Re: [PATCH v12 1/5] kernel: Add helper macros for loop unrolling

John Johansen
2024-05-17T08:04:10Z

On 5/15/24 17:35, KP Singh wrote:
> This helps in easily initializing blocks of code (e.g. static calls and
> keys).
>
> UNROLL(N, MACRO, __VA_ARGS__) calls MACRO N times with the first
> argument as the index of the iteration. This allows string pasting to
> create unique tokens for variable names, function calls etc.
>
> As an example:
>
> #include <linux/unroll.h>
>
> #define MACRO(N, a, b) \
> int add_##N(int a, int b) \
> { \
> return a + b + N; \
> }
>
> UNROLL(2, MACRO, x, y)
>
> expands to:
>
> int add_0(int x, int y)
> {
> return x + y + 0;
> }
>
> int add_1(int x, int y)
> {
> return x + y + 1;
> }
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
> Acked-by: Song Liu <song@kernel.org>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: KP Singh <kpsingh@kernel.org>

looks good

Reviewed-by: John Johansen <john.johansen@canonical.com>

> ---
> include/linux/unroll.h | 36 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
> create mode 100644 include/linux/unroll.h
>
> diff --git a/include/linux/unroll.h b/include/linux/unroll.h
> new file mode 100644
> index 000000000000..d42fd6366373
> --- /dev/null
> +++ b/include/linux/unroll.h
> @@ -0,0 +1,36 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +/*
> + * Copyright (C) 2023 Google LLC.
> + */
> +
> +#ifndef __UNROLL_H
> +#define __UNROLL_H
> +
> +#include <linux/args.h>
> +
> +#define UNROLL(N, MACRO, args...) CONCATENATE(__UNROLL_, N)(MACRO, args)
> +
> +#define __UNROLL_0(MACRO, args...)
> +#define __UNROLL_1(MACRO, args...) __UNROLL_0(MACRO, args) MACRO(0, args)
> +#define __UNROLL_2(MACRO, args...) __UNROLL_1(MACRO, args) MACRO(1, args)
> +#define __UNROLL_3(MACRO, args...) __UNROLL_2(MACRO, args) MACRO(2, args)
> +#define __UNROLL_4(MACRO, args...) __UNROLL_3(MACRO, args) MACRO(3, args)
> +#define __UNROLL_5(MACRO, args...) __UNROLL_4(MACRO, args) MACRO(4, args)
> +#define __UNROLL_6(MACRO, args...) __UNROLL_5(MACRO, args) MACRO(5, args)
> +#define __UNROLL_7(MACRO, args...) __UNROLL_6(MACRO, args) MACRO(6, args)
> +#define __UNROLL_8(MACRO, args...) __UNROLL_7(MACRO, args) MACRO(7, args)
> +#define __UNROLL_9(MACRO, args...) __UNROLL_8(MACRO, args) MACRO(8, args)
> +#define __UNROLL_10(MACRO, args...) __UNROLL_9(MACRO, args) MACRO(9, args)
> +#define __UNROLL_11(MACRO, args...) __UNROLL_10(MACRO, args) MACRO(10, args)
> +#define __UNROLL_12(MACRO, args...) __UNROLL_11(MACRO, args) MACRO(11, args)
> +#define __UNROLL_13(MACRO, args...) __UNROLL_12(MACRO, args) MACRO(12, args)
> +#define __UNROLL_14(MACRO, args...) __UNROLL_13(MACRO, args) MACRO(13, args)
> +#define __UNROLL_15(MACRO, args...) __UNROLL_14(MACRO, args) MACRO(14, args)
> +#define __UNROLL_16(MACRO, args...) __UNROLL_15(MACRO, args) MACRO(15, args)
> +#define __UNROLL_17(MACRO, args...) __UNROLL_16(MACRO, args) MACRO(16, args)
> +#define __UNROLL_18(MACRO, args...) __UNROLL_17(MACRO, args) MACRO(17, args)
> +#define __UNROLL_19(MACRO, args...) __UNROLL_18(MACRO, args) MACRO(18, args)
> +#define __UNROLL_20(MACRO, args...) __UNROLL_19(MACRO, args) MACRO(19, args)
> +
> +#endif /* __UNROLL_H */