[PATCH] rust: alloc: add ARCH_KMALLOC_MINALIGN to bindgen blocklist

[PATCH] rust: alloc: add ARCH_KMALLOC_MINALIGN to bindgen blocklist

[Danilo Krummrich]

For some architectures, such as X86_64, ARCH_KMALLOC_MINALIGN is not
resolvable for bindgen. E.g. due to being defined as
__alignof__(unsigned long long).

Hence, we have to create a rust helper, i.e. let the C compiler evaluate
the expression and store it in a const.

However, if for other architectures, such as arm64,
ARCH_KMALLOC_MINALIGN does evaluate to something that can be directly
processed by bindgen, we end up with multiple definitions of
ARCH_KMALLOC_MINALIGN in the generated bindings.

	error[E0428]: the name `ARCH_KMALLOC_MINALIGN` is defined multiple times
	      --> /builddir/build/BUILD/kernel-6.17.0-build/kernel-next-20250818/linux-6.17.0-0.0.next.20250818.423.vanilla.fc44.aarch64/rust/bindings/bindings_generated.rs:134545:1
	       |
	9622   | pub const ARCH_KMALLOC_MINALIGN: u32 = 8;
	       | ----------------------------------------- previous definition of the value `ARCH_KMALLOC_MINALIGN` here
	...
	134545 | pub const ARCH_KMALLOC_MINALIGN: usize = 8;
	       | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `ARCH_KMALLOC_MINALIGN` redefined here
	       |
	       = note: `ARCH_KMALLOC_MINALIGN` must be defined only once in the value namespace of this module

To fix this up, add ARCH_KMALLOC_MINALIGN to the blocklist of bindgen,
such that we always only generate the symbol from the rust helper.

Reported-by: Thorsten Leemhuis <linux@leemhuis.info>
Closes: https://lore.kernel.org/all/8aa05f08-ef6e-4dfe-9453-beaab7b3cb98@leemhuis.info/
Fixes: 1b1a946dc2b5 ("rust: alloc: specify the minimum alignment of each allocator")
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/bindgen_parameters | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters
index 0f96af8b9a7f..02b371b98b39 100644
--- a/rust/bindgen_parameters
+++ b/rust/bindgen_parameters
@@ -34,3 +34,4 @@
 # We use const helpers to aid bindgen, to avoid conflicts when constants are
 # recognized, block generation of the non-helper constants.
 --blocklist-item ARCH_SLAB_MINALIGN
+--blocklist-item ARCH_KMALLOC_MINALIGN

base-commit: 7e25d84f460c59322bf01dfeb1fb4745b488f714
-- 
2.50.1

Re: [PATCH] rust: alloc: add ARCH_KMALLOC_MINALIGN to bindgen blocklist

[Alice Ryhl]

On Mon, Aug 18, 2025 at 8:09 PM Danilo Krummrich <dakr@kernel.org> wrote:
>
> For some architectures, such as X86_64, ARCH_KMALLOC_MINALIGN is not
> resolvable for bindgen. E.g. due to being defined as
> __alignof__(unsigned long long).
>
> Hence, we have to create a rust helper, i.e. let the C compiler evaluate
> the expression and store it in a const.
>
> However, if for other architectures, such as arm64,
> ARCH_KMALLOC_MINALIGN does evaluate to something that can be directly
> processed by bindgen, we end up with multiple definitions of
> ARCH_KMALLOC_MINALIGN in the generated bindings.
>
>         error[E0428]: the name `ARCH_KMALLOC_MINALIGN` is defined multiple times
>               --> /builddir/build/BUILD/kernel-6.17.0-build/kernel-next-20250818/linux-6.17.0-0.0.next.20250818.423.vanilla.fc44.aarch64/rust/bindings/bindings_generated.rs:134545:1
>                |
>         9622   | pub const ARCH_KMALLOC_MINALIGN: u32 = 8;
>                | ----------------------------------------- previous definition of the value `ARCH_KMALLOC_MINALIGN` here
>         ...
>         134545 | pub const ARCH_KMALLOC_MINALIGN: usize = 8;
>                | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `ARCH_KMALLOC_MINALIGN` redefined here
>                |
>                = note: `ARCH_KMALLOC_MINALIGN` must be defined only once in the value namespace of this module
>
> To fix this up, add ARCH_KMALLOC_MINALIGN to the blocklist of bindgen,
> such that we always only generate the symbol from the rust helper.
>
> Reported-by: Thorsten Leemhuis <linux@leemhuis.info>
> Closes: https://lore.kernel.org/all/8aa05f08-ef6e-4dfe-9453-beaab7b3cb98@leemhuis.info/
> Fixes: 1b1a946dc2b5 ("rust: alloc: specify the minimum alignment of each allocator")
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Reviewed-by: Alice Ryhl <aliceryhl@google.com>

