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authorBrendan Jackman <jackmanb@google.com>2021-01-14 18:17:49 +0000
committerAlexei Starovoitov <ast@kernel.org>2021-01-14 18:34:29 -0800
commit981f94c3e92146705baf97fb417a5ed1ab1a79a5 (patch)
tree3e9cd30902659db0e4de8f9afad972f259d9dcf9 /include
parent462910670e4ac91509829c5549bd0227668176fb (diff)
bpf: Add bitwise atomic instructions
This adds instructions for atomic[64]_[fetch_]and atomic[64]_[fetch_]or atomic[64]_[fetch_]xor All these operations are isomorphic enough to implement with the same verifier, interpreter, and x86 JIT code, hence being a single commit. The main interesting thing here is that x86 doesn't directly support the fetch_ version these operations, so we need to generate a CMPXCHG loop in the JIT. This requires the use of two temporary registers, IIUC it's safe to use BPF_REG_AX and x86's AUX_REG for this purpose. Signed-off-by: Brendan Jackman <jackmanb@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/20210114181751.768687-10-jackmanb@google.com
Diffstat (limited to 'include')
-rw-r--r--include/linux/filter.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/filter.h b/include/linux/filter.h
index d563820f197d..7fdce5407214 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -264,7 +264,13 @@ static inline bool insn_is_zext(const struct bpf_insn *insn)
* Atomic operations:
*
* BPF_ADD *(uint *) (dst_reg + off16) += src_reg
+ * BPF_AND *(uint *) (dst_reg + off16) &= src_reg
+ * BPF_OR *(uint *) (dst_reg + off16) |= src_reg
+ * BPF_XOR *(uint *) (dst_reg + off16) ^= src_reg
* BPF_ADD | BPF_FETCH src_reg = atomic_fetch_add(dst_reg + off16, src_reg);
+ * BPF_AND | BPF_FETCH src_reg = atomic_fetch_and(dst_reg + off16, src_reg);
+ * BPF_OR | BPF_FETCH src_reg = atomic_fetch_or(dst_reg + off16, src_reg);
+ * BPF_XOR | BPF_FETCH src_reg = atomic_fetch_xor(dst_reg + off16, src_reg);
* BPF_XCHG src_reg = atomic_xchg(dst_reg + off16, src_reg)
* BPF_CMPXCHG r0 = atomic_cmpxchg(dst_reg + off16, r0, src_reg)
*/