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SubjectRe: [BUGFIX PATCH] perf probe: Do not depend on dwfl_module_addrsym()
On Thu, 27 Feb 2020 17:20:39 +0100
Alexandre Ghiti <alex@ghiti.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@ghiti.fr>
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.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@ghiti.fr>

Thanks Alexandre,
Arnaldo, could you also pick this for fix?

Thank you,

--
Masami Hiramatsu <mhiramat@kernel.org>

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