sh: Tidy up and generalize page fault error paths.

This follows the x86 changes for tidying up the page fault error paths.
We'll build on top of this for _32/_64 unification.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh64: Provide EXPEVT helper.

We need a lookup_exception_vector() helper for sh64 in order to use the
common page fault code.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh: Support thread fault code encoding.

This provides a simple interface modelled after sparc64/m32r to encode
the error code in the upper byte of thread_info for finer-grained
handling in the page fault path.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh64: Utilize thread fault code encoding.

This plugs in fault code encoding for the sh64 page fault, too.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh: Ensure fixmap and store queue space can co-exist.

At the moment the top of the fixmap space is calculated from P4SEG, which
places it at the end of the store queue space when that API is enabled.
Make sure we use P3_ADDR_MAX here instead to find the proper address
limit. With this done, it's also possible to switch to the generic
vmalloc address range check now that VMALLOC_START/END encapsulate the
translatable areas that we care about.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh64: Kill off unused fixed I/O mapping window.

This was reworked some time ago to go through fixmaps instead, leaving
the range itself unused. As such, kill off the remaining references and
hand over the remaining space for fixmaps directly. This also makes it
possible to simplify the vmalloc fault case as we no longer have to care
about the special section.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh: Enable shared page fault handler for _32/_64.

This moves the now generic _32 page fault handling code to a shared place
and adapts the _64 implementation to make use of it.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh64: Migrate to __update_tlb() API.

Now that we have a method for finding out if we're handling an ITLB fault
or not without passing it all the way down the chain, it's possible to
use the __update_tlb() interface in place of a special __do_tlb_refill().

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh64: Invert page fault fast-path error path values.

This brings the sh64 version in line with the sh32 one with regards to
how errors are handled. Base work for further unification of the
implementations.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh64: Fix up caller-save register settings for fast-path.

Now that the fast-path handler has been moved, we also need to update the
Makefile to ensure that the same restrictions for caller-save registers
are observed.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh64: Tidy up and consolidate the TLB miss fast path.

This unifies the fast-path TLB miss handler, allowing for further cleanup
and eventual utilization of a shared _32/_64 handler.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
sh64: Set additional fault code values.

The SSR.MD status amongst other things are already made available, which
can be used for encoding a more precise fault code value.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>