linux-stable/include/linux/btf_ids.h

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

#ifndef _LINUX_BTF_IDS_H
#define _LINUX_BTF_IDS_H

#ifdef CONFIG_DEBUG_INFO_BTF

#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 ", STT_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");

#else

#define BTF_ID_LIST(name) static u32 name[5];
#define BTF_ID(prefix, name)
#define BTF_ID_UNUSED

#endif /* CONFIG_DEBUG_INFO_BTF */

#endif