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libbpf: Support modules in bpf_program__set_attach_target() API

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Support finding kernel targets in kernel modules when using
bpf_program__set_attach_target() API. This brings it up to par with what
libbpf supports when doing declarative SEC()-based target determination.

Some minor internal refactoring was needed to make sure vmlinux BTF can be
loaded before bpf_object's load phase.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20201211215825.3646154-2-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2020-12-11 13:58:24 -08:00 committed by Daniel Borkmann
parent b4fe9fec51
commit fe62de310e
1 changed files with 40 additions and 24 deletions
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64
tools/lib/bpf/libbpf.c
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@ -2518,7 +2518,7 @@ static int bpf_object__finalize_btf(struct bpf_object *obj)
return 0;
}
static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
static bool prog_needs_vmlinux_btf(struct bpf_program *prog)
{
if (prog->type == BPF_PROG_TYPE_STRUCT_OPS ||
prog->type == BPF_PROG_TYPE_LSM)
@ -2533,37 +2533,43 @@ static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
return false;
}
static int bpf_object__load_vmlinux_btf(struct bpf_object *obj)
static bool obj_needs_vmlinux_btf(const struct bpf_object *obj)
{
bool need_vmlinux_btf = false;
struct bpf_program *prog;
int i, err;
int i;
/* CO-RE relocations need kernel BTF */
if (obj->btf_ext && obj->btf_ext->core_relo_info.len)
need_vmlinux_btf = true;
return true;
/* Support for typed ksyms needs kernel BTF */
for (i = 0; i < obj->nr_extern; i++) {
const struct extern_desc *ext;
ext = &obj->externs[i];
if (ext->type == EXT_KSYM && ext->ksym.type_id) {
need_vmlinux_btf = true;
break;
}
if (ext->type == EXT_KSYM && ext->ksym.type_id)
return true;
}
bpf_object__for_each_program(prog, obj) {
if (!prog->load)
continue;
if (libbpf_prog_needs_vmlinux_btf(prog)) {
need_vmlinux_btf = true;
break;
}
if (prog_needs_vmlinux_btf(prog))
return true;
}
if (!need_vmlinux_btf)
return false;
}
static int bpf_object__load_vmlinux_btf(struct bpf_object *obj, bool force)
{
int err;
/* btf_vmlinux could be loaded earlier */
if (obj->btf_vmlinux)
return 0;
if (!force && !obj_needs_vmlinux_btf(obj))
return 0;
obj->btf_vmlinux = libbpf_find_kernel_btf();
@ -7475,7 +7481,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
}
err = bpf_object__probe_loading(obj);
err = err ? : bpf_object__load_vmlinux_btf(obj);
err = err ? : bpf_object__load_vmlinux_btf(obj, false);
err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
err = err ? : bpf_object__sanitize_and_load_btf(obj);
err = err ? : bpf_object__sanitize_maps(obj);
@ -10870,23 +10876,33 @@ int bpf_program__set_attach_target(struct bpf_program *prog,
int attach_prog_fd,
const char *attach_func_name)
{
int btf_id;
int btf_obj_fd = 0, btf_id = 0, err;
if (!prog || attach_prog_fd < 0 || !attach_func_name)
return -EINVAL;
if (attach_prog_fd)
if (prog->obj->loaded)
return -EINVAL;
if (attach_prog_fd) {
btf_id = libbpf_find_prog_btf_id(attach_func_name,
attach_prog_fd);
else
btf_id = libbpf_find_vmlinux_btf_id(attach_func_name,
prog->expected_attach_type);
if (btf_id < 0)
return btf_id;
if (btf_id < 0)
return btf_id;
} else {
/* load btf_vmlinux, if not yet */
err = bpf_object__load_vmlinux_btf(prog->obj, true);
if (err)
return err;
err = find_kernel_btf_id(prog->obj, attach_func_name,
prog->expected_attach_type,
&btf_obj_fd, &btf_id);
if (err)
return err;
}
prog->attach_btf_id = btf_id;
prog->attach_btf_obj_fd = 0;
prog->attach_btf_obj_fd = btf_obj_fd;
prog->attach_prog_fd = attach_prog_fd;
return 0;
}