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From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Yaniv Agman <yanivagman@gmail.com>
Cc: bpf <bpf@vger.kernel.org>
Subject: Re: libbpf: Loading kprobes fail on some distros
Date: Mon, 12 Oct 2020 10:01:51 -0700	[thread overview]
Message-ID: <CAEf4BzYnELT0tE8Y4goPWxuBGN+G-37A8A1yjspFL=LK842geQ@mail.gmail.com> (raw)
In-Reply-To: <CAMy7=ZWoL7w97aR5_02OEjKEkJT8R7OEzpL5Zp8Cycm=yZSLJQ@mail.gmail.com>

On Sun, Oct 11, 2020 at 7:10 PM Yaniv Agman <yanivagman@gmail.com> wrote:
>
> Trying to load kprobes on ubuntu 4.15.0, I get the following error:
> libbpf: load bpf program failed: Invalid argument
>
> The same kprobes load successfully using bcc
>
> After some digging, I found that the issue was with the kernel version
> given to the bpf syscall. While libbpf calculated the value 265984 for
> the kern_version argument, bcc used 266002.
> It turns out that some distros (e.g. ubuntu, debian) change the patch
> number of the kernel version, as detailed in:
> https://github.com/ajor/bpftrace/issues/8
>
> I didn't find a proper API in libbpf to load kprobes in such cases -
> is there any?

Yes, you can override kernel version that libbpf determines from
utsname with a special variable in your BPF code:

int KERNEL_VERSION SEC("version") = 123;

  reply	other threads:[~2020-10-12 17:02 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-11 19:28 libbpf: Loading kprobes fail on some distros Yaniv Agman
2020-10-12 17:01 ` Andrii Nakryiko [this message]
2020-10-12 21:20   ` Yaniv Agman
2020-10-12 22:10     ` Andrii Nakryiko

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