Commit 927609d6 ("kernel: tighten rules for ACCESS ONCE") results in
sparse warnings like "Using plain integer as NULL pointer" - Let's add a
type cast to the dummy assignment.
To avoid warnings lik "sparse: warning: cast to restricted __hc32" we also
use __force on that cast.

Fixes: 927609d6 ("kernel: tighten rules for ACCESS ONCE")
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>

Now that all non-scalar users of ACCESS_ONCE have been converted
to READ_ONCE or ASSIGN once, lets tighten ACCESS_ONCE to only
work on scalar types.
This variant was proposed by Alexei Starovoitov.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

ACCESS_ONCE does not work reliably on non-scalar types. For
example gcc 4.6 and 4.7 might remove the volatile tag for such
accesses during the SRA (scalar replacement of aggregates) step
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145)

Let's provide READ_ONCE/ASSIGN_ONCE that will do all accesses via
scalar types as suggested by Linus Torvalds. Accesses larger than
the machines word size cannot be guaranteed to be atomic. These
macros will use memcpy and emit a build warning.
Signed-off-by: NChristian Borntraeger <borntraeger@de.ibm.com>

Usually, BUG_ON and friends aren't even evaluated in sparse, but recently
compiletime_assert_atomic_type() was added, and that now results in a
sparse warning every time it is used.

The reason turns out to be the temporary variable, after it sparse no
longer considers the value to be a constant, and results in a warning and
an error.  The error is the more annoying part of this as it suppresses
any further warnings in the same file, hiding other problems.

Unfortunately the condition cannot be simply expanded out to avoid the
temporary variable since it breaks compiletime_assert on old versions of
GCC such as GCC 4.2.4 which the latest metag compiler is based on.

Therefore #ifndef __CHECKER__ out the __compiletime_error_fallback which
uses the potentially negative size array to trigger a conditional compiler
error, so that sparse doesn't see it.
Signed-off-by: NJames Hogan <james.hogan@imgtec.com>
Cc: Johannes Berg <johannes.berg@intel.com>
Cc: Daniel Santos <daniel.santos@pobox.com>
Cc: Luciano Coelho <luciano.coelho@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: NJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Introduce NOKPROBE_SYMBOL() macro which builds a kprobes
blacklist at kernel build time.

The usage of this macro is similar to EXPORT_SYMBOL(),
placed after the function definition:

  NOKPROBE_SYMBOL(function);

Since this macro will inhibit inlining of static/inline
functions, this patch also introduces a nokprobe_inline macro
for static/inline functions. In this case, we must use
NOKPROBE_SYMBOL() for the inline function caller.

When CONFIG_KPROBES=y, the macro stores the given function
address in the "_kprobe_blacklist" section.

Since the data structures are not fully initialized by the
macro (because there is no "size" information),  those
are re-initialized at boot time by using kallsyms.
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Link: http://lkml.kernel.org/r/20140417081705.26341.96719.stgit@ltc230.yrl.intra.hitachi.co.jp
Cc: Alok Kataria <akataria@vmware.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jan-Simon Möller <dl9pf@gmx.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: linux-arch@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-sparse@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Add a compiler-clang.h file to add specific macros needed for compiling the
kernel with clang.

Initially the only override required is the macro for silencing the
compiler for a purposefully uninintialized variable.

Author: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: NMark Charlebois <charlebm@gmail.com>
Signed-off-by: NBehan Webster <behanw@converseincode.com>

A number of situations currently require the heavyweight smp_mb(),
even though there is no need to order prior stores against later
loads.  Many architectures have much cheaper ways to handle these
situations, but the Linux kernel currently has no portable way
to make use of them.

This commit therefore supplies smp_load_acquire() and
smp_store_release() to remedy this situation.  The new
smp_load_acquire() primitive orders the specified load against
any subsequent reads or writes, while the new smp_store_release()
primitive orders the specifed store against any prior reads or
writes.  These primitives allow array-based circular FIFOs to be
implemented without an smp_mb(), and also allow a theoretical
hole in rcu_assign_pointer() to be closed at no additional
expense on most architectures.

In addition, the RCU experience transitioning from explicit
smp_read_barrier_depends() and smp_wmb() to rcu_dereference()
and rcu_assign_pointer(), respectively resulted in substantial
improvements in readability.  It therefore seems likely that
replacing other explicit barriers with smp_load_acquire() and
smp_store_release() will provide similar benefits.  It appears
that roughly half of the explicit barriers in core kernel code
might be so replaced.

[Changelog by PaulMck]
Reviewed-by: N"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: NPeter Zijlstra <peterz@infