Messages in this thread Patch in this message | | | Date | Thu, 26 Jul 2018 09:51:05 -0700 | Subject | [PATCH v2] Add BPF_SYNCHRONIZE_MAPS bpf(2) command | From | Daniel Colascione <> |
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BPF_SYNCHRONIZE_MAPS waits for the release of any references to a BPF map made by a BPF program that is running at the time the BPF_SYNCHRONIZE_MAPS command is issued. 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 | 9 +++++++++ kernel/bpf/syscall.c | 13 +++++++++++++ 2 files changed, 22 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index b7db3261c62d..5b27e9117d3e 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -75,6 +75,14 @@ struct bpf_lpm_trie_key { __u8 data[0]; /* Arbitrary size */ }; +/* BPF_SYNCHRONIZE_MAPS waits for the release of any references to a + * BPF map made by a BPF program that is running at the time the + * BPF_SYNCHRONIZE_MAPS command is issued. 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 +106,7 @@ enum bpf_cmd { BPF_BTF_LOAD, BPF_BTF_GET_FD_BY_ID, BPF_TASK_FD_QUERY, + BPF_SYNCHRONIZE_MAPS, }; enum bpf_map_type { diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index a31a1ba0f8ea..8bbd1a5d01d1 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_MAPS) { + 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; -- 2.18.0.233.g985f88cf7e-goog
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