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 <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Christophe Leroy <[email protected]>
Signed-off-by: Jan Stancek <[email protected]>
---
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,
--
2.27.0
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 <[email protected]>
> Cc: Benjamin Herrenschmidt <[email protected]>
> Cc: Paul Mackerras <[email protected]>
> Cc: Christophe Leroy <[email protected]>
> Signed-off-by: Jan Stancek <[email protected]>
> ---
> I wasn't able to trace the comment:
> "We don't handle .init for the moment: rename to _init"
Original patch there: https://github.com/mpe/linux-fullhistory/commit/d6ad6690aa72
> 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
Please avoid #ifdefery as much as possible.
I think here you can do:
if (IS_ENABLED(CONFIG_CONSTRUCTORS) &&
strstr(secstrings + sechdrs[i].sh_name, ".init_array"))
> + /* find_module_sections() needs .init_array intact */
> + if (strstr(secstrings + sechdrs[i].sh_name,
> + ".init_array")) {
No { } for single statements (See
https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces)
> + break;
> + }
> +#endif
> p[0] = '_';
> + }
>
> if (sechdrs[i].sh_type == SHT_SYMTAB)
> dedotify((void *)hdr + sechdrs[i].sh_offset,
>
Jan Stancek <[email protected]> writes:
> 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.
This (the existing renaming) breaks a KASAN test too, so I'd love to see
this fixed.
However, I don't know that renaming the section is a complete fix: from
memory it is still be possible to get relocations that are too far away
and require separate trampolines. But I wasn't able to construct a
module that exhibited this behaviour and test a fix before I got pulled
away to other things.
Kind regards,
Daniel
>
> Cc: Michael Ellerman <[email protected]>
> Cc: Benjamin Herrenschmidt <[email protected]>
> Cc: Paul Mackerras <[email protected]>
> Cc: Christophe Leroy <[email protected]>
> Signed-off-by: Jan Stancek <[email protected]>
> ---
> 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,
> --
> 2.27.0
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 <[email protected]>
> Cc: Benjamin Herrenschmidt <[email protected]>
> Cc: Paul Mackerras <[email protected]>
> Cc: Christophe Leroy <[email protected]>
> Signed-off-by: Jan Stancek <[email protected]>
Does commit d4be60fe66b7 ("powerpc/module_64: use module_init_section
instead of patching names") fixes your issue ?
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,
On Thu, Jul 7, 2022 at 1:20 PM Christophe Leroy
<[email protected]> 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 <[email protected]>
> > Cc: Benjamin Herrenschmidt <[email protected]>
> > Cc: Paul Mackerras <[email protected]>
> > Cc: Christophe Leroy <[email protected]>
> > Signed-off-by: Jan Stancek <[email protected]>
>
> 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,
>