On Fri, Aug 26, 2016 at 09:58:49PM +0200, Daniel Mack wrote: > Extend the bpf(2) syscall by two new commands, BPF_PROG_ATTACH and > BPF_PROG_DETACH which allow attaching and detaching eBPF programs > to a target. > > On the API level, the target could be anything that has an fd in > userspace, hence the name of the field in union bpf_attr is called > 'target_fd'. > > When called with BPF_ATTACH_TYPE_CGROUP_INET_{E,IN}GRESS, the target is > expected to be a valid file descriptor of a cgroup v2 directory which > has the bpf controller enabled. These are the only use-cases > implemented by this patch at this point, but more can be added. > > If a program of the given type already exists in the given cgroup, > the program is swapped automically, so userspace does not have to drop > an existing program first before installing a new one, which would > otherwise leave a gap in which no program is attached. > > For more information on the propagation logic to subcgroups, please > refer to the bpf cgroup controller implementation. > > The API is guarded by CAP_NET_ADMIN. > > Signed-off-by: Daniel Mack <dan...@zonque.org> > syscall > --- > include/uapi/linux/bpf.h | 9 ++++++ > kernel/bpf/syscall.c | 83 > ++++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 92 insertions(+) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index 1d5db42..4cc2dcf 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -73,6 +73,8 @@ enum bpf_cmd { > BPF_PROG_LOAD, > BPF_OBJ_PIN, > BPF_OBJ_GET, > + BPF_PROG_ATTACH, > + BPF_PROG_DETACH, > }; > > enum bpf_map_type { > @@ -147,6 +149,13 @@ union bpf_attr { > __aligned_u64 pathname; > __u32 bpf_fd; > }; > + > + struct { /* anonymous struct used by BPF_PROG_ATTACH/DETACH commands */ > + __u32 target_fd; /* container object to attach > to */ > + __u32 attach_bpf_fd; /* eBPF program to attach */ > + __u32 attach_type; /* BPF_ATTACH_TYPE_* */ > + __u64 attach_flags; > + };
there is a 4 byte hole in this struct. Can we pack it differently? > } __attribute__((aligned(8))); > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 228f962..cc4d603 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -822,6 +822,79 @@ static int bpf_obj_get(const union bpf_attr *attr) > return bpf_obj_get_user(u64_to_ptr(attr->pathname)); > } > > +#ifdef CONFIG_CGROUP_BPF > +static int bpf_prog_attach(const union bpf_attr *attr) > +{ > + struct bpf_prog *prog; > + > + if (!capable(CAP_NET_ADMIN)) > + return -EPERM; > + > + /* Flags are unused for now */ > + if (attr->attach_flags != 0) > + return -EINVAL; > + > + switch (attr->attach_type) { > + case BPF_ATTACH_TYPE_CGROUP_INET_INGRESS: > + case BPF_ATTACH_TYPE_CGROUP_INET_EGRESS: { > + struct cgroup *cgrp; > + > + prog = bpf_prog_get_type(attr->attach_bpf_fd, > + BPF_PROG_TYPE_CGROUP_SOCKET_FILTER); > + if (IS_ERR(prog)) > + return PTR_ERR(prog); > + > + cgrp = cgroup_get_from_fd(attr->target_fd); > + if (IS_ERR(cgrp)) { > + bpf_prog_put(prog); > + return PTR_ERR(cgrp); > + } > + > + cgroup_bpf_update(cgrp, prog, attr->attach_type); > + cgroup_put(cgrp); > + > + break; > + } this } formatting style is confusing. The above } looks like it matches 'switch () {'. May be move 'struct cgroup *cgrp' to the top to avoid that?