[PATCH RFC v2 net-next 11/16] bpf: allow eBPF programs to use maps
From: Alexei Starovoitov <hidden>
Date: 2014-07-18 04:20:54
Also in:
lkml, netdev
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
expose bpf_map_lookup_elem(), bpf_map_update_elem(), bpf_map_delete_elem() map accessors to eBPF programs Signed-off-by: Alexei Starovoitov <redacted> --- include/linux/bpf.h | 5 +++ include/uapi/linux/bpf.h | 3 ++ kernel/bpf/syscall.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 93 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index b5e90efddfcf..a7566afbe23b 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h@@ -128,4 +128,9 @@ struct sk_filter *bpf_prog_get(u32 ufd); /* verify correctness of eBPF program */ int bpf_check(struct sk_filter *fp); +/* in-kernel helper functions called from eBPF programs */ +u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5); +u64 bpf_map_update_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5); +u64 bpf_map_delete_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5); + #endif /* _LINUX_BPF_H */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 3f288e1d08f1..06e0f63055fb 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h@@ -377,6 +377,9 @@ enum bpf_prog_type { */ enum bpf_func_id { BPF_FUNC_unspec, + BPF_FUNC_map_lookup_elem, /* void *map_lookup_elem(map_id, void *key) */ + BPF_FUNC_map_update_elem, /* int map_update_elem(map_id, void *key, void *value) */ + BPF_FUNC_map_delete_elem, /* int map_delete_elem(map_id, void *key) */ __BPF_FUNC_MAX_ID, };
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 9d441f17548e..2d6e6a171594 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c@@ -741,3 +741,88 @@ SYSCALL_DEFINE5(bpf, int, cmd, unsigned long, arg2, unsigned long, arg3, return -EINVAL; } } + +/* called from eBPF program under rcu lock + * + * if kernel subsystem is allowing eBPF programs to call this function, + * inside its own verifier_ops->get_func_proto() callback it should return + * (struct bpf_func_proto) { + * .ret_type = PTR_TO_MAP_CONDITIONAL, + * .arg1_type = CONST_ARG_MAP_ID, + * .arg2_type = PTR_TO_STACK_IMM_MAP_KEY, + * } + * so that eBPF verifier properly checks the arguments + */ +u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) +{ + struct bpf_map *map; + int map_id = r1; + void *key = (void *) (unsigned long) r2; + void *value; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + map = idr_find(&bpf_map_id_idr, map_id); + /* eBPF verifier guarantees that map_id is valid for the life of + * the program + */ + BUG_ON(!map); + + value = map->ops->map_lookup_elem(map, key); + + return (unsigned long) value; +} + +/* called from eBPF program under rcu lock + * + * if kernel subsystem is allowing eBPF programs to call this function, + * inside its own verifier_ops->get_func_proto() callback it should return + * (struct bpf_func_proto) { + * .ret_type = RET_INTEGER, + * .arg1_type = CONST_ARG_MAP_ID, + * .arg2_type = PTR_TO_STACK_IMM_MAP_KEY, + * .arg3_type = PTR_TO_STACK_IMM_MAP_VALUE, + * } + * so that eBPF verifier properly checks the arguments + */ +u64 bpf_map_update_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) +{ + struct bpf_map *map; + int map_id = r1; + void *key = (void *) (unsigned long) r2; + void *value = (void *) (unsigned long) r3; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + map = idr_find(&bpf_map_id_idr, map_id); + /* eBPF verifier guarantees that map_id is valid */ + BUG_ON(!map); + + return map->ops->map_update_elem(map, key, value); +} + +/* called from eBPF program under rcu lock + * + * if kernel subsystem is allowing eBPF programs to call this function, + * inside its own verifier_ops->get_func_proto() callback it should return + * (struct bpf_func_proto) { + * .ret_type = RET_INTEGER, + * .arg1_type = CONST_ARG_MAP_ID, + * .arg2_type = PTR_TO_STACK_IMM_MAP_KEY, + * } + * so that eBPF verifier properly checks the arguments + */ +u64 bpf_map_delete_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) +{ + struct bpf_map *map; + int map_id = r1; + void *key = (void *) (unsigned long) r2; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + map = idr_find(&bpf_map_id_idr, map_id); + /* eBPF verifier guarantees that map_id is valid */ + BUG_ON(!map); + + return map->ops->map_delete_elem(map, key); +}
--
1.7.9.5