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Date:   Wed, 29 Mar 2023 21:25:52 +0100
From:   Gary Guo <gary@garyguo.net>
To:     Asahi Lina <lina@asahilina.net>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        =?UTF-8?B?QmrDtnJu?= Roy Baron <bjorn3_gh@protonmail.com>,
        linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org,
        asahi@lists.linux.dev
Subject: Re: [PATCH 1/2] rust: uapi: Add UAPI crate
Message-ID: <20230329212552.0d7b575a.gary@garyguo.net>
In-Reply-To: <20230329-rust-uapi-v1-1-ee78f2933726@asahilina.net>
References: <20230329-rust-uapi-v1-0-ee78f2933726@asahilina.net>
        <20230329-rust-uapi-v1-1-ee78f2933726@asahilina.net>
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On Wed, 29 Mar 2023 20:40:18 +0900
Asahi Lina <lina@asahilina.net> wrote:

> This crate mirrors the `bindings` crate, but will contain only UAPI
> bindings. Unlike the bindings crate, drivers may directly use this crate
> if they have to interface with userspace.
> 
> Initially, just bind the generic ioctl stuff.
> 
> In the future, we would also like to add additional checks to ensure
> that all types exposed by this crate satisfy UAPI-safety guarantees
> (that is, they are safely castable to/from a "bag of bits").
> 
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> ---
>  rust/.gitignore         |  1 +
>  rust/Makefile           | 18 ++++++++++++++++--
>  rust/kernel/lib.rs      |  1 +
>  rust/uapi/lib.rs        | 27 +++++++++++++++++++++++++++
>  rust/uapi/uapi_helper.h |  9 +++++++++
>  5 files changed, 54 insertions(+), 2 deletions(-)
> 
> diff --git a/rust/.gitignore b/rust/.gitignore
> index 168cb26a31b9..21552992b401 100644
> --- a/rust/.gitignore
> +++ b/rust/.gitignore
> @@ -2,6 +2,7 @@
>  
>  bindings_generated.rs
>  bindings_helpers_generated.rs
> +uapi_generated.rs
>  exports_*_generated.h
>  doc/
>  test/
> diff --git a/rust/Makefile b/rust/Makefile
> index f88d108fbef0..59a327f0fa1a 100644
> --- a/rust/Makefile
> +++ b/rust/Makefile
> @@ -16,6 +16,9 @@ obj-$(CONFIG_RUST) += alloc.o bindings.o kernel.o
>  always-$(CONFIG_RUST) += exports_alloc_generated.h exports_bindings_generated.h \
>      exports_kernel_generated.h
>  
> +always-$(CONFIG_RUST) += uapi/uapi_generated.rs
> +obj-$(CONFIG_RUST) += uapi.o
> +
>  ifdef CONFIG_RUST_BUILD_ASSERT_ALLOW
>  obj-$(CONFIG_RUST) += build_error.o
>  else
> @@ -288,6 +291,12 @@ $(obj)/bindings/bindings_generated.rs: $(src)/bindings/bindings_helper.h \
>      $(src)/bindgen_parameters FORCE
>  	$(call if_changed_dep,bindgen)
>  
> +$(obj)/uapi/uapi_generated.rs: private bindgen_target_flags = \
> +    $(shell grep -v '^\#\|^$$' $(srctree)/$(src)/bindgen_parameters)
> +$(obj)/uapi/uapi_generated.rs: $(src)/uapi/uapi_helper.h \
> +    $(src)/bindgen_parameters FORCE
> +	$(call if_changed_dep,bindgen)
> +
>  # See `CFLAGS_REMOVE_helpers.o` above. In addition, Clang on C does not warn
>  # with `-Wmissing-declarations` (unlike GCC), so it is not strictly needed here
>  # given it is `libclang`; but for consistency, future Clang changes and/or
> @@ -388,10 +397,15 @@ $(obj)/bindings.o: $(src)/bindings/lib.rs \
>      $(obj)/bindings/bindings_helpers_generated.rs FORCE
>  	$(call if_changed_dep,rustc_library)
>  
> +$(obj)/uapi.o: $(src)/uapi/lib.rs \
> +    $(obj)/compiler_builtins.o \
> +    $(obj)/uapi/uapi_generated.rs FORCE
> +	$(call if_changed_dep,rustc_library)
> +
>  $(obj)/kernel.o: private rustc_target_flags = --extern alloc \
> -    --extern build_error --extern macros --extern bindings
> +    --extern build_error --extern macros --extern bindings --extern uapi
>  $(obj)/kernel.o: $(src)/kernel/lib.rs $(obj)/alloc.o $(obj)/build_error.o \
> -    $(obj)/libmacros.so $(obj)/bindings.o FORCE
> +    $(obj)/libmacros.so $(obj)/bindings.o $(obj)/uapi.o FORCE
>  	$(call if_changed_dep,rustc_library)
>  
>  endif # CONFIG_RUST
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 7610b18ee642..63f796781b7c 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -43,6 +43,7 @@ pub mod types;
>  #[doc(hidden)]
>  pub use bindings;
>  pub use macros;
> +pub use uapi;
>  
>  #[doc(hidden)]
>  pub use build_error::build_error;
> diff --git a/rust/uapi/lib.rs b/rust/uapi/lib.rs
> new file mode 100644
> index 000000000000..29f69f3a52de
> --- /dev/null
> +++ b/rust/uapi/lib.rs
> @@ -0,0 +1,27 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! UAPI Bindings.
> +//!
> +//! Contains the bindings generated by `bindgen` for UAPI interfaces.
> +//!
> +//! This crate may be used directly by drivers that need to interact with
> +//! userspace APIs.
> +
> +#![no_std]
> +#![feature(core_ffi_c)]
> +// See <https://github.com/rust-lang/rust-bindgen/issues/1651>.
> +#![cfg_attr(test, allow(deref_nullptr))]
> +#![cfg_attr(test, allow(unaligned_references))]
> +#![cfg_attr(test, allow(unsafe_op_in_unsafe_fn))]

Looks like that we should bump our bindgen version.

> +#![allow(
> +    clippy::all,
> +    missing_docs,
> +    non_camel_case_types,
> +    non_upper_case_globals,
> +    non_snake_case,
> +    improper_ctypes,
> +    unreachable_pub,
> +    unsafe_op_in_unsafe_fn
> +)]
> +
> +include!(concat!(env!("OBJTREE"), "/rust/uapi/uapi_generated.rs"));
> diff --git a/rust/uapi/uapi_helper.h b/rust/uapi/uapi_helper.h
> new file mode 100644
> index 000000000000..301f5207f023
> --- /dev/null
> +++ b/rust/uapi/uapi_helper.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Header that contains the headers for which Rust UAPI bindings
> + * will be automatically generated by `bindgen`.
> + *
> + * Sorted alphabetically.
> + */
> +
> +#include <uapi/asm-generic/ioctl.h>
> 

Best,
Gary