expose bpf_map_lookup_elem(), bpf_map_update_elem(), bpf_map_delete_elem() map accessors to eBPF programs
Signed-off-by: Alexei Starovoitov <a...@plumgrid.com> --- Note, these helpers are exposed as '.gpl_only = false', so non-GPL eBPF programs can use them. That was requested by AndyL and DavidL before. include/linux/bpf.h | 5 +++ include/uapi/linux/bpf.h | 3 ++ kernel/bpf/Makefile | 2 +- kernel/bpf/helpers.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 97 insertions(+), 1 deletion(-) create mode 100644 kernel/bpf/helpers.c diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 51e9242e4803..75e94eaa228b 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -133,4 +133,9 @@ struct bpf_prog *bpf_prog_get(u32 ufd); /* verify correctness of eBPF program */ int bpf_check(struct bpf_prog *fp, union bpf_attr *attr); +/* verifier prototypes for helper functions called from eBPF programs */ +extern struct bpf_func_proto bpf_map_lookup_elem_proto; +extern struct bpf_func_proto bpf_map_update_elem_proto; +extern struct bpf_func_proto bpf_map_delete_elem_proto; + #endif /* _LINUX_BPF_H */ diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 9811d012b766..84a7fc3a23ec 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -160,6 +160,9 @@ union bpf_attr { */ enum bpf_func_id { BPF_FUNC_unspec, + BPF_FUNC_map_lookup_elem, /* void *map_lookup_elem(&map, &key) */ + BPF_FUNC_map_update_elem, /* int map_update_elem(&map, &key, &value, flags) */ + BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */ __BPF_FUNC_MAX_ID, }; diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index 72ec98ba2d42..a5ae60f0b0a2 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -1,5 +1,5 @@ obj-y := core.o -obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o hashtab.o arraymap.o +obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o hashtab.o arraymap.o helpers.o ifdef CONFIG_TEST_BPF obj-$(CONFIG_BPF_SYSCALL) += test_stub.o endif diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c new file mode 100644 index 000000000000..3fa78babe728 --- /dev/null +++ b/kernel/bpf/helpers.c @@ -0,0 +1,88 @@ +/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + */ +#include <linux/bpf.h> +#include <linux/rcupdate.h> + +/* 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 + * bpf_map_lookup_elem_proto, so that verifier can properly checks the arguments + */ +static u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) +{ + /* verifier checked that R1 contains a valid pointer to bpf_map + * and R2 points to a program stack and map->key_size bytes were + * initialized + */ + struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; + void *key = (void *) (unsigned long) r2; + void *value; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + value = map->ops->map_lookup_elem(map, key); + + /* lookup() returns either pointer to element value or NULL + * which is the meaning of PTR_TO_MAP_VALUE_OR_NULL type + */ + return (unsigned long) value; +} + +struct bpf_func_proto bpf_map_lookup_elem_proto = { + .func = bpf_map_lookup_elem, + .gpl_only = false, + .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL, + .arg1_type = ARG_CONST_MAP_PTR, + .arg2_type = ARG_PTR_TO_MAP_KEY, +}; + +/* called from eBPF program under rcu lock */ +static u64 bpf_map_update_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) +{ + struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; + void *key = (void *) (unsigned long) r2; + void *value = (void *) (unsigned long) r3; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + return map->ops->map_update_elem(map, key, value, r4); +} + +struct bpf_func_proto bpf_map_update_elem_proto = { + .func = bpf_map_update_elem, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_CONST_MAP_PTR, + .arg2_type = ARG_PTR_TO_MAP_KEY, + .arg3_type = ARG_PTR_TO_MAP_VALUE, + .arg4_type = ARG_ANYTHING, +}; + +/* called from eBPF program under rcu lock */ +static u64 bpf_map_delete_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) +{ + struct bpf_map *map = (struct bpf_map *) (unsigned long) r1; + void *key = (void *) (unsigned long) r2; + + WARN_ON_ONCE(!rcu_read_lock_held()); + + return map->ops->map_delete_elem(map, key); +} + +struct bpf_func_proto bpf_map_delete_elem_proto = { + .func = bpf_map_delete_elem, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_CONST_MAP_PTR, + .arg2_type = ARG_PTR_TO_MAP_KEY, +}; -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/