[PATCH] arm64: pass machine size to sparse

[PATCH] arm64: pass machine size to sparse

[Luc Van Oostenryck]

When using sparse on the arm64 tree we get many thousands of
warnings like 'constant ... is so big it is unsigned long long'
or 'shift too big (32) for type unsigned long'. This happens
because by default sparse considers the machine as 32bit and
defines the size of the types accordingly.

Fix this by passing the '-m64' flag to sparse so that
sparse can correctly define longs as being 64bit.

CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will.deacon@arm.com>
CC: linux-arm-kernel at lists.infradead.org
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
---
 arch/arm64/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index f839ecd91..15d6c1476 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -62,7 +62,7 @@ LD		+= -EL
 UTS_MACHINE	:= aarch64
 endif
 
-CHECKFLAGS	+= -D__aarch64__
+CHECKFLAGS	+= -D__aarch64__ -m64
 
 ifeq ($(CONFIG_ARM64_MODULE_CMODEL_LARGE), y)
 KBUILD_CFLAGS_MODULE	+= -mcmodel=large
-- 
2.13.0

[PATCH] arm64: pass machine size to sparse

[Will Deacon]

On Tue, Jun 20, 2017 at 02:24:43PM +0200, Luc Van Oostenryck wrote:
> When using sparse on the arm64 tree we get many thousands of
> warnings like 'constant ... is so big it is unsigned long long'
> or 'shift too big (32) for type unsigned long'. This happens
> because by default sparse considers the machine as 32bit and
> defines the size of the types accordingly.
> 
> Fix this by passing the '-m64' flag to sparse so that
> sparse can correctly define longs as being 64bit.
> 
> CC: Catalin Marinas <catalin.marinas@arm.com>
> CC: Will Deacon <will.deacon@arm.com>
> CC: linux-arm-kernel at lists.infradead.org
> Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> ---
>  arch/arm64/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index f839ecd91..15d6c1476 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -62,7 +62,7 @@ LD		+= -EL
>  UTS_MACHINE	:= aarch64
>  endif
>  
> -CHECKFLAGS	+= -D__aarch64__
> +CHECKFLAGS	+= -D__aarch64__ -m64

Looks fine to me, but just wondering whether or not we should also be
passing something to indicate the endianness of the target. Does sparse care
about that?

Will

Re: [PATCH] arm64: pass machine size to sparse

[Luc Van Oostenryck]

On Tue, Jun 20, 2017 at 04:49:39PM +0100, Will Deacon wrote:
> On Tue, Jun 20, 2017 at 02:24:43PM +0200, Luc Van Oostenryck wrote:
> > When using sparse on the arm64 tree we get many thousands of
> > warnings like 'constant ... is so big it is unsigned long long'
> > or 'shift too big (32) for type unsigned long'. This happens
> > because by default sparse considers the machine as 32bit and
> > defines the size of the types accordingly.
> > 
> > Fix this by passing the '-m64' flag to sparse so that
> > sparse can correctly define longs as being 64bit.
> > 
> > CC: Catalin Marinas <catalin.marinas@arm.com>
> > CC: Will Deacon <will.deacon@arm.com>
> > CC: linux-arm-kernel@lists.infradead.org
> > Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> > ---
> >  arch/arm64/Makefile | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> > index f839ecd91..15d6c1476 100644
> > --- a/arch/arm64/Makefile
> > +++ b/arch/arm64/Makefile
> > @@ -62,7 +62,7 @@ LD		+= -EL
> >  UTS_MACHINE	:= aarch64
> >  endif
> >  
> > -CHECKFLAGS	+= -D__aarch64__
> > +CHECKFLAGS	+= -D__aarch64__ -m64
> 
> Looks fine to me, but just wondering whether or not we should also be
> passing something to indicate the endianness of the target. Does sparse care
> about that?

Yes, we should. sparse doesn't care per-se but some macros, structures
or whole portion of code may depends on '__{LITTLE,BIG}_ENDIAN__'
being defined or not, for example (but I don't think it will make
a big difference, at least nothing like the 629904 'constant is so big'
warnings we have now due to the missing -m64).

