2t9ikClNPL5YVhQNUna8NZ1lwhLuT9lhaB++h80+AvQ== X-Received: by 2002:a05:6402:3595:b0:5e0:8c55:536 with SMTP id 4fb4d7f45d1cf-5e444481531mr13914532a12.4.1740666145018; Thu, 27 Feb 2025 06:22:25 -0800 (PST) Received: from [192.168.10.48] ([176.206.102.52]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5e4c3fb58f7sm1145654a12.57.2025.02.27.06.22.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Feb 2025 06:22:24 -0800 (PST) From: Paolo Bonzini To: qemu-devel@nongnu.org Cc: qemu-rust@nongnu.org, zhao1.liu@intel.com Subject: [PATCH 02/12] rust: qemu_api_macros: add Wrapper derive macro Date: Thu, 27 Feb 2025 15:22:09 +0100 Message-ID: <20250227142219.812270-3-pbonzini@redhat.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250227142219.812270-1-pbonzini@redhat.com> References: <20250227142219.812270-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: CYSDUeiH8-7PtH5Veei5-kvfOYHEnh4i2SLz1gQcEl8_1740666146 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true Received-SPF: pass client-ip=170.10.133.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.438, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-rust@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: QEMU Rust-related patches and discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Feb 2025 14:22:46 -0000 Add a derive macro that makes it easy to peel off all the layers of specialness (UnsafeCell, MaybeUninit, etc.) and just get a pointer to the wrapped type; and likewise add them back starting from a *mut. Reviewed-by: Zhao Liu Signed-off-by: Paolo Bonzini --- docs/devel/rust.rst | 8 +-- rust/qemu-api-macros/src/lib.rs | 86 ++++++++++++++++++++++++++++++++- rust/qemu-api/meson.build | 7 +-- rust/qemu-api/src/cell.rs | 31 ++++++++++++ 4 files changed, 123 insertions(+), 9 deletions(-) diff --git a/docs/devel/rust.rst b/docs/devel/rust.rst index 784c3e40bdc..64e04bc5c41 100644 --- a/docs/devel/rust.rst +++ b/docs/devel/rust.rst @@ -315,11 +315,13 @@ a raw pointer, for use in calls to C functions. It can be used for example as follows:: #[repr(transparent)] - #[derive(Debug)] + #[derive(Debug, qemu_api_macros::Wrapper)] pub struct Object(Opaque); -The bindings will then manually check for the big QEMU lock with -assertions, which allows the wrapper to be declared thread-safe:: +where the special ``derive`` macro provides useful methods such as +``from_raw``, ``as_ptr`` and ``as_mut_ptr``. The bindings will then +manually check for the big QEMU lock with assertions, which allows +the wrapper to be declared thread-safe:: unsafe impl Send for Object {} unsafe impl Sync for Object {} diff --git a/rust/qemu-api-macros/src/lib.rs b/rust/qemu-api-macros/src/lib.rs index 7ec218202f4..3df9c48035d 100644 --- a/rust/qemu-api-macros/src/lib.rs +++ b/rust/qemu-api-macros/src/lib.rs @@ -6,7 +6,7 @@ use quote::quote; use syn::{ parse_macro_input, parse_quote, punctuated::Punctuated, spanned::Spanned, token::Comma, Data, - DeriveInput, Field, Fields, Ident, Meta, Path, Token, Type, Variant, Visibility, + DeriveInput, Field, Fields, FieldsUnnamed, Ident, Meta, Path, Token, Type, Variant, Visibility, }; mod utils; @@ -33,6 +33,35 @@ fn get_fields<'a>( } } +fn get_unnamed_field<'a>(input: &'a DeriveInput, msg: &str) -> Result<&'a Field, MacroError> { + if let Data::Struct(s) = &input.data { + let unnamed = match &s.fields { + Fields::Unnamed(FieldsUnnamed { + unnamed: ref fields, + .. + }) => fields, + _ => { + return Err(MacroError::Message( + format!("Tuple struct required for {}", msg), + s.fields.span(), + )) + } + }; + if unnamed.len() != 1 { + return Err(MacroError::Message( + format!("A single field is required for {}", msg), + s.fields.span(), + )); + } + Ok(&unnamed[0]) + } else { + Err(MacroError::Message( + format!