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Subject: Re: [PATCH 5/7] printk: Make %pS and friends print module build ID
From:   Stephen Boyd <swboyd@chromium.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, Jiri Olsa <jolsa@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Jessica Yu <jeyu@kernel.org>,
        Evan Green <evgreen@chromium.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        linux-doc@vger.kernel.org
To:     Matthew Wilcox <willy@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>
Date:   Thu, 04 Mar 2021 11:11:48 -0800
Message-ID: <161488510845.1478170.2089177121697044390@swboyd.mtv.corp.google.com>
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Quoting Matthew Wilcox (2021-03-04 09:19:40)
> On Mon, Mar 01, 2021 at 09:43:19PM -0500, Steven Rostedt wrote:
> > On Mon,  1 Mar 2021 09:47:47 -0800
> > Stephen Boyd <swboyd@chromium.org> wrote:
> >=20
> > > The %pS printk format (among some others) is used to print kernel
> > > addresses symbolically. When the kernel prints an address inside of a
> > > module, the kernel prints the addresses' symbol name along with the
> > > module's name that contains the address. Let's make kernel stacktraces
> > > easier to identify on KALLSYMS builds by including the build ID of a
> > > module when we print the address.
> >=20
> > Please no!
> >=20
> > This kills the output of tracing with offset, and can possibly break
> > scripts. I don't want to look at traces like this!
> >=20
> >           <idle>-0       [004] ..s1   353.842577: ipv4_conntrack_in+0x0=
/0x10 [nf_conntrack] (3b39eb771b2566331887f671c741f90bfba0b051) <-nf_hook_s=
low+0x40/0xb0
>=20
> Would it make sense to only print the build-id if it differs from the
> build-id of the kernel which has loaded it?

No. The build-id of the module is different from the kernel that loaded
it all the time, so it would always be printed.