releases/6.12.19/rust-str-test-replace-alloc-format.patch

From stable+bounces-121500-greg=kroah.com@vger.kernel.org Fri Mar  7 23:52:58 2025
From: Miguel Ojeda <ojeda@kernel.org>
Date: Fri,  7 Mar 2025 23:49:52 +0100
Subject: rust: str: test: replace `alloc::format`
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Sasha Levin <sashal@kernel.org>, stable@vger.kernel.org
Cc: Danilo Krummrich <dakr@kernel.org>, Alice Ryhl <aliceryhl@google.com>, Alyssa Ross <hi@alyssa.is>, NoisyCoil <noisycoil@disroot.org>, patches@lists.linux.dev, Miguel Ojeda <ojeda@kernel.org>
Message-ID: <20250307225008.779961-46-ojeda@kernel.org>

From: Danilo Krummrich <dakr@kernel.org>

commit eb6f92cd3f755c179204ea1f933b07cf992892fd upstream.

The current implementation of tests in str.rs use `format!` to format
strings for comparison, which, internally, creates a new `String`.

In order to prepare for getting rid of Rust's alloc crate, we have to
cut this dependency. Instead, implement `format!` for `CString`.

Note that for userspace tests, `Kmalloc`, which is backing `CString`'s
memory, is just a type alias to `Cmalloc`.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241004154149.93856-27-dakr@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 rust/kernel/str.rs |   23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -524,7 +524,28 @@ macro_rules! c_str {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use alloc::format;
+
+    struct String(CString);
+
+    impl String {
+        fn from_fmt(args: fmt::Arguments<'_>) -> Self {
+            String(CString::try_from_fmt(args).unwrap())
+        }
+    }
+
+    impl Deref for String {
+        type Target = str;
+
+        fn deref(&self) -> &str {
+            self.0.to_str().unwrap()
+        }
+    }
+
+    macro_rules! format {
+        ($($f:tt)*) => ({
+            &*String::from_fmt(kernel::fmt!($($f)*))
+        })
+    }
 
     const ALL_ASCII_CHARS: &'static str =
         "\\x01\\x02\\x03\\x04\\x05\\x06\\x07\\x08\\x09\\x0a\\x0b\\x0c\\x0d\\x0e\\x0f\