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Thu, 30 Apr 2020 18:03:07 +0000 Subject: Re: [PATCH bpf-next v1 08/19] bpf: create file bpf iterator To: Andrii Nakryiko CC: Andrii Nakryiko , bpf , Martin KaFai Lau , Networking , Alexei Starovoitov , Daniel Borkmann , Kernel Team References: <20200427201235.2994549-1-yhs@fb.com> <20200427201244.2995241-1-yhs@fb.com> From: Yonghong Song Message-ID: <419c2909-349a-2495-e2dd-1cd647e21d4a@fb.com> Date: Thu, 30 Apr 2020 11:02:54 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MWHPR1701CA0013.namprd17.prod.outlook.com (2603:10b6:301:14::23) 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:ea21) by MWHPR1701CA0013.namprd17.prod.outlook.com (2603:10b6:301:14::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.2958.19 via Frontend Transport; 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When the pinned file is >> opened, a seq_file will be generated. >> >> Signed-off-by: Yonghong Song >> --- >> include/linux/bpf.h | 3 +++ >> kernel/bpf/bpf_iter.c | 48 ++++++++++++++++++++++++++++++++++++++++++- >> kernel/bpf/inode.c | 28 +++++++++++++++++++++++++ >> kernel/bpf/syscall.c | 2 +- >> 4 files changed, 79 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h >> index 0f0cafc65a04..601b3299b7e4 100644 >> --- a/include/linux/bpf.h >> +++ b/include/linux/bpf.h >> @@ -1021,6 +1021,8 @@ static inline void bpf_enable_instrumentation(void) >> >> extern const struct file_operations bpf_map_fops; >> extern const struct file_operations bpf_prog_fops; >> +extern const struct file_operations bpf_link_fops; >> +extern const struct file_operations bpffs_iter_fops; >> >> #define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \ >> extern const struct bpf_prog_ops _name ## _prog_ops; \ >> @@ -1136,6 +1138,7 @@ int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog); >> int bpf_iter_link_replace(struct bpf_link *link, struct bpf_prog *old_prog, >> struct bpf_prog *new_prog); >> int bpf_iter_new_fd(struct bpf_link *link); >> +void *bpf_iter_get_from_fd(u32 ufd); >> >> int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value); >> int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value); >> diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c >> index 1f4e778d1814..f5e933236996 100644 >> --- a/kernel/bpf/bpf_iter.c >> +++ b/kernel/bpf/bpf_iter.c >> @@ -123,7 +123,8 @@ struct bpf_prog *bpf_iter_get_prog(struct seq_file *seq, u32 priv_data_size, >> { >> struct extra_priv_data *extra_data; >> >> - if (seq->file->f_op != &anon_bpf_iter_fops) >> + if (seq->file->f_op != &anon_bpf_iter_fops && >> + seq->file->f_op != &bpffs_iter_fops) > > Do we really need anon_bpf_iter_fops and bpffs_iter_fops? Seems like > the only difference is bpffs_iter_open. Could it be implemented as > part of anon_bpf_iter_ops as well? Seems like open() is never called > for anon_inode_file, so it should work for both? Yes, open() will not be used for anon_bpf_iter. I used two file_operations just for this reason. But I guess, I can just use one. It won't hurt. > >> return NULL; >> >> extra_data = get_extra_priv_dptr(seq->private, priv_data_size); >> @@ -310,3 +311,48 @@ int bpf_iter_new_fd(struct bpf_link *link) >> put_unused_fd(fd); >> return err; >> } >> + >> +static int bpffs_iter_open(struct inode *inode, struct file *file) >> +{ >> + struct bpf_iter_link *link = inode->i_private; >> + >> + return prepare_seq_file(file, link); >> +} >> + >> +static int bpffs_iter_release(struct inode *inode, struct file *file) >> +{ >> + return anon_iter_release(inode, file); >> +} >> + >> +const struct file_operations bpffs_iter_fops = { >> + .open = bpffs_iter_open, >> + .read = seq_read, >> + .release = bpffs_iter_release, >> +}; >> + >> +void *bpf_iter_get_from_fd(u32 ufd) > > return struct bpf_iter_link * here, given this is specific constructor > for bpf_iter_link? > >> +{ >> + struct bpf_link *link; >> + struct bpf_prog *prog; >> + struct fd f; >> + >> + f = fdget(ufd); >> + if (!f.file) >> + return ERR_PTR(-EBADF); >> + if (f.file->f_op != &bpf_link_fops) { >> + link = ERR_PTR(-EINVAL); >> + goto out; >> + } >> + >> + link = f.file->private_data; >> + prog = link->prog; >> + if (prog->expected_attach_type != BPF_TRACE_ITER) { >> + link = ERR_PTR(-EINVAL); >> + goto out; >> + } >> + >> + bpf_link_inc(link); >> +out: >> + fdput(f); >> + return link; >> +} >> diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c >> index 95087d9f4ed3..de4493983a37 100644 >> --- a/kernel/bpf/inode.c >> +++ b/kernel/bpf/inode.c >> @@ -26,6 +26,7 @@ enum bpf_type { >> BPF_TYPE_PROG, >> BPF_TYPE_MAP, >> BPF_TYPE_LINK, >> + BPF_TYPE_ITER, > > Adding ITER as an alternative type of pinned object to BPF_TYPE_LINK > seems undesirable. We can allow opening bpf_iter's seq_file by doing > the same trick as is done for bpf_maps, supporting seq_show (see > bpf_mkmap() and bpf_map_support_seq_show()). Do you think we can do > the same here? If we later see that more kinds of links would want to > allow direct open() to create a file with some output from BPF > program, we can generalize this as part of bpf_link infrastructure. > For now having a custom check similar to bpf_map's seems sufficient. > > What do you think? Sounds good. Will use the mechanism similar to bpf_map. > >> }; >> >> static void *bpf_any_get(void *raw, enum bpf_type type) >> @@ -38,6 +39,7 @@ static void *bpf_any_get(void *raw, enum bpf_type type) >> bpf_map_inc_with_uref(raw); >> break; >> case BPF_TYPE_LINK: >> + case BPF_TYPE_ITER: >> bpf_link_inc(raw); >> break; >> default: >> @@ -58,6 +60,7 @@ static void bpf_any_put(void *raw, enum bpf_type type) >> bpf_map_put_with_uref(raw); >> break; >> case BPF_TYPE_LINK: >> + case BPF_TYPE_ITER: >> bpf_link_put(raw); >> break; >> default: >> @@ -82,6 +85,15 @@ static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type) >> return raw; >> } >> > > [...] >