Messages in this thread Patch in this message | | | Date | Sun, 29 Jul 2018 13:58:35 -0700 | Subject | [PATCH v3] Add BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES bpf(2) command | From | Daniel Colascione <> |
| |
BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES waits for the release of all references to maps active at the instant the BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES is issued. BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES waits only for the expiration of map references obtained by BPF programs from other maps.
The purpose of this command is to provide a means for userspace to replace a BPF map with another, newer version, then ensure that no component is still using the "old" map before manipulating the "old" map in some way.
Signed-off-by: Daniel Colascione <dancol@google.com> --- include/uapi/linux/bpf.h | 14 ++++++++++++++ kernel/bpf/syscall.c | 13 +++++++++++++ 2 files changed, 27 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index b7db3261c62d..ca3cfca76edc 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -75,6 +75,19 @@ struct bpf_lpm_trie_key { __u8 data[0]; /* Arbitrary size */ }; +/* BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES waits for the release of all + * references to maps active at the instant the + * BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES is + * issued. BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES waits only for the + * expiration of map references obtained by BPF programs from + * other maps. + * + * The purpose of this command is to provide a means for userspace to + * replace a BPF map with another, newer version, then ensure that no + * component is still using the "old" map before manipulating the + * "old" map in some way. + */ + /* BPF syscall commands, see bpf(2) man-page for details. */ enum bpf_cmd { BPF_MAP_CREATE, @@ -98,6 +111,7 @@ enum bpf_cmd { BPF_BTF_LOAD, BPF_BTF_GET_FD_BY_ID, BPF_TASK_FD_QUERY, + BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES, }; enum bpf_map_type { diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index a31a1ba0f8ea..bc9a0713f47d 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2274,6 +2274,19 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) return -EPERM; + if (cmd == BPF_SYNCHRONIZE_MAP_TO_MAP_REFERENCES) { + if (uattr != NULL || size != 0) + return -EINVAL; + err = security_bpf(cmd, NULL, 0); + if (err < 0) + return err; + /* BPF programs always enter a critical section while + * they have a map reference outstanding. + */ + synchronize_rcu(); + return 0; + } + err = bpf_check_uarg_tail_zero(uattr, sizeof(attr), size); if (err) return err; -- 2.18.0.345.g5c9ce644c3-goog
| |