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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Wed, 4 Sep 2019 08:37:22 -0700
Message-ID: <CAADnVQ+Cwe27pwTwJ3TNiatKe8dXAwXBf_2jJDqxB0RFUbr7_A@mail.gmail.com>
Subject: Re: [PATCH 2/2] sched/debug: add sched_update_nr_running tracepoint
To:     Joel Fernandes <joel@joelfernandes.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Valentin Schneider <valentin.schneider@arm.com>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@kernel.org>,
        =?UTF-8?Q?Jirka_Hladk=C3=BD?= <jhladky@redhat.com>,
        =?UTF-8?B?SmnFmcOtIFZvesOhcg==?= <jvozar@redhat.com>,
        X86 ML <x86@kernel.org>, Qais Yousef <qais.yousef@arm.com>
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On Wed, Sep 4, 2019 at 8:33 AM Joel Fernandes <joel@joelfernandes.org> wrote:
>
> On Wed, Sep 04, 2019 at 08:26:52AM -0700, Alexei Starovoitov wrote:
> > On Wed, Sep 4, 2019 at 6:14 AM Joel Fernandes <joel@joelfernandes.org> wrote:
> > >
> > > True. However, for kprobes-based BPF program - it does check for kernel
> > > version to ensure that the BPF program is built against the right kernel
> > > version (in order to ensure the program is built against the right set of
> > > kernel headers). If it is not, then BPF refuses to load the program.
> >
> > This is not true anymore. Users found few ways to workaround that check
> > in practice. It became useless and it was deleted some time ago.
>
> Wow, Ok! Interesting!

the other part of your email says about kernel header requirement.
This is not true any more as well :)
BTF relocations are already supported by the kernel, llvm, libbpf,
bpftool, pahole.
We'll be posting sample code soon.