On 9/25/23 15:58, Andrii Nakryiko wrote:
On Wed, Sep 20, 2023 at 9:00 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. + */we have attach_btf_obj_fd for BPF_PROG_LOAD command, so I guess consistent naming would be "<something>_btf_obj_fd" where <something> would make it more-or-less clear that this is BTF for btf_vmlinux_value_type_id?
Got it! I will rename it to value_type_btf_obj_fd.
}; 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 */Do we need these XXX: comments? I think you had some more in previous patches
Will be removed.
+ if (attr->mod_btf_fd) { + btf = btf_get_by_fd(attr->mod_btf_fd); + 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);should we make sure that module's BTF is put properly on error?
Yes, this issue has been addressed locally.
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 85c1d908f70f..fed3870fec7a 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 mod_btf_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 99b45501951c..11f85dbc911b 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_id, btf_vmlinux); + st_ops = bpf_struct_ops_find(btf_id, btf); 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..178d6fa45fa0 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/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 */ -- 2.34.1
