Commit 0f12e584 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

bpf: Add BTF_ID_LIST_GLOBAL in btf_ids.h 



Existing BTF_ID_LIST used a local static variable
to store btf_ids. This patch provided a new macro
BTF_ID_LIST_GLOBAL to store btf_ids in a global
variable which can be shared among multiple files.

The existing BTF_ID_LIST is still retained.
Two reasons. First, BTF_ID_LIST is also used to build
btf_ids for helper arguments which typically
is an array of 5. Since typically different
helpers have different signature, it makes
little sense to share them. Second, some
current computed btf_ids are indeed local.
If later those btf_ids are shared between
different files, they can use BTF_ID_LIST_GLOBAL then.

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarJiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/bpf/20200720163401.1393159-1-yhs@fb.com
parent d8dfe5bf

include/linux/btf_ids.h

+7 −3
Original line number Diff line number Diff line
@@ -57,17 +57,20 @@ asm( \ 
 * .zero 4

 *

 */

#define __BTF_ID_LIST(name)				\

#define __BTF_ID_LIST(name, scope)			\

asm(							\

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

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

"." #scope " " #name ";                        \n"	\

#name ":;                                      \n"	\

".popsection;                                  \n");	\



#define BTF_ID_LIST(name)				\

__BTF_ID_LIST(name)					\

__BTF_ID_LIST(name, local)				\

extern u32 name[];



#define BTF_ID_LIST_GLOBAL(name)			\

__BTF_ID_LIST(name, globl)



/*

 * The BTF_ID_UNUSED macro defines 4 zero bytes.

 * It's used when we want to define 'unused' entry
@@ -90,6 +93,7 @@ asm( \ 
#define BTF_ID_LIST(name) static u32 name[5];

#define BTF_ID(prefix, name)

#define BTF_ID_UNUSED

#define BTF_ID_LIST_GLOBAL(name) u32 name[1];



#endif /* CONFIG_DEBUG_INFO_BTF */

tools/include/linux/btf_ids.h

+7 −3
Original line number Diff line number Diff line
@@ -57,17 +57,20 @@ asm( \ 
 * .zero 4

 *

 */

#define __BTF_ID_LIST(name)				\

#define __BTF_ID_LIST(name, scope)			\

asm(							\

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

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

"." #scope " " #name ";                        \n"	\

#name ":;                                      \n"	\

".popsection;                                  \n");	\



#define BTF_ID_LIST(name)				\

__BTF_ID_LIST(name)					\

__BTF_ID_LIST(name, local)				\

extern u32 name[];



#define BTF_ID_LIST_GLOBAL(name)			\

__BTF_ID_LIST(name, globl)



/*

 * The BTF_ID_UNUSED macro defines 4 zero bytes.

 * It's used when we want to define 'unused' entry
@@ -90,6 +93,7 @@ asm( \ 
#define BTF_ID_LIST(name) static u32 name[5];

#define BTF_ID(prefix, name)

#define BTF_ID_UNUSED

#define BTF_ID_LIST_GLOBAL(name) u32 name[1];



#endif /* CONFIG_DEBUG_INFO_BTF */

tools/testing/selftests/bpf/prog_tests/resolve_btfids.c

+25 −8
Original line number Diff line number Diff line
@@ -28,7 +28,17 @@ struct symbol test_symbols[] = { 
	{ "func",    BTF_KIND_FUNC,    -1 },

};



BTF_ID_LIST(test_list)

BTF_ID_LIST(test_list_local)

BTF_ID_UNUSED

BTF_ID(typedef, S)

BTF_ID(typedef, T)

BTF_ID(typedef, U)

BTF_ID(struct,  S)

BTF_ID(union,   U)

BTF_ID(func,    func)



extern __u32 test_list_global[];

BTF_ID_LIST_GLOBAL(test_list_global)

BTF_ID_UNUSED

BTF_ID(typedef, S)

BTF_ID(typedef, T)
@@ -94,19 +104,26 @@ static int resolve_symbols(void) 


int test_resolve_btfids(void)

{

	unsigned int i;

	__u32 *test_list, *test_lists[] = { test_list_local, test_list_global };

	unsigned int i, j;

	int ret = 0;



	if (resolve_symbols())

		return -1;



	/* Check BTF_ID_LIST(test_list) IDs */

	/* Check BTF_ID_LIST(test_list_local) and

	 * BTF_ID_LIST_GLOBAL(test_list_global) IDs

	 */

	for (j = 0; j < ARRAY_SIZE(test_lists); j++) {

		test_list = test_lists[j];

		for (i = 0; i < ARRAY_SIZE(test_symbols) && !ret; i++) {

			ret = CHECK(test_list[i] != test_symbols[i].id,

				    "id_check",

			    "wrong ID for %s (%d != %d)\n", test_symbols[i].name,

				    "wrong ID for %s (%d != %d)\n",

				    test_symbols[i].name,

				    test_list[i], test_symbols[i].id);

		}

	}



	return ret;

}

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