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: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230418002148.3255690-6-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko
Alexei Starovoitov
Родитель
30bbfe3236
Коммит
c5e6474167
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@ -291,4 +291,107 @@ enum libbpf_tristate {
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/* Helper macro to print out debug messages */
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#define bpf_printk(fmt, args...) ___bpf_pick_printk(args)(fmt, ##args)
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struct bpf_iter_num;
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extern int bpf_iter_num_new(struct bpf_iter_num *it, int start, int end) __ksym;
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extern int *bpf_iter_num_next(struct bpf_iter_num *it) __ksym;
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extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __ksym;
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#ifndef bpf_for_each
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/* bpf_for_each(iter_type, cur_elem, args...) provides generic construct for
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* using BPF open-coded iterators without having to write mundane explicit
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* low-level loop logic. Instead, it provides for()-like generic construct
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* that can be used pretty naturally. E.g., for some hypothetical cgroup
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* iterator, you'd write:
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*
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* struct cgroup *cg, *parent_cg = <...>;
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*
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* bpf_for_each(cgroup, cg, parent_cg, CG_ITER_CHILDREN) {
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* bpf_printk("Child cgroup id = %d", cg->cgroup_id);
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* if (cg->cgroup_id == 123)
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* break;
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* }
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*
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* I.e., it looks almost like high-level for each loop in other languages,
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* supports continue/break, and is verifiable by BPF verifier.
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*
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* For iterating integers, the difference betwen bpf_for_each(num, i, N, M)
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* and bpf_for(i, N, M) is in that bpf_for() provides additional proof to
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* verifier that i is in [N, M) range, and in bpf_for_each() case i is `int
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* *`, not just `int`. So for integers bpf_for() is more convenient.
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*
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* Note: this macro relies on C99 feature of allowing to declare variables
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* inside for() loop, bound to for() loop lifetime. It also utilizes GCC
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* extension: __attribute__((cleanup(<func>))), supported by both GCC and
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* Clang.
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*/
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#define bpf_for_each(type, cur, args...) for ( \
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/* initialize and define destructor */ \
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struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */, \
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cleanup(bpf_iter_##type##_destroy))), \
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/* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */ \
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*___p __attribute__((unused)) = ( \
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bpf_iter_##type##_new(&___it, ##args), \
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/* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
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/* for bpf_iter_##type##_destroy() when used from cleanup() attribute */ \
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(void)bpf_iter_##type##_destroy, (void *)0); \
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/* iteration and termination check */ \
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(((cur) = bpf_iter_##type##_next(&___it))); \
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)
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#endif /* bpf_for_each */
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#ifndef bpf_for
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/* bpf_for(i, start, end) implements a for()-like looping construct that sets
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* provided integer variable *i* to values starting from *start* through,
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* but not including, *end*. It also proves to BPF verifier that *i* belongs
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* to range [start, end), so this can be used for accessing arrays without
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* extra checks.
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*
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* Note: *start* and *end* are assumed to be expressions with no side effects
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* and whose values do not change throughout bpf_for() loop execution. They do
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* not have to be statically known or constant, though.
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*
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* Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()
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* loop bound variables and cleanup attribute, supported by GCC and Clang.
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*/
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#define bpf_for(i, start, end) for ( \
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/* initialize and define destructor */ \
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struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \
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cleanup(bpf_iter_num_destroy))), \
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/* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \
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*___p __attribute__((unused)) = ( \
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bpf_iter_num_new(&___it, (start), (end)), \
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/* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
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/* for bpf_iter_num_destroy() when used from cleanup() attribute */ \
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(void)bpf_iter_num_destroy, (void *)0); \
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({ \
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/* iteration step */ \
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int *___t = bpf_iter_num_next(&___it); \
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/* termination and bounds check */ \
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(___t && ((i) = *___t, (i) >= (start) && (i) < (end))); \
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}); \
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)
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#endif /* bpf_for */
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#ifndef bpf_repeat
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/* bpf_repeat(N) performs N iterations without exposing iteration number
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*
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* Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()
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* loop bound variables and cleanup attribute, supported by GCC and Clang.
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*/
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#define bpf_repeat(N) for ( \
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/* initialize and define destructor */ \
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struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \
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cleanup(bpf_iter_num_destroy))), \
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/* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \
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*___p __attribute__((unused)) = ( \
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bpf_iter_num_new(&___it, 0, (N)), \
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/* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
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/* for bpf_iter_num_destroy() when used from cleanup() attribute */ \
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(void)bpf_iter_num_destroy, (void *)0); \
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bpf_iter_num_next(&___it); \
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/* nothing here */ \
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)
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#endif /* bpf_repeat */
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#endif
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@ -121,107 +121,4 @@
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/* make it look to compiler like value is read and written */
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#define __sink(expr) asm volatile("" : "+g"(expr))
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struct bpf_iter_num;
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extern int bpf_iter_num_new(struct bpf_iter_num *it, int start, int end) __ksym;
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extern int *bpf_iter_num_next(struct bpf_iter_num *it) __ksym;
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extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __ksym;
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#ifndef bpf_for_each
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/* bpf_for_each(iter_type, cur_elem, args...) provides generic construct for
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* using BPF open-coded iterators without having to write mundane explicit
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* low-level loop logic. Instead, it provides for()-like generic construct
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* that can be used pretty naturally. E.g., for some hypothetical cgroup
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* iterator, you'd write:
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*
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* struct cgroup *cg, *parent_cg = <...>;
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*
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* bpf_for_each(cgroup, cg, parent_cg, CG_ITER_CHILDREN) {
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* bpf_printk("Child cgroup id = %d", cg->cgroup_id);
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* if (cg->cgroup_id == 123)
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* break;
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* }
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*
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* I.e., it looks almost like high-level for each loop in other languages,
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* supports continue/break, and is verifiable by BPF verifier.
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*
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* For iterating integers, the difference betwen bpf_for_each(num, i, N, M)
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* and bpf_for(i, N, M) is in that bpf_for() provides additional proof to
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* verifier that i is in [N, M) range, and in bpf_for_each() case i is `int
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* *`, not just `int`. So for integers bpf_for() is more convenient.
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*
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* Note: this macro relies on C99 feature of allowing to declare variables
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* inside for() loop, bound to for() loop lifetime. It also utilizes GCC
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* extension: __attribute__((cleanup(<func>))), supported by both GCC and
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* Clang.
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*/
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#define bpf_for_each(type, cur, args...) for ( \
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/* initialize and define destructor */ \
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struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */, \
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cleanup(bpf_iter_##type##_destroy))), \
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/* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */ \
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*___p __attribute__((unused)) = ( \
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bpf_iter_##type##_new(&___it, ##args), \
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/* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
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/* for bpf_iter_##type##_destroy() when used from cleanup() attribute */ \
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(void)bpf_iter_##type##_destroy, (void *)0); \
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/* iteration and termination check */ \
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(((cur) = bpf_iter_##type##_next(&___it))); \
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)
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#endif /* bpf_for_each */
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#ifndef bpf_for
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/* bpf_for(i, start, end) implements a for()-like looping construct that sets
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* provided integer variable *i* to values starting from *start* through,
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* but not including, *end*. It also proves to BPF verifier that *i* belongs
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* to range [start, end), so this can be used for accessing arrays without
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* extra checks.
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*
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* Note: *start* and *end* are assumed to be expressions with no side effects
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* and whose values do not change throughout bpf_for() loop execution. They do
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* not have to be statically known or constant, though.
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*
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* Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()
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* loop bound variables and cleanup attribute, supported by GCC and Clang.
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*/
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#define bpf_for(i, start, end) for ( \
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/* initialize and define destructor */ \
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struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \
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cleanup(bpf_iter_num_destroy))), \
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/* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \
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*___p __attribute__((unused)) = ( \
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bpf_iter_num_new(&___it, (start), (end)), \
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/* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
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/* for bpf_iter_num_destroy() when used from cleanup() attribute */ \
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(void)bpf_iter_num_destroy, (void *)0); \
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({ \
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/* iteration step */ \
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int *___t = bpf_iter_num_next(&___it); \
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/* termination and bounds check */ \
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(___t && ((i) = *___t, (i) >= (start) && (i) < (end))); \
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}); \
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)
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#endif /* bpf_for */
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#ifndef bpf_repeat
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/* bpf_repeat(N) performs N iterations without exposing iteration number
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*
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* Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()
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* loop bound variables and cleanup attribute, supported by GCC and Clang.
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*/
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#define bpf_repeat(N) for ( \
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/* initialize and define destructor */ \
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struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \
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cleanup(bpf_iter_num_destroy))), \
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/* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \
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*___p __attribute__((unused)) = ( \
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bpf_iter_num_new(&___it, 0, (N)), \
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/* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
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/* for bpf_iter_num_destroy() when used from cleanup() attribute */ \
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(void)bpf_iter_num_destroy, (void *)0); \
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bpf_iter_num_next(&___it); \
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/* nothing here */ \
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)
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#endif /* bpf_repeat */
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#endif
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