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From: duchangbin <changbin.du@huawei.com>
To: Adrian Hunter <adrian.hunter@intel.com>
CC: duchangbin <changbin.du@huawei.com>, Peter Zijlstra
	<peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, "Arnaldo Carvalho de
 Melo" <acme@kernel.org>, Namhyung Kim <namhyung@kernel.org>, Nathan
 Chancellor <nathan@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa
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	<kan.liang@linux.intel.com>, "Nick Desaulniers" <ndesaulniers@google.com>,
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	"llvm@lists.linux.dev" <llvm@lists.linux.dev>
Subject: Re: [PATCH 1/2] perf: support specify vdso path in cmdline
Thread-Topic: [PATCH 1/2] perf: support specify vdso path in cmdline
Thread-Index: AQHavVvgPApptK0OsE6+S63iYUbWKrHE1RgAgACeKQD//4I5AIABrPmA
Date: Fri, 14 Jun 2024 03:55:05 +0000
Message-ID: <d5309643a85144b4abbb8705b6e7bd8e@huawei.com>
References: <20240613063510.348692-1-changbin.du@huawei.com>
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On Thu, Jun 13, 2024 at 01:19:20PM +0300, Adrian Hunter wrote:
> On 13/06/24 12:49, duchangbin wrote:
> > On Thu, Jun 13, 2024 at 11:23:26AM +0300, Adrian Hunter wrote:
> >> On 13/06/24 09:35, Changbin Du wrote:
> >>> The vdso dumped from process memory (in buildid-cache) lacks debuggin=
g
> >>> info. To annotate vdso symbols with source lines we need specify a
> >>> debugging version.
> >>>
> >>> For x86, we can find them from your local build as
> >>> arch/x86/entry/vdso/vdso{32,64}.so.dbg. Or they may reside in
> >>> /lib/modules/<version>/vdso/vdso{32,64}.so on Ubuntu. But notice that
> >>> the buildid has to match.
> >>>
> >>> $ sudo perf record -a
> >>> $ sudo perf report --objdump=3Dllvm-objdump \
> >>>   --vdso arch/x86/entry/vdso/vdso64.so.dbg,arch/x86/entry/vdso/vdso32=
.so.dbg
> >>>
> >>> When doing cross platform analysis, we also need specify the vdso pat=
h if
> >>> we are interested in its symbols.
> >>
> >> We already have logic to find debug files, and to deal with a symbol s=
ource
> >> (syms_ss) and runtime symbol source (runtime_ss).
> >>
> >> Can't we make that work transparently for vdso so that the user does
> >> not have to.
> >>
> > For Ubuntu, we can find the debug files of vdso in
> > /lib/modules/<version>/vdso/vdso{32,64}.so. These two are debug version=
.
> >=20
> > For local build, seems vdso{32,64}.so.dbg are not installed in /lib/mod=
ules/ nor
> > other locations.
>=20
> Isn't there /lib/modules/<version>/build symbolic link to follow?
>=20
hm, we can try /lib/modules/<version>/build/arch/x86/entry/vdso/vdso*.so.db=
g.
Other arches are similar.

So, we will try these pathes internally. And keep '--vdso' if someone reall=
y
want a special path. (just like vmlinux)

--=20
Cheers,
Changbin Du