1. For VM_EXEC based delayed dcache/icache flush, reduces the number of
   flushes.

2. Makes this security feature ON by default rather than OFF before.

3. Applications can use mprotect() to selectively override this.

4. ELF binaries have a GNU_STACK segment which can easily override the
   kernel default permissions.
   For nested-functions/trampolines, gcc already auto-enables executable
   stack in elf. Others needing this can use -Wl,-z,execstack option.
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

gdbserver inserting a breakpoint ends up calling copy_user_page() for a
code page. The generic version of which (non-aliasing config) didn't set
the PG_arch_1 bit hence update_mmu_cache() didn't sync dcache/icache for
corresponding dynamic loader code page - causing garbade to be executed.

So now aliasing versions of copy_user_highpage()/clear_page() are made
default. There is no significant overhead since all of special alias
handling code is compiled out for non-aliasing build
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

This is the meat of the series which prevents any dcache alias creation
by always keeping the U and K mapping of a page congruent.
If a mapping already exists, and other tries to access the page, prev
one is flushed to physical page (wback+inv)

Essentially flush_dcache_page()/copy_user_highpage() create K-mapping
of a page, but try to defer flushing, unless U-mapping exist.
When page is actually mapped to userspace, update_mmu_cache() flushes
the K-mapping (in certain cases this can be optimised out)

Additonally flush_cache_mm(), flush_cache_range(), flush_cache_page()
handle the puring of stale userspace mappings on exit/munmap...

flush_anon_page() handles the existing U-mapping for anon page before
kernel reads it via the GUP path.

Note that while not complete, this is enough to boot a simple
dynamically linked Busybox based rootfs
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

Implement ioremap_prot() to allow mapping IO memory with variable
protection
via TLB.

Implementing this allows the /dev/mem driver to use its generic access()
VMA callback, which in turn allows ptrace to examine data in memory
mapped regions mapped via /dev/mem, such as Arc DCCM.

The end result is that it is possible to examine values of variables
placed into DCCM in user space programs via GDB.

CC: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
CC: Noam Camus <noamc@ezchip.com>
Acked-by: NVineet Gupta <vgupta@synopsys.com>
Signed-off-by: NGilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

1. ./genfilelist.pl arch/arc/include/asm/

2. Create arch/arc/include/uapi/asm/Kbuild as follows

	+# UAPI Header export list
	+include include/uapi/asm-generic/Kbuild.asm

3. ./disintegrate-one.pl arch/arc/include/{,uapi/}asm/<above-list>

4. Edit arch/arc/include/asm/Kbuild to remove ref to
	asm-generic/Kbuild.asm

- To work around empty uapi/asm/setup.h added a placholder comment.
- Also a manual #ifdef __ASSEMBLY__ for a late ptrace change
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: David Howells <dhowells@redhat.com>

Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

* L1_CACHE_SHIFT
* PAGE_SIZE, PAGE_OFFSET
* struct pt_regs, struct user_regs_struct
* struct thread_struct, cpu_relax(), task_pt_regs(), start_thread(), ...
* struct thread_info, THREAD_SIZE, INIT_THREAD_INFO(), TIF_*, ...
* BUG()
* ELF_*
* Elf_*

To disallow user-space visibility into some of the core kernel data-types
such as struct pt_regs, #ifdef __KERNEL__ which also makes the UAPI header
spit (further patch in the series) to NOT export it to asm/uapi/ptrace.h
Signed-off-by: NVineet Gupta <vgupta@synopsys.com>
Cc: Jonas Bonn <jonas.bonn@gmail.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Acked-by: NArnd Bergmann <arnd@arndb.de>