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bpf: Add BPF_FETCH field / create atomic_fetch_add instruction

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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
This commit is contained in:
Brendan Jackman
2021-01-14 18:17:46 +00:00
committed by Alexei Starovoitov
parent c5bcb5eb4d
commit 5ca419f286
8 changed files with 56 additions and 9 deletions
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tools/include/linux/filter.h
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@@ -173,6 +173,7 @@
* Atomic operations:
*
* BPF_ADD *(uint *) (dst_reg + off16) += src_reg
* BPF_ADD | BPF_FETCH src_reg = atomic_fetch_add(dst_reg + off16, src_reg);
*/
#define BPF_ATOMIC_OP(SIZE, OP, DST, SRC, OFF) \