linux-kernel - Re: [PATCH -tip ] [BUGFIX/URGENT] perf-probe: Do not add offset to uprobe address

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Date:	Thu, 06 Feb 2014 16:48:02 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	David Ahern <dsahern@...il.com>, linux-kernel@...r.kernel.org,
	"Steven Rostedt \(Red Hat\)" <rostedt@...dmis.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	"David A. Long" <dave.long@...aro.org>,
	yrl.pp-manager.tt@...achi.com
Subject: Re: [PATCH -tip ] [BUGFIX/URGENT] perf-probe: Do not add offset to uprobe address

Hi Masami,

On Wed, 05 Feb 2014 05:18:58 +0000, Masami Hiramatsu wrote:
> Fix perf-probe not to add offset value to uprobe probe
> address when post processing.
> tevs[i].point.address is the address of symbol+offset,
> but current perf-probe adjusts the point.address by
> adding the offset. As a result, the probe address becomes
> symbol+offset+offset. This may cause unexpected
> code corruption. Urgent fix is needed.
>
> Without this fix
>   ---
>   # ./perf probe -x ./perf dso__load_vmlinux+4
>   # ./perf probe -l
>     probe_perf:dso__load_vmlinux (on 0x000000000006d2b8)
>   # nm ./perf.orig | grep dso__load_vmlinux\$
>   000000000046d0a0 T dso__load_vmlinux

Shouldn't the original symbol address be

    000000000046d2b0

?

>   ---
> You can see the given offset is 3 but the actual probed

s/3/4/ ?

Thanks,
Namhyung


> address is dso__load_vmlinux+8.
>
> With this fix
>   ---
>   # ./perf probe -x ./perf dso__load_vmlinux+4
>   # ./perf probe -l
>     probe_perf:dso__load_vmlinux (on 0x000000000006d2b4)
>   ---
> Now the problem is fixed.
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