[PATCH] x86/Kconfig: Fix allnoconfig without explicitly specified ARCH

[PATCH] x86/Kconfig: Fix allnoconfig without explicitly specified ARCH

[Borislav Petkov]

From: Borislav Petkov <bp@suse.de>

Doing

  $ make allnoconfig

I get a 32-bit allnoconfig:

  $ grep -i x86 .config
  # Linux/x86 4.0.0-rc6 Kernel Configuration
  CONFIG_X86_32=y
  CONFIG_X86=y
  CONFIG_ARCH_DEFCONFIG="arch/x86/configs/i386_defconfig"

The same if I do:

  $ make ARCH=i386 allnoconfig
  $ grep -i x86 .config | head -20
  CONFIG_X86_32=y
  CONFIG_X86=y
  CONFIG_ARCH_DEFCONFIG="arch/x86/configs/i386_defconfig"

Make allnoconfig without ARCH specified on the command line default to
64-bit.

Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0a37094e458e..04dfb4e7aeff 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2,6 +2,7 @@
 config 64BIT
 	bool "64-bit kernel" if ARCH = "x86"
 	default ARCH != "i386"
+	option allnoconfig_y
 	---help---
 	  Say yes to build a 64-bit kernel - formerly known as x86_64
 	  Say no to build a 32-bit kernel - formerly known as i386
-- 
2.3.3

Re: [PATCH] x86/Kconfig: Fix allnoconfig without explicitly specified ARCH

[Paul Bolle]

Borislav Petkov schreef op vr 03-04-2015 om 13:00 [+0200]:
> From: Borislav Petkov <bp@suse.de>
> 
> Doing
> 
>   $ make allnoconfig
> 
> I get a 32-bit allnoconfig:
> 
>   $ grep -i x86 .config
>   # Linux/x86 4.0.0-rc6 Kernel Configuration
>   CONFIG_X86_32=y
>   CONFIG_X86=y
>   CONFIG_ARCH_DEFCONFIG="arch/x86/configs/i386_defconfig"
> 
> The same if I do:
> 
>   $ make ARCH=i386 allnoconfig
>   $ grep -i x86 .config | head -20
>   CONFIG_X86_32=y
>   CONFIG_X86=y
>   CONFIG_ARCH_DEFCONFIG="arch/x86/configs/i386_defconfig"
> 
> Make allnoconfig without ARCH specified on the command line default to
> 64-bit.
> 
> Signed-off-by: Borislav Petkov <bp@suse.de>
> ---
>  arch/x86/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 0a37094e458e..04dfb4e7aeff 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2,6 +2,7 @@
>  config 64BIT
>  	bool "64-bit kernel" if ARCH = "x86"
>  	default ARCH != "i386"
> +	option allnoconfig_y
>  	---help---
>  	  Say yes to build a 64-bit kernel - formerly known as x86_64
>  	  Say no to build a 32-bit kernel - formerly known as i386

A side effect of this patch is that allnoconfig when building on 32 bits
now also requires to set ARCH=i386, which is surprising. This seems to
help with that:

--- a/Makefile
+++ b/Makefile
@@ -221,7 +221,7 @@ export srctree objtree VPATH
 # then ARCH is assigned, getting whatever value it gets normally, and
 # SUBARCH is subsequently ignored.
 
-SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
+SUBARCH := $(shell uname -m | sed -e s/i.86/i386/ -e s/x86_64/x86/ \
                                  -e s/sun4u/sparc64/ \
                                  -e s/arm.*/arm/ -e s/sa110/arm/ \
                                  -e s/s390x/s390/ -e s/parisc64/parisc/ \

And that will also set 64BIT to 'n' when doing an allyesconfig on 32
bits. So it removes another surprising configuration one can currently
generate.

(I think that has no further side effects. But I need to double check.)

Would some solution that pins 64BIT to 'y' for x86_64 and to 'n' for
i386 - even for allnoconfig and allyesconfig - do what you want?


