Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Wed, 29 Mar 2023 21:35:48 +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>,
        Sven Van Asbroeck <thesven73@gmail.com>,
        Fox Chen <foxhlchen@gmail.com>,
        Martin Rodriguez Reboredo <yakoyoku@gmail.com>,
        Andreas Hindborg <a.hindborg@samsung.com>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        asahi@lists.linux.dev
Subject: Re: [PATCH v2 3/6] rust: error: Add Error::from_errno()
Message-ID: <20230329213548.14a47ede.gary@garyguo.net>
In-Reply-To: <20230224-rust-error-v2-3-3900319812da@asahilina.net>
References: <20230224-rust-error-v2-0-3900319812da@asahilina.net>
        <20230224-rust-error-v2-3-3900319812da@asahilina.net>
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?w1ZswPClcfZ6Z3219uqgYw20V1Xc+SToR2Bjv7XxfDFROHebtkzjALRl6esp?=
 =?us-ascii?Q?NMjF3UPPpGeRhHgXXCBMyFS6sMTwUWix/N4PS4p2b5E7GxS/xy0PXvslv1pV?=
 =?us-ascii?Q?xTmtyh6c0bHe7oGjsvdwUPWvTDguHDeVsXhudu6PbD8OQVAXw4p/TMwwf7I4?=
 =?us-ascii?Q?rYbjYpper6u+kQpQ2o8nJzUcymBlW2YRtaFtS//VfOARtpbZBtX+NNXBqkw5?=
 =?us-ascii?Q?tpGn47Yv5e5+3qi+eTR9yxNO9nnSlTP45du24Dl9LUmkp5/gaIymKvI4T+7Y?=
 =?us-ascii?Q?+ckafY6L1uiZPa5+mwgIK03g+NwU28x9i1FzpWsAtcNI15YHiiLgC09v10az?=
 =?us-ascii?Q?v00GHpgAUOE95KgKXGlidmq9uMBVbcBoRog/KpqTMLwbILCS7+bG2uMehDfl?=
 =?us-ascii?Q?zxDe0buMMvLUnTO8bUwnsDCvq7EftAYhVSoF5XyunmKyCNt0qAMxz5JoUlXu?=
 =?us-ascii?Q?QorKgFALz5iR0I+zix9Jnl2QMQP8mb8lh58by4w0KLpDGCxylDR2YW2r2W90?=
 =?us-ascii?Q?PUmo0ggNFrhokZHLkPkA9xgc4t0KQtF9RcruQrKSY0BjmEQETXlxGVYzJfRw?=
 =?us-ascii?Q?caKRlluxbchskA8H9GT0DqbPFpCKRVie+n/9Za+qxabh+kgYs4xta0R2hqNd?=
 =?us-ascii?Q?eS3pM9F7owHk1XuUm6Kpb0JnhKnpLM/NntoBJvy6u5XJaan5gt4SQuUppbm3?=
 =?us-ascii?Q?qlFzpVELEwfFO4NpKRTiQhnT74ilkIW0v2BVDBNcNW3HK8WBjXpgeYdbo0ZY?=
 =?us-ascii?Q?UmOc4gdw+f6e3pdbh66cb+p0HqDi0ACSDAGba5bIJIH72ZxbqIlEgQ+JJVxR?=
 =?us-ascii?Q?eeDUfBeXvXEx3P9E3Fjipz6FB/3D1SkY+0cWYdCHyQEi+DYxAGJwrZ5xce0b?=
 =?us-ascii?Q?OYUNSnUbH5hGTTEkZBRH60vRKP5rTbq0gComZxzeszZWRu5pn1roXmOeS4Zd?=
 =?us-ascii?Q?21Mugll5XDl+PesMAi702ymHed7vTOYeuhruwzvDnEpKu4Ivse5bzzA0Rpyx?=
 =?us-ascii?Q?/fDs5bp9Ft8DB/1x+nf+ux0nW15Zi14SxczeyXVLiwcn5pBlExlPgfSC84Uj?=
 =?us-ascii?Q?W14ZTesG/395olxuYhdBapIvim8tJyepkGMbnm3aBomcz5F9xfAyt50CTYj7?=
 =?us-ascii?Q?YMlMd3iE50QLV+Ok0W4swTQGxkcozSjEVPGpUtoBFNk7WoeYQV9l/mJ3xqk4?=
 =?us-ascii?Q?hByfwdeCwE3pJSgfYr+dlHYxmu+W37ghVX3Mto8OaFD5JeDW3LoICvbaEKNA?=
 =?us-ascii?Q?mbMFhF01oGGP1PxUGT73ImTE4J+8WIVBtwh96XActMAVVH4QCfKNSekebssl?=
 =?us-ascii?Q?E+ar9MghmjWZSRDUSu9ZVV7sw6agg3XsgLy4gaR1KkH+0mlWHuGl4RJ1pydr?=
 =?us-ascii?Q?c2eXGFIoiHObu2K74fFyA19CesmTfhXgPeW4lHdo32gmtTZHlGqoTfLuzv12?=
 =?us-ascii?Q?ezofa3n7qLVpx3mMfIrPgFL/d9x3p5g/8n9sjZWbearYWkYdAArFGJ1hU/oh?=
 =?us-ascii?Q?RGCeAy0p8eOsbdx/DqUECw+MCuQ7LYnF1oLj6ciGqR1zW3KcFIEP2wq26dUl?=
