linux-kernel - Re: [PATCH] libbpf: fix multi-uprobe attach not working with dynamic symbols

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Message-ID: <Z-5Yq5q8ddkJUO0k@krava>
Date: Thu, 3 Apr 2025 11:45:15 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Mateusz Bieganski <bieganski.gm@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>,
	"open list:BPF [LIBRARY] (libbpf)" <bpf@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] libbpf: fix multi-uprobe attach not working with dynamic
 symbols

On Fri, Mar 28, 2025 at 11:14:54AM -0700, Andrii Nakryiko wrote:
> On Thu, Mar 27, 2025 at 3:08 AM Mateusz Bieganski
> <bieganski.gm@...il.com> wrote:
> >
> > ENOENT is incorrectly propagated to caller, if requested symbol is
> > present in dynamic linker symbol table and not present in symbol table.
> >
> > Signed-off-by: Mateusz Bieganski <bieganski.gm@...il.com>
> > ---
> >  tools/lib/bpf/elf.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c
> > index 823f83ad819c..41839ef5bc97 100644
> > --- a/tools/lib/bpf/elf.c
> > +++ b/tools/lib/bpf/elf.c
> > @@ -439,8 +439,10 @@ int elf_resolve_syms_offsets(const char *binary_path, int cnt,
> >                 struct elf_sym *sym;
> >
> >                 err = elf_sym_iter_new(&iter, elf_fd.elf, binary_path, sh_types[i], st_type);
> > -               if (err == -ENOENT)
> > +               if (err == -ENOENT) {
> > +                       err = 0;
> >                         continue;
> > +               }
> 
> Don't we have the same problem in elf_resolve_pattern_offsets() as
> well? Can you please fix both issues in one go?
> 
> It seems it's only elf_find_func_offset() that do want to preserve
> that -ENOENT, all others are just error-prone implementations.

+1, thanks for the fix

jirka

> 
> pw-bot: cr
> 
> >                 if (err)
> >                         goto out;
> >
> > --
> > 2.39.5
> >