in 32 bit alu
Daniel Borkmann wrote:
Very minor optimization; saves 1 byte per program in x86_64
JIT in cBPF prologue.
... but increases program size by 4 bytes on ppc64 :(
In general, this is an area I've been wanting to spend some time on.
Powerpc doesn't have 32-bit sub-registers, so we need to emit an
additional instruction to clear the higher 32-bits for all 32-bit
operations. I need to look at the performance impact.
- Naveen
Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
Acked-by: Alexei Starovoitov <a...@kernel.org>
---
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 18da42a..cba2f73 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -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
--
2.9.5
