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SubjectRe: [PATCH/RFC] powerpc/module_64: allow .init_array constructors to run
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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@ellerman.id.au>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
> Signed-off-by: Jan Stancek <jstancek@redhat.com>
> ---
> 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,
>

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