From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753182AbbJZGhT (ORCPT ); Mon, 26 Oct 2015 02:37:19 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:47263 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750982AbbJZGhR (ORCPT ); Mon, 26 Oct 2015 02:37:17 -0400 From: Wang Nan To: , CC: , , , Wang Nan , Arnaldo Carvalho de Melo , "David S. Miller" Subject: [net-next PATCH] bpf: Output error message to logbuf when loading Date: Mon, 26 Oct 2015 06:36:34 +0000 Message-ID: <1445841394-142865-1-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.193.248] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Many reason can make bpf_prog_load() return EINVAL. This patch utilizes logbuf passed from user to deliver the actual reason of failure. Without this patch, people is easy to forget fixing the "version" section in their BPF objects. Signed-off-by: Wang Nan Cc: Alexei Starovoitov Cc: Arnaldo Carvalho de Melo Cc: David S. Miller --- kernel/bpf/syscall.c | 41 ++++++++++++++++++++++++++++++++++++++--- 1 file changed, 38 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 687dd6c..3a0e4e7 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -574,6 +574,32 @@ struct bpf_prog *bpf_prog_get(u32 ufd) } EXPORT_SYMBOL_GPL(bpf_prog_get); +static void +bpf_prog_load_note(union bpf_attr *attr, const char *fmt, ...) +{ + u32 log_level, log_size, log_len; + char __user *log_ubuf = NULL; + /* 64 chars should be long enough for a one line note. */ + char log_buf[64]; + va_list args; + + log_ubuf = (char __user *) (unsigned long) attr->log_buf; + log_level = attr->log_level; + log_size = sizeof(log_buf); + if (attr->log_size < log_size) + log_size = attr->log_size; + + if (log_level == 0 || !log_size || !log_ubuf) + return; + + va_start(args, fmt); + log_len = vscnprintf(log_buf, log_size, fmt, args); + va_end(args); + + /* Don't need to care the copying result too much */ + copy_to_user(log_ubuf, log_buf, log_size); +} + /* last field in 'union bpf_attr' used by this command */ #define BPF_PROG_LOAD_LAST_FIELD kern_version @@ -597,12 +623,19 @@ static int bpf_prog_load(union bpf_attr *attr) /* eBPF programs must be GPL compatible to use GPL-ed functions */ is_gpl = license_is_gpl_compatible(license); - if (attr->insn_cnt >= BPF_MAXINSNS) + if (attr->insn_cnt >= BPF_MAXINSNS) { + bpf_prog_load_note(attr, "Too many instructions: %d > %d\n", + attr->insn_cnt, BPF_MAXINSNS); return -EINVAL; + } if (type == BPF_PROG_TYPE_KPROBE && - attr->kern_version != LINUX_VERSION_CODE) + attr->kern_version != LINUX_VERSION_CODE) { + bpf_prog_load_note(attr, + "Kernel version mismatch: 0x%x != 0x%x\n", + attr->kern_version, LINUX_VERSION_CODE); return -EINVAL; + } if (type != BPF_PROG_TYPE_SOCKET_FILTER && !capable(CAP_SYS_ADMIN)) return -EPERM; @@ -631,8 +664,10 @@ static int bpf_prog_load(union bpf_attr *attr) /* find program type: socket_filter vs tracing_filter */ err = find_prog_type(type, prog); - if (err < 0) + if (err < 0) { + bpf_prog_load_note(attr, "Invalid program type: %d\n", type); goto free_prog; + } /* run eBPF verifier */ err = bpf_check(&prog, attr); -- 1.8.3.4