[6.12.y,45/60] rust: str: test: replace `alloc::format`

Commit Message

Miguel Ojeda March 7, 2025, 10:49 p.m. UTC

From: Danilo Krummrich <[e-mail]>

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 <[e-mail]>
Reviewed-by: Benno Lossin <[e-mail]>
Reviewed-by: Gary Guo <[e-mail]>
Signed-off-by: Danilo Krummrich <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Miguel Ojeda <[e-mail]>
---
 rust/kernel/str.rs | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

Patch

diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index 6053bc7a98d1..aff6baa521d4 100644
--- 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\