For this, you have two possibilities:
1) just doing something like PPC:
	+ifdef CONFIG_CPU_BIG_ENDIAN
	+CHECKFLAGS     += -D__BIG_ENDIAN__
	+else
	+CHECKFLAGS     += -D__LITTLE_ENDIAN__
	+endif
   This will work now. I can't send you a proper patch if you wish.

2) a cleaner solution, IMO, would be to teach sparse about
   -mlittle-endian/-mbig-endian. In fact I already wrote the patch
   earlier today. But of course, you will need to wait for the patch
   to reach sparse's master and then compile sparse yourself or wait
   for a new release (which shouldn't take much long, though).

Regards,
-- Luc Van Oostenryck

[PATCH] arm64: pass machine size to sparse

[Luc Van Oostenryck]

On Tue, Jun 20, 2017 at 04:49:39PM +0100, Will Deacon wrote:
> On Tue, Jun 20, 2017 at 02:24:43PM +0200, Luc Van Oostenryck wrote:
> > When using sparse on the arm64 tree we get many thousands of
> > warnings like 'constant ... is so big it is unsigned long long'
> > or 'shift too big (32) for type unsigned long'. This happens
> > because by default sparse considers the machine as 32bit and
> > defines the size of the types accordingly.
> > 
> > Fix this by passing the '-m64' flag to sparse so that
> > sparse can correctly define longs as being 64bit.
> > 
> > CC: Catalin Marinas <catalin.marinas@arm.com>
> > CC: Will Deacon <will.deacon@arm.com>
> > CC: linux-arm-kernel at lists.infradead.org
> > Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> > ---
> >  arch/arm64/Makefile | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> > index f839ecd91..15d6c1476 100644
> > --- a/arch/arm64/Makefile
> > +++ b/arch/arm64/Makefile
> > @@ -62,7 +62,7 @@ LD		+= -EL
> >  UTS_MACHINE	:= aarch64
> >  endif
> >  
> > -CHECKFLAGS	+= -D__aarch64__
> > +CHECKFLAGS	+= -D__aarch64__ -m64
> 
> Looks fine to me, but just wondering whether or not we should also be
> passing something to indicate the endianness of the target. Does sparse care
> about that?

Yes, we should. sparse doesn't care per-se but some macros, structures
or whole portion of code may depends on '__{LITTLE,BIG}_ENDIAN__'
being defined or not, for example (but I don't think it will make
a big difference, at least nothing like the 629904 'constant is so big'
warnings we have now due to the missing -m64).

For this, you have two possibilities:
1) just doing something like PPC:
	+ifdef CONFIG_CPU_BIG_ENDIAN
	+CHECKFLAGS     += -D__BIG_ENDIAN__
	+else
	+CHECKFLAGS     += -D__LITTLE_ENDIAN__
	+endif
   This will work now. I can't send you a proper patch if you wish.

2) a cleaner solution, IMO, would be to teach sparse about
   -mlittle-endian/-mbig-endian. In fact I already wrote the patch
   earlier today. But of course, you will need to wait for the patch
   to reach sparse's master and then compile sparse yourself or wait
   for a new release (which shouldn't take much long, though).

Regards,
-- Luc Van Oostenryck

Re: [PATCH] arm64: pass machine size to sparse

[Will Deacon]

