Page table entries on ARM64 are 64 bits, and some pte functions such as
pte_dirty return a bitwise-and of a flag with the pte value. If the
flag to be tested resides in the upper 32 bits of the pte, then we run
into the danger of the result being dropped if downcast.

For example:
	gather_stats(page, md, pte_dirty(*pte), 1);
where pte_dirty(*pte) is downcast to an int.

This patch adds a double logical invert to all the pte_ accessors to
ensure predictable downcasting.
Signed-off-by: NSteve Capper <steve.capper@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

We have the following means for encoding writable or dirty ptes:

                                PTE_DIRTY       PTE_RDONLY
!pte_dirty && !pte_write        0               1
!pte_dirty && pte_write         0               1
pte_dirty && !pte_write         1               1
pte_dirty && pte_write          1               0

So we can't distinguish between writable clean ptes and read only
ptes. This can cause problems with ptes being incorrectly flagged as
read only when they are writable but not dirty.

This patch introduces a new software bit PTE_WRITE which allows us to
correctly identify writable ptes. PTE_RDONLY is now only clear for
valid ptes where a page is both writable and dirty.
Signed-off-by: NSteve Capper <steve.capper@arm.com>
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Expand out the pte manipulation functions. This makes our life easier
when using things like tags and cscope.
Signed-off-by: NSteve Capper <steve.capper@arm.com>
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

PTE_PROT_NONE means that a pte is present but does not have any
read/write attributes. However, setting the memory type like
pgprot_writecombine() is allowed and such bits overlap with
PTE_PROT_NONE. This causes mmap/munmap issues in drivers that change the
vma->vm_pg_prot on PROT_NONE mappings.

This patch reverts the PTE_FILE/PTE_PROT_NONE shift in commit
59911ca4 (ARM64: mm: Move PTE_PROT_NONE bit) and moves PTE_PROT_NONE
together with the other software bits.
Signed-off-by: NSteve Capper <steve.capper@linaro.org>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Tested-by: NSteve Capper <steve.capper@linaro.org>
Cc: <stable@vger.kernel.org> # 3.11+

This provides better performance compared to Device GRE and also allows
unaligned accesses. Such memory is intended to be used with standard RAM
(e.g. framebuffers) and not I/O.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

This patch expands the VA_BITS to 42 when the 64K page configuration is
enabled allowing 2TB kernel linear mapping. Linux still uses 2 levels of
page tables in this configuration with pgd now being a full page.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Acked-by: NMarc Zyngier <marc.zyngier@arm.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Bring Transparent HugePage support to ARM. The size of a
transparent huge page depends on the normal page size. A
transparent huge page is always represented as a pmd.

If PAGE_SIZE is 4KB, THPs are 2MB.
If PAGE_SIZE is 64KB, THPs are 512MB.
Signed-off-by: NSteve Capper <steve.capper@linaro.org>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>

Add huge page support to ARM64, different huge page sizes are
supported depending on the size of normal pages:

PAGE_SIZE is 4KB:
   2MB - (pmds) these can be allocated at any time.
1024MB - (puds) usually allocated on bootup with the command line
         with something like: hugepagesz=1G hugepages=6

PAGE_SIZE is 64KB:
 512MB - (pmds) usually allocated on bootup via command line.
Signed-off-by: NSteve Capper <steve.capper@linaro.org>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>

Under ARM64, PTEs can be broadly categorised as follows:
   - Present and valid: Bit #0 is set. The PTE is valid and memory
     access to the region may fault.

   - Present and invalid: Bit #0 is clear and bit #1 is set.
     Represents present memory with PROT_NONE protection. The PTE
     is an invalid entry, and the user fault handler will raise a
     SIGSEGV.

   - Not present (file or swap): Bits #0 and #1 are clear.
     Memory represented has been paged out. The PTE is an invalid
     entry, and the fault handler will try and re-populate the
     memory where necessary.

Huge PTEs are block descriptors that have bit #1 clear. If we wish
to represent PROT_NONE huge PTEs we then run into a problem as
there is no way to distinguish between regular and huge PTEs if we
set bit #1.

To resolve this ambiguity this patch moves PTE_PROT_NONE from
bit #1 to bit #2 and moves PTE_FILE from bit #2 to bit #3. The
number of swap/file bits is reduced by 1 as a consequence, leaving
60 bits for file and swap entries.
Signed-off-by: NSteve Capper <steve.capper@linaro.org>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>

If we consider the following code sequence:

	my_pte = pte_modify(entry, myprot);
	x = pte_write(my_pte);
	y = pte_exec(my_pte);

If myprot comes from a PROT_NONE page, then x and y will both be
true which is undesireable behaviour.

This patch sets the no-execute and read-only bits for PAGE_NONE
such that the code above will return false for both x and y.
Signed-off-by: NSteve Capper <steve.capper@linaro.org>
Acked-by: NCatalin Marinas <catalin.marinas@arm.com>

pte_index is a useful helper outside of arch/arm64, for things like the
ARM SMMU driver, so rename __pte_index to pte_index to be consistent
with both arch/arm/ and also the definitions of pmd_index and pgd_index.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Add HYP and S2 page flags, for both normal and device memory.
Reviewed-by: NChristopher Covington <cov@codeaurora.org>
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

This is mostly a port of dbf62d50 ("ARM: mm: introduce L_PTE_VALID
for page table entries") and 26ffd0d4 ("ARM: mm: introduce present,
faulting entries for PAGE_NONE") from ARM, which makes use of present,
faulting page table entries for page table entries mapped as PROT_NONE.

The main difference with this implementation is that we can make use of
the two pte type bits in order to avoid allocating a software bit for
identifying PROT_NONE pages, instead reserving the 10b suffix for these
types of mappings.

This is required to prevent users from accessing such pages via syscalls
such as read/write over a pipe.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

Marking non-present ptes as read-only can corrupt file ptes, breaking
things like swap and file mappings.

This patch ensures that we only manipulate user pte bits when the pte
is marked present.

Cc: <stable@vger.kernel.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The AArch64 Linux port relies on the mm code to wrprotect clean ptes.
This however is not the case with newly created ptes and
PAGE_SHARED(_EXEC) is writable but !dirty.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Cc: <stable@vger.kernel.org>

On AArch64, the meaning of the XN bit has changed to UXN (user). The PXN
(privileged) bit must be set to prevent kernel execution. Without the
PXN bit set, the CPU may speculatively access device memory. This patch
ensures that all the mappings that the kernel must not execute from
(including user mappings) have the PXN bit set.
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>

The virtual memory layout is described in
Documentation/arm64/memory.txt. This patch adds the MMU definitions for
the 4KB and 64KB translation table configurations. The SECTION_SIZE is
2MB with 4KB page and 512MB with 64KB page configuration.

PHYS_OFFSET is calculated at run-time and stored in a variable (no
run-time code patching at this stage).

On the current implementation, both user and kernel address spaces are
512G (39-bit) each with a maximum of 256G for the RAM linear mapping.
Linux uses 3 levels of translation tables with the 4K page configuration
and 2 levels with the 64K configuration. Extending the memory space
beyond 39-bit with the 4K pages or 42-bit with 64K pages requires an
additional level of translation tables.

The SPARSEMEM configuration is global to all AArch64 platforms and
allows for 1GB sections with SPARSEMEM_VMEMMAP enabled by default.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Acked-by: NTony Lindgren <tony@atomide.com>
Acked-by: NNicolas Pitre <nico@linaro.org>
Acked-by: NOlof Johansson <olof@lixom.net>
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>