Fix following warning:
ftrace.c:123:15: warning: symbol 'prepare_ftrace_return' was not declared. Should it be static?

Add prototype for asm/ftrace.h
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Drop extern for all prototypes and adjust alignment of parameters
as required after the removal.
In a few rare cases adjust linelength to conform to maximum 80 chars,
and likewise in a few rare cases adjust alignment of parameters
to static functions.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Acked-by: NIngo Molnar <mingo@elte.hu>

Impact: build fix for non-ftrace architectures

Not all archs implement ftrace, and therefore do not have an asm/ftrace.h.
This patch corrects the problem.

The ftrace_nmi_enter/exit now must be defined for all archs that implement
dynamic ftrace. Currently, only x86 does.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

This patch cleans up the NMI safe code for dynamic ftrace as suggested
by Andrew Morton.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix crashes that can occur in NMI handlers, if their code is modified

Modifying code is something that needs special care. On SMP boxes,
if code that is being modified is also being executed on another CPU,
that CPU will have undefined results.

The dynamic ftrace uses kstop_machine to make the system act like a
uniprocessor system. But this does not address NMIs, that can still
run on other CPUs.

One approach to handle this is to make all code that are used by NMIs
not be traced. But NMIs can call notifiers that spread throughout the
kernel and this will be very hard to maintain, and the chance of missing
a function is very high.

The approach that this patch takes is to have the NMIs modify the code
if the modification is taking place. The way this works is that just
writing to code executing on another CPU is not harmful if what is
written is the same as what exists.

Two buffers are used: an IP buffer and a "code" buffer.

The steps that the patcher takes are:

 1) Put in the instruction pointer into the IP buffer
    and the new code into the "code" buffer.
 2) Set a flag that says we are modifying code
 3) Wait for any running NMIs to finish.
 4) Write the code
 5) clear the flag.
 6) Wait for any running NMIs to finish.

If an NMI is executed, it will also write the pending code.
Multiple writes are OK, because what is being written is the same.
Then the patcher must wait for all running NMIs to finish before
going to the next line that must be patched.

This is basically the RCU approach to code modification.

Thanks to Ingo Molnar for suggesting the idea, and to Arjan van de Ven
for his guidence on what is safe and what is not.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The majority of this patch was created by the following script:

***
ASM=arch/sparc/include/asm
mkdir -p $ASM
git mv include/asm-sparc64/ftrace.h $ASM
git rm include/asm-sparc64/*
git mv include/asm-sparc/* $ASM
sed -ie 's/asm-sparc64/asm/g' $ASM/*
sed -ie 's/asm-sparc/asm/g' $ASM/*
***

The rest was an update of the top-level Makefile to use sparc
for header files when sparc64 is being build.
And a small fixlet to pick up the correct unistd.h from
sparc64 code.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

Alexander Beregalov reported this build failure:

$ make CROSS_COMPILE=sparc64-unknown-linux-gnu- image modules && sudo
make modules_install
  CHK     include/linux/version.h
  CHK     include/linux/utsrelease.h
  CALL    scripts/checksyscalls.sh
  CHK     include/linux/compile.h
dnsdomainname: Unknown host
  CC      arch/sparc64/kernel/sparc64_ksyms.o
arch/sparc64/kernel/sparc64_ksyms.c:116: error: '_mcount' undeclared
here (not in a function)
cc1: warnings being treated as errors
arch/sparc64/kernel/sparc64_ksyms.c:116: error: type defaults to 'int'
in declaration of '_mcount'

And bisected it back to:

| commit 395a59d0
| Author: Abhishek Sagar <sagar.abhishek@gmail.com>
| Date:   Sat Jun 21 23:47:27 2008 +0530
|
|     ftrace: store mcount address in rec->ip

the mcount prototype is only available under CONFIG_FTRACE,
extend it to CONFIG_MCOUNT as well.
Reported-and-bisected-by: NAlexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Record the address of the mcount call-site. Currently all archs except sparc64
record the address of the instruction following the mcount call-site. Some
general cleanups are entailed. Storing mcount addresses in rec->ip enables
looking them up in the kprobe hash table later on to check if they're kprobe'd.
Signed-off-by: NAbhishek Sagar <sagar.abhishek@gmail.com>
Cc: davem@davemloft.net
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>