Add the TIF_NOHZ flag appropriately.

Add call to user_exit() on entry to do_work_pending() and on entry
to syscalls via do_syscall_trace_enter(), and also the top of
do_syscall_trace_exit() just because it's done in x86.

Add call to user_enter() at the bottom of do_work_pending() once we
have no more work to do before returning to userspace.

Wrap all the trap code in exception_enter() / exception_exit().
Signed-off-by: NChris Metcalf <cmetcalf@ezchip.com>
Acked-by: NFrederic Weisbecker <fweisbec@gmail.com>

And other message logging neatening.

Other miscellanea:

o coalesce formats
o realign arguments
o standardize a couple of macros
o use __func__ instead of embedding the function name
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>

There is a risk that the variable will be used without being initialized.

This was largely found by using a static code analysis program called cppcheck.
Signed-off-by: NRickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> [minor cleanups]

Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>

This change enables unaligned userspace memory access via a kernel
fast path on tilegx.  The kernel tracks user PC/instruction pairs
per-thread using a direct-mapped cache in userspace.  The cache
maps those PC/instruction pairs to JIT'ed instruction sequences that
load or store using byte-wide load store intructions and then
synthesize 2-, 4- or 8-byte load or store results.  Once an
instruction has been seen to generate an unaligned access once,
subsequent hits on that instruction typically require overhead
of only around 50 cycles if cache and TLB is hot.

We support the prctl() PR_GET_UNALIGN / PR_SET_UNALIGN sys call to
enable or disable unaligned fixups on a per-process basis.

To do this we pull some of the tilepro unaligned support out of the
single_step.c file; tilepro uses instruction disassembly for both
single-step and unaligned access support.  Since tilegx actually has
hardware singlestep support, though, it's cleaner to keep the tilegx
unaligned access code in a separate file.  While we're at it,
properly rename the tilepro-specific types, etc., to have tilepro
suffixes instead of generic tile suffixes.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>