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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org, Jiri Benc <jbenc@redhat.com>
Subject: Reason for libbpf rejecting SECTION symbols in 'maps' section
Date: Fri, 24 Sep 2021 18:49:10 +0200	[thread overview]
Message-ID: <87wnn5yl4p.fsf@toke.dk> (raw)

Hi Andrii

We ran into an issue with binutils[0] mangling BPF object files, which
makes libbpf sad. Specifically, binutils will create SECTION symbols for
every section in .symtab, which trips this check in
bpf_object__init_user_maps():

if (GELF_ST_TYPE(sym.st_info) == STT_SECTION
    || GELF_ST_BIND(sym.st_info) == STB_LOCAL) {
	pr_warn("map '%s' (legacy): static maps are not supported\n", map_name);
	return -ENOTSUP;
}

Given the error message I can understand why it's checking for
STB_LOCAL, but why is the check for STT_SECTION there? And is there any
reason why libbpf couldn't just skip the SECTION symbols instead of
bugging out?

Hope you can help shed some light on the history here.

-Toke


[0] This happens because rpmbuild has a script that automatically that
runs 'strip' on every object file in an rpm; and so when we package up
the kernel selftests, we end up with mangled object files. Newer
versions of binutils don't do this, but the one on RHEL does.


             reply	other threads:[~2021-09-24 16:49 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-24 16:49 Toke Høiland-Jørgensen [this message]
2021-09-24 23:52 ` Reason for libbpf rejecting SECTION symbols in 'maps' section Andrii Nakryiko
2021-09-25  9:19   ` Toke Høiland-Jørgensen

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