On Tue, Jun 20, 2017 at 06:24:32PM +0200, Luc Van Oostenryck wrote:
> On Tue, Jun 20, 2017 at 04:49:39PM +0100, Will Deacon wrote:
> > On Tue, Jun 20, 2017 at 02:24:43PM +0200, Luc Van Oostenryck wrote:
> > > When using sparse on the arm64 tree we get many thousands of
> > > warnings like 'constant ... is so big it is unsigned long long'
> > > or 'shift too big (32) for type unsigned long'. This happens
> > > because by default sparse considers the machine as 32bit and
> > > defines the size of the types accordingly.
> > > 
> > > Fix this by passing the '-m64' flag to sparse so that
> > > sparse can correctly define longs as being 64bit.
> > > 
> > > CC: Catalin Marinas <catalin.marinas@arm.com>
> > > CC: Will Deacon <will.deacon@arm.com>
> > > CC: linux-arm-kernel@lists.infradead.org
> > > Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> > > ---
> > >  arch/arm64/Makefile | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> > > index f839ecd91..15d6c1476 100644
> > > --- a/arch/arm64/Makefile
> > > +++ b/arch/arm64/Makefile
> > > @@ -62,7 +62,7 @@ LD		+= -EL
> > >  UTS_MACHINE	:= aarch64
> > >  endif
> > >  
> > > -CHECKFLAGS	+= -D__aarch64__
> > > +CHECKFLAGS	+= -D__aarch64__ -m64
> > 
> > Looks fine to me, but just wondering whether or not we should also be
> > passing something to indicate the endianness of the target. Does sparse care
> > about that?
> 
> Yes, we should. sparse doesn't care per-se but some macros, structures
> or whole portion of code may depends on '__{LITTLE,BIG}_ENDIAN__'
> being defined or not, for example (but I don't think it will make
> a big difference, at least nothing like the 629904 'constant is so big'
> warnings we have now due to the missing -m64).
> 
> For this, you have two possibilities:
> 1) just doing something like PPC:
> 	+ifdef CONFIG_CPU_BIG_ENDIAN
> 	+CHECKFLAGS     += -D__BIG_ENDIAN__
> 	+else
> 	+CHECKFLAGS     += -D__LITTLE_ENDIAN__
> 	+endif
>    This will work now. I can't send you a proper patch if you wish.
> 
> 2) a cleaner solution, IMO, would be to teach sparse about
>    -mlittle-endian/-mbig-endian. In fact I already wrote the patch
>    earlier today. But of course, you will need to wait for the patch
>    to reach sparse's master and then compile sparse yourself or wait
>    for a new release (which shouldn't take much long, though).

If you do that, you could also teach it that AArch64 is 64-bit ;)

Will

[PATCH] arm64: pass machine size to sparse

[Will Deacon]

On Tue, Jun 20, 2017 at 06:24:32PM +0200, Luc Van Oostenryck wrote:
> On Tue, Jun 20, 2017 at 04:49:39PM +0100, Will Deacon wrote:
> > On Tue, Jun 20, 2017 at 02:24:43PM +0200, Luc Van Oostenryck wrote:
> > > When using sparse on the arm64 tree we get many thousands of
> > > warnings like 'constant ... is so big it is unsigned long long'
> > > or 'shift too big (32) for type unsigned long'. This happens
> > > because by default sparse considers the machine as 32bit and
> > > defines the size of the types accordingly.
> > > 
> > > Fix this by passing the '-m64' flag to sparse so that
> > > sparse can correctly define longs as being 64bit.
> > > 
> > > CC: Catalin Marinas <catalin.marinas@arm.com>
> > > CC: Will Deacon <will.deacon@arm.com>
> > > CC: linux-arm-kernel at lists.infradead.org
> > > Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
> > > ---
> > >  arch/arm64/Makefile | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> > > index f839ecd91..15d6c1476 100644
> > > --- a/arch/arm64/Makefile
> > > +++ b/arch/arm64/Makefile
> > > @@ -62,7 +62,7 @@ LD		+= -EL
> > >  UTS_MACHINE	:= aarch64
> > >  endif
> > >  
> > > -CHECKFLAGS	+= -D__aarch64__
> > > +CHECKFLAGS	+= -D__aarch64__ -m64
> > 
> > Looks fine to me, but just wondering whether or not we should also be
> > passing something to indicate the endianness of the target. Does sparse care
> > about that?
> 
> Yes, we should. sparse doesn't care per-se but some macros, structures
> or whole portion of code may depends on '__{LITTLE,BIG}_ENDIAN__'
> being defined or not, for example (but I don't think it will make
> a big difference, at least nothing like the 629904 'constant is so big'
> warnings we have now due to the missing -m64).
> 
> For this, you have two possibilities:
> 1) just doing something like PPC:
> 	+ifdef CONFIG_CPU_BIG_ENDIAN
> 	+CHECKFLAGS     += -D__BIG_ENDIAN__
> 	+else
> 	+CHECKFLAGS     += -D__LITTLE_ENDIAN__
> 	+endif
>    This will work now. I can't send you a proper patch if you wish.
> 
> 2) a cleaner solution, IMO, would be to teach sparse about
>    -mlittle-endian/-mbig-endian. In fact I already wrote the patch
>    earlier today. But of course, you will need to wait for the patch
>    to reach sparse's master and then compile sparse yourself or wait
>    for a new release (which shouldn't take much long, though).

If you do that, you could also teach it that AArch64 is 64-bit ;)

Will

Re: [PATCH] arm64: pass machine size to sparse

[Luc Van Oostenryck]

On Tue, Jun 20, 2017 at 06:04:01PM +0100, Will Deacon wrote:
> On Tue, Jun 20, 2017 at 06:24:32PM +0200, Luc Van Oostenryck wrote:
> > On Tue, Jun 20, 2017 at 04:49:39PM +0100, Will Deacon wrote:
> > > Looks fine to me, but just wondering whether or not we should also be
> > > passing something to indicate the endianness of the target. Does sparse care
> > > about that?
> > 
> > Yes, we should. sparse doesn't care per-se but some macros, structures
> > or whole portion of code may depends on '__{LITTLE,BIG}_ENDIAN__'
> > being defined or not, for example (but I don't think it will make
> > a big difference, at least nothing like the 629904 'constant is so big'
> > warnings we have now due to the missing -m64).
> > 
> > For this, you have two possibilities:
> > 1) just doing something like PPC:
> > 	+ifdef CONFIG_CPU_BIG_ENDIAN
> > 	+CHECKFLAGS     += -D__BIG_ENDIAN__
> > 	+else
> > 	+CHECKFLAGS     += -D__LITTLE_ENDIAN__
> > 	+endif
> >    This will work now. I can't send you a proper patch if you wish.
> > 
> > 2) a cleaner solution, IMO, would be to teach sparse about
> >    -mlittle-endian/-mbig-endian. In fact I already wrote the patch
> >    earlier today. But of course, you will need to wait for the patch
> >    to reach sparse's master and then compile sparse yourself or wait
> >    for a new release (which shouldn't take much long, though).
> 
> If you do that, you could also teach it that AArch64 is 64-bit ;)

Well, currently sparse is arch agnostic and I think it's a good thing.
For the few arch specifities you have to use some of the '-m' flags
(like -m32/-m64, -msize-long). So, for the moment the '-m64' flag
is needed, thus the patch.

-- Luc

[PATCH] arm64: pass machine size to sparse

[Luc Van Oostenryck]

On Tue, Jun 20, 2017 at 06:04:01PM +0100, Will Deacon wrote:
> On Tue, Jun 20, 2017 at 06:24:32PM +0200, Luc Van Oostenryck wrote:
> > On Tue, Jun 20, 2017 at 04:49:39PM +0100, Will Deacon wrote:
> > > Looks fine to me, but just wondering whether or not we should also be
> > > passing something to indicate the endianness of the target. Does sparse care
> > > about that?
> > 
> > Yes, we should. sparse doesn't care per-se but some macros, structures
> > or whole portion of code may depends on '__{LITTLE,BIG}_ENDIAN__'
> > being defined or not, for example (but I don't think it will make
> > a big difference, at least nothing like the 629904 'constant is so big'
> > warnings we have now due to the missing -m64).
> > 
> > For this, you have two possibilities:
> > 1) just doing something like PPC:
> > 	+ifdef CONFIG_CPU_BIG_ENDIAN
> > 	+CHECKFLAGS     += -D__BIG_ENDIAN__
> > 	+else
> > 	+CHECKFLAGS     += -D__LITTLE_ENDIAN__
> > 	+endif
> >    This will work now. I can't send you a proper patch if you wish.
> > 
> > 2) a cleaner solution, IMO, would be to teach sparse about
> >    -mlittle-endian/-mbig-endian. In fact I already wrote the patch
> >    earlier today. But of course, you will need to wait for the patch
> >    to reach sparse's master and then compile sparse yourself or wait
> >    for a new release (which shouldn't take much long, though).
> 
> If you do that, you could also teach it that AArch64 is 64-bit ;)

Well, currently sparse is arch agnostic and I think it's a good thing.
For the few arch specifities you have to use some of the '-m' flags
(like -m32/-m64, -msize-long). So, for the moment the '-m64' flag
is needed, thus the patch.