 =?us-ascii?Q?2H0eFOUcqSZTFQlHT4PZI8eIS1B+7cd4f1UwI5jh?=
X-OriginatorOrg: garyguo.net
X-MS-Exchange-CrossTenant-Network-Message-Id: f2521da6-f3d4-4bf9-54b4-08db30952f06
X-MS-Exchange-CrossTenant-AuthSource: LO2P265MB5183.GBRP265.PROD.OUTLOOK.COM
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Mar 2023 20:35:50.1282
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: bbc898ad-b10f-4e10-8552-d9377b823d45
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 7H8HC6GepUOQO2c3DN3htNfTj0r9imSfq26ZJFqGd/cN5tBoySvI9FM3aSc2ZIp44biG2wpgiNcc8BzXZmDY/g==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: LO6P265MB5984
X-Spam-Status: No, score=-0.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
        DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,
        SPF_HELO_PASS,SPF_PASS autolearn=unavailable autolearn_force=no
        version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, 29 Mar 2023 21:04:35 +0900
Asahi Lina <lina@asahilina.net> wrote:

> From: Miguel Ojeda <ojeda@kernel.org>
> 
> Add a function to create `Error` values out of a kernel error return,
> which safely upholds the invariant that the error code is well-formed
> (negative and greater than -MAX_ERRNO). If a malformed code is passed
> in, it will be converted to EINVAL.
> 
> Lina: Imported from rust-for-linux/rust as authored by Miguel and Fox
> with refactoring from Wedson, renamed from_kernel_errno() to
> from_errno().
> 
> Co-developed-by: Fox Chen <foxhlchen@gmail.com>
> Signed-off-by: Fox Chen <foxhlchen@gmail.com>
> Co-developed-by: Wedson Almeida Filho <wedsonaf@gmail.com>
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> ---
>  rust/kernel/error.rs | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
> index e97e652a1aec..659468bd1735 100644
> --- a/rust/kernel/error.rs
> +++ b/rust/kernel/error.rs
> @@ -72,6 +72,25 @@ pub mod code {
>  pub struct Error(core::ffi::c_int);
>  
>  impl Error {
> +    /// Creates an [`Error`] from a kernel error code.
> +    ///
> +    /// It is a bug to pass an out-of-range `errno`. `EINVAL` would
> +    /// be returned in such a case.
> +    pub(crate) fn from_errno(errno: core::ffi::c_int) -> Error {
> +        if errno < -(bindings::MAX_ERRNO as i32) || errno >= 0 {
> +            // TODO: Make it a `WARN_ONCE` once available.
> +            crate::pr_warn!(
> +                "attempted to create `Error` with out of range `errno`: {}",
> +                errno
> +            );
> +            return code::EINVAL;
> +        }
> +
> +        // INVARIANT: The check above ensures the type invariant
> +        // will hold.
> +        Error(errno)
> +    }
> +
>      /// Returns the kernel error code.
>      pub fn to_errno(self) -> core::ffi::c_int {
>          self.0
> 

Reviewed-by: Gary Guo <gary@garyguo.net>