Messages in this thread | | | Date | Tue, 2 Nov 2021 13:11:11 -0700 | Subject | Re: [PATCH bpf-next v4 1/2] bpf: support BPF_PROG_QUERY for progs attached to sockmap | From | Yonghong Song <> |
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On 11/2/21 1:48 AM, Di Zhu wrote: > Right now there is no way to query whether BPF programs are > attached to a sockmap or not. > > we can use the standard interface in libbpf to query, such as: > bpf_prog_query(mapFd, BPF_SK_SKB_STREAM_PARSER, 0, NULL, ...); > the mapFd is the fd of sockmap. > > Signed-off-by: Di Zhu <zhudi2@huawei.com> > --- > include/linux/bpf.h | 9 +++++ > kernel/bpf/syscall.c | 5 +++ > net/core/sock_map.c | 88 ++++++++++++++++++++++++++++++++++++++++---- > 3 files changed, 95 insertions(+), 7 deletions(-) > > diff --git a/include/linux/bpf.h b/include/linux/bpf.h > index d604c8251d88..594ca91992db 100644 > --- a/include/linux/bpf.h > +++ b/include/linux/bpf.h > @@ -1961,6 +1961,9 @@ int bpf_prog_test_run_syscall(struct bpf_prog *prog, > int sock_map_get_from_fd(const union bpf_attr *attr, struct bpf_prog *prog); > int sock_map_prog_detach(const union bpf_attr *attr, enum bpf_prog_type ptype); > int sock_map_update_elem_sys(struct bpf_map *map, void *key, void *value, u64 flags); > +int sockmap_bpf_prog_query(const union bpf_attr *attr, > + union bpf_attr __user *uattr);
All previous functions are with prefix "sock_map". Why you choose a different prefix "sockmap"?
> + > void sock_map_unhash(struct sock *sk); > void sock_map_close(struct sock *sk, long timeout); > #else > @@ -2014,6 +2017,12 @@ static inline int sock_map_update_elem_sys(struct bpf_map *map, void *key, void > { > return -EOPNOTSUPP; > } > + > +static inline int sockmap_bpf_prog_query(const union bpf_attr *attr, > + union bpf_attr __user *uattr) > +{ > + return -EINVAL; > +} > #endif /* CONFIG_BPF_SYSCALL */ > #endif /* CONFIG_NET && CONFIG_BPF_SYSCALL */ > > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 4e50c0bfdb7d..17faeff8f85f 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -3275,6 +3275,11 @@ static int bpf_prog_query(const union bpf_attr *attr, > case BPF_FLOW_DISSECTOR: > case BPF_SK_LOOKUP: > return netns_bpf_prog_query(attr, uattr); > + case BPF_SK_SKB_STREAM_PARSER: > + case BPF_SK_SKB_STREAM_VERDICT: > + case BPF_SK_MSG_VERDICT: > + case BPF_SK_SKB_VERDICT: > + return sockmap_bpf_prog_query(attr, uattr); > default: > return -EINVAL; > } > diff --git a/net/core/sock_map.c b/net/core/sock_map.c > index e252b8ec2b85..ca65ed0004d3 100644 > --- a/net/core/sock_map.c > +++ b/net/core/sock_map.c > @@ -1412,38 +1412,50 @@ static struct sk_psock_progs *sock_map_progs(struct bpf_map *map) > return NULL; > } > > -static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog, > - struct bpf_prog *old, u32 which) > +static int sock_map_prog_lookup(struct bpf_map *map, struct bpf_prog **pprog[],
Can we just change "**pprog[]" to "***pprog"? In the code, you really just pass the address of the decl "struct bpf_prog **pprog;" to the function.
> + u32 which)
Some format issue here?
