linux-kernel - Re: [PATCH] bpf: mark get_entry_ip as __maybe

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Message-ID: <Y2jVGX7syVuMdAlu@kroah.com>
Date:   Mon, 7 Nov 2022 10:51:21 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Jonas Rabenstein <rabenstein@...fau.de>
Cc:     stable@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
        Song Liu <song@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] bpf: mark get_entry_ip as __maybe_unused

On Mon, Nov 07, 2022 at 10:48:49AM +0100, Jonas Rabenstein wrote:
> On Mon, Nov 07, 2022 at 10:29:55AM +0100, Greg KH wrote:
> > On Mon, Nov 07, 2022 at 09:56:42AM +0100, Greg KH wrote:
> > > On Thu, Nov 03, 2022 at 04:32:47PM +0100, Jonas Rabenstein wrote:
> > > > Hi again,
> > > > after sending this out, I noticed this is only a problem in the stable
> > > > versions (starting from v6.0.3), as c09eb2e578eb1668bbc has been applied (as
> > > > 03f148c159a250dd454) but not 0e253f7e558a3e250902 ("bpf: Return value in kprobe
> > > > get_func_ip only for entry address") which makes always use of get_entry_ip.
> > > > I therefore think, 0e253f7e558a3e250902 needs to be added to the stable v6.0
> > > > series as well as otherwise it can't be compiled with -Werror if
> > > > CONFIG_X6_KERNEL_IBT is set but CONFIG_FPROBE isn't.
> > > 
> > > Ok, now queued up, thanks.
> > 
> > Oops, this breaks the build, now dropping.
> Sorry, 0e253f7e558a3e250902 ("bpf: Return value in kprobe get_func_ip only for
> entry address") uses the macro KPROBE_FLAG_ON_FUNC_ENTRY that was introduced
> in bf7a87f1075f67c286f7 ("kprobes: Add new KPROBE_FLAG_ON_FUNC_ENTRY kprobe
> flag"). Applying those on top of v6.0.7 fixes the original compilation problem
> (CONFIG_X6_KERNEL_IBT but !CONFIG_FPROBE) and should not break anything

Please submit a set of backports that you have verified works properly
so that I know it is correct.

thanks,

greg k-h