From patchwork Thu Nov 27 05:02:26 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexei Starovoitov X-Patchwork-Id: 415371 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 911CF14017B for ; Thu, 27 Nov 2014 16:02:55 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751446AbaK0FCj (ORCPT ); Thu, 27 Nov 2014 00:02:39 -0500 Received: from mail-pd0-f172.google.com ([209.85.192.172]:62793 "EHLO mail-pd0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751371AbaK0FCh (ORCPT ); Thu, 27 Nov 2014 00:02:37 -0500 Received: by mail-pd0-f172.google.com with SMTP id y13so4168302pdi.31 for ; Wed, 26 Nov 2014 21:02:37 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=kItEYJHkGeA90m+VXIbYhms32dl9p+YcIyErpeILNs4=; b=RWrjqmfbqTjl7njzF2nN4JNnPv6JyDtGeubujxK3GuaZ2Mm45JOyZobdXaOyKGkO/M f35YR7A/60d2R1jQUwkC5JpS8bgvOiV5WiLe1HiGtNB1NLOguXL5KaQm7qxeDBJEgGqM Gpjmm+mcbopGgc5xqa+F+syR+5C6+TSULzyEBwT6mOtqXGzmoBz+mruDm+JqR6MK7Pf+ CMoxbFEQeMg/ha6SEdzFb5IWILX578bMxxchUiGWq5aZY+y3XpwPEyKY8PIU/t6g8sYx XAM/hEggOlkVlfs/plWEfEJEkP8GkCIV0mkOpbcfd3kPDpk29WGnOXHDjJ5ZvqbGfu5Z VB8A== X-Gm-Message-State: ALoCoQnQq1Whd8uURDs3lmgDb5dI0F4KylSuD6/nAzQwiWOd+oiDWXLL+2sSOLJuY9oMgxqVi2pp X-Received: by 10.68.68.130 with SMTP id w2mr59346906pbt.167.1417064557109; Wed, 26 Nov 2014 21:02:37 -0800 (PST) Received: from localhost.localdomain ([12.229.56.226]) by mx.google.com with ESMTPSA id y10sm5823468pdq.15.2014.11.26.21.02.35 for (version=TLSv1.1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 26 Nov 2014 21:02:36 -0800 (PST) From: Alexei Starovoitov To: "David S. Miller" Cc: Zi Shen Lim , Eric Dumazet , Daniel Borkmann , "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net] bpf: x86: fix epilogue generation for eBPF programs Date: Wed, 26 Nov 2014 21:02:26 -0800 Message-Id: <1417064546-4129-1-git-send-email-ast@plumgrid.com> X-Mailer: git-send-email 1.7.9.5 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org classic BPF has a restriction that last insn is always BPF_RET. eBPF doesn't have BPF_RET instruction and this restriction. It has BPF_EXIT insn which can appear anywhere in the program one or more times and it doesn't have to be last insn. Fix eBPF JIT to emit epilogue when first BPF_EXIT is seen and all other BPF_EXIT instructions will be emitted as jump. Signed-off-by: Alexei Starovoitov --- Note, this bug is applicable only to native eBPF programs which first were introduced in 3.18, so no need to send it to stable and therefore no 'Fixes' tag. arm64 JIT has the same problem, but the fix is not as trivial, so will be done as separate patch. Since 3.18 can only load eBPF programs and cannot execute them, this patch can even be done in net-next only, but I think it's worth to apply it to 3.18(net), so that JITed output for native eBPF programs is correct when bpf syscall loads it with net.core.bpf_jit_enable=2 arch/x86/net/bpf_jit_comp.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 3f62734..7e90244 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -178,7 +178,7 @@ static void jit_fill_hole(void *area, unsigned int size) } struct jit_context { - unsigned int cleanup_addr; /* epilogue code offset */ + int cleanup_addr; /* epilogue code offset */ bool seen_ld_abs; }; @@ -192,6 +192,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, struct bpf_insn *insn = bpf_prog->insnsi; int insn_cnt = bpf_prog->len; bool seen_ld_abs = ctx->seen_ld_abs | (oldproglen == 0); + bool seen_exit = false; u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY]; int i; int proglen = 0; @@ -854,10 +855,11 @@ common_load: goto common_load; case BPF_JMP | BPF_EXIT: - if (i != insn_cnt - 1) { + if (seen_exit) { jmp_offset = ctx->cleanup_addr - addrs[i]; goto emit_jmp; } + seen_exit = true; /* update cleanup_addr */ ctx->cleanup_addr = proglen; /* mov rbx, qword ptr [rbp-X] */