linux-kernel - Re: [PATCH/RFC] powerpc/module_64: allow .init

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Date:   Thu, 7 Jul 2022 14:14:47 +0200
From:   Jan Stancek <jstancek@...hat.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        linuxppc-dev@...ts.ozlabs.org,
        Wedson Almeida Filho <wedsonaf@...gle.com>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH/RFC] powerpc/module_64: allow .init_array constructors to run

On Thu, Jul 7, 2022 at 1:20 PM Christophe Leroy
<christophe.leroy@...roup.eu> wrote:
>
>
>
> Le 17/08/2021 à 15:02, Jan Stancek a écrit :
> > gcov and kasan rely on compiler generated constructor code.
> > For modules, gcc-8 with gcov enabled generates .init_array section,
> > but on ppc64le it doesn't get executed. find_module_sections() never
> > finds .init_array section, because module_frob_arch_sections() renames
> > it to _init_array.
> >
> > Avoid renaming .init_array section, so do_mod_ctors() can use it.
> >
> > Cc: Michael Ellerman <mpe@...erman.id.au>
> > Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> > Cc: Paul Mackerras <paulus@...ba.org>
> > Cc: Christophe Leroy <christophe.leroy@...roup.eu>
> > Signed-off-by: Jan Stancek <jstancek@...hat.com>
>
> Does commit d4be60fe66b7 ("powerpc/module_64: use module_init_section
> instead of patching names") fixes your issue ?

Yes, it does gcov for me. Thanks

>
> If not, please rebase and resubmit.
>
> Thanks
> Christophe
>
>
> > ---
> > I wasn't able to trace the comment:
> >    "We don't handle .init for the moment: rename to _init"
> > to original patch (it pre-dates .git). I'm not sure if it
> > still applies today, so I limited patch to .init_array. This
> > fixes gcov for modules for me on ppc64le 5.14.0-rc6.
> >
> > Renaming issue is also mentioned in kasan patches here:
> >    https://patchwork.ozlabs.org/project/linuxppc-dev/cover/20210319144058.772525-1-dja@axtens
> >
> >   arch/powerpc/kernel/module_64.c | 10 +++++++++-
> >   1 file changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> > index 6baa676e7cb6..c604b13ea6bf 100644
> > --- a/arch/powerpc/kernel/module_64.c
> > +++ b/arch/powerpc/kernel/module_64.c
> > @@ -299,8 +299,16 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr,
> >                                         sechdrs[i].sh_size);
> >
> >               /* We don't handle .init for the moment: rename to _init */
> > -             while ((p = strstr(secstrings + sechdrs[i].sh_name, ".init")))
> > +             while ((p = strstr(secstrings + sechdrs[i].sh_name, ".init"))) {
> > +#ifdef CONFIG_CONSTRUCTORS
> > +                     /* find_module_sections() needs .init_array intact */
> > +                     if (strstr(secstrings + sechdrs[i].sh_name,
> > +                             ".init_array")) {
> > +                             break;
> > +                     }
> > +#endif
> >                       p[0] = '_';
> > +             }
> >
> >               if (sechdrs[i].sh_type == SHT_SYMTAB)
> >                       dedotify((void *)hdr + sechdrs[i].sh_offset,
>