[PATCH] arm: pass endianness info to sparse

[PATCH] arm: pass endianness info to sparse

[Luc Van Oostenryck]

ARM depends on the macros '__ARMEL__' & '__ARMEB__' being defined
or not to correctly select or define endian-specific macros,
structures or pieces of code.

These macros are predefined by the compiler but sparse knows
nothing about them and thus may pre-process files differently
from what gcc would.

Fix this by passing '-D__ARMEL__' or '-D__ARMEB__' to sparse,
depending of the endianness of the kernel, like defined by GCC.

Note: In most case it won't change anything since most ARMs use
      little-endian (but an allyesconfig would use big-endian!).

CC: Russell King <linux@armlinux.org.uk>
CC: linux-arm-kernel at lists.infradead.org
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
---
 arch/arm/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 65f4e2a4e..0fca46d7f 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -44,10 +44,12 @@ endif
 
 ifeq ($(CONFIG_CPU_BIG_ENDIAN),y)
 KBUILD_CPPFLAGS	+= -mbig-endian
+CHECKFLAGS	+= -D__ARMEB__
 AS		+= -EB
 LD		+= -EB
 else
 KBUILD_CPPFLAGS	+= -mlittle-endian
+CHECKFLAGS	+= -D__ARMEL__
 AS		+= -EL
 LD		+= -EL
 endif
-- 
2.13.0

[PATCH] arm: pass endianness info to sparse

[Russell King - ARM Linux]

On Sat, Jun 24, 2017 at 05:38:42PM +0200, Luc Van Oostenryck wrote:
> ARM depends on the macros '__ARMEL__' & '__ARMEB__' being defined
> or not to correctly select or define endian-specific macros,
> structures or pieces of code.
> 
> These macros are predefined by the compiler but sparse knows
> nothing about them and thus may pre-process files differently
> from what gcc would.
> 
> Fix this by passing '-D__ARMEL__' or '-D__ARMEB__' to sparse,
> depending of the endianness of the kernel, like defined by GCC.
> 
> Note: In most case it won't change anything since most ARMs use
>       little-endian (but an allyesconfig would use big-endian!).

I wonder if that's a good thing - as this changes the endian conversion
macros and ifdefs around bitfield declarations, it means that we're not
testing the "popular" paths with an allyesconfig sparse - but then again,
I think allyesconfig with sparse is a very bad idea, it needs to be
targetted to the area being worked in.

> CC: Russell King <linux@armlinux.org.uk>
> CC: linux-arm-kernel at lists.infradead.org
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> ---
>  arch/arm/Makefile | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> index 65f4e2a4e..0fca46d7f 100644
> --- a/arch/arm/Makefile
> +++ b/arch/arm/Makefile
> @@ -44,10 +44,12 @@ endif
>  
>  ifeq ($(CONFIG_CPU_BIG_ENDIAN),y)
>  KBUILD_CPPFLAGS	+= -mbig-endian
> +CHECKFLAGS	+= -D__ARMEB__
>  AS		+= -EB
>  LD		+= -EB
>  else
>  KBUILD_CPPFLAGS	+= -mlittle-endian
> +CHECKFLAGS	+= -D__ARMEL__
>  AS		+= -EL
>  LD		+= -EL
>  endif
> -- 
> 2.13.0
> 

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

[PATCH] arm: pass endianness info to sparse

[Luc Van Oostenryck]

On Mon, Jun 26, 2017 at 09:53:11AM +0100, Russell King - ARM Linux wrote:
> On Sat, Jun 24, 2017 at 05:38:42PM +0200, Luc Van Oostenryck wrote:
> > ARM depends on the macros '__ARMEL__' & '__ARMEB__' being defined
> > or not to correctly select or define endian-specific macros,
> > structures or pieces of code.
> > 
> > These macros are predefined by the compiler but sparse knows
> > nothing about them and thus may pre-process files differently
> > from what gcc would.
> > 
> > Fix this by passing '-D__ARMEL__' or '-D__ARMEB__' to sparse,
> > depending of the endianness of the kernel, like defined by GCC.
> > 
> > Note: In most case it won't change anything since most ARMs use
> >       little-endian (but an allyesconfig would use big-endian!).
> 
> I wonder if that's a good thing - as this changes the endian conversion
> macros and ifdefs around bitfield declarations, it means that we're not
> testing the "popular" paths with an allyesconfig sparse - but then again,
> I think allyesconfig with sparse is a very bad idea, it needs to be
> targetted to the area being worked in.

The problem is that on any CONFIG_CPU_BIG_ENDIAN config, sparse
will process the wrong code after a '#if[n]def __ARMEB__'. Same,
of course with a little-endian config and '#if[n]def __ARMEL__'.

Since only two files test after __ARMEL__ :
- crypto/sha1-armv4-large.S
- crypto/sha512-core.S
most of the code are checked correctly for a little-endian config.
The same is not true for a big endian config since all the others
tests are made against __ARMEB__.

In short no big-endian config have never been sparse-checked for
endiannness problems on ARM. Worse, they are wrongly checked.

 
-- Luc Van Oostenryck

[PATCH] arm: pass endianness info to sparse

[Luc Van Oostenryck]

ARM depends on the macros '__ARMEL__' & '__ARMEB__' being defined
or not to correctly select or define endian-specific macros,
structures or pieces of code.

These macros are predefined by the compiler but sparse knows
nothing about them and thus may pre-process files differently
from what gcc would.

Fix this by passing '-D__ARMEL__' or '-D__ARMEB__' to sparse,
depending on the endianness of the kernel, like defined by GCC.

Note: In most case it won't change anything since most ARMs use
      little-endian (but an allyesconfig would use big-endian!).

To: Russell King <linux@armlinux.org.uk>
CC: linux-arm-kernel at lists.infradead.org
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
---
 arch/arm/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 817e5cfef..36ae44545 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -44,10 +44,12 @@ endif
 
 ifeq ($(CONFIG_CPU_BIG_ENDIAN),y)
 KBUILD_CPPFLAGS	+= -mbig-endian
+CHECKFLAGS	+= -D__ARMEB__
 AS		+= -EB
 LD		+= -EB
 else
 KBUILD_CPPFLAGS	+= -mlittle-endian
+CHECKFLAGS	+= -D__ARMEL__
 AS		+= -EL
 LD		+= -EL
 endif
-- 
2.14.0