From de4e05cac46d206f9090051ef09930514bff73e4 Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Sat, 9 May 2020 10:59:01 -0700 Subject: [PATCH] bpf: Support bpf tracing/iter programs for BPF_LINK_CREATE Given a bpf program, the step to create an anonymous bpf iterator is: - create a bpf_iter_link, which combines bpf program and the target. In the future, there could be more information recorded in the link. A link_fd will be returned to the user space. - create an anonymous bpf iterator with the given link_fd. The bpf_iter_link can be pinned to bpffs mount file system to create a file based bpf iterator as well. The benefit to use of bpf_iter_link: - using bpf link simplifies design and implementation as bpf link is used for other tracing bpf programs. - for file based bpf iterator, bpf_iter_link provides a standard way to replace underlying bpf programs. - for both anonymous and free based iterators, bpf link query capability can be leveraged. The patch added support of tracing/iter programs for BPF_LINK_CREATE. A new link type BPF_LINK_TYPE_ITER is added to facilitate link querying. Currently, only prog_id is needed, so there is no additional in-kernel show_fdinfo() and fill_link_info() hook is needed for BPF_LINK_TYPE_ITER link. Signed-off-by: Yonghong Song Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20200509175901.2475084-1-yhs@fb.com --- include/linux/bpf.h | 1 + include/linux/bpf_types.h | 1 + include/uapi/linux/bpf.h | 1 + kernel/bpf/bpf_iter.c | 62 ++++++++++++++++++++++++++++++++++ kernel/bpf/syscall.c | 14 ++++++++ tools/include/uapi/linux/bpf.h | 1 + 6 files changed, 80 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index f28bdd714754..e93d2d33c82c 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1143,6 +1143,7 @@ struct bpf_iter_reg { int bpf_iter_reg_target(struct bpf_iter_reg *reg_info); void bpf_iter_unreg_target(const char *target); bool bpf_iter_prog_supported(struct bpf_prog *prog); +int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog); 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/include/linux/bpf_types.h b/include/linux/bpf_types.h index 8345cdf553b8..29d22752fc87 100644 --- a/include/linux/bpf_types.h +++ b/include/linux/bpf_types.h @@ -124,3 +124,4 @@ BPF_LINK_TYPE(BPF_LINK_TYPE_TRACING, tracing) #ifdef CONFIG_CGROUP_BPF BPF_LINK_TYPE(BPF_LINK_TYPE_CGROUP, cgroup) #endif +BPF_LINK_TYPE(BPF_LINK_TYPE_ITER, iter) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index c8a5325cc8d0..1e8dfff5d5d4 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -229,6 +229,7 @@ enum bpf_link_type { BPF_LINK_TYPE_RAW_TRACEPOINT = 1, BPF_LINK_TYPE_TRACING = 2, BPF_LINK_TYPE_CGROUP = 3, + BPF_LINK_TYPE_ITER = 4, MAX_BPF_LINK_TYPE, }; diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c index dec182d8395a..03f5832909db 100644 --- a/kernel/bpf/bpf_iter.c +++ b/kernel/bpf/bpf_iter.c @@ -15,6 +15,11 @@ struct bpf_iter_target_info { u32 btf_id; /* cached value */ }; +struct bpf_iter_link { + struct bpf_link link; + struct bpf_iter_target_info *tinfo; +}; + static struct list_head targets = LIST_HEAD_INIT(targets); static DEFINE_MUTEX(targets_mutex); @@ -93,3 +98,60 @@ bool bpf_iter_prog_supported(struct bpf_prog *prog) return supported; } + +static void bpf_iter_link_release(struct bpf_link *link) +{ +} + +static void bpf_iter_link_dealloc(struct bpf_link *link) +{ + struct bpf_iter_link *iter_link = + container_of(link, struct bpf_iter_link, link); + + kfree(iter_link); +} + +static const struct bpf_link_ops bpf_iter_link_lops = { + .release = bpf_iter_link_release, + .dealloc = bpf_iter_link_dealloc, +}; + +int bpf_iter_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) +{ + struct bpf_link_primer link_primer; + struct bpf_iter_target_info *tinfo; + struct bpf_iter_link *link; + bool existed = false; + u32 prog_btf_id; + int err; + + if (attr->link_create.target_fd || attr->link_create.flags) + return -EINVAL; + + prog_btf_id = prog->aux->attach_btf_id; + mutex_lock(&targets_mutex); + list_for_each_entry(tinfo, &targets, list) { + if (tinfo->btf_id == prog_btf_id) { + existed = true; + break; + } + } + mutex_unlock(&targets_mutex); + if (!existed) + return -ENOENT; + + link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN); + if (!link) + return -ENOMEM; + + bpf_link_init(&link->link, BPF_LINK_TYPE_ITER, &bpf_iter_link_lops, prog); + link->tinfo = tinfo; + + err = bpf_link_prime(&link->link, &link_primer); + if (err) { + kfree(link); + return err; + } + + return bpf_link_settle(&link_primer); +} diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index bb1ab7da6103..6ffe2d8fb6c7 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2729,6 +2729,8 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type) case BPF_CGROUP_GETSOCKOPT: case BPF_CGROUP_SETSOCKOPT: return BPF_PROG_TYPE_CGROUP_SOCKOPT; + case BPF_TRACE_ITER: + return BPF_PROG_TYPE_TRACING; default: return BPF_PROG_TYPE_UNSPEC; } @@ -3729,6 +3731,15 @@ err_put: return err; } +static int tracing_bpf_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) +{ + if (attr->link_create.attach_type == BPF_TRACE_ITER && + prog->expected_attach_type == BPF_TRACE_ITER) + return bpf_iter_link_attach(attr, prog); + + return -EINVAL; +} + #define BPF_LINK_CREATE_LAST_FIELD link_create.flags static int link_create(union bpf_attr *attr) { @@ -3765,6 +3776,9 @@ static int link_create(union bpf_attr *attr) case BPF_PROG_TYPE_CGROUP_SOCKOPT: ret = cgroup_bpf_link_attach(attr, prog); break; + case BPF_PROG_TYPE_TRACING: + ret = tracing_bpf_link_attach(attr, prog); + break; default: ret = -EINVAL; } diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index c8a5325cc8d0..1e8dfff5d5d4 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -229,6 +229,7 @@ enum bpf_link_type { BPF_LINK_TYPE_RAW_TRACEPOINT = 1, BPF_LINK_TYPE_TRACING = 2, BPF_LINK_TYPE_CGROUP = 3, + BPF_LINK_TYPE_ITER = 4, MAX_BPF_LINK_TYPE, };