From: Kui-Feng Lee <thinker.li@xxxxxxxxx>
Giving a BTF, the bpf_struct_ops knows the right place to look up type info
associated with a type ID. This enables a user space program to load a
struct_ops object linked to a struct_ops type defined by a module, by
providing the module BTF (fd).
The bpf_prog includes attach_btf in aux which is passed along with the
bpf_attr when loading the program. The purpose of attach_btf is to
determine the btf type of attach_btf_id. The attach_btf_id is then used to
identify the traced function for a trace program. In the case of struct_ops
programs, it is used to identify the struct_ops type of the struct_ops
object that a program is attached to.
Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
---
include/uapi/linux/bpf.h | 5 +++++
kernel/bpf/bpf_struct_ops.c | 34 +++++++++++++++++++++++++++-------
kernel/bpf/syscall.c | 2 +-
kernel/bpf/verifier.c | 4 +++-
tools/include/uapi/linux/bpf.h | 5 +++++
5 files changed, 41 insertions(+), 9 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 73b155e52204..b5ef22f65f35 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1390,6 +1390,11 @@ union bpf_attr {
* to using 5 hash functions).
*/
__u64 map_extra;
+
+ __u32 value_type_btf_obj_fd; /* fd pointing to a BTF
+ * type data for
+ * btf_vmlinux_value_type_id.
+ */
};
struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 69703584fa4a..60445ff32275 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -677,6 +677,7 @@ static void __bpf_struct_ops_map_free(struct bpf_map *map)
bpf_jit_uncharge_modmem(PAGE_SIZE);
}
bpf_map_area_free(st_map->uvalue);
+ btf_put(st_map->st_ops->btf);
module_put(st_map->st_ops->owner);
bpf_map_area_free(st_map);
}
@@ -718,23 +719,36 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
struct bpf_struct_ops_map *st_map;
const struct btf_type *t, *vt;
struct bpf_map *map;
+ struct btf *btf;
int ret;
- st_ops = bpf_struct_ops_find_value(btf_vmlinux, attr->btf_vmlinux_value_type_id);
- if (!st_ops)
+ if (attr->value_type_btf_obj_fd) {
+ btf = btf_get_by_fd(attr->value_type_btf_obj_fd);
+ if (IS_ERR(btf))
+ return ERR_PTR(PTR_ERR(btf));
+ } else {
+ btf = btf_vmlinux;
+ btf_get(btf);
+ }
+ st_ops = bpf_struct_ops_find_value(btf, attr->btf_vmlinux_value_type_id);
+ if (!st_ops) {
+ btf_put(btf);
return ERR_PTR(-ENOTSUPP);
+ }
/* If st_ops->owner is NULL, it means the struct_ops is
* statically defined in the kernel. We don't need to
* take a refcount on it.
*/
- if (st_ops->owner && !btf_try_get_module(st_ops->btf))
+ if (st_ops->owner && !btf_try_get_module(st_ops->btf)) {
+ btf_put(btf);
return ERR_PTR(-EINVAL);
+ }
vt = st_ops->value_type;
if (attr->value_size != vt->size) {
- module_put(st_ops->owner);
- return ERR_PTR(-EINVAL);
+ ret = -EINVAL;
+ goto errout;
}
t = st_ops->type;
@@ -747,8 +761,8 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);
if (!st_map) {
- module_put(st_ops->owner);
- return ERR_PTR(-ENOMEM);
+ ret = -ENOMEM;
+ goto errout;
}
st_map->st_ops = st_ops;
@@ -784,6 +798,12 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
bpf_map_init_from_attr(map, attr);
return map;
+
+errout:
+ btf_put(btf);
+ module_put(st_ops->owner);
+
+ return ERR_PTR(ret);
}
static u64 bpf_struct_ops_map_mem_usage(const struct bpf_map *map)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 85c1d908f70f..5daf8a2c2bba 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1097,7 +1097,7 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf,
return ret;
}
-#define BPF_MAP_CREATE_LAST_FIELD map_extra
+#define BPF_MAP_CREATE_LAST_FIELD value_type_btf_obj_fd
/* called via syscall */
static int map_create(union bpf_attr *attr)
{
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6564a03c425d..ce4df24eb03b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19623,6 +19623,7 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
const struct btf_member *member;
struct bpf_prog *prog = env->prog;
u32 btf_id, member_idx;
+ struct btf *btf;
const char *mname;
if (!prog->gpl_compatible) {
@@ -19630,8 +19631,9 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
return -EINVAL;
}
+ btf = prog->aux->attach_btf;
btf_id = prog->aux->attach_btf_id;
- st_ops = bpf_struct_ops_find(btf_vmlinux, btf_id);
+ st_ops = bpf_struct_ops_find(btf, btf_id);
if (!st_ops) {
verbose(env, "attach_btf_id %u is not a supported struct\n",
btf_id);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 73b155e52204..b5ef22f65f35 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1390,6 +1390,11 @@ union bpf_attr {
* to using 5 hash functions).
*/
__u64 map_extra;
+
+ __u32 value_type_btf_obj_fd; /* fd pointing to a BTF
+ * type data for
+ * btf_vmlinux_value_type_id.
+ */
};
struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */
--
2.34.1
