klibc - Feb 2011 - [PATCH] build: Define __EXPORTED_HEADER__

The kernel header guard to ensure that headers aren't included from
userland moved in commit 69c8f52b.  This causes the following message to
be emitted when building klibc (which is designed to use kernel headers
explicitly):

/usr/local/src/git/linux-2.6//include/linux/types.h:13:2: warning: #warning
"Attempt to use kernel headers from user space, see
http://kernelnewbies.org/KernelHeaders"

In order to silence this warning, make sure we define
__EXPORTED_HEADERS__ when building klibc userland.

Signed-off-by: Mike Waychison <mikew at google.com>
---
 scripts/Kbuild.klibc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/scripts/Kbuild.klibc b/scripts/Kbuild.klibc
index fb399f5..52a95c4 100644
--- a/scripts/Kbuild.klibc
+++ b/scripts/Kbuild.klibc
@@ -74,7 +74,7 @@ KLIBCWARNFLAGS    := -W -Wall -Wno-sign-compare
-Wno-unused-parameter
 KLIBCSHAREDFLAGS  : KLIBCBITSIZE      : KLIBCLDFLAGS      :-KLIBCCFLAGS      
:+KLIBCCFLAGS       := -D__EXPORTED_HEADERS__
 
 # Defaults for arch to override
 KLIBCARCHINCFLAGS = -I$(KLIBCKERNELOBJ)/arch/$(KLIBCARCH)/include
-- 
1.7.3.1

On Thursday 24 February 2011, Mike Waychison wrote:
> The kernel header guard to ensure that headers aren't included from
> userland moved in commit 69c8f52b.  This causes the following message to
> be emitted when building klibc (which is designed to use kernel headers
> explicitly):
> 
> /usr/local/src/git/linux-2.6//include/linux/types.h:13:2: warning: #warning
"Attempt to use kernel headers from user space, see
http://kernelnewbies.org/KernelHeaders"
> 
> In order to silence this warning, make sure we define
> __EXPORTED_HEADERS__ when building klibc userland.
> 
> Signed-off-by: Mike Waychison <mikew at google.com>
Well, klibc uses the kernel headers, but I don't think it's a good idea
to use them directly without make headers_install. Since klibc also
doesn't set -D__KERNEL__, the result should be the same, except that
it makes sure not to use any headers that are meant to be internal.

	Arnd

On Thu, Feb 24, 2011 at 6:19 AM, Arnd Bergmann <arnd at arndb.de>
wrote:
> On Thursday 24 February 2011, Mike Waychison wrote:
>> The kernel header guard to ensure that headers aren't included from
>> userland moved in commit 69c8f52b. ?This causes the following message
to
>> be emitted when building klibc (which is designed to use kernel headers
>> explicitly):
>>
>> /usr/local/src/git/linux-2.6//include/linux/types.h:13:2: warning:
#warning "Attempt to use kernel headers from user space, see
http://kernelnewbies.org/KernelHeaders"
>>
>> In order to silence this warning, make sure we define
>> __EXPORTED_HEADERS__ when building klibc userland.
>>
>> Signed-off-by: Mike Waychison <mikew at google.com>
>
> Well, klibc uses the kernel headers, but I don't think it's a good
idea
> to use them directly without make headers_install. Since klibc also
> doesn't set -D__KERNEL__, the result should be the same, except that
> it makes sure not to use any headers that are meant to be internal.
I'm not sure I follow.  The warning happens when __KERNEL__ isn't set.

Also, the build for klibc explicitly supports using kernel headers
without installing them first via setting KLIBCKERNELSRC.

On Sun, Feb 27, 2011 at 12:07 PM, Arnd Bergmann <arnd at arndb.de>
wrote:
> On Saturday 26 February 2011, Sam Ravnborg wrote:
>> >
>> > What you are proposing seems to me like a step towards giving up
on
>> > this noble goal :(
>> You seem to be confusing something here. Even if klibc is one day
>> included in the kernel source then we should continue to use
>> the headers generated using "make headers_install" for
building klibc.
>
> Absolutely, yes.
>
> Mike, just think of the generated header files as intermediate files
> required for building, just like the .o files that are use to build
> the library.
How is one expected to test if the files should be rebuild or not?
Forcing a headers_install as part of a build will cause the entire
userland to be rebuilt.

On Monday 28 February 2011, Mike Waychison wrote:
> How is one expected to test if the files should be rebuild or not?
> Forcing a headers_install as part of a build will cause the entire
> userland to be rebuilt.
How about changing headers_install to only install files that have
changed? Make headers_install alreadh knows the list of all files
it is installing.

	Arnd

On Mon, Feb 28, 2011 at 01:11:16PM +0100, Arnd Bergmann
wrote:
> On Monday 28 February 2011, Mike Waychison wrote:
> > How is one expected to test if the files should be rebuild or not?
> > Forcing a headers_install as part of a build will cause the entire
> > userland to be rebuilt.
> 
> How about changing headers_install to only install files that have
> changed? Make headers_install alreadh knows the list of all files
> it is installing.
make headers_install already does so. Only changes fiels are updated.
So I consider this a non-issue.

	Sam