From: Daniel Borkmann <daniel@iogearbox.net>
Date: Fri, 26 Jan 2018 23:33:36 +0100
Subject: bpf: xor of a/x in cbpf can be done in 32 bit alu
Patch-mainline: v4.16-rc1
Git-commit: 1d621674d923790d09cab9e2c7da7da6446a6257
References: bsc#1109837
Very minor optimization; saves 1 byte per program in x86_64
JIT in cBPF prologue.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
net/core/filter.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- 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