Paul Bolle

Re: [PATCH] x86/Kconfig: Fix allnoconfig without explicitly specified ARCH

[Borislav Petkov]

On Fri, Apr 03, 2015 at 03:42:18PM +0200, Paul Bolle wrote:
> A side effect of this patch is that allnoconfig when building on 32 bits
> now also requires to set ARCH=i386, which is surprising. This seems to

How else would you build a 32-bit allnoconfig?

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

Re: [PATCH] x86/Kconfig: Fix allnoconfig without explicitly specified ARCH

[Paul Bolle]

Borislav Petkov schreef op vr 03-04-2015 om 16:59 [+0200]:
> On Fri, Apr 03, 2015 at 03:42:18PM +0200, Paul Bolle wrote:
> > A side effect of this patch is that allnoconfig when building on 32 bits
> > now also requires to set ARCH=i386, which is surprising. This seems to
> 
> How else would you build a 32-bit allnoconfig?

Well, "when building on 32 bits" it currently suffices to do:
    make allnoconfig

and the patch changes that.

Just like it is surprising to get a CONFIG_X86_32=y .config when doing
allnoconfig on x86_64 it is also surprising to get a
CONFIG_X86_64=y .config when doing allyesconfig on i386. So I think a
more general solution to these surprising .configs should be considered.
 
Thanks,


Paul Bolle

Re: [PATCH] x86/Kconfig: Fix allnoconfig without explicitly specified ARCH

[Borislav Petkov]

On Fri, Apr 03, 2015 at 05:33:03PM +0200, Paul Bolle wrote:
> Well, "when building on 32 bits" it currently suffices to do:
>     make allnoconfig
> 
> and the patch changes that.

Hmm, so this would need more staring. The fact that 64-bit needs to set
CONFIG_64BIT, we would need a way to say:

	option allnoconfig_y if ARCH = "x86"

And Kconfig doesn't support that yet...

:-\

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

Re: [PATCH] x86/Kconfig: Fix allnoconfig without explicitly specified ARCH

[Paul Bolle]

On Fri, 2015-04-03 at 19:23 +0200, Borislav Petkov wrote:
> On Fri, Apr 03, 2015 at 05:33:03PM +0200, Paul Bolle wrote:
> > Well, "when building on 32 bits" it currently suffices to do:
> >     make allnoconfig
> > 
> > and the patch changes that.
> 
> Hmm, so this would need more staring. The fact that 64-bit needs to set
> CONFIG_64BIT, we would need a way to say:
> 
> 	option allnoconfig_y if ARCH = "x86"
> 
> And Kconfig doesn't support that yet...

The fact that "make allnoconfig" and "make allyesconfig" can give you
a .config for another subarchitecture is annoying. I think it would be
nice if we teach those make targets (through tweaks in Kconfig files
and/or Makefiles) to avoid doing that.

Not sure, yet, how a clean way to do that might look like, sorry.


Paul Bolle

Re: [PATCH] x86/Kconfig: Fix allnoconfig without explicitly specified ARCH

[Ingo Molnar]

* Paul Bolle <pebolle@tiscali.nl> wrote:

> On Fri, 2015-04-03 at 19:23 +0200, Borislav Petkov wrote:
> > On Fri, Apr 03, 2015 at 05:33:03PM +0200, Paul Bolle wrote:
> > > Well, "when building on 32 bits" it currently suffices to do:
> > >     make allnoconfig
> > > 
> > > and the patch changes that.
> > 
> > Hmm, so this would need more staring. The fact that 64-bit needs to set
> > CONFIG_64BIT, we would need a way to say:
> > 
> > 	option allnoconfig_y if ARCH = "x86"
> > 
> > And Kconfig doesn't support that yet...
> 
> The fact that "make allnoconfig" and "make allyesconfig" can give you
> a .config for another subarchitecture is annoying. [...]

Absolutely! No 'make *config' option should change the current 
.config's architecture, except if ARCH= is specified on the command 
line.

Thanks,

	Ingo