Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751367AbbEJLcb (ORCPT ); Sun, 10 May 2015 07:32:31 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:37613 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750887AbbEJLc3 (ORCPT ); Sun, 10 May 2015 07:32:29 -0400 Message-ID: <554F418E.7010402@gmail.com> Date: Sun, 10 May 2015 13:31:26 +0200 From: Mircea Gherzan User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.6.0 MIME-Version: 1.0 To: Nicolas Schichan , Russell King , "David S. Miller" , Daniel Borkmann CC: Alexei Starovoitov , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction. References: <1430929916-15852-1-git-send-email-nschichan@freebox.fr> In-Reply-To: <1430929916-15852-1-git-send-email-nschichan@freebox.fr> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2201 Lines: 57 On 05/06/2015 06:31 PM, 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 > Cc: # v3.13+ > Fixes: aee636c4809f (bpf: do not use reciprocal divide) > --- > arch/arm/net/bpf_jit_32.c | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) > > This patch was part of a serie adding support to JITed seccomp filters > to ARM but as it is an unrelated fix, it is more appropriate to send > it separately. > > Changes from previous version: add a comment clarifying how > emit_udiv() is called when translating BPF_ALU | BPF_DIV | BPF_K and > BPF_ALU | BPF_DIV | BPF_X with respect to the rm and rn parameters. > > diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c > index e1268f9..f412b53 100644 > --- a/arch/arm/net/bpf_jit_32.c > +++ b/arch/arm/net/bpf_jit_32.c > @@ -449,10 +449,21 @@ 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); > + > + /* > + * For BPF_ALU | BPF_DIV | BPF_K instructions, rm is ARM_R4 > + * (r_A) and rn is ARM_R0 (r_scratch) so load rn first into > + * ARM_R1 to avoid accidentally overwriting ARM_R0 with rm > + * before using it as a source for ARM_R1. > + * > + * For BPF_ALU | BPF_DIV | BPF_X rm is ARM_R4 (r_A) and rn is > + * ARM_R5 (r_X) so there is no particular register overlap > + * issues. > + */ > if (rn != ARM_R1) > emit(ARM_MOV_R(ARM_R1, rn), ctx); > + if (rm != ARM_R0) > + emit(ARM_MOV_R(ARM_R0, rm), ctx); > > ctx->seen |= SEEN_CALL; > emit_mov_i(ARM_R3, (u32)jit_udiv, ctx); > Acked-by: Mircea Gherzan -- 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/