Re: [PATCH] rust: alloc: add ARCH_KMALLOC_MINALIGN to bindgen blocklist

[Thorsten Leemhuis]

On 18.08.25 20:08, Danilo Krummrich wrote:
> For some architectures, such as X86_64, ARCH_KMALLOC_MINALIGN is not
> resolvable for bindgen. E.g. due to being defined as
> __alignof__(unsigned long long).
> 
> Hence, we have to create a rust helper, i.e. let the C compiler evaluate
> the expression and store it in a const.
> 
> However, if for other architectures, such as arm64,
> ARCH_KMALLOC_MINALIGN does evaluate to something that can be directly
> processed by bindgen, we end up with multiple definitions of
> ARCH_KMALLOC_MINALIGN in the generated bindings.
> [...]

Thx, applied it on today's -next and everything went smoothly:

Tested-by: Thorsten Leemhuis <linux@leemhuis.info>

Ciao, Thorsten

Re: [PATCH] rust: alloc: add ARCH_KMALLOC_MINALIGN to bindgen blocklist

[Danilo Krummrich]

On Mon Aug 18, 2025 at 8:08 PM CEST, Danilo Krummrich wrote:
> For some architectures, such as X86_64, ARCH_KMALLOC_MINALIGN is not
> resolvable for bindgen. E.g. due to being defined as
> __alignof__(unsigned long long).
>
> Hence, we have to create a rust helper, i.e. let the C compiler evaluate
> the expression and store it in a const.
>
> However, if for other architectures, such as arm64,
> ARCH_KMALLOC_MINALIGN does evaluate to something that can be directly
> processed by bindgen, we end up with multiple definitions of
> ARCH_KMALLOC_MINALIGN in the generated bindings.
>
> 	error[E0428]: the name `ARCH_KMALLOC_MINALIGN` is defined multiple times
> 	      --> /builddir/build/BUILD/kernel-6.17.0-build/kernel-next-20250818/linux-6.17.0-0.0.next.20250818.423.vanilla.fc44.aarch64/rust/bindings/bindings_generated.rs:134545:1
> 	       |
> 	9622   | pub const ARCH_KMALLOC_MINALIGN: u32 = 8;
> 	       | ----------------------------------------- previous definition of the value `ARCH_KMALLOC_MINALIGN` here
> 	...
> 	134545 | pub const ARCH_KMALLOC_MINALIGN: usize = 8;
> 	       | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `ARCH_KMALLOC_MINALIGN` redefined here
> 	       |
> 	       = note: `ARCH_KMALLOC_MINALIGN` must be defined only once in the value namespace of this module
>
> To fix this up, add ARCH_KMALLOC_MINALIGN to the blocklist of bindgen,
> such that we always only generate the symbol from the rust helper.
>
> Reported-by: Thorsten Leemhuis <linux@leemhuis.info>
> Closes: https://lore.kernel.org/all/8aa05f08-ef6e-4dfe-9453-beaab7b3cb98@leemhuis.info/
> Fixes: 1b1a946dc2b5 ("rust: alloc: specify the minimum alignment of each allocator")
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Applied to alloc-next, thanks!