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authorDaniel Borkmann <daniel@iogearbox.net>2015-10-29 16:58:09 +0300
committerDavid S. Miller <davem@davemloft.net>2015-11-03 06:48:39 +0300
commitb2197755b2633e164a439682fb05a9b5ea48f706 (patch)
tree71d9694754b0e4511e7cec0c2f57c130e96e71fb /include/uapi
parente9d8afa90b789b07d414637ab557d169d6b2b84e (diff)
downloadlinux-b2197755b2633e164a439682fb05a9b5ea48f706.tar.xz
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/uapi')
-rw-r--r--include/uapi/linux/bpf.h45
-rw-r--r--include/uapi/linux/magic.h1
2 files changed, 9 insertions, 37 deletions
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2e032426cfb7..9ea2d22fa2cb 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -63,50 +63,16 @@ struct bpf_insn {
__s32 imm; /* signed immediate constant */
};
-/* BPF syscall commands */
+/* BPF syscall commands, see bpf(2) man-page for details. */
enum bpf_cmd {
- /* create a map with given type and attributes
- * fd = bpf(BPF_MAP_CREATE, union bpf_attr *, u32 size)
- * returns fd or negative error
- * map is deleted when fd is closed
- */
BPF_MAP_CREATE,
-
- /* lookup key in a given map
- * err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)
- * Using attr->map_fd, attr->key, attr->value
- * returns zero and stores found elem into value
- * or negative error
- */
BPF_MAP_LOOKUP_ELEM,
-
- /* create or update key/value pair in a given map
- * err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)
- * Using attr->map_fd, attr->key, attr->value, attr->flags
- * returns zero or negative error
- */
BPF_MAP_UPDATE_ELEM,
-
- /* find and delete elem by key in a given map
- * err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)
- * Using attr->map_fd, attr->key
- * returns zero or negative error
- */
BPF_MAP_DELETE_ELEM,
-
- /* lookup key in a given map and return next key
- * err = bpf(BPF_MAP_GET_NEXT_KEY, union bpf_attr *attr, u32 size)
- * Using attr->map_fd, attr->key, attr->next_key
- * returns zero and stores next key or negative error
- */
BPF_MAP_GET_NEXT_KEY,
-
- /* verify and load eBPF program
- * prog_fd = bpf(BPF_PROG_LOAD, union bpf_attr *attr, u32 size)
- * Using attr->prog_type, attr->insns, attr->license
- * returns fd or negative error
- */
BPF_PROG_LOAD,
+ BPF_OBJ_PIN,
+ BPF_OBJ_GET,
};
enum bpf_map_type {
@@ -160,6 +126,11 @@ union bpf_attr {
__aligned_u64 log_buf; /* user supplied buffer */
__u32 kern_version; /* checked when prog_type=kprobe */
};
+
+ struct { /* anonymous struct used by BPF_OBJ_* commands */
+ __aligned_u64 pathname;
+ __u32 bpf_fd;
+ };
} __attribute__((aligned(8)));
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index 7b1425a6b370..accb036bbc9c 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -75,5 +75,6 @@
#define ANON_INODE_FS_MAGIC 0x09041934
#define BTRFS_TEST_MAGIC 0x73727279
#define NSFS_MAGIC 0x6e736673
+#define BPF_FS_MAGIC 0xcafe4a11
#endif /* __LINUX_MAGIC_H__ */