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authorDaniel Borkmann <daniel@iogearbox.net>2015-10-29 14:58:09 +0100
committerDavid S. Miller <davem@davemloft.net>2015-11-02 22:48:39 -0500
commitb2197755b2633e164a439682fb05a9b5ea48f706 (patch)
tree71d9694754b0e4511e7cec0c2f57c130e96e71fb /include/linux/bpf.h
parente9d8afa90b789b07d414637ab557d169d6b2b84e (diff)
bpf: add support for persistent maps/progs
This work adds support for "persistent" eBPF maps/programs. The term "persistent" is to be understood that maps/programs have a facility that lets them survive process termination. This is desired by various eBPF subsystem users. Just to name one example: tc classifier/action. Whenever tc parses the ELF object, extracts and loads maps/progs into the kernel, these file descriptors will be out of reach after the tc instance exits. So a subsequent tc invocation won't be able to access/relocate on this resource, and therefore maps cannot easily be shared, f.e. between the ingress and egress networking data path. The current workaround is that Unix domain sockets (UDS) need to be instrumented in order to pass the created eBPF map/program file descriptors to a third party management daemon through UDS' socket passing facility. This makes it a bit complicated to deploy shared eBPF maps or programs (programs f.e. for tail calls) among various processes. We've been brainstorming on how we could tackle this issue and various approches have been tried out so far, which can be read up further in the below reference. The architecture we eventually ended up with is a minimal file system that can hold map/prog objects. The file system is a per mount namespace singleton, and the default mount point is /sys/fs/bpf/. Any subsequent mounts within a given namespace will point to the same instance. The file system allows for creating a user-defined directory structure. The objects for maps/progs are created/fetched through bpf(2) with two new commands (BPF_OBJ_PIN/BPF_OBJ_GET). I.e. a bpf file descriptor along with a pathname is being passed to bpf(2) that in turn creates (we call it eBPF object pinning) the file system nodes. Only the pathname is being passed to bpf(2) for getting a new BPF file descriptor to an existing node. The user can use that to access maps and progs later on, through bpf(2). Removal of file system nodes is being managed through normal VFS functions such as unlink(2), etc. The file system code is kept to a very minimum and can be further extended later on. The next step I'm working on is to add dump eBPF map/prog commands to bpf(2), so that a specification from a given file descriptor can be retrieved. This can be used by things like CRIU but also applications can inspect the meta data after calling BPF_OBJ_GET. Big thanks also to Alexei and Hannes who significantly contributed in the design discussion that eventually let us end up with this architecture here. Reference: https://lkml.org/lkml/2015/10/15/925 Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/bpf.h')
-rw-r--r--include/linux/bpf.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 0b5fb6acef64..de464e6683b6 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -167,11 +167,18 @@ struct bpf_prog *bpf_prog_get(u32 ufd);
void bpf_prog_put(struct bpf_prog *prog);
void bpf_prog_put_rcu(struct bpf_prog *prog);
+struct bpf_map *bpf_map_get(u32 ufd);
struct bpf_map *__bpf_map_get(struct fd f);
void bpf_map_put(struct bpf_map *map);
extern int sysctl_unprivileged_bpf_disabled;
+int bpf_map_new_fd(struct bpf_map *map);
+int bpf_prog_new_fd(struct bpf_prog *prog);
+
+int bpf_obj_pin_user(u32 ufd, const char __user *pathname);
+int bpf_obj_get_user(const char __user *pathname);
+
/* verify correctness of eBPF program */
int bpf_check(struct bpf_prog **fp, union bpf_attr *attr);
#else