linux-kernel - [PATCH 1/5] rust: error: Add Error::to

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Message-Id: <20230224-rust-error-v1-1-f8f9a9a87303@asahilina.net>
Date:   Fri, 24 Feb 2023 17:50:19 +0900
From:   Asahi Lina <lina@...hilina.net>
To:     Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Sven Van Asbroeck <thesven73@...il.com>
Cc:     Fox Chen <foxhlchen@...il.com>, rust-for-linux@...r.kernel.org,
        linux-kernel@...r.kernel.org, asahi@...ts.linux.dev,
        Asahi Lina <lina@...hilina.net>
Subject: [PATCH 1/5] rust: error: Add Error::to_ptr()

This is the Rust equivalent to ERR_PTR(), for use in C callbacks.
Marked as #[allow(dead_code)] for now, since it does not have any
consumers yet.

Signed-off-by: Asahi Lina <lina@...hilina.net>
---
 rust/helpers.c       | 7 +++++++
 rust/kernel/error.rs | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/rust/helpers.c b/rust/helpers.c
index 09a4d93f9d62..89f4cd1e0df3 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -20,6 +20,7 @@
 
 #include <linux/bug.h>
 #include <linux/build_bug.h>
+#include <linux/err.h>
 #include <linux/refcount.h>
 
 __noreturn void rust_helper_BUG(void)
@@ -46,6 +47,12 @@ bool rust_helper_refcount_dec_and_test(refcount_t *r)
 }
 EXPORT_SYMBOL_GPL(rust_helper_refcount_dec_and_test);
 
+__force void *rust_helper_ERR_PTR(long err)
+{
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(rust_helper_ERR_PTR);
+
 /*
  * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type
  * as the Rust `usize` type, so we can use it in contexts where Rust
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index 5b9751d7ff1d..8611758e27f4 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -76,6 +76,13 @@ impl Error {
     pub fn to_kernel_errno(self) -> core::ffi::c_int {
         self.0
     }
+
+    /// Returns the error encoded as a pointer.
+    #[allow(dead_code)]
+    pub(crate) fn to_ptr<T>(self) -> *mut T {
+        // SAFETY: Valid as long as self.0 is a valid error
+        unsafe { bindings::ERR_PTR(self.0.into()) as *mut _ }
+    }
 }
 
 impl From<AllocError> for Error {

-- 
2.35.1