From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753390AbbFAKCg (ORCPT ); Mon, 1 Jun 2015 06:02:36 -0400 Received: from lhrrgout.huawei.com ([194.213.3.17]:11200 "EHLO lhrrgout.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752463AbbFAJy6 (ORCPT ); Mon, 1 Jun 2015 05:54:58 -0400 From: Wang Nan To: , , , , , , , , , , CC: , , , , Subject: [RFC PATCH v5 07/30] bpf tools: Check endianess and make libbpf fail early Date: Mon, 1 Jun 2015 07:37:53 +0000 Message-ID: <1433144296-74992-8-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1433144296-74992-1-git-send-email-wangnan0@huawei.com> References: <1433144296-74992-1-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.197.200] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Check endianess according to EHDR. Code is taken from tools/perf/util/symbol-elf.c. Libbpf doesn't magically convert missmatched endianess. See discussion on https://lkml.org/lkml/2015/5/18/650 that, even if we swap eBPF instructions to correct byte order, we are unable to deal with endianess in code logical generated by LLVM. Therefore, libbpf should simply reject missmatched ELF object, and let LLVM to create good code. Signed-off-by: Wang Nan Acked-by: Alexei Starovoitov --- tools/lib/bpf/libbpf.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 0824822..5d56c40 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -166,6 +166,34 @@ errout: return err; } +static int +bpf_object__check_endianess(struct bpf_object *obj) +{ + static unsigned int const endian = 1; + + switch (obj->efile.ehdr.e_ident[EI_DATA]) { + case ELFDATA2LSB: + /* We are big endian, BPF obj is little endian. */ + if (*(unsigned char const *)&endian != 1) + goto mismatch; + break; + + case ELFDATA2MSB: + /* We are little endian, BPF obj is big endian. */ + if (*(unsigned char const *)&endian != 0) + goto mismatch; + break; + default: + return -EINVAL; + } + + return 0; + +mismatch: + pr_warning("Error: endianess mismatch.\n"); + return -EINVAL; +} + struct bpf_object *bpf_object__open(const char *path) { struct bpf_object *obj; @@ -187,6 +215,8 @@ struct bpf_object *bpf_object__open(const char *path) if (bpf_object__elf_init(obj)) goto out; + if (bpf_object__check_endianess(obj)) + goto out; bpf_object__elf_finish(obj); return obj; -- 1.8.3.4