> { > struct sk_psock_progs *progs = sock_map_progs(map); > - struct bpf_prog **pprog; > > if (!progs) > return -EOPNOTSUPP; > > switch (which) { > case BPF_SK_MSG_VERDICT: > - pprog = &progs->msg_parser; > + *pprog = &progs->msg_parser; > break; > #if IS_ENABLED(CONFIG_BPF_STREAM_PARSER) > case BPF_SK_SKB_STREAM_PARSER: > - pprog = &progs->stream_parser; > + *pprog = &progs->stream_parser; > break; > #endif > case BPF_SK_SKB_STREAM_VERDICT: > if (progs->skb_verdict) > return -EBUSY; > - pprog = &progs->stream_verdict; > + *pprog = &progs->stream_verdict; > break; > case BPF_SK_SKB_VERDICT: > if (progs->stream_verdict) > return -EBUSY; > - pprog = &progs->skb_verdict; > + *pprog = &progs->skb_verdict; > break; > default: > return -EOPNOTSUPP; > } > > + return 0; > +} > + > +static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog, > + struct bpf_prog *old, u32 which)
Some format issue here?
> +{ > + struct bpf_prog **pprog; > + int ret; > + > + ret = sock_map_prog_lookup(map, &pprog, which); > + if (ret) > + return ret; > + > if (old) > return psock_replace_prog(pprog, prog, old); > > @@ -1451,6 +1463,68 @@ static int sock_map_prog_update(struct bpf_map *map, struct bpf_prog *prog, > return 0; > } > > +int sockmap_bpf_prog_query(const union bpf_attr *attr, > + union bpf_attr __user *uattr)
Format issue here?
> +{ > + __u32 __user *prog_ids = u64_to_user_ptr(attr->query.prog_ids);
Typically we use u32 in the kernel code. But I know there are __u32 usage as well, esp. with __user attributes. I put a comment here just in case that somebody else has a different opinion.
> + u32 prog_cnt = 0, flags = 0; > + u32 ufd = attr->target_fd;
You can merge the above u32 together.
> + struct bpf_prog **pprog; > + struct bpf_prog *prog; > + struct bpf_map *map; > + struct fd f; > + int ret; > + u32 id = 0;
to maintain reverse christmas tree?
> + > + if (attr->query.query_flags) > + return -EINVAL; > + > + f = fdget(ufd); > + map = __bpf_map_get(f); > + if (IS_ERR(map)) > + return PTR_ERR(map); > + > + rcu_read_lock(); > + > + ret = sock_map_prog_lookup(map, &pprog, attr->query.attach_type); > + if (ret) > + goto end; > + > + prog = *pprog; > + prog_cnt = (!prog) ? 0 : 1; > + > + if (!attr->query.prog_cnt || !prog_ids || !prog_cnt) > + goto end; > + > + prog = bpf_prog_inc_not_zero(prog);
Could you explain why we need bpf_prog_inc_not_zero here? We are inside rcu_read_lock/unlock region. We got a program from *pprog. If this program is not NULL, this program should not disappear since we are in rcu read lock region, right? Maybe I missed something, it would be good you can explain the scenario you try to pretect here.
> + if (IS_ERR(prog)) { > + ret = PTR_ERR(prog); > + goto end; > + } > + id = prog->aux->id; > + bpf_prog_put(prog); > + > +end: > + rcu_read_unlock(); > + > + if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags))) { > + ret = -EFAULT; > + goto err; > + } > + if (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) { > + ret = -EFAULT; > + goto err; > + } > + if (copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt))) { > + ret = -EFAULT; > + goto err; > + }
You can do
if (copy_to_user(&uattr->query.attach_flags, &flags, sizeof(flags)) || (id != 0 && copy_to_user(prog_ids, &id, sizeof(u32))) || copy_to_user(&uattr->query.prog_cnt, &prog_cnt, sizeof(prog_cnt))) ret = -EFAULT;
to make code a little bit concise.
> + > +err: > + fdput(f); > + return ret; > +} > + > static void sock_map_unlink(struct sock *sk, struct sk_psock_link *link) > { > switch (link->map->map_type) { >
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