We generate an <asm/foo.h> which includes either <asm-$ARCH/foo.h> or
<asm-$ALTARCH/foo.h> as appropriate.  But we were doing this dependent on
whether the file in question existed in the _unexported_ tree, not the
exported tree.  So if a file was exported to userspace in one asm- directory
but not the other, the generated file in asm/ was incorrect.

This only changed the failure mode if it _was_ included from a nice #error to
a less explicable #include failure -- but it also gave false errors in 'make
headers_check' output.  Fix it by looking in the right place instead.
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Based on the 'headers_install' target, this performs a basic sanity check
on the exported headers -- so far only checking that they do not include
any other headers which aren't selected for import, but easily extendable.
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>

This adds a make target which exports a subset of headers which contain
definitions which are useful for system libraries and tools. It uses the
BSD 'unifdef' tool to remove instances of #ifdef __KERNEL__, and uses
sed to remove markers like __user.

Based on an original implementation by Arnd Bergmann <arnd@arndb.de>
Hacked about by David Woodhouse <dwmw2@infradead.org>
Reviewed and cleaned up by Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>