[PATCH] rust: add safety comment in rust_fmt_argument

[Konstantin Andrikopoulos <kernel@mandragore.io>]

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The function rust_fmt_argument derefernces a c_void pointer, and thus it
needs an unsafe block. The safety comment for that block was missing.

Part of Rust-for-Linux#351.

Signed-off-by: Konstantin Andrikopoulos <kernel@mandragore.io>
---
 rust/kernel/print.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
index a28077a7cb30..3545dd08fde0 100644
--- a/rust/kernel/print.rs
+++ b/rust/kernel/print.rs
@@ -24,7 +24,7 @@
     use fmt::Write;
     // SAFETY: The C contract guarantees that `buf` is valid if it's less than `end`.
     let mut w = unsafe { RawFormatter::from_ptrs(buf.cast(), end.cast()) };
-    // SAFETY: TODO.
+    // SAFETY: The Rust contract guarantees that `ptr` is a valid pointer to a `fmt::Arguments` struct.
     let _ = w.write_fmt(unsafe { *(ptr as *const fmt::Arguments<'_>) });
     w.pos().cast()
 }
-- 
2.47.0


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