Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 1d621674 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by Alexei Starovoitov
Browse files

bpf: xor of a/x in cbpf can be done in 32 bit alu 



Very minor optimization; saves 1 byte per program in x86_64
JIT in cBPF prologue.

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent c25ef6a5

net/core/filter.c

+2 −2
Original line number Diff line number Diff line
@@ -401,8 +401,8 @@ static int bpf_convert_filter(struct sock_filter *prog, int len, 
		/* Classic BPF expects A and X to be reset first. These need

		 * to be guaranteed to be the first two instructions.

		 */

		*new_insn++ = BPF_ALU64_REG(BPF_XOR, BPF_REG_A, BPF_REG_A);

		*new_insn++ = BPF_ALU64_REG(BPF_XOR, BPF_REG_X, BPF_REG_X);

		*new_insn++ = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_A);

		*new_insn++ = BPF_ALU32_REG(BPF_XOR, BPF_REG_X, BPF_REG_X);



		/* All programs must keep CTX in callee saved BPF_REG_CTX.

		 * In eBPF case it's done by the compiler, here we need to