Kbuild, lto: Set TMPDIR for LTO v4

LTO gcc puts a lot of data into $TMPDIR, essentially another copy
of the object directory to pass the repartitioned object files
to the code generation processes.

TMPDIR defaults to /tmp With /tmp as tmpfs it's easy to drive systems to
out of memory, because they will compete with the already high anonymous
memory consumption of the wpa LTO pass.

When LTO is set always set TMPDIR to the object directory. This could
be slightly slower, but is far safer and eliminates another parameter
the LTO user would need to set manually.

I made it conditional on LTO for now.

v2: Allow user to override (H. Peter Anvin)
v3: Use standard kernel variable style
v4: Print message for redirection (M.Marek)
Signed-off-by: Andi Kleen <ak@linux.intel.com>
lto, workaround: Disable LTO for filter.c

Disable LTO for filter.c. This works around a gcc bug in the LTO
partitioner that partitions the jumptable from the BPF interpreter
into a different LTO unit. This in term causes assembler
errors because the jump table contains references to the
code labels in the original file.

Better workaround needed.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
asmlinkage: Revert "lto: Make asmlinkage __visible"

As requested by Linus, revert adding __visible to asmlinkage.
Instead we add __visible explicitely to all the symbols
that need it.

This reverts commit 128ea04a9885af9629059e631ddf0cab4815b589.

Link: http://lkml.kernel.org/r/1398984278-29319-2-git-send-email-andi@firstfloor.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
x86, asmlinkage, paravirt: Make paravirt thunks global

The paravirt thunks use a hack of using a static reference to a static
function to reference that function from the top level statement.

This assumes that gcc always generates static function names in a specific
format, which is not necessarily true.

Simply make these functions global and asmlinkage or __visible. This way the
static __used variables are not needed and everything works.

Functions with arguments are __visible to keep the register calling
convention on 32bit.

Changed in paravirt and in all users (Xen and vsmp)

v2: Use __visible for functions with arguments

Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Ido Yariv <ido@wizery.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1382458079-24450-5-git-send-email-andi@firstfloor.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>