From: Daniel Borkmann <daniel@iogearbox.net>
To: ast@kernel.org
Cc: netdev@vger.kernel.org, Daniel Borkmann <daniel@iogearbox.net>
Subject: [PATCH bpf-next 7/9] bpf, x86: small optimization in alu ops with imm
Date: Sat, 20 Jan 2018 01:24:35 +0100 [thread overview]
Message-ID: <20180120002437.3528-8-daniel@iogearbox.net> (raw)
In-Reply-To: <20180120002437.3528-1-daniel@iogearbox.net>
For the BPF_REG_0 (BPF_REG_A in cBPF, respectively), we can use
the short form of the opcode as dst mapping is on eax/rax and
thus save a byte per such operation. Added to add/sub/and/or/xor
for 32/64 bit when K immediate is used. There may be more such
low-hanging fruit to add in future as well.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
---
arch/x86/net/bpf_jit_comp.c | 35 ++++++++++++++++++++++++++++++-----
1 file changed, 30 insertions(+), 5 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index b881a97..5acee51 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -152,6 +152,11 @@ static bool is_ereg(u32 reg)
BIT(BPF_REG_AX));
}
+static bool is_axreg(u32 reg)
+{
+ return reg == BPF_REG_0;
+}
+
/* add modifiers if 'reg' maps to x64 registers r8..r15 */
static u8 add_1mod(u8 byte, u32 reg)
{
@@ -445,16 +450,36 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
else if (is_ereg(dst_reg))
EMIT1(add_1mod(0x40, dst_reg));
+ /* b3 holds 'normal' opcode, b2 short form only valid
+ * in case dst is eax/rax.
+ */
switch (BPF_OP(insn->code)) {
- case BPF_ADD: b3 = 0xC0; break;
- case BPF_SUB: b3 = 0xE8; break;
- case BPF_AND: b3 = 0xE0; break;
- case BPF_OR: b3 = 0xC8; break;
- case BPF_XOR: b3 = 0xF0; break;
+ case BPF_ADD:
+ b3 = 0xC0;
+ b2 = 0x05;
+ break;
+ case BPF_SUB:
+ b3 = 0xE8;
+ b2 = 0x2D;
+ break;
+ case BPF_AND:
+ b3 = 0xE0;
+ b2 = 0x25;
+ break;
+ case BPF_OR:
+ b3 = 0xC8;
+ b2 = 0x0D;
+ break;
+ case BPF_XOR:
+ b3 = 0xF0;
+ b2 = 0x35;
+ break;
}
if (is_imm8(imm32))
EMIT3(0x83, add_1reg(b3, dst_reg), imm32);
+ else if (is_axreg(dst_reg))
+ EMIT1_off32(b2, imm32);
else
EMIT2_off32(0x81, add_1reg(b3, dst_reg), imm32);
break;
--
2.9.5
next prev parent reply other threads:[~2018-01-20 0:24 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-20 0:24 [PATCH bpf-next 0/9] BPF misc improvements Daniel Borkmann
2018-01-20 0:24 ` [PATCH bpf-next 1/9] bpf, verifier: detect misconfigured mem,size argument pair Daniel Borkmann
2018-01-20 0:24 ` [PATCH bpf-next 2/9] bpf: add csum_diff helper to xdp as well Daniel Borkmann
2018-01-20 0:24 ` [PATCH bpf-next 3/9] bpf: add couple of test cases for signed extended imms Daniel Borkmann
2018-01-20 0:24 ` [PATCH bpf-next 4/9] bpf: add couple of test cases for div/mod by zero Daniel Borkmann
2018-01-20 0:24 ` [PATCH bpf-next 5/9] bpf: get rid of pure_initcall dependency to enable jits Daniel Borkmann
2018-01-20 0:24 ` [PATCH bpf-next 6/9] bpf: restrict access to core bpf sysctls Daniel Borkmann
2018-01-20 0:24 ` Daniel Borkmann [this message]
2018-01-20 0:24 ` [PATCH bpf-next 8/9] bpf: add upper complexity limit to verifier log Daniel Borkmann
2018-01-20 0:24 ` [PATCH bpf-next 9/9] bpf: move event_output to const_size_or_zero for xdp/skb as well Daniel Borkmann
2018-01-20 2:54 ` [PATCH bpf-next 0/9] BPF misc improvements Alexei Starovoitov
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