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6018e1f407
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>
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| .. | ||
| tc_act | ||
| bpf_common.h | ||
| bpf_perf_event.h | ||
| bpf.h | ||
| btf.h | ||
| const.h | ||
| erspan.h | ||
| ethtool.h | ||
| fadvise.h | ||
| fcntl.h | ||
| filter.h | ||
| fs.h | ||
| fscrypt.h | ||
| hw_breakpoint.h | ||
| if_link.h | ||
| if_tun.h | ||
| if_xdp.h | ||
| in.h | ||
| kcmp.h | ||
| kvm.h | ||
| mman.h | ||
| mount.h | ||
| netdev.h | ||
| netlink.h | ||
| openat2.h | ||
| perf_event.h | ||
| pkt_cls.h | ||
| pkt_sched.h | ||
| prctl.h | ||
| sched.h | ||
| seg6_local.h | ||
| seg6.h | ||
| stat.h | ||
| stddef.h | ||
| tcp.h | ||
| tls.h | ||
| types.h | ||
| usbdevice_fs.h | ||
| vhost.h | ||