-- Luc

Re: [PATCH] arm64: pass machine size to sparse

[Will Deacon]

On Tue, Jun 20, 2017 at 09:07:40PM +0200, Luc Van Oostenryck wrote:
> On Tue, Jun 20, 2017 at 06:04:01PM +0100, Will Deacon wrote:
> > On Tue, Jun 20, 2017 at 06:24:32PM +0200, Luc Van Oostenryck wrote:
> > > On Tue, Jun 20, 2017 at 04:49:39PM +0100, Will Deacon wrote:
> > > > Looks fine to me, but just wondering whether or not we should also be
> > > > passing something to indicate the endianness of the target. Does sparse care
> > > > about that?
> > > 
> > > Yes, we should. sparse doesn't care per-se but some macros, structures
> > > or whole portion of code may depends on '__{LITTLE,BIG}_ENDIAN__'
> > > being defined or not, for example (but I don't think it will make
> > > a big difference, at least nothing like the 629904 'constant is so big'
> > > warnings we have now due to the missing -m64).
> > > 
> > > For this, you have two possibilities:
> > > 1) just doing something like PPC:
> > > 	+ifdef CONFIG_CPU_BIG_ENDIAN
> > > 	+CHECKFLAGS     += -D__BIG_ENDIAN__
> > > 	+else
> > > 	+CHECKFLAGS     += -D__LITTLE_ENDIAN__
> > > 	+endif
> > >    This will work now. I can't send you a proper patch if you wish.
> > > 
> > > 2) a cleaner solution, IMO, would be to teach sparse about
> > >    -mlittle-endian/-mbig-endian. In fact I already wrote the patch
> > >    earlier today. But of course, you will need to wait for the patch
> > >    to reach sparse's master and then compile sparse yourself or wait
> > >    for a new release (which shouldn't take much long, though).
> > 
> > If you do that, you could also teach it that AArch64 is 64-bit ;)
> 
> Well, currently sparse is arch agnostic and I think it's a good thing.
> For the few arch specifities you have to use some of the '-m' flags
> (like -m32/-m64, -msize-long). So, for the moment the '-m64' flag
> is needed, thus the patch.

Ok, I'll pick your patch up then. The endianness case is more interesting,
because I don't think __BIG_ENDIAN__ and __LITTLE_ENDIAN__ are the defines
to use; the kernel seems to omit the trailing underscores afaict.

Will

[PATCH] arm64: pass machine size to sparse

[Will Deacon]

On Tue, Jun 20, 2017 at 09:07:40PM +0200, Luc Van Oostenryck wrote:
> On Tue, Jun 20, 2017 at 06:04:01PM +0100, Will Deacon wrote:
> > On Tue, Jun 20, 2017 at 06:24:32PM +0200, Luc Van Oostenryck wrote:
> > > On Tue, Jun 20, 2017 at 04:49:39PM +0100, Will Deacon wrote:
> > > > Looks fine to me, but just wondering whether or not we should also be
> > > > passing something to indicate the endianness of the target. Does sparse care
> > > > about that?
> > > 
> > > Yes, we should. sparse doesn't care per-se but some macros, structures
> > > or whole portion of code may depends on '__{LITTLE,BIG}_ENDIAN__'
> > > being defined or not, for example (but I don't think it will make
> > > a big difference, at least nothing like the 629904 'constant is so big'
> > > warnings we have now due to the missing -m64).
> > > 
> > > For this, you have two possibilities:
> > > 1) just doing something like PPC:
> > > 	+ifdef CONFIG_CPU_BIG_ENDIAN
> > > 	+CHECKFLAGS     += -D__BIG_ENDIAN__
> > > 	+else
> > > 	+CHECKFLAGS     += -D__LITTLE_ENDIAN__
> > > 	+endif
> > >    This will work now. I can't send you a proper patch if you wish.
> > > 
> > > 2) a cleaner solution, IMO, would be to teach sparse about
> > >    -mlittle-endian/-mbig-endian. In fact I already wrote the patch
> > >    earlier today. But of course, you will need to wait for the patch
> > >    to reach sparse's master and then compile sparse yourself or wait
> > >    for a new release (which shouldn't take much long, though).
> > 
> > If you do that, you could also teach it that AArch64 is 64-bit ;)
> 
> Well, currently sparse is arch agnostic and I think it's a good thing.
> For the few arch specifities you have to use some of the '-m' flags
> (like -m32/-m64, -msize-long). So, for the moment the '-m64' flag
> is needed, thus the patch.

