linux-kernel - Re: [PATCH v9 25/29] rust: alloc: implement `Cmalloc` in module allocator

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Message-ID: <ZwVCeQK4qu3HPBGQ@cassiopeiae>
Date: Tue, 8 Oct 2024 16:32:25 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: ojeda@...nel.org, alex.gaynor@...il.com, wedsonaf@...il.com,
	boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com,
	benno.lossin@...ton.me, a.hindborg@...sung.com,
	aliceryhl@...gle.com, akpm@...ux-foundation.org
Cc: daniel.almeida@...labora.com, faith.ekstrand@...labora.com,
	boris.brezillon@...labora.com, lina@...hilina.net,
	mcanal@...lia.com, zhiw@...dia.com, cjia@...dia.com,
	jhubbard@...dia.com, airlied@...hat.com, ajanulgu@...hat.com,
	lyude@...hat.com, linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v9 25/29] rust: alloc: implement `Cmalloc` in module
 allocator_test

On Fri, Oct 04, 2024 at 05:41:29PM +0200, Danilo Krummrich wrote:
> So far the kernel's `Box` and `Vec` types can't be used by userspace
> test cases, since all users of those types (e.g. `CString`) use kernel
> allocators for instantiation.
> 
> In order to allow userspace test cases to make use of such types as
> well, implement the `Cmalloc` allocator within the allocator_test module
> and type alias all kernel allocators to `Cmalloc`. The `Cmalloc`
> allocator uses libc's realloc() function as allocator backend.
> 
> Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
> Reviewed-by: Gary Guo <gary@...yguo.net>
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>
> ---
>  rust/kernel/alloc/allocator_test.rs | 88 ++++++++++++++++++++++++++---
>  1 file changed, 81 insertions(+), 7 deletions(-)
> 

Here we can remove it again:

diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index 912b6ba2abaa..8acaa24a8f1f 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -215,7 +215,6 @@ unsafe fn free(ptr: NonNull<u8>, layout: Layout) {
     }
 }

-#[allow(dead_code)]
 /// Returns a properly aligned dangling pointer from the given `layout`.
 pub(crate) fn dangling_from_layout(layout: Layout) -> NonNull<u8> {
     let ptr = layout.align() as *mut u8;

@Miguel: I pushed [1], which is already rebased to rust-next (-rc2) and contains
the fixups.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=rust/mm