Commit c5e64741 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

libbpf: move bpf_for(), bpf_for_each(), and bpf_repeat() into bpf_helpers.h 



To make it easier for bleeding-edge BPF applications, such as sched_ext,
to utilize open-coded iterators, move bpf_for(), bpf_for_each(), and
bpf_repeat() macros from selftests/bpf-internal bpf_misc.h helper, to
libbpf-provided bpf_helpers.h header.

Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230418002148.3255690-6-andrii@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 30bbfe32

tools/lib/bpf/bpf_helpers.h

+103 −0
Original line number Diff line number Diff line
@@ -291,4 +291,107 @@ enum libbpf_tristate { 
/* Helper macro to print out debug messages */

#define bpf_printk(fmt, args...) ___bpf_pick_printk(args)(fmt, ##args)



struct bpf_iter_num;



extern int bpf_iter_num_new(struct bpf_iter_num *it, int start, int end) __ksym;

extern int *bpf_iter_num_next(struct bpf_iter_num *it) __ksym;

extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __ksym;



#ifndef bpf_for_each

/* bpf_for_each(iter_type, cur_elem, args...) provides generic construct for

 * using BPF open-coded iterators without having to write mundane explicit

 * low-level loop logic. Instead, it provides for()-like generic construct

 * that can be used pretty naturally. E.g., for some hypothetical cgroup

 * iterator, you'd write:

 *

 * struct cgroup *cg, *parent_cg = <...>;

 *

 * bpf_for_each(cgroup, cg, parent_cg, CG_ITER_CHILDREN) {

 *     bpf_printk("Child cgroup id = %d", cg->cgroup_id);

 *     if (cg->cgroup_id == 123)

 *         break;

 * }

 *

 * I.e., it looks almost like high-level for each loop in other languages,

 * supports continue/break, and is verifiable by BPF verifier.

 *

 * For iterating integers, the difference betwen bpf_for_each(num, i, N, M)

 * and bpf_for(i, N, M) is in that bpf_for() provides additional proof to

 * verifier that i is in [N, M) range, and in bpf_for_each() case i is `int

 * *`, not just `int`. So for integers bpf_for() is more convenient.

 *

 * Note: this macro relies on C99 feature of allowing to declare variables

 * inside for() loop, bound to for() loop lifetime. It also utilizes GCC

 * extension: __attribute__((cleanup(<func>))), supported by both GCC and

 * Clang.

 */

#define bpf_for_each(type, cur, args...) for (							\

	/* initialize and define destructor */							\

	struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */,	\

						    cleanup(bpf_iter_##type##_destroy))),	\

	/* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */		\

			       *___p __attribute__((unused)) = (				\

					bpf_iter_##type##_new(&___it, ##args),			\

	/* this is a workaround for Clang bug: it currently doesn't emit BTF */			\

	/* for bpf_iter_##type##_destroy() when used from cleanup() attribute */		\

					(void)bpf_iter_##type##_destroy, (void *)0);		\

	/* iteration and termination check */							\

	(((cur) = bpf_iter_##type##_next(&___it)));						\

)

#endif /* bpf_for_each */



#ifndef bpf_for

/* bpf_for(i, start, end) implements a for()-like looping construct that sets

 * provided integer variable *i* to values starting from *start* through,

 * but not including, *end*. It also proves to BPF verifier that *i* belongs

 * to range [start, end), so this can be used for accessing arrays without

 * extra checks.

 *

 * Note: *start* and *end* are assumed to be expressions with no side effects

 * and whose values do not change throughout bpf_for() loop execution. They do

 * not have to be statically known or constant, though.

 *

 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()

 * loop bound variables and cleanup attribute, supported by GCC and Clang.

 */

#define bpf_for(i, start, end) for (								\

	/* initialize and define destructor */							\

	struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */	\

						 cleanup(bpf_iter_num_destroy))),		\

	/* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */		\

			    *___p __attribute__((unused)) = (					\

				bpf_iter_num_new(&___it, (start), (end)),			\

	/* this is a workaround for Clang bug: it currently doesn't emit BTF */			\

	/* for bpf_iter_num_destroy() when used from cleanup() attribute */			\

				(void)bpf_iter_num_destroy, (void *)0);				\

	({											\

		/* iteration step */								\

		int *___t = bpf_iter_num_next(&___it);						\

		/* termination and bounds check */						\

		(___t && ((i) = *___t, (i) >= (start) && (i) < (end)));				\

	});											\

)

#endif /* bpf_for */



#ifndef bpf_repeat

/* bpf_repeat(N) performs N iterations without exposing iteration number

 *

 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()

 * loop bound variables and cleanup attribute, supported by GCC and Clang.

