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([fe80::d886:b658:e2eb:a906]) by SN6PR1501MB2064.namprd15.prod.outlook.com ([fe80::d886:b658:e2eb:a906%5]) with mapi id 15.20.4195.030; Mon, 7 Jun 2021 19:42:54 +0000 Subject: Re: [PATCH 15/19] libbpf: Add support to link multi func tracing program To: Jiri Olsa CC: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , "Steven Rostedt (VMware)" , , , Martin KaFai Lau , Song Liu , John Fastabend , KP Singh , Daniel Xu , Viktor Malik References: <20210605111034.1810858-1-jolsa@kernel.org> <20210605111034.1810858-16-jolsa@kernel.org> <50f92d1e-1138-656c-4318-8fecf61f2025@fb.com> From: Yonghong Song Message-ID: Date: Mon, 7 Jun 2021 12:42:51 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [2620:10d:c090:400::5:db22] X-ClientProxiedBy: BYAPR04CA0025.namprd04.prod.outlook.com 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SN6PR1501MB2064.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Jun 2021 19:42:54.0685 (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: tEvJHHBqbv6p3Duy+1gklllK6CoeR7WrmvhY/3j9evtQheaWU2FLO0xGr7h4Vu5Q X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR15MB4871 X-OriginatorOrg: fb.com X-Proofpoint-GUID: 9UCHFt_xQVxqFyfBPqh2tnNivN0_u-MO X-Proofpoint-ORIG-GUID: 9UCHFt_xQVxqFyfBPqh2tnNivN0_u-MO X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-06-07_14:2021-06-04,2021-06-07 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 bulkscore=0 clxscore=1015 spamscore=0 impostorscore=0 lowpriorityscore=0 mlxlogscore=999 adultscore=0 mlxscore=0 phishscore=0 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2106070133 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 6/7/21 11:28 AM, Jiri Olsa wrote: > On Sun, Jun 06, 2021 at 10:49:16PM -0700, Yonghong Song wrote: >> >> >> On 6/5/21 4:10 AM, Jiri Olsa wrote: >>> Adding support to link multi func tracing program >>> through link_create interface. >>> >>> Adding special types for multi func programs: >>> >>> fentry.multi >>> fexit.multi >>> >>> so you can define multi func programs like: >>> >>> SEC("fentry.multi/bpf_fentry_test*") >>> int BPF_PROG(test1, unsigned long ip, __u64 a, __u64 b, __u64 c, __u64 d, __u64 e, __u64 f) >>> >>> that defines test1 to be attached to bpf_fentry_test* functions, >>> and able to attach ip and 6 arguments. >>> >>> If functions are not specified the program needs to be attached >>> manually. >>> >>> Adding new btf id related fields to bpf_link_create_opts and >>> bpf_link_create to use them. >>> >>> Signed-off-by: Jiri Olsa >>> --- >>> tools/lib/bpf/bpf.c | 11 ++++++- >>> tools/lib/bpf/bpf.h | 4 ++- >>> tools/lib/bpf/libbpf.c | 72 ++++++++++++++++++++++++++++++++++++++++++ >>> 3 files changed, 85 insertions(+), 2 deletions(-) >>> >>> diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c >>> index 86dcac44f32f..da892737b522 100644 >>> --- a/tools/lib/bpf/bpf.c >>> +++ b/tools/lib/bpf/bpf.c >>> @@ -674,7 +674,8 @@ int bpf_link_create(int prog_fd, int target_fd, >>> enum bpf_attach_type attach_type, >>> const struct bpf_link_create_opts *opts) >>> { >>> - __u32 target_btf_id, iter_info_len; >>> + __u32 target_btf_id, iter_info_len, multi_btf_ids_cnt; >>> + __s32 *multi_btf_ids; >>> union bpf_attr attr; >>> int fd; >> [...] >>> @@ -9584,6 +9597,9 @@ static int libbpf_find_attach_btf_id(struct bpf_program *prog, int *btf_obj_fd, >>> if (!name) >>> return -EINVAL; >>> + if (prog->prog_flags & BPF_F_MULTI_FUNC) >>> + return 0; >>> + >>> for (i = 0; i < ARRAY_SIZE(section_defs); i++) { >>> if (!section_defs[i].is_attach_btf) >>> continue; >>> @@ -10537,6 +10553,62 @@ static struct bpf_link *bpf_program__attach_btf_id(struct bpf_program *prog) >>> return (struct bpf_link *)link; >>> } >>> +static struct bpf_link *bpf_program__attach_multi(struct bpf_program *prog) >>> +{ >>> + char *pattern = prog->sec_name + prog->sec_def->len; >>> + DECLARE_LIBBPF_OPTS(bpf_link_create_opts, opts); >>> + enum bpf_attach_type attach_type; >>> + int prog_fd, link_fd, cnt, err; >>> + struct bpf_link *link = NULL; >>> + __s32 *ids = NULL; >>> + >>> + prog_fd = bpf_program__fd(prog); >>> + if (prog_fd < 0) { >>> + pr_warn("prog '%s': can't attach before loaded\n", prog->name); >>> + return ERR_PTR(-EINVAL); >>> + } >>> + >>> + err = bpf_object__load_vmlinux_btf(prog->obj, true); >>> + if (err) >>> + return ERR_PTR(err); >>> + >>> + cnt = btf__find_by_pattern_kind(prog->obj->btf_vmlinux, pattern, >>> + BTF_KIND_FUNC, &ids); >>> + if (cnt <= 0) >>> + return ERR_PTR(-EINVAL); >> >> In kernel, looks like we support cnt = 0, here we error out. >> Should we also error out in the kernel if cnt == 0? > > hum, I'm not what you mean.. what kernel code are you referring to? I am referring to the following kernel code: +static int bpf_tracing_multi_attach(struct bpf_prog *prog, + const union bpf_attr *attr) +{ + void __user *ubtf_ids = u64_to_user_ptr(attr->link_create.multi_btf_ids); + u32 size, i, cnt = attr->link_create.multi_btf_ids_cnt; + struct bpf_tracing_multi_link *link = NULL; + struct bpf_link_primer link_primer; + struct bpf_trampoline *tr = NULL; + int err = -EINVAL; + u8 nr_args = 0; + u32 *btf_ids; + + if (check_multi_prog_type(prog)) + return -EINVAL; + + size = cnt * sizeof(*btf_ids); + btf_ids = kmalloc(size, GFP_USER | __GFP_NOWARN); + if (!btf_ids) + return -ENOMEM; + + err = -EFAULT; + if (ubtf_ids && copy_from_user(btf_ids, ubtf_ids, size)) + goto out_free; + + link = kzalloc(sizeof(*link), GFP_USER); + if (!link) + goto out_free; + + for (i = 0; i < cnt; i++) { + struct bpf_attach_target_info tgt_info = {}; + + err = bpf_check_attach_target(NULL, prog, NULL, btf_ids[i], + &tgt_info); + if (err) + goto out_free; + + if (ftrace_set_filter_ip(&link->ops, tgt_info.tgt_addr, 0, 0)) + goto out_free; + + if (nr_args < tgt_info.fmodel.nr_args) + nr_args = tgt_info.fmodel.nr_args; + } + + tr = bpf_trampoline_multi_alloc(); + if (!tr) + goto out_free; + + bpf_func_model_nargs(&tr->func.model, nr_args); + + err = bpf_trampoline_link_prog(prog, tr); + if (err) + goto out_free; + + err = register_ftrace_direct_multi(&link->ops, (unsigned long) tr->cur_image->image); + if (err) + goto out_free; + + bpf_link_init(&link->link, BPF_LINK_TYPE_TRACING_MULTI, + &bpf_tracing_multi_link_lops, prog); + link->attach_type = prog->expected_attach_type; + + err = bpf_link_prime(&link->link, &link_primer); + if (err) + goto out_unlink; + + link->tr = tr; + /* Take extra ref so we are even with progs added by link_update. */ + bpf_prog_inc(prog); + return bpf_link_settle(&link_primer); + +out_unlink: + unregister_ftrace_direct_multi(&link->ops); +out_free: + kfree(tr); + kfree(btf_ids); + kfree(link); + return err; +} + Looks like cnt = 0 is okay in bpf_tracing_multi_attach(). > > thanks, > jirka >