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kernel: Add helper macros for loop unrolling

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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;
	}

Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: John Johansen <john.johansen@canonical.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Nacked-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
KP Singh 2024-08-16 17:43:05 +02:00 committed by Paul Moore
parent 77b644c39d
commit 7cff549daa
1 changed files with 36 additions and 0 deletions
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36
include/linux/unroll.h Normal file
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/* 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 */