From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Oleg Nesterov <oleg@redhat.com>,
linux-kernel@vger.kernel.org, Andi Kleen <andi@firstfloor.org>,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v2 4/4] perf-probe: Warn if the target function is GNU Indirect function
Date: Fri, 10 Jul 2020 14:25:29 -0300 [thread overview]
Message-ID: <20200710172529.GE7487@kernel.org> (raw)
In-Reply-To: <20200710135712.GO874@linux.vnet.ibm.com>
Em Fri, Jul 10, 2020 at 07:27:12PM +0530, Srikar Dronamraju escreveu:
> * Masami Hiramatsu <mhiramat@kernel.org> [2020-07-10 22:11:33]:
>
> > Warn if the probe target function is GNU indirect function (GNU_IFUNC)
> > because it may not what the user want to probe.
> >
> > The GNU indirect function ( https://sourceware.org/glibc/wiki/GNU_IFUNC )
> > is the dynamic solved symbol at runtime. IFUNC function is a selector
> > which is invoked from the elf loader, but the symbol address of the
> > function which will be modified by the IFUNC is same as the IFUNC in
> > the symbol table. This can confuse users who is trying to probe on
> > such functions.
> >
> > For example, the memcpy is one of IFUNC.
> >
> > # perf probe -x /lib64/libc-2.30.so -a memcpy
> > # perf probe -l
> > probe_libc:memcpy (on __new_memcpy_ifunc@x86_64/multiarch/memcpy.c in /usr/lib64/libc-2.30.so)
> >
> > the probe is put on a IFUNC.
> >
> > # perf record -e probe_libc:memcpy --call-graph dwarf -aR ./perf
> >
> > Thus, I decided to warn user when the perf probe detects the probe point
> > is on the GNU IFUNC symbol. Someone who wants to probe an IFUNC symbol to
> > debug the IFUNC function, they can ignore this warning.
> >
> > Reported-by: Andi Kleen <andi@firstfloor.org>
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
>
> Looks good to me.
>
> Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Thanks, applied.
- Arnaldo
prev parent reply other threads:[~2020-07-10 17:25 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-10 13:10 [PATCH v2 0/4] perf-probe: Fix GNU IFUNC probe issue etc Masami Hiramatsu
2020-07-10 13:11 ` [PATCH v2 1/4] perf-probe: Avoid setting probes on same address on same event Masami Hiramatsu
2020-07-16 21:47 ` Arnaldo Carvalho de Melo
2020-07-20 12:01 ` Masami Hiramatsu
2020-07-10 13:11 ` [PATCH v2 2/4] perf-probe: Fix wrong variable warning when the probe point is not found Masami Hiramatsu
2020-07-10 13:11 ` [PATCH v2 3/4] perf-probe: Fix memory leakage " Masami Hiramatsu
2020-07-10 13:11 ` [PATCH v2 4/4] perf-probe: Warn if the target function is GNU Indirect function Masami Hiramatsu
2020-07-10 13:57 ` Srikar Dronamraju
2020-07-10 17:25 ` Arnaldo Carvalho de Melo [this message]
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