From 1d621674d923790d09cab9e2c7da7da6446a6257 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 26 Jan 2018 23:33:36 +0100 Subject: [PATCH] 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: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov --- net/core/filter.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index fe2c7937351f..60d8c8712652 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -401,8 +401,8 @@ do_pass: /* 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 -- 2.11.0