On 9/20/23 8:59 AM, thinker.li@xxxxxxxxx wrote:
From: Kui-Feng Lee <thinker.li@xxxxxxxxx>
The type info of a struct_ops type may be in a module. So, we need to know
which module BTF to look for type information. The later patches will make
libbpf to attach module BTFs to programs. This patch passes attached BTF
from syscall to bpf_struct_ops subsystem to make sure attached BTF is
available when the bpf_struct_ops subsystem is ready to use it.
bpf_prog has attach_btf in aux from attach_btf_obj_fd, that is pass along
with the bpf_attr loading the program. attach_btf is used to find the btf
type of attach_btf_id. attach_btf_id is used to identify the traced
function for a trace program. For struct_ops programs, it is used to
identify the struct_ops type of the struct_ops object a program attached
to.
Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx>
---
include/uapi/linux/bpf.h | 4 ++++
kernel/bpf/bpf_struct_ops.c | 12 +++++++++++-
kernel/bpf/syscall.c | 2 +-
kernel/bpf/verifier.c | 4 +++-
tools/include/uapi/linux/bpf.h | 4 ++++
5 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 73b155e52204..178d6fa45fa0 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1390,6 +1390,10 @@ union bpf_attr {
* to using 5 hash functions).
*/
__u64 map_extra;
+
+ __u32 mod_btf_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 8b5c859377e9..d5600d9ad302 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -765,9 +765,19 @@ 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(attr->btf_vmlinux_value_type_id, btf_vmlinux);
+ /* XXX: We need a module name or ID to find a BTF type. */
+ /* XXX: should use btf from attr->btf_fd */
+ if (attr->mod_btf_fd) {
+ btf = btf_get_by_fd(attr->mod_btf_fd);
The btf is leaked in all cases because it is not stored (and owned) in st_map
during map_alloc. This circle back to the earlier comment in patch 4 about where
btf is stored.
+ if (IS_ERR(btf))
+ return ERR_PTR(PTR_ERR(btf));
+ } else {
+ btf = btf_vmlinux;
+ }
+ st_ops = bpf_struct_ops_find_value(attr->btf_vmlinux_value_type_id, btf);
if (!st_ops)
return ERR_PTR(-ENOTSUPP);
