The Montgomery Multiply, Montgomery Square, and Multiple-Precision
Multiply instructions work by loading a combination of the floating
point and multiple register windows worth of integer registers
with the inputs.

These values are 64-bit.  But for 32-bit userland processes we only
save the low 32-bits of each integer register during a register spill.
This is because the register window save area is in the user stack and
has a fixed layout.

Therefore, the only way to use these instruction in 32-bit mode is to
perform the following sequence:

1) Load the top-32bits of a choosen integer register with a sentinel,
   say "-1".  This will be in the outer-most register window.

   The idea is that we're trying to see if the outer-most register
   window gets spilled, and thus the 64-bit values were truncated.

2) Load all the inputs for the montmul/montsqr/mpmul instruction,
   down to the inner-most register window.

3) Execute the opcode.

4) Traverse back up to the outer-most register window.

5) Check the sentinel, if it's still "-1" store the results.
   Otherwise retry the entire sequence.

This retry is extremely troublesome.  If you're just unlucky and an
interrupt or other trap happens, it'll push that outer-most window to
the stack and clear the sentinel when we restore it.

We could retry forever and never make forward progress if interrupts
arrive at a fast enough rate (consider perf events as one example).
So we have do limited retries and fallback to software which is
extremely non-deterministic.

Luckily it's very straightforward to provide a mechanism to let
32-bit applications use a 64-bit stack.  Stacks in 64-bit mode are
biased by 2047 bytes, which means that the lowest bit is set in the
actual %sp register value.

So if we see bit zero set in a 32-bit application's stack we treat
it like a 64-bit stack.

Runtime detection of such a facility is tricky, and cumbersome at
best.  For example, just trying to use a biased stack and seeing if it
works is hard to recover from (the signal handler will need to use an
alt stack, plus something along the lines of longjmp).  Therefore, we
add a system call to report a bitmask of arch specific features like
this in a cheap and less hairy way.

With help from Andy Polyakov.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Disintegrate asm/system.h for Sparc.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
cc: sparclinux@vger.kernel.org

Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The nmi parameter indicated if we could do wakeups from the current
context, if not, we would set some state and self-IPI and let the
resulting interrupt do the wakeup.

For the various event classes:

  - hardware: nmi=0; PMI is in fact an NMI or we run irq_work_run from
    the PMI-tail (ARM etc.)
  - tracepoint: nmi=0; since tracepoint could be from NMI context.
  - software: nmi=[0,1]; some, like the schedule thing cannot
    perform wakeups, and hence need 0.

As one can see, there is very little nmi=1 usage, and the down-side of
not using it is that on some platforms some software events can have a
jiffy delay in wakeup (when arch_irq_work_raise isn't implemented).

The up-side however is that we can remove the nmi parameter and save a
bunch of conditionals in fast paths.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Michael Cree <mcree@orcon.net.nz>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
Cc: Anton Blanchard <anton@samba.org>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Don Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/n/tip-agjev8eu666tvknpb3iaj0fg@git.kernel.orgSigned-off-by: NIngo Molnar <mingo@elte.hu>

Semicolons are not necessary after switch/while/for/if braces
so remove them.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This mirrors commit 196f02bf
(powerpc: perf_event: Add alignment-faults and emulation-faults software events)
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

`>>' has a higher precedence than `?' so src2 evaluated to
either 16 or 0 dependent on the bits set in rs2.
Signed-off-by: NRoel Kluin <roel.kluin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

o Move all files from sparc64/kernel/ to sparc/kernel
  - rename as appropriate
o Update sparc/Makefile to the changes
o Update sparc/kernel/Makefile to include the sparc64 files

NOTE: This commit changes link order on sparc64!

Link order had to change for either of sparc32 and sparc64.
And assuming sparc64 see more testing than sparc32 change link
order on sparc64 where issues will be caught faster.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Copy the FPU state to the task's thread_info->fpregs for the VIS emulation
functions to access.
Signed-off-by: NHong H. Pham <hong.pham@windriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch fixes some bugs in VIS emulation that cause the GCC test
failure

FAIL: gcc.target/sparc/pdist-3.c execution test

for both 32-bit and 64-bit testing on hardware lacking these
instructions.  The emulation code for the pdist instruction uses
RS1(insn) for both source registers rs1 and rs2, which is obviously
wrong and leads to the instruction doing nothing (the observed
problem), and further inspection of the code shows that RS1 uses a
shift of 24 and RD a shift of 25, which clearly cannot both be right;
examining SPARC documentation indicates the correct shift for RS1 is
14.

This patch fixes the bug if single-stepping over the affected
instruction in the debugger, but not if the testcase is run
standalone.  For that, Wind River has another patch I hope they will
send as a followup to this patch submission.
Signed-off-by: NJoseph Myers <joseph@codesourcery.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

1) edge8 tables should be static
2) add vis_emul() extern decl. to asm/visasm.h
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

To add this logic, put the VIS instruction check at the
vis_emul() call site instead of inside of vis_emul().
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Niagara does not implement some of the VIS instructions in
hardware, so we have to emulate them.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>