netdev - [PATCH] x86: bpf_jit_comp: Reduce is

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 04 Dec 2014 15:00:48 -0800
From:	Joe Perches <joe@...ches.com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Quentin Lambert <lambert.quentin@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86: bpf_jit_comp: Reduce is_ereg() code size

Use the (1 << reg) & mask trick to reduce code size.

x86-64 size difference -O2 without profiling for various
gcc versions:

$ size arch/x86/net/bpf_jit_comp.o*
   text    data     bss     dec     hex filename
   9266       4       0    9270    2436 arch/x86/net/bpf_jit_comp.o.4.4.new
  10042       4       0   10046    273e arch/x86/net/bpf_jit_comp.o.4.4.old
   9109       4       0    9113    2399 arch/x86/net/bpf_jit_comp.o.4.6.new
   9717       4       0    9721    25f9 arch/x86/net/bpf_jit_comp.o.4.6.old
   8789       4       0    8793    2259 arch/x86/net/bpf_jit_comp.o.4.7.new
  10245       4       0   10249    2809 arch/x86/net/bpf_jit_comp.o.4.7.old
   9671       4       0    9675    25cb arch/x86/net/bpf_jit_comp.o.4.9.new
  10679       4       0   10683    29bb arch/x86/net/bpf_jit_comp.o.4.9.old

Signed-off-by: Joe Perches <joe@...ches.com>
---

compiled, untested by me, but per Alexei Starovoitov this passes
the test_bpf suite

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 3f62734..09e2cea 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -135,11 +135,11 @@ static const int reg2hex[] = {
  */
 static inline bool is_ereg(u32 reg)
 {
-	if (reg == BPF_REG_5 || reg == AUX_REG ||
-	    (reg >= BPF_REG_7 && reg <= BPF_REG_9))
-		return true;
-	else
-		return false;
+	return (1 << reg) & (BIT(BPF_REG_5) |
+			     BIT(AUX_REG) |
+			     BIT(BPF_REG_7) |
+			     BIT(BPF_REG_8) |
+			     BIT(BPF_REG_9));
 }
 
 /* add modifiers if 'reg' maps to x64 registers r8..r15 */


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html