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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Evgenii Shatokhin <eshatokhin@virtuozzo.com>,
	Masami Hiramatsu <mhiramat@kernel.org>
Cc: Evgenii Shatokhin <eshatokhin@virtuozzo.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Kristen Carlson Accardi <kristen@linux.intel.com>,
	live-patching@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org,
	Konstantin Khorenko <khorenko@virtuozzo.com>
Subject: Re: 'perf probe' and symbols from .text.<something>
Date: Tue, 23 Feb 2021 00:12:01 +0900	[thread overview]
Message-ID: <20210223001201.c478d4cb6481385d31b3f09b@kernel.org> (raw)
In-Reply-To: <20210223000508.cab3cddaa3a3790525f49247@kernel.org>

On Tue, 23 Feb 2021 00:05:08 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Hi Evgenii,
> 
> On Thu, 18 Feb 2021 20:09:17 +0300
> Evgenii Shatokhin <eshatokhin@virtuozzo.com> wrote:
> 
> > Hi,
> > 
> > It seems, 'perf probe' can only see functions from .text section in the 
> > kernel modules, but not from .text.unlikely or other .text.* sections.
> > 
> > For example, with kernel 5.11 and nf_conntrack.ko with debug info, 'perf 
> > probe' succeeds for nf_conntrack_attach() from .text and fails for 
> > nf_ct_resolve_clash() from .text.unlikely:
> 
> Thanks for reporting it!
> 
> > 
> > ------------
> > # perf probe -v -m nf_conntrack nf_ct_resolve_clash
> > probe-definition(0): nf_ct_resolve_clash
> > symbol:nf_ct_resolve_clash file:(null) line:0 offset:0 return:0 lazy:(null)
> > 0 arguments
> > Failed to get build-id from nf_conntrack.
> > Cache open error: -1
> > Open Debuginfo file: 
> > /lib/modules/5.11.0-test01/kernel/net/netfilter/nf_conntrack.ko
> > Try to find probe point from debuginfo.
> > Matched function: nf_ct_resolve_clash [33616]
> > Probe point found: nf_ct_resolve_clash+0
> > Found 1 probe_trace_events.
> > Post processing failed or all events are skipped. (-2)
> > Probe point 'nf_ct_resolve_clash' not found.
> >    Error: Failed to add events. Reason: No such file or directory (Code: -2)
> 
[...]

> > Is there a way to allow probing of functions in .text.<something> ?

BTW, just for putting a probe on nf_ct_resolve_clash, please give the module *path*
instead of the module *name*. For example,

perf probe -v -m /lib/modules/5.11.0-test01/kernel/net/netfilter/nf_conntrack.ko nf_ct_resolve_clash

This should work (at least works for me), because it directly loads the symbols from the .ko file.

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

  reply	other threads:[~2021-02-22 15:13 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-18 17:09 Evgenii Shatokhin
2021-02-18 19:35 ` Josh Poimboeuf
2021-02-22 15:05 ` Masami Hiramatsu
2021-02-22 15:12   ` Masami Hiramatsu [this message]
2021-02-22 17:51   ` Josh Poimboeuf
2021-02-23  1:23     ` Masami Hiramatsu
2021-02-23  7:36       ` Masami Hiramatsu
2021-02-23 19:45         ` Josh Poimboeuf
2021-02-24  8:00           ` Masami Hiramatsu
2021-02-23  1:48   ` [PATCH] perf-probe: Failback to symbol-base probe for probes on module Masami Hiramatsu
2021-02-23  7:36     ` Masami Hiramatsu
2021-02-23  7:09   ` 'perf probe' and symbols from .text.<something> Masami Hiramatsu
2021-02-23  7:37   ` [PATCH] perf-probe: dso: Add symbols in .text.* subsections to text symbol map in kenrel modules Masami Hiramatsu
2021-02-23 15:02     ` Evgenii Shatokhin
2021-02-23 20:11       ` Arnaldo Carvalho de Melo
2021-02-24  7:47         ` Evgenii Shatokhin

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