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Mon, 11 May 2020 20:43:05 +0000 Subject: Re: [PATCH bpf-next v3] libbpf: fix probe code to return EPERM if encountered To: Eelco Chaudron , CC: , , , , , , , References: <158920079637.7533.5703299045869368435.stgit@ebuild> From: Yonghong Song Message-ID: <7008d545-ac78-3e22-aeaa-1d6639611225@fb.com> Date: Mon, 11 May 2020 13:43:03 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 In-Reply-To: <158920079637.7533.5703299045869368435.stgit@ebuild> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR11CA0080.namprd11.prod.outlook.com (2603:10b6:a03:f4::21) To BYAPR15MB4088.namprd15.prod.outlook.com (2603:10b6:a02:c3::18) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from macbook-pro-52.local.dhcp.thefacebook.com (2620:10d:c090:400::5:3585) by BYAPR11CA0080.namprd11.prod.outlook.com (2603:10b6:a03:f4::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2979.26 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 11f572d9-be73-451c-5ae5-08d7f5ebe7e9 X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 May 2020 20:43:05.5223 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: skjxOSYCzKuPW6LuuXsO2+BK9eVLKPcsi4lIz9dHj6Lm/wj63cHPm056Wu4VeYMb X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB4133 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.676 definitions=2020-05-11_10:2020-05-11,2020-05-11 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 mlxlogscore=999 priorityscore=1501 bulkscore=0 clxscore=1015 phishscore=0 lowpriorityscore=0 spamscore=0 adultscore=0 malwarescore=0 impostorscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2005110157 X-FB-Internal: deliver Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 5/11/20 5:40 AM, Eelco Chaudron wrote: > When the probe code was failing for any reason ENOTSUP was returned, even > if this was due to no having enough lock space. This patch fixes this by > returning EPERM to the user application, so it can respond and increase > the RLIMIT_MEMLOCK size. > > Signed-off-by: Eelco Chaudron > --- > v3: Updated error message to be more specific as suggested by Andrii > v2: Split bpf_object__probe_name() in two functions as suggested by Andrii > > tools/lib/bpf/libbpf.c | 31 ++++++++++++++++++++++++++----- > 1 file changed, 26 insertions(+), 5 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 8f480e29a6b0..ad3043c5db13 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -3149,7 +3149,7 @@ int bpf_map__resize(struct bpf_map *map, __u32 max_entries) > } > > static int > -bpf_object__probe_name(struct bpf_object *obj) > +bpf_object__probe_loading(struct bpf_object *obj) > { > struct bpf_load_program_attr attr; > char *cp, errmsg[STRERR_BUFSIZE]; > @@ -3170,14 +3170,34 @@ bpf_object__probe_name(struct bpf_object *obj) > ret = bpf_load_program_xattr(&attr, NULL, 0); > if (ret < 0) { > cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg)); > - pr_warn("Error in %s():%s(%d). Couldn't load basic 'r0 = 0' BPF program.\n", > - __func__, cp, errno); > + pr_warn("Error in %s():%s(%d). Couldn't load trivial BPF " > + "program. Make sure your kernel supports BPF " > + "(CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is " > + "set to big enough value.\n", __func__, cp, errno); > return -errno; Just curious. Did "errno" always survive pr_warn() here? pr_warn() may call user supplied print function which it outside libbpf control. Maybe should cache errno before calling pr_warn()? > } > close(ret); > > - /* now try the same program, but with the name */ > + return 0; > +} > + > +static int > +bpf_object__probe_name(struct bpf_object *obj) > +{ > + struct bpf_load_program_attr attr; > + struct bpf_insn insns[] = { > + BPF_MOV64_IMM(BPF_REG_0, 0), > + BPF_EXIT_INSN(), > + }; > + int ret; > + > + /* make sure loading with name works */ > > + memset(&attr, 0, sizeof(attr)); > + attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER; > + attr.insns = insns; > + attr.insns_cnt = ARRAY_SIZE(insns); > + attr.license = "GPL"; > attr.name = "test"; > ret = bpf_load_program_xattr(&attr, NULL, 0); > if (ret >= 0) { > @@ -5386,7 +5406,8 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr) > > obj->loaded = true; > > - err = bpf_object__probe_caps(obj); > + err = bpf_object__probe_loading(obj); > + err = err ? : bpf_object__probe_caps(obj); > err = err ? : bpf_object__resolve_externs(obj, obj->kconfig); > err = err ? : bpf_object__sanitize_and_load_btf(obj); > err = err ? : bpf_object__sanitize_maps(obj); >