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Subject: Re: [PATCH 5.4 252/434] perf probe: Fix to probe a function which has
 no entry pc
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        <linux-kernel@vger.kernel.org>
CC:     <stable@vger.kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Sasha Levin <sashal@kernel.org>
References: <20191229172702.393141737@linuxfoundation.org>
 <20191229172718.657510315@linuxfoundation.org>
From:   Thomas Backlund <tmb@mageia.org>
Message-ID: <b1df96c5-60eb-3b97-d03b-7fe1bf567755@mageia.org>
Date:   Sun, 29 Dec 2019 20:40:09 +0200
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Den 29-12-2019 kl. 19:25, skrev Greg Kroah-Hartman:
> From: Masami Hiramatsu <mhiramat@kernel.org>
> 
> [ Upstream commit 5d16dbcc311d91267ddb45c6da4f187be320ecee ]
> 
> Fix 'perf probe' to probe a function which has no entry pc or low pc but
> only has ranges attribute.
> 
> probe_point_search_cb() uses dwarf_entrypc() to get the probe address,
> but that doesn't work for the function DIE which has only ranges
> attribute. Use die_entrypc() instead.
> 
> Without this fix:
> 
>    # perf probe -k ../build-x86_64/vmlinux -D clear_tasks_mm_cpumask:0
>    Probe point 'clear_tasks_mm_cpumask' not found.
>      Error: Failed to add events.
> 
> With this:
> 
>    # perf probe -k ../build-x86_64/vmlinux -D clear_tasks_mm_cpumask:0
>    p:probe/clear_tasks_mm_cpumask clear_tasks_mm_cpumask+0
> 
> Committer testing:
> 
> Before:
> 
>    [root@quaco ~]# perf probe clear_tasks_mm_cpumask:0
>    Probe point 'clear_tasks_mm_cpumask' not found.
>      Error: Failed to add events.
>    [root@quaco ~]#
> 
> After:
> 
>    [root@quaco ~]# perf probe clear_tasks_mm_cpumask:0
>    Added new event:
>      probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask)
> 
>    You can now use it in all perf tools, such as:
> 
>    	perf record -e probe:clear_tasks_mm_cpumask -aR sleep 1
> 
>    [root@quaco ~]#
> 
> Using it with 'perf trace':
> 
>    [root@quaco ~]# perf trace -e probe:clear_tasks_mm_cpumask
> 
> Doesn't seem to be used in x86_64:
> 
>    $ find . -name "*.c" | xargs grep clear_tasks_mm_cpumask
>    ./kernel/cpu.c: * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
>    ./kernel/cpu.c:void clear_tasks_mm_cpumask(int cpu)
>    ./arch/xtensa/kernel/smp.c:	clear_tasks_mm_cpumask(cpu);
>    ./arch/csky/kernel/smp.c:	clear_tasks_mm_cpumask(cpu);
>    ./arch/sh/kernel/smp.c:	clear_tasks_mm_cpumask(cpu);
>    ./arch/arm/kernel/smp.c:	clear_tasks_mm_cpumask(cpu);
>    ./arch/powerpc/mm/nohash/mmu_context.c:	clear_tasks_mm_cpumask(cpu);
>    $ find . -name "*.h" | xargs grep clear_tasks_mm_cpumask
>    ./include/linux/cpu.h:void clear_tasks_mm_cpumask(int cpu);
>    $ find . -name "*.S" | xargs grep clear_tasks_mm_cpumask
>    $
> 
> Fixes: e1ecbbc3fa83 ("perf probe: Fix to handle optimized not-inlined functions")
> Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
> Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Jiri Olsa <jolsa@redhat.com>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Link: http://lore.kernel.org/lkml/157199319438.8075.4695576954550638618.stgit@devnote2
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>   tools/perf/util/probe-finder.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> index 7857ae7a10b7..4079ed617f53 100644
> --- a/tools/perf/util/probe-finder.c
> +++ b/tools/perf/util/probe-finder.c
> @@ -994,7 +994,7 @@ static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
>   		param->retval = find_probe_point_by_line(pf);
>   	} else if (die_is_func_instance(sp_die)) {
>   		/* Instances always have the entry address */
> -		dwarf_entrypc(sp_die, &pf->addr);
> +		die_entrypc(sp_die, &pf->addr);
>   		/* But in some case the entry address is 0 */
>   		if (pf->addr == 0) {
>   			pr_debug("%s has no entry PC. Skipped\n",
> 

Still broken...

/usr/bin/ld: perf-in.o: in function `probe_point_search_cb':
/work/rpmbuild/BUILD/kernel-x86_64/linux-5.4/tools/perf/util/probe-finder.c:1012: 
undefined reference to `die_entrypc'

--
Thomas