 */

#define bpf_repeat(N) for (									\

	/* initialize and define destructor */							\

	struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */	\

						 cleanup(bpf_iter_num_destroy))),		\

	/* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */		\

			    *___p __attribute__((unused)) = (					\

				bpf_iter_num_new(&___it, 0, (N)),				\

	/* this is a workaround for Clang bug: it currently doesn't emit BTF */			\

	/* for bpf_iter_num_destroy() when used from cleanup() attribute */			\

				(void)bpf_iter_num_destroy, (void *)0);				\

	bpf_iter_num_next(&___it);								\

	/* nothing here  */									\

)

#endif /* bpf_repeat */



#endif

tools/testing/selftests/bpf/progs/bpf_misc.h

+0 −103
Original line number Diff line number Diff line
@@ -121,107 +121,4 @@ 
/* make it look to compiler like value is read and written */

#define __sink(expr) asm volatile("" : "+g"(expr))



struct bpf_iter_num;



extern int bpf_iter_num_new(struct bpf_iter_num *it, int start, int end) __ksym;

extern int *bpf_iter_num_next(struct bpf_iter_num *it) __ksym;

extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __ksym;



#ifndef bpf_for_each

/* bpf_for_each(iter_type, cur_elem, args...) provides generic construct for

 * using BPF open-coded iterators without having to write mundane explicit

 * low-level loop logic. Instead, it provides for()-like generic construct

 * that can be used pretty naturally. E.g., for some hypothetical cgroup

 * iterator, you'd write:

 *

 * struct cgroup *cg, *parent_cg = <...>;

 *

 * bpf_for_each(cgroup, cg, parent_cg, CG_ITER_CHILDREN) {

 *     bpf_printk("Child cgroup id = %d", cg->cgroup_id);

 *     if (cg->cgroup_id == 123)

 *         break;

 * }

 *

 * I.e., it looks almost like high-level for each loop in other languages,

 * supports continue/break, and is verifiable by BPF verifier.

 *

 * For iterating integers, the difference betwen bpf_for_each(num, i, N, M)

 * and bpf_for(i, N, M) is in that bpf_for() provides additional proof to

 * verifier that i is in [N, M) range, and in bpf_for_each() case i is `int

 * *`, not just `int`. So for integers bpf_for() is more convenient.

 *

 * Note: this macro relies on C99 feature of allowing to declare variables

 * inside for() loop, bound to for() loop lifetime. It also utilizes GCC

 * extension: __attribute__((cleanup(<func>))), supported by both GCC and

 * Clang.

 */

#define bpf_for_each(type, cur, args...) for (							\

	/* initialize and define destructor */							\

	struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */,	\

						    cleanup(bpf_iter_##type##_destroy))),	\

	/* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */		\

			       *___p __attribute__((unused)) = (				\

					bpf_iter_##type##_new(&___it, ##args),			\

	/* this is a workaround for Clang bug: it currently doesn't emit BTF */			\

	/* for bpf_iter_##type##_destroy() when used from cleanup() attribute */		\

					(void)bpf_iter_##type##_destroy, (void *)0);		\

	/* iteration and termination check */							\

	(((cur) = bpf_iter_##type##_next(&___it)));						\

)

#endif /* bpf_for_each */



#ifndef bpf_for

/* bpf_for(i, start, end) implements a for()-like looping construct that sets

 * provided integer variable *i* to values starting from *start* through,

 * but not including, *end*. It also proves to BPF verifier that *i* belongs

 * to range [start, end), so this can be used for accessing arrays without

 * extra checks.

 *

 * Note: *start* and *end* are assumed to be expressions with no side effects

 * and whose values do not change throughout bpf_for() loop execution. They do

 * not have to be statically known or constant, though.

 *

 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()

 * loop bound variables and cleanup attribute, supported by GCC and Clang.

 */

#define bpf_for(i, start, end) for (								\

	/* initialize and define destructor */							\

	struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */	\

						 cleanup(bpf_iter_num_destroy))),		\

	/* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */		\

			    *___p __attribute__((unused)) = (					\

				bpf_iter_num_new(&___it, (start), (end)),			\

	/* this is a workaround for Clang bug: it currently doesn't emit BTF */			\

	/* for bpf_iter_num_destroy() when used from cleanup() attribute */			\

				(void)bpf_iter_num_destroy, (void *)0);				\

	({											\

		/* iteration step */								\

		int *___t = bpf_iter_num_next(&___it);						\

		/* termination and bounds check */						\

		(___t && ((i) = *___t, (i) >= (start) && (i) < (end)));				\

	});											\

)

#endif /* bpf_for */



#ifndef bpf_repeat

/* bpf_repeat(N) performs N iterations without exposing iteration number

 *

 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()

 * loop bound variables and cleanup attribute, supported by GCC and Clang.

 */

#define bpf_repeat(N) for (									\

	/* initialize and define destructor */							\

	struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */	\

						 cleanup(bpf_iter_num_destroy))),		\

	/* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */		\

			    *___p __attribute__((unused)) = (					\

				bpf_iter_num_new(&___it, 0, (N)),				\

	/* this is a workaround for Clang bug: it currently doesn't emit BTF */			\

	/* for bpf_iter_num_destroy() when used from cleanup() attribute */			\

				(void)bpf_iter_num_destroy, (void *)0);				\

	bpf_iter_num_next(&___it);								\

	/* nothing here  */									\

)

#endif /* bpf_repeat */



#endif