From: Daniel Borkmann <daniel@iogearbox.net>
To: Tony Ambardar <tony.ambardar@gmail.com>,
Alexei Starovoitov <ast@kernel.org>
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
linux-arch@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH bpf v1 0/3] fix BTF usage on embedded systems
Date: Mon, 21 Sep 2020 22:52:42 +0200 [thread overview]
Message-ID: <898b6212-0521-6a37-c982-7bb2ef31264f@iogearbox.net> (raw)
In-Reply-To: <cover.1600417359.git.Tony.Ambardar@gmail.com>
On 9/20/20 7:01 AM, Tony Ambardar wrote:
> Hello,
>
> I've been experimenting with BPF and BTF on small, emebedded platforms
> requiring cross-compilation to varying archs, word-sizes, and endianness.
> These environments are not the most common for the majority of eBPF users,
> and have exposed multiple problems with basic functionality. This patch
> series addresses some of these issues.
>
> Enabling BTF support in the kernel can sometimes result in sysfs export
> of /sys/kernel/btf/vmlinux as a zero-length file, which is still readable
> and seen to leak non-zero kernel data. Patch #1 adds a sanity-check to
> avoid this situation.
>
> Small systems commonly enable LD_DEAD_CODE_DATA_ELIMINATION, which causes
> the .BTF section data to be incorrectly removed and can trigger the problem
> above. Patch #2 preserves the BTF data.
>
> Even if BTF data is generated and embedded in the kernel, it may be encoded
> as non-native endianness due to another bug [1] currently being worked on.
> Patch #3 lets bpftool recognize the wrong BTF endianness rather than output
> a confusing/misleading ELF header error message.
>
> Patches #1 and #2 were first developed for Linux 5.4.x and should be
> backported if possible. Feedback and suggestions for improvement are
> welcome!
>
> Thanks,
> Tony
>
> [1] https://lore.kernel.org/bpf/CAPGftE8ipAacAnm9xMHFabXCL-XrCXGmOsX-Nsjvz9wnh3Zx-w@mail.gmail.com/
>
> Tony Ambardar (3):
> bpf: fix sysfs export of empty BTF section
> bpf: prevent .BTF section elimination
> libbpf: fix native endian assumption when parsing BTF
>
> include/asm-generic/vmlinux.lds.h | 2 +-
> kernel/bpf/sysfs_btf.c | 6 +++---
> tools/lib/bpf/btf.c | 6 ++++++
> 3 files changed, 10 insertions(+), 4 deletions(-)
>
Applied, thanks!
prev parent reply other threads:[~2020-09-21 20:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-20 5:01 [PATCH bpf v1 0/3] fix BTF usage on embedded systems Tony Ambardar
2020-09-20 5:01 ` [PATCH bpf v1 1/3] bpf: fix sysfs export of empty BTF section Tony Ambardar
2020-09-21 15:44 ` John Fastabend
2020-09-21 19:21 ` Andrii Nakryiko
2020-09-20 5:01 ` [PATCH bpf v1 2/3] bpf: prevent .BTF section elimination Tony Ambardar
2020-09-21 15:45 ` John Fastabend
2020-09-20 5:01 ` [PATCH bpf v1 3/3] libbpf: fix native endian assumption when parsing BTF Tony Ambardar
2020-09-21 15:46 ` John Fastabend
2020-09-21 19:24 ` [PATCH bpf v1 0/3] fix BTF usage on embedded systems Andrii Nakryiko
2020-09-21 20:52 ` Daniel Borkmann [this message]
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