On Fri, Sep 13, 2024 at 08:16:27PM +0800, Tao Chen wrote:
> The commit "5902da6d8a52" set expected_attach_type again with
> filed of bpf_program after libpf_prepare_prog_load, which makes
> expected_attach_type = 0 no sense when kenrel not support the
> attach_type feature, so fix it.
>
> Fixes: 5902da6d8a52 ("libbpf: Add uprobe multi link support to bpf_program__attach_usdt")
> Signed-off-by: Tao Chen <chen.dylane@xxxxxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 219facd0e66e..9035edf763a3 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -7343,7 +7343,7 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog,
>
> /* old kernels might not support specifying expected_attach_type */
> if ((def & SEC_EXP_ATTACH_OPT) && !kernel_supports(prog->obj, FEAT_EXP_ATTACH_TYPE))
> - opts->expected_attach_type = 0;
> + prog->expected_attach_type = 0;
>
> if (def & SEC_SLEEPABLE)
> opts->prog_flags |= BPF_F_SLEEPABLE;
> --
> 2.25.1
>
good catch! thanks
I can't remember why it was needed, perhaps we should go back to where it
was before?
I'm guessing prog->expected_attach_type might not get updated properly and
that might cause issues, not sure
thanks,
jirka
---
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 219facd0e66e..df2244397ba1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -7353,7 +7353,7 @@ static int libbpf_prepare_prog_load(struct bpf_program *prog,
/* special check for usdt to use uprobe_multi link */
if ((def & SEC_USDT) && kernel_supports(prog->obj, FEAT_UPROBE_MULTI_LINK))
- prog->expected_attach_type = BPF_TRACE_UPROBE_MULTI;
+ opts->expected_attach_type = BPF_TRACE_UPROBE_MULTI;
if ((def & SEC_ATTACH_BTF) && !prog->attach_btf_id) {
int btf_obj_fd = 0, btf_type_id = 0, err;
@@ -7443,6 +7443,7 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
load_attr.attach_btf_id = prog->attach_btf_id;
load_attr.kern_version = kern_version;
load_attr.prog_ifindex = prog->prog_ifindex;
+ load_attr.expected_attach_type = prog->expected_attach_type;
/* specify func_info/line_info only if kernel supports them */
if (obj->btf && btf__fd(obj->btf) >= 0 && kernel_supports(obj, FEAT_BTF_FUNC)) {
@@ -7474,9 +7475,6 @@ static int bpf_object_load_prog(struct bpf_object *obj, struct bpf_program *prog
insns_cnt = prog->insns_cnt;
}
- /* allow prog_prepare_load_fn to change expected_attach_type */
- load_attr.expected_attach_type = prog->expected_attach_type;
-
if (obj->gen_loader) {
bpf_gen__prog_load(obj->gen_loader, prog->type, prog->name,
license, insns, insns_cnt, &load_attr,
