From: Kui-Feng Lee <thinker.li@xxxxxxxxx>
Every kernel module has its BTF, comprising information on types defined in
the module. The BTF fd (attr->value_type_btf_obj_fd) passed from userspace
helps the bpf_struct_ops to lookup type information and description of the
struct_ops type, which is necessary for parsing the layout of map element
values and registering maps. The descriptions are looked up by matching a
type id (attr->btf_vmlinux_value_type_id) against bpf_struct_ops_desc(s)
defined in a BTF. If the struct_ops type is defined in a module, the
bpf_struct_ops needs to know the module BTF to lookup the
bpf_struct_ops_desc.
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/linux/bpf_verifier.h | 1 +
include/uapi/linux/bpf.h | 5 +++++
kernel/bpf/bpf_struct_ops.c | 36 +++++++++++++++++++++++++---------
kernel/bpf/syscall.c | 2 +-
kernel/bpf/verifier.c | 19 +++++++++++++++---
tools/include/uapi/linux/bpf.h | 5 +++++
6 files changed, 55 insertions(+), 13 deletions(-)
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 24213a99cc79..c1461342f19e 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -598,6 +598,7 @@ struct bpf_verifier_env {
u32 prev_insn_idx;
struct bpf_prog *prog; /* eBPF program being verified */
const struct bpf_verifier_ops *ops;
+ struct module *attach_btf_mod; /* The owner module of prog->aux->attach_btf */
struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
int stack_size; /* number of states to be processed */
bool strict_alignment; /* perform strict pointer alignment checks */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 0f6cdf52b1da..fd20c52606b2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1398,6 +1398,11 @@ 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 bc855b2ef97e..2d853431bf09 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->btf);
bpf_map_area_free(st_map);
}
@@ -718,16 +719,31 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
const struct btf_type *t, *vt;
struct module *mod = NULL;
struct bpf_map *map;
+ struct btf *btf;
int ret;
- st_ops_desc = bpf_struct_ops_find_value(btf_vmlinux, attr->btf_vmlinux_value_type_id);
- if (!st_ops_desc)
- return ERR_PTR(-ENOTSUPP);
+ if (attr->value_type_btf_obj_fd) {
+ /* The map holds btf for its whole life time. */
+ btf = btf_get_by_fd(attr->value_type_btf_obj_fd);
+ if (IS_ERR(btf))
+ return ERR_PTR(PTR_ERR(btf));
+
+ if (btf != btf_vmlinux) {
+ mod = btf_try_get_module(btf);
+ if (!mod) {
+ ret = -EINVAL;
+ goto errout;
+ }
+ }
+ } else {
+ btf = btf_vmlinux;
+ btf_get(btf);
+ }
- if (st_ops_desc->btf != btf_vmlinux) {
- mod = btf_try_get_module(st_ops_desc->btf);
- if (!mod)
- return ERR_PTR(-EINVAL);
+ st_ops_desc = bpf_struct_ops_find_value(btf, attr->btf_vmlinux_value_type_id);
+ if (!st_ops_desc) {
+ ret = -ENOTSUPP;
+ goto errout;
}
vt = st_ops_desc->value_type;
@@ -750,6 +766,7 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
goto errout;
}
+ st_map->btf = btf;
st_map->st_ops_desc = st_ops_desc;
map = &st_map->map;
@@ -776,8 +793,6 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
goto errout_free;
}
- st_map->btf = btf_vmlinux;
-
mutex_init(&st_map->lock);
set_vm_flush_reset_perms(st_map->image);
bpf_map_init_from_attr(map, attr);
@@ -788,8 +803,11 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
errout_free:
__bpf_struct_ops_map_free(map);
+ btf = NULL; /* has been released */
errout:
+ btf_put(btf);
module_put(mod);
+
return ERR_PTR(ret);
}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0ed286b8a0f0..974651fe2bee 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1096,7 +1096,7 @@ 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 bdd166cab977..20d6d9665983 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -20086,6 +20086,7 @@ 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) {
@@ -20093,8 +20094,18 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
return -EINVAL;
}
+ btf = prog->aux->attach_btf;
+ if (btf != btf_vmlinux) {
+ /* Make sure st_ops is valid through the lifetime of env */
+ env->attach_btf_mod = btf_try_get_module(btf);
+ if (!env->attach_btf_mod) {
+ verbose(env, "owner module of btf is not found\n");
+ return -ENOTSUPP;
+ }
+ }
+
btf_id = prog->aux->attach_btf_id;
- st_ops_desc = bpf_struct_ops_find(btf_vmlinux, btf_id);
+ st_ops_desc = bpf_struct_ops_find(btf, btf_id);
if (!st_ops_desc) {
verbose(env, "attach_btf_id %u is not a supported struct\n",
btf_id);
@@ -20111,8 +20122,8 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
}
member = &btf_type_member(t)[member_idx];
- mname = btf_name_by_offset(btf_vmlinux, member->name_off);
- func_proto = btf_type_resolve_func_ptr(btf_vmlinux, member->type,
+ mname = btf_name_by_offset(btf, member->name_off);
+ func_proto = btf_type_resolve_func_ptr(btf, member->type,
NULL);
if (!func_proto) {
verbose(env, "attach to invalid member %s(@idx %u) of struct %s\n",
@@ -20805,6 +20816,8 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr, __u3
env->prog->expected_attach_type = 0;
*prog = env->prog;
+
+ module_put(env->attach_btf_mod);
err_unlock:
if (!is_priv)
mutex_unlock(&bpf_verifier_lock);
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 0f6cdf52b1da..fd20c52606b2 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -1398,6 +1398,11 @@ 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
