tools headers: Adopt verbatim copy of btf_ids.h from kernel sources

/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _LINUX_BTF_IDS_H

#define _LINUX_BTF_IDS_H

#include <linux/compiler.h> /* for __PASTE */

/*

 * Following macros help to define lists of BTF IDs placed

 * in .BTF_ids section. They are initially filled with zeros

 * (during compilation) and resolved later during the

 * linking phase by resolve_btfids tool.

 *

 * Any change in list layout must be reflected in resolve_btfids

 * tool logic.

 */

#define BTF_IDS_SECTION ".BTF_ids"

#define ____BTF_ID(symbol)				\

asm(							\

".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\

".local " #symbol " ;                          \n"	\

".type  " #symbol ", @object;                  \n"	\

".size  " #symbol ", 4;                        \n"	\

#symbol ":                                     \n"	\

".zero 4                                       \n"	\

".popsection;                                  \n");

#define __BTF_ID(symbol) \

	____BTF_ID(symbol)

#define __ID(prefix) \

	__PASTE(prefix, __COUNTER__)

/*

 * The BTF_ID defines unique symbol for each ID pointing

 * to 4 zero bytes.

 */

#define BTF_ID(prefix, name) \

	__BTF_ID(__ID(__BTF_ID__##prefix##__##name##__))

/*

 * The BTF_ID_LIST macro defines pure (unsorted) list

 * of BTF IDs, with following layout:

 *

 * BTF_ID_LIST(list1)

 * BTF_ID(type1, name1)

 * BTF_ID(type2, name2)

 *

 * list1:

 * __BTF_ID__type1__name1__1:

 * .zero 4

 * __BTF_ID__type2__name2__2:

 * .zero 4

 *

 */

#define __BTF_ID_LIST(name)				\

asm(							\

".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\

".local " #name ";                             \n"	\

#name ":;                                      \n"	\

".popsection;                                  \n");	\

#define BTF_ID_LIST(name)				\

__BTF_ID_LIST(name)					\

extern u32 name[];

/*

 * The BTF_ID_UNUSED macro defines 4 zero bytes.

 * It's used when we want to define 'unused' entry

 * in BTF_ID_LIST, like:

 *

 *   BTF_ID_LIST(bpf_skb_output_btf_ids)

 *   BTF_ID(struct, sk_buff)

 *   BTF_ID_UNUSED

 *   BTF_ID(struct, task_struct)

 */

#define BTF_ID_UNUSED					\

asm(							\

".pushsection " BTF_IDS_SECTION ",\"a\";       \n"	\

".zero 4                                       \n"	\

".popsection;                                  \n");

#endif

# define __fallthrough

#endif

/* Indirect macros required for expanded argument pasting, eg. __LINE__. */

#define ___PASTE(a, b) a##b

#define __PASTE(a, b) ___PASTE(a, b)

#endif /* _TOOLS_LINUX_COMPILER_H */