linux-kernel - Re: [BUGFIX PATCH] perf probe: Do not depend on dwfl_module

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Date:   Mon, 9 Mar 2020 10:44:30 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Alexandre Ghiti <alex@...ti.fr>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Sasha Levin <sashal@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [BUGFIX PATCH] perf probe: Do not depend on dwfl_module_addrsym()

Em Fri, Feb 28, 2020 at 08:52:38AM +0900, Masami Hiramatsu escreveu:
> On Thu, 27 Feb 2020 17:20:39 +0100
> Alexandre Ghiti <alex@...ti.fr> wrote:
> 
> > On 2/27/20 4:42 PM, Masami Hiramatsu wrote:
> > > Do not depend on dwfl_module_addrsym() because it can fail
> > > on user-space shared libraries.
> > > 
> > > Actually, same bug was fixed by commit 664fee3dc379 ("perf
> > > probe: Do not use dwfl_module_addrsym if dwarf_diename finds
> > > symbol name"), but commit 07d369857808 ("perf probe: Fix
> > > wrong address verification) reverted to get actual symbol
> > > address from symtab.
> > > 
> > > This fixes it again by getting symbol address from DIE,
> > > and only if the DIE has only address range, it uses
> > > dwfl_module_addrsym().
> > > 
> > > Fixes: 07d369857808 ("perf probe: Fix wrong address verification)
> > > Reported-by: Alexandre Ghiti <alex@...ti.fr>
> > > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> > > ---
> > >   tools/perf/util/probe-finder.c |   11 ++++++++---
> > >   1 file changed, 8 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > > index 1c817add6ca4..e4cff49384f4 100644
> > > --- a/tools/perf/util/probe-finder.c
> > > +++ b/tools/perf/util/probe-finder.c
> > > @@ -637,14 +637,19 @@ static int convert_to_trace_point(Dwarf_Die *sp_die, Dwfl_Module *mod,
> > >   		return -EINVAL;
> > >   	}
> > >   
> > > -	/* Try to get actual symbol name from symtab */
> > > -	symbol = dwfl_module_addrsym(mod, paddr, &sym, NULL);
> > > +	if (dwarf_entrypc(sp_die, &eaddr) == 0) {
> > > +		/* If the DIE has entrypc, use it. */
> > > +		symbol = dwarf_diename(sp_die);
> > > +	} else {
> > > +		/* Try to get actual symbol name and address from symtab */
> > > +		symbol = dwfl_module_addrsym(mod, paddr, &sym, NULL);
> > > +		eaddr = sym.st_value;
> > > +	}
> > >   	if (!symbol) {
> > >   		pr_warning("Failed to find symbol at 0x%lx\n",
> > >   			   (unsigned long)paddr);
> > >   		return -ENOENT;
> > >   	}
> > > -	eaddr = sym.st_value;
> > >   
> > >   	tp->offset = (unsigned long)(paddr - eaddr);
> > >   	tp->address = (unsigned long)paddr;
> > > 
> > 
> > I have just tested your patch, that fixes the issue, so you can add:
> > 
> > Tested-by: Alexandre Ghiti <alex@...ti.fr>
> 
> Thanks Alexandre,
> Arnaldo, could you also pick this for fix?


Thanks, applied.

- Arnaldo