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Author SHA1 Message Date
Brendan Jackman ac86f42e4a bpf: Add BPF_FETCH field / create atomic_fetch_add instruction 
The BPF_FETCH field can be set in bpf_insn.imm, for BPF_ATOMIC
instructions, in order to have the previous value of the
atomically-modified memory location loaded into the src register
after an atomic op is carried out.

Suggested-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-7-jackmanb@google.com
 2021-01-26 19:32:13 -08:00
Brendan Jackman 03fbe22a59 bpf: Rename BPF_XADD and prepare to encode other atomics in .imm 
A subsequent patch will add additional atomic operations. These new
operations will use the same opcode field as the existing XADD, with
the immediate discriminating different operations.

In preparation, rename the instruction mode BPF_ATOMIC and start
calling the zero immediate BPF_ADD.

This is possible (doesn't break existing valid BPF progs) because the
immediate field is currently reserved MBZ and BPF_ADD is zero.

All uses are removed from the tree but the BPF_XADD definition is
kept around to avoid breaking builds for people including kernel
headers.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-5-jackmanb@google.com
 2021-01-26 19:32:13 -08:00
Brendan Jackman 0de8b9a906 bpf: Clarify return value of probe str helpers 
When the buffer is too small to contain the input string, these helpers
return the length of the buffer, not the length of the original string.
This tries to make the docs totally clear about that, since "the length
of the [copied ]string" could also refer to the length of the input.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: KP Singh <kpsingh@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210112123422.2011234-1-jackmanb@google.com
 2021-01-26 19:32:13 -08:00
Brendan Jackman 30e2c16571 libbpf: Expose libbpf ring_buffer epoll_fd 
This provides a convenient perf ringbuf -> libbpf ringbuf migration
path for users of external polling systems. It is analogous to
perf_buffer__epoll_fd.

Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201214113812.305274-1-jackmanb@google.com
 2020-12-20 17:00:58 -08:00