linux-kernel - Re: [BUG] perf top reports not being able to resolve kernel symbols

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Message-ID: <Z3gRcBeuaQ16IQSO@x1>
Date: Fri, 3 Jan 2025 13:33:52 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Namhyung Kim <namhyung@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Ian Rogers <irogers@...gle.com>,
	James Clark <james.clark@...aro.org>, Jiri Olsa <jolsa@...nel.org>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org
Subject: Re: [BUG] perf top reports not being able to resolve kernel symbols

On Thu, Jan 02, 2025 at 10:16:35PM -0300, Arnaldo Carvalho de Melo wrote:
> On Thu, Jan 02, 2025 at 12:58:54PM -0800, Namhyung Kim wrote:
> > On Thu, Jan 02, 2025 at 04:51:06PM -0300, Arnaldo Carvalho de Melo wrote:
> > > So there are symbols that are not being resolved anymore that were
> > > before your patch, namely:
> 
> > > arch/x86/entry/entry_64.S
> 
> > > nmi_no_fsgsbase:
> > >         /* EBX == 0 -> invoke SWAPGS */
> > >         testl   %ebx, %ebx
> > >         jnz     nmi_restore
> 
> > > nmi_swapgs:
> > >         swapgs
> 
> > > nmi_restore:
> > >         POP_REGS
>  
> > Sorry about that, maybe I should've done this instead.  Can you check
> > if it works correctly?
> 
> Its late here, but basic test shows samples being resolved to
> nmi_restore, when using the TUI 'perf top' interface and pressing / to
> ask for samples resolved to samples with 'nmi' on its name, several
> other such routines appeared on the radar, including:
> 
> Samples: 2K of event 'cpu_atom/cycles/P', 4000 Hz, Event count (approx.): 496683332 lost: 0/0 drop: 0/0
> Overhead  Shared O  Symbol
>    0.05%  [kernel]  [k] ct_nmi_enter
>    0.04%  [kernel]  [k] local_touch_nmi
>    0.01%  [kernel]  [k] ct_nmi_exit
>    0.01%  [kernel]  [k] nmi_restore
>    0.00%  [kernel]  [k] nmi_handle
> 
> [1]+  Stopped                 perf top
> root@...ber:~#
> 
> So:
> 
> Reported-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> And preliminarly:
> 
> Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>

Please also add a:

Closes: https://lore.kernel.org/lkml/Z3buKhcCsZi3_aGb@x1

So that further details are provided about what those asm symbols are.

- Arnaldo
 
> Thanks, I'll submit the other patch, that now doesn't need to go into
> the 6.13 window and thus can be added to the perf-tools-next branch,
> tomorrow.