Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751295AbbEARhj (ORCPT ); Fri, 1 May 2015 13:37:39 -0400 Received: from pandora.arm.linux.org.uk ([78.32.30.218]:38951 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750913AbbEARhg (ORCPT ); Fri, 1 May 2015 13:37:36 -0400 Date: Fri, 1 May 2015 18:37:21 +0100 From: Russell King - ARM Linux To: Nicolas Schichan Cc: "David S. Miller" , Alexei Starovoitov , Daniel Borkmann , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4] ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction. Message-ID: <20150501173721.GO12732@n2100.arm.linux.org.uk> References: <1430314657-2552-1-git-send-email-nschichan@freebox.fr> <1430314657-2552-5-git-send-email-nschichan@freebox.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1430314657-2552-5-git-send-email-nschichan@freebox.fr> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1917 Lines: 54 On Wed, Apr 29, 2015 at 03:37:37PM +0200, Nicolas Schichan wrote: > In that case, emit_udiv() will be called with rn == ARM_R0 (r_scratch) > and loading rm first into ARM_R0 will result in jit_udiv() function > being called the same dividend and divisor. Fix that by loading rn > first into ARM_R1 and then rm into ARM_R0. > > Signed-off-by: Nicolas Schichan > --- > arch/arm/net/bpf_jit_32.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c > index b5f470d..ffaf311 100644 > --- a/arch/arm/net/bpf_jit_32.c > +++ b/arch/arm/net/bpf_jit_32.c > @@ -449,10 +449,10 @@ static inline void emit_udiv(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx) > return; > } > #endif > - if (rm != ARM_R0) > - emit(ARM_MOV_R(ARM_R0, rm), ctx); > if (rn != ARM_R1) > emit(ARM_MOV_R(ARM_R1, rn), ctx); > + if (rm != ARM_R0) > + emit(ARM_MOV_R(ARM_R0, rm), ctx); I don't think you've thought enough about this. What if rm is ARM_R1? What if rn = ARM_R0 and rm = ARM_R1? How about: if (rn == ARM_R0 && rm == ARM_R1) { emit(ARM_MOV_R(ARM_R3, rn), ctx); // r3 <- r0(rn) emit(ARM_MOV_R(ARM_R0, rm), ctx); // r0 <- r1(rm) emit(ARM_MOV_R(ARM_R1, ARM_R3), ctx); // r1 <- r3 } else if (rn == ARM_R0) { emit(ARM_MOV_R(ARM_R1, rn), ctx); // r1 <- rn if (rm != ARM_R0) emit(ARM_MOV_R(ARM_R0, rm), ctx); // r0 <- rm } else { if (rm != ARM_R0) emit(ARM_MOV_R(ARM_R0, rm), ctx); // r0 <- rm if (rn != ARM_R1) emit(ARM_MOV_R(ARM_R1, rn), ctx); // r1 <- rn } -- FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/