Bug#996852: "Error: failed to load BTF from ./fat: Invalid argument"

[Salvatore Bonaccorso <carnil@debian.org>]

Control: tags -1 + upstream

Hi Philipp,

On Tue, Oct 19, 2021 at 05:59:41PM +0200, Philipp Marek wrote:
> Package: bpftool
> Version: 5.14.12-1
> Severity: minor
> X-Debbugs-Cc: philipp@marek.priv.at
> 
> Using an absolute path, I get output:
> 
>     [/sys/kernel/btf]$ bpftool btf dump file $PWD/fat | head -2
>     [85705] STRUCT 'fat_mount_options' size=48 vlen=27
>             'fs_uid' type_id=506 bits_offset=0
>     [/sys/kernel/btf]$ bpftool btf dump file $PWD/fat | wc
>         685    2274   25834
> 
> Using a relative path, "bpftool btf dump" doesn't work:
> 
>     [/sys/kernel/btf]$ bpftool btf dump file ./fat
>     Error: failed to load BTF from ./fat: Invalid argument
> 
> 
> "strace" shows that with a full path "bpftool" reads
> "/sys/kernel/btf/vmlinux", but doesn't even try to find that in the
> second case.
> 
> Dumping "vmlinux" works with a relative path,
> I guess because it's self-contained.
> 
> 
> Copying "fat" and "vmlinux" to /tmp/ and using a relative or absolute
> path works for "vmlinux", but not "fat".
> 
> I think it would be great if a relative path would just be translated
> to absolute when needed, or that required files would be searched via
> some path list (configurable via environment, like $PATH or
> $LD_LIBRARY_PATH etc.?).

Can you please report this directly to upstream
(scripts/get_maintainer.pl can help to get who to contact) and once
the upstream report is done, reference it here please?

Regards,
Salvatore