Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752818AbbEFQcT (ORCPT ); Wed, 6 May 2015 12:32:19 -0400 Received: from smtp3-g21.free.fr ([212.27.42.3]:13488 "EHLO smtp3-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751442AbbEFQcP (ORCPT ); Wed, 6 May 2015 12:32:15 -0400 From: Nicolas Schichan To: Russell King , "David S. Miller" , Mircea Gherzan , Daniel Borkmann Cc: Alexei Starovoitov , Nicolas Schichan , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Subject: [PATCH v2] ARM: net fix emit_udiv() for BPF_ALU | BPF_DIV | BPF_K intruction. Date: Wed, 6 May 2015 18:31:56 +0200 Message-Id: <1430929916-15852-1-git-send-email-nschichan@freebox.fr> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2016 Lines: 56 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); -- 1.9.1 -- 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/