Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753757AbbGACQa (ORCPT ); Tue, 30 Jun 2015 22:16:30 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:65488 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753263AbbGACPR (ORCPT ); Tue, 30 Jun 2015 22:15:17 -0400 From: Wang Nan To: , , , , , , , , , , CC: , , , , Subject: [RFC PATCH v10 07/50] bpf tools: Check endianness and make libbpf fail early Date: Wed, 1 Jul 2015 02:13:55 +0000 Message-ID: <1435716878-189507-8-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1435716878-189507-1-git-send-email-wangnan0@huawei.com> References: <1435716878-189507-1-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 Content-Length: 1949 Lines: 72 Check endianness according to EHDR. Code is taken from tools/perf/util/symbol-elf.c. Libbpf doesn't magically convert missmatched endianness. Even if we swap eBPF instructions to correct byte order, we are unable to deal with endianness 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 36dfbc1..15b3e82 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -192,6 +192,34 @@ errout: return err; } +static int +bpf_object__check_endianness(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: endianness mismatch.\n"); + return -EINVAL; +} + static struct bpf_object * __bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz) { @@ -208,6 +236,8 @@ __bpf_object__open(const char *path, void *obj_buf, size_t obj_buf_sz) if (bpf_object__elf_init(obj)) goto out; + if (bpf_object__check_endianness(obj)) + goto out; bpf_object__elf_finish(obj); return obj; -- 1.8.3.4 -- 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/