Commit 5a2798ab authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov
Browse files

bpf: Add BTF_ID_LIST/BTF_ID/BTF_ID_UNUSED macros 



Adding support to generate .BTF_ids section that will hold BTF
ID lists for verifier.

Adding macros that will help to define lists of BTF ID values
placed in .BTF_ids section. They are initially filled with zeros
(during compilation) and resolved later during the linking phase
by resolve_btfids tool.

Following defines list of one BTF ID value:

  BTF_ID_LIST(bpf_skb_output_btf_ids)
  BTF_ID(struct, sk_buff)

It also defines following variable to access the list:

  extern u32 bpf_skb_output_btf_ids[];

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)

Suggested-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Tested-by: default avatarAndrii Nakryiko <andriin@fb.com>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200711215329.41165-4-jolsa@kernel.org
parent 33a57ce0

include/asm-generic/vmlinux.lds.h

+4 −0
Original line number Diff line number Diff line
@@ -641,6 +641,10 @@ 
		__start_BTF = .;					\

		*(.BTF)							\

		__stop_BTF = .;						\

	}								\

	. = ALIGN(4);							\

	.BTF_ids : AT(ADDR(.BTF_ids) - LOAD_OFFSET) {			\

		*(.BTF_ids)						\

	}

#else

#define BTF

include/linux/btf_ids.h

0 → 100644
+87 −0
Original line number Diff line number Diff line 
/* 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

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