Ok, I'll pick your patch up then. The endianness case is more interesting,
because I don't think __BIG_ENDIAN__ and __LITTLE_ENDIAN__ are the defines
to use; the kernel seems to omit the trailing underscores afaict.

Will

Re: [PATCH] arm64: pass machine size to sparse

[Luc Van Oostenryck]

On Wed, Jun 21, 2017 at 05:12:54PM +0100, Will Deacon wrote:
> On Tue, Jun 20, 2017 at 09:07:40PM +0200, Luc Van Oostenryck wrote:
> > Well, currently sparse is arch agnostic and I think it's a good thing.
> > For the few arch specifities you have to use some of the '-m' flags
> > (like -m32/-m64, -msize-long). So, for the moment the '-m64' flag
> > is needed, thus the patch.
> 
> Ok, I'll pick your patch up then. The endianness case is more interesting,
> because I don't think __BIG_ENDIAN__ and __LITTLE_ENDIAN__ are the defines
> to use; the kernel seems to omit the trailing underscores afaict.

I just checked, it's a bit messy.
The kernel seems to rely, at least partly, maybe mostly, on
CONFIG_CPU_{BIG,LITTLE}_ENDIAN and then __{BIG,LITTLE}_ENDIAN is
defined via include/uapi/linux/byteorder/{big,little}_endian.h

Otherwise, from the compiler side it seems that __BYTE_ORDER__ &
__ORDER_{BIG,LITTLE}_ENDIAN__ is defined consistently.
But, for example for arm64, 'gcc -mlittle-endian' gives
	#define __LITTLE_ENDIAN__ 1
while 'gcc -mbig-endian' doesn't define __BIG_ENDIAN__ but
	#define __ARM_BIG_ENDIAN 1

*shrugh*

I've added support for the -m{big,little}-endian flag to sparse
but it seems it will be more complicated for the defines.

-- Luc

[PATCH] arm64: pass machine size to sparse

[Luc Van Oostenryck]

On Wed, Jun 21, 2017 at 05:12:54PM +0100, Will Deacon wrote:
> On Tue, Jun 20, 2017 at 09:07:40PM +0200, Luc Van Oostenryck wrote:
> > Well, currently sparse is arch agnostic and I think it's a good thing.
> > For the few arch specifities you have to use some of the '-m' flags
> > (like -m32/-m64, -msize-long). So, for the moment the '-m64' flag
> > is needed, thus the patch.
> 
> Ok, I'll pick your patch up then. The endianness case is more interesting,
> because I don't think __BIG_ENDIAN__ and __LITTLE_ENDIAN__ are the defines
> to use; the kernel seems to omit the trailing underscores afaict.

I just checked, it's a bit messy.
The kernel seems to rely, at least partly, maybe mostly, on
CONFIG_CPU_{BIG,LITTLE}_ENDIAN and then __{BIG,LITTLE}_ENDIAN is
defined via include/uapi/linux/byteorder/{big,little}_endian.h

Otherwise, from the compiler side it seems that __BYTE_ORDER__ &
__ORDER_{BIG,LITTLE}_ENDIAN__ is defined consistently.
But, for example for arm64, 'gcc -mlittle-endian' gives
	#define __LITTLE_ENDIAN__ 1
while 'gcc -mbig-endian' doesn't define __BIG_ENDIAN__ but
	#define __ARM_BIG_ENDIAN 1

*shrugh*

I've added support for the -m{big,little}-endian flag to sparse
but it seems it will be more complicated for the defines.

-- Luc