("Struct required for {}", msg), + input.ident.span(), + )) + } +} + fn is_c_repr(input: &DeriveInput, msg: &str) -> Result<(), MacroError> { let expected = parse_quote! { #[repr(C)] }; @@ -46,6 +75,19 @@ fn is_c_repr(input: &DeriveInput, msg: &str) -> Result<(), MacroError> { } } +fn is_transparent_repr(input: &DeriveInput, msg: &str) -> Result<(), MacroError> { + let expected = parse_quote! { #[repr(transparent)] }; + + if input.attrs.iter().any(|attr| attr == &expected) { + Ok(()) + } else { + Err(MacroError::Message( + format!("#[repr(transparent)] required for {}", msg), + input.ident.span(), + )) + } +} + fn derive_object_or_error(input: DeriveInput) -> Result { is_c_repr(&input, "#[derive(Object)]")?; @@ -72,6 +114,48 @@ pub fn derive_object(input: TokenStream) -> TokenStream { TokenStream::from(expanded) } +fn derive_opaque_or_error(input: DeriveInput) -> Result { + is_transparent_repr(&input, "#[derive(Wrapper)]")?; + + let name = &input.ident; + let field = &get_unnamed_field(&input, "#[derive(Wrapper)]")?; + let typ = &field.ty; + + // TODO: how to add "::qemu_api"? For now, this is only used in the + // qemu_api crate so it's not a problem. + Ok(quote! { + unsafe impl crate::cell::Wrapper for #name { + type Wrapped = <#typ as crate::cell::Wrapper>::Wrapped; + } + impl #name { + pub unsafe fn from_raw<'a>(ptr: *mut ::Wrapped) -> &'a Self { + let ptr = ::std::ptr::NonNull::new(ptr).unwrap().cast::(); + unsafe { ptr.as_ref() } + } + + pub const fn as_mut_ptr(&self) -> *mut ::Wrapped { + self.0.as_mut_ptr() + } + + pub const fn as_ptr(&self) -> *const ::Wrapped { + self.0.as_ptr() + } + + pub const fn as_void_ptr(&self) -> *mut ::core::ffi::c_void { + self.0.as_void_ptr() + } + } + }) +} + +#[proc_macro_derive(Wrapper)] +pub fn derive_opaque(input: TokenStream) -> TokenStream { + let input = parse_macro_input!(input as DeriveInput); + let expanded = derive_opaque_or_error(input).unwrap_or_else(Into::into); + + TokenStream::from(expanded) +} + #[rustfmt::skip::macros(quote)] fn derive_offsets_or_error(input: DeriveInput) -> Result { is_c_repr(&input, "#[derive(offsets)]")?; diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build index bcf1cf780f3..6e52c4bad74 100644 --- a/rust/qemu-api/meson.build +++ b/rust/qemu-api/meson.build @@ -42,16 +42,13 @@ _qemu_api_rs = static_library( override_options: ['rust_std=2021', 'build.rust_std=2021'], rust_abi: 'rust', rust_args: _qemu_api_cfg, - dependencies: libc_dep, + dependencies: [libc_dep, qemu_api_macros], ) rust.test('rust-qemu-api-tests', _qemu_api_rs, suite: ['unit', 'rust']) -qemu_api = declare_dependency( - link_with: _qemu_api_rs, - dependencies: qemu_api_macros, -) +qemu_api = declare_dependency(link_with: _qemu_api_rs) # Rust executables do not support objects, so add an intermediate step. rust_qemu_api_objs = static_library( diff --git a/rust/qemu-api/src/cell.rs b/rust/qemu-api/src/cell.rs index 7c00109d0e9..24efb3a2f2a 100644 --- a/rust/qemu-api/src/cell.rs +++ b/rust/qemu-api/src/cell.rs @@ -1023,3 +1023,34 @@ pub unsafe fn new() -> Self { } } } + +/// Annotates [`Self`] as a transparent wrapper for another type. +/// +/// Usually defined via the [`qemu_api_macros::Wrapper`] derive macro. +/// +/// # Examples +/// +/// ``` +/// # use std::mem::ManuallyDrop; +/// # use qemu_api::cell::Wrapper; +/// #[repr(transparent)] +/// pub struct Example { +/// inner: ManuallyDrop, +/// } +/// +/// unsafe impl Wrapper for Example { +/// type Wrapped = String; +/// } +/// ``` +/// +/// # Safety +/// +/// `Self` must be a `#[repr(transparent)]` wrapper for the `Wrapped` type, +/// whether directly or indirectly. +pub unsafe trait Wrapper { + type Wrapped; +} + +unsafe impl Wrapper for Opaque { + type Wrapped = T; +} -- 2.48.1