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From: Tony Ambardar <tony.ambardar@gmail.com>
To: bpf@vger.kernel.org, dwarves@vger.kernel.org
Subject: Problem with endianess of pahole BTF output for vmlinux
Date: Sat, 5 Sep 2020 21:16:23 -0700
Message-ID: <CAPGftE8ipAacAnm9xMHFabXCL-XrCXGmOsX-Nsjvz9wnh3Zx-w@mail.gmail.com> (raw)

Hello,

I'm using GCC 8.4.0, binutils 2.34 and pahole 1.17, compiling on an
Ubuntu/x86_64 host and targeting both little- and big-endian mips
running on malta/qemu. When cross-compiling Linux 5.4.x LTS and
testing bpftool/BTF functionality on the target, I encounter errors on
big-endian targets:

> root@OpenWrt:/# bpftool btf dump file /sys/kernel/btf/vmlinux
> libbpf: failed to get EHDR from /sys/kernel/btf/vmlinux
> Error: failed to load BTF from /sys/kernel/btf/vmlinux: No error information

After investigating, the problem appears to be that "pahole -J"
running on the x86_64 little-endian host will always generate raw BTF
of native endianness (based on BTF magic), which causes the error
above on big-endian targets.

Is this expected? Is DEBUG_INFO_BTF supported in general when
cross-compiling? How does one generate BTF encoded for the target
endianness with pahole?

Thanks for any feedback or suggestions,
Tony

             reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-06  4:16 Tony Ambardar [this message]
2020-09-07 15:59 ` Ilya Leoshkevich
2020-09-08 20:18   ` Andrii Nakryiko
2020-09-09  9:02     ` Ilya Leoshkevich
2020-09-09 14:27       ` Arnaldo Carvalho de Melo
2020-09-19  7:58         ` Tony Ambardar
2020-09-21 18:19           ` Andrii Nakryiko
2020-09-28 20:18             ` Andrii Nakryiko
2020-09-28 20:27               ` Luka Perkov
2020-09-29  3:41               ` Tony Ambardar
2020-09-29  4:15                 ` Andrii Nakryiko
2020-09-29  6:48                   ` Tony Ambardar
2020-09-29 17:36                     ` Juraj Vijtiuk
2020-09-29 17:57                     ` Andrii Nakryiko

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