From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EF1E5C2D0C0 for ; Mon, 23 Dec 2019 18:03:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C929220643 for ; Mon, 23 Dec 2019 18:03:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=fb.com header.i=@fb.com header.b="LxR+cUe8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726871AbfLWSDV (ORCPT ); Mon, 23 Dec 2019 13:03:21 -0500 Received: from mx0a-00082601.pphosted.com ([67.231.145.42]:24586 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726766AbfLWSDV (ORCPT ); Mon, 23 Dec 2019 13:03:21 -0500 Received: from pps.filterd (m0044012.ppops.net [127.0.0.1]) by mx0a-00082601.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id xBNI0KjL009653 for ; Mon, 23 Dec 2019 10:03:20 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fb.com; h=from : to : cc : subject : date : message-id : mime-version : content-type; s=facebook; bh=Wu85cQXWCEoswfqnumcZzCb1zfQYhPBo2sSFwLFNKxc=; b=LxR+cUe82RdYC8VUjC4HS+hq0Xi+2T8XB07Zxcs09bRYAyEC9bFvnqqp+mT85mkopI9N KAjm4nGhGKnYOnJ/NOIaWK0Y9u8MCbHVuKVD+ZOivMdwgQJA1nkfnAIW072QqAOhdI5R iC0nKFcFDNTCLh4ieZlsy4zZYazkLhy/SmE= Received: from maileast.thefacebook.com ([163.114.130.16]) by mx0a-00082601.pphosted.com with ESMTP id 2x2410dcfh-2 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NOT) for ; Mon, 23 Dec 2019 10:03:20 -0800 Received: from intmgw002.06.prn3.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:83::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1713.5; Mon, 23 Dec 2019 10:03:18 -0800 Received: by devbig012.ftw2.facebook.com (Postfix, from userid 137359) id 20E362EC19BA; Mon, 23 Dec 2019 10:03:15 -0800 (PST) Smtp-Origin-Hostprefix: devbig From: Andrii Nakryiko Smtp-Origin-Hostname: devbig012.ftw2.facebook.com To: , , , , CC: , , Andrii Nakryiko Smtp-Origin-Cluster: ftw2c04 Subject: [PATCH v2 bpf-next] libbpf: support CO-RE relocations for LDX/ST/STX instructions Date: Mon, 23 Dec 2019 10:03:05 -0800 Message-ID: <20191223180305.86417-1-andriin@fb.com> X-Mailer: git-send-email 2.17.1 X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572 definitions=2019-12-23_07:2019-12-23,2019-12-23 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 adultscore=0 phishscore=0 mlxlogscore=999 mlxscore=0 bulkscore=0 suspectscore=0 clxscore=1015 spamscore=0 impostorscore=0 malwarescore=0 lowpriorityscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-1910280000 definitions=main-1912230154 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Clang patch [0] enables emitting relocatable generic ALU/ALU64 instructions (i.e, shifts and arithmetic operations), as well as generic load/store instructions. The former ones are already supported by libbpf as is. This patch adds further support for load/store instructions. Relocatable field offset is encoded in BPF instruction's 16-bit offset section and are adjusted by libbpf based on target kernel BTF. These Clang changes and corresponding libbpf changes allow for more succinct generated BPF code by encoding relocatable field reads as a single ST/LDX/STX instruction. It also enables relocatable access to BPF context. Previously, if context struct (e.g., __sk_buff) was accessed with CO-RE relocations (e.g., due to preserve_access_index attribute), it would be rejected by BPF verifier due to modified context pointer dereference. With Clang patch, such context accesses are both relocatable and have a fixed offset from the point of view of BPF verifier. [0] https://reviews.llvm.org/D71790 Signed-off-by: Andrii Nakryiko --- tools/lib/bpf/libbpf.c | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 9576a90c5a1c..7513165b104f 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #include #include @@ -3810,11 +3811,13 @@ static int bpf_core_reloc_insn(struct bpf_program *prog, insn = &prog->insns[insn_idx]; class = BPF_CLASS(insn->code); - if (class == BPF_ALU || class == BPF_ALU64) { + switch (class) { + case BPF_ALU: + case BPF_ALU64: if (BPF_SRC(insn->code) != BPF_K) return -EINVAL; if (!failed && validate && insn->imm != orig_val) { - pr_warn("prog '%s': unexpected insn #%d value: got %u, exp %u -> %u\n", + pr_warn("prog '%s': unexpected insn #%d (ALU/ALU64) value: got %u, exp %u -> %u\n", bpf_program__title(prog, false), insn_idx, insn->imm, orig_val, new_val); return -EINVAL; @@ -3824,7 +3827,29 @@ static int bpf_core_reloc_insn(struct bpf_program *prog, pr_debug("prog '%s': patched insn #%d (ALU/ALU64)%s imm %u -> %u\n", bpf_program__title(prog, false), insn_idx, failed ? " w/ failed reloc" : "", orig_val, new_val); - } else { + break; + case BPF_LDX: + case BPF_ST: + case BPF_STX: + if (!failed && validate && insn->off != orig_val) { + pr_warn("prog '%s': unexpected insn #%d (LD/LDX/ST/STX) value: got %u, exp %u -> %u\n", + bpf_program__title(prog, false), insn_idx, + insn->off, orig_val, new_val); + return -EINVAL; + } + if (new_val > SHRT_MAX) { + pr_warn("prog '%s': insn #%d (LD/LDX/ST/STX) value too big: %u\n", + bpf_program__title(prog, false), insn_idx, + new_val); + return -ERANGE; + } + orig_val = insn->off; + insn->off = new_val; + pr_debug("prog '%s': patched insn #%d (LD/LDX/ST/STX)%s off %u -> %u\n", + bpf_program__title(prog, false), insn_idx, + failed ? " w/ failed reloc" : "", orig_val, new_val); + break; + default: pr_warn("prog '%s': trying to relocate unrecognized insn #%d, code:%x, src:%x, dst:%x, off:%x, imm:%x\n", bpf_program__title(prog, false), insn_idx, insn->code, insn->src_reg, insn->dst_reg, -- 2.17.1