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authorAndrii Nakryiko <andrii@kernel.org>2023-03-08 19:41:17 +0100
committerAlexei Starovoitov <ast@kernel.org>2023-03-09 01:19:51 +0100
commit6018e1f407cccf39b804d1f75ad4de7be4e6cc45 (patch)
treeb3d7b1c9d651bc851c4504e31017f6c187a6e1f5 /kernel/bpf/helpers.c
parentbpf: add support for open-coded iterator loops (diff)
downloadlinux-6018e1f407cccf39b804d1f75ad4de7be4e6cc45.tar.xz
linux-6018e1f407cccf39b804d1f75ad4de7be4e6cc45.zip
bpf: implement numbers iterator
Implement the first open-coded iterator type over a range of integers. It's public API consists of: - bpf_iter_num_new() constructor, which accepts [start, end) range (that is, start is inclusive, end is exclusive). - bpf_iter_num_next() which will keep returning read-only pointer to int until the range is exhausted, at which point NULL will be returned. If bpf_iter_num_next() is kept calling after this, NULL will be persistently returned. - bpf_iter_num_destroy() destructor, which needs to be called at some point to clean up iterator state. BPF verifier enforces that iterator destructor is called at some point before BPF program exits. Note that `start = end = X` is a valid combination to setup an empty iterator. bpf_iter_num_new() will return 0 (success) for any such combination. If bpf_iter_num_new() detects invalid combination of input arguments, it returns error, resets iterator state to, effectively, empty iterator, so any subsequent call to bpf_iter_num_next() will keep returning NULL. BPF verifier has no knowledge that returned integers are in the [start, end) value range, as both `start` and `end` are not statically known and enforced: they are runtime values. While the implementation is pretty trivial, some care needs to be taken to avoid overflows and underflows. Subsequent selftests will validate correctness of [start, end) semantics, especially around extremes (INT_MIN and INT_MAX). Similarly to bpf_loop(), we enforce that no more than BPF_MAX_LOOPS can be specified. bpf_iter_num_{new,next,destroy}() is a logical evolution from bounded BPF loops and bpf_loop() helper and is the basis for implementing ergonomic BPF loops with no statically known or verified bounds. Subsequent patches implement bpf_for() macro, demonstrating how this can be wrapped into something that works and feels like a normal for() loop in C language. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/r/20230308184121.1165081-5-andrii@kernel.org Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf/helpers.c')
-rw-r--r--kernel/bpf/helpers.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 637ac4e92e75..f9b7eeedce08 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2411,6 +2411,9 @@ BTF_ID_FLAGS(func, bpf_rcu_read_lock)
BTF_ID_FLAGS(func, bpf_rcu_read_unlock)
BTF_ID_FLAGS(func, bpf_dynptr_slice, KF_RET_NULL)
BTF_ID_FLAGS(func, bpf_dynptr_slice_rdwr, KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_iter_num_new, KF_ITER_NEW)
+BTF_ID_FLAGS(func, bpf_iter_num_next, KF_ITER_NEXT | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_iter_num_destroy, KF_ITER_DESTROY)
BTF_SET8_END(common_btf_ids)
static const struct btf_kfunc_id_set common_kfunc_set = {