Am Tue, 25 Sep 2012 22:37:13 +0200
schrieb Geert Uytterhoeven [off-list ref]:

On Tue, Sep 25, 2012 at 9:43 PM, Al Viro [off-list ref]
wrote:

quoted

On Tue, Sep 25, 2012 at 12:20:55PM -0700, Linus Torvalds wrote:

quoted

IOW, this part of the patch:

-       c_flags = -Wp,-MD,$(depfile) $(USER_CFLAGS) -include user.h
$(CFLAGS_$(basetarget).o)
+       c_flags = -Wp,-MD,$(depfile) $(USER_CFLAGS) -include
$(srctree)/include/linux/kern_levels.h -include user.h
$(CFLAGS_$(basetarget).o)

just makes me go want to puke. The user.h file already has other
#include's in it, so I really don't see why you create this insane
special case.

And why does UM have those "UM_KERN_XYZ" defines in the first
place? Why isn't it just using KERN_XYZ directly? Is it because
kern_levels.h didn't use to exist, so it was some kind of "let's
create our own that we can hide in our special headers".

Because user.h is included *without* kernel headers in include path.

Indeed.

quoted

It's for the stuff that is compiled with host libc headers.  Keep in
mind that UML talks to libc like normal architecture would talk to
hardware.  IOW, analogs of asm glue are in (host) userland C.  And
they need libc headers instead of the kernel ones.  That's what that
USER_OBJ thing is about.  Kernel-side constants, etc. are delivered
to that sucker using the same mechanism we normally use to give them
to assembler - asm-offsets.c.  And here, of course, slapping ifndef
__ASSEMBLER__ around the tricky bits will not work - the header
itself is just fine, but getting kernel headers in the search path
really isn't.

        I agree that proposed solution is ugly.  What we can do is
copy the damn header into include/generated and #include
<generated/kern_levels.h> from user.h.  And kill UM_KERN_...
stuff.  Objections?

My first submission had "We may convert all UM_KERN_* users to KERN_*
and drop the extra defines?" as a suggestion, but so far I haven't
found time to implement that...

Still, no one came up with a better patch, and this is a regression.

Yeah, I'd like to take the "ugly" patch to get rid of the regresion.
Later we can get rid of UM_KERN_*, which is IMHO also very ugly.

Thanks,
//richard