The test to check whether we have _PAGE_SPECIAL defined is broken,
since we always define it, just not always to a meaninful value :-)

That broke 8xx and 40x under some circumstances.

This fixes it by adding _PAGE_SPECIAL for both of these since they
had a free PTE bit, and removing the condition around advertising
it.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This is an attempt at cleaning up a bit the way we handle execute
permission on powerpc. _PAGE_HWEXEC is gone, _PAGE_EXEC is now only
defined by CPUs that can do something with it, and the myriad of
#ifdef's in the I$/D$ coherency code is reduced to 2 cases that
hopefully should cover everything.

The logic on BookE is a little bit different than what it was though
not by much. Since now, _PAGE_EXEC will be set by the generic code
for executable pages, we need to filter out if they are unclean and
recover it. However, I don't expect the code to be more bloated than
it already was in that area due to that change.

I could boast that this brings proper enforcing of per-page execute
permissions to all BookE and 40x but in fact, we've had that now for
some time as a side effect of my previous rework in that area (and
I didn't even know it :-) We would only enable execute permission if
the page was cache clean and we would only cache clean it if we took
and exec fault. Since we now enforce that the later only work if
VM_EXEC is part of the VMA flags, we de-fact already enforce per-page
execute permissions... Unless I missed something
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This adds the PTE and pgtable format definitions, along with changes
to the kernel memory map and other definitions related to implementing
support for 64-bit Book3E. This also shields some asm-offset bits that
are currently only relevant on 32-bit

We also move the definition of the "linux" page size constants to
the common mmu.h file and add a few sizes that are relevant to
embedded processors.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This fixes a problem reported by Sean MacLennan where loading any
module would cause an oops.  We weren't marking the pages containing
the module text as having hardware execute permission, due to a bug
introduced in commit 8d1cf34e ("powerpc/mm: Tweak PTE bit combination
definitions"), hence trying to execute the module text caused an
exception on processors that support hardware execute permission.

This adds _PAGE_HWEXEC to the definitions of PAGE_KERNEL_X and
PAGE_KERNEL_ROX to fix this problem.
Reported-by: NSean MacLennan <smaclennan@pikatech.com>
Signed-off-by: NPaul Mackerras <paulus@samba.org>

Now that they are almost identical, we can merge some of the definitions
related to the PTE format into common files.

This creates a new pte-common.h which is included by both 32 and 64-bit
right after the CPU specific pte-*.h file, and which defines some
bits to "default" values if they haven't been defined already, and
then provides a generic definition of most of the bit combinations
based on these and exposed to the rest of the kernel.

I also moved to the common pgtable.h most of the "small" accessors to the
PTE bits and modification helpers (pte_mk*). The actual accessors remain
in their separate files.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>