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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Wed, 10 Apr 2019 09:26:30 -0700
Message-ID: <CAKwvOdmRVK8t=CL5h0MXykm00R39e17dy8EkgFrLuhg1Yr0HJQ@mail.gmail.com>
Subject: Re: [PATCH 02/12] s390: don't build vdso32 with clang
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        clang-built-linux@googlegroups.com,
        Nathan Chancellor <natechancellor@gmail.com>,
        linux-s390 <linux-s390@vger.kernel.org>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Ursula Braun <ubraun@linux.ibm.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        LKML <linux-kernel@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Mon, Apr 8, 2019 at 2:27 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> clang does not support 31 bit object files on s390, so skip
> the 32-bit vdso here, and only build it when using gcc to compile
> the kernel.

What's the build failure?  Would you mind filing a bug against LLVM's
issue tracker for it, please?

>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  arch/s390/Kconfig         |  3 +++
>  arch/s390/kernel/Makefile |  2 +-
>  arch/s390/kernel/vdso.c   | 10 +++++-----
>  3 files changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index b6e3d0653002..8cd860cba4d1 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -388,6 +388,9 @@ config COMPAT
>           (and some other stuff like libraries and such) is needed for
>           executing 31 bit applications.  It is safe to say "Y".
>
> +config COMPAT_VDSO
> +       def_bool COMPAT && !CC_IS_CLANG
> +
>  config SYSVIPC_COMPAT
>         def_bool y if COMPAT && SYSVIPC
>
> diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
> index 8a62c7f72e1b..1222db6d4ee9 100644
> --- a/arch/s390/kernel/Makefile
> +++ b/arch/s390/kernel/Makefile
> @@ -86,7 +86,7 @@ obj-$(CONFIG_TRACEPOINTS)     += trace.o
>
>  # vdso
>  obj-y                          += vdso64/
> -obj-$(CONFIG_COMPAT)           += vdso32/
> +obj-$(CONFIG_COMPAT_VDSO)      += vdso32/
>
>  chkbss := head64.o early_nobss.o
>  include $(srctree)/arch/s390/scripts/Makefile.chkbss
> diff --git a/arch/s390/kernel/vdso.c b/arch/s390/kernel/vdso.c
> index e7920a68a12e..243d8b1185bf 100644
> --- a/arch/s390/kernel/vdso.c
> +++ b/arch/s390/kernel/vdso.c
> @@ -29,7 +29,7 @@
>  #include <asm/vdso.h>
>  #include <asm/facility.h>
>
> -#ifdef CONFIG_COMPAT
> +#ifdef CONFIG_COMPAT_VDSO
>  extern char vdso32_start, vdso32_end;
>  static void *vdso32_kbase = &vdso32_start;
>  static unsigned int vdso32_pages;
> @@ -55,7 +55,7 @@ static vm_fault_t vdso_fault(const struct vm_special_mapping *sm,
>
>         vdso_pagelist = vdso64_pagelist;
>         vdso_pages = vdso64_pages;
> -#ifdef CONFIG_COMPAT
> +#ifdef CONFIG_COMPAT_VDSO
>         if (vma->vm_mm->context.compat_mm) {
>                 vdso_pagelist = vdso32_pagelist;
>                 vdso_pages = vdso32_pages;
> @@ -76,7 +76,7 @@ static int vdso_mremap(const struct vm_special_mapping *sm,
>         unsigned long vdso_pages;
>
>         vdso_pages = vdso64_pages;
> -#ifdef CONFIG_COMPAT
> +#ifdef CONFIG_COMPAT_VDSO
>         if (vma->vm_mm->context.compat_mm)
>                 vdso_pages = vdso32_pages;
>  #endif
> @@ -223,7 +223,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
>                 return 0;
>
>         vdso_pages = vdso64_pages;
> -#ifdef CONFIG_COMPAT
> +#ifdef CONFIG_COMPAT_VDSO
>         mm->context.compat_mm = is_compat_task();
>         if (mm->context.compat_mm)
>                 vdso_pages = vdso32_pages;
> @@ -280,7 +280,7 @@ static int __init vdso_init(void)
>         int i;
>
>         vdso_init_data(vdso_data);
> -#ifdef CONFIG_COMPAT
> +#ifdef CONFIG_COMPAT_VDSO
>         /* Calculate the size of the 32 bit vDSO */
>         vdso32_pages = ((&vdso32_end - &vdso32_start
>                          + PAGE_SIZE - 1) >> PAGE_SHIFT) + 1;
> --
> 2.20.0
>


-- 
Thanks,
~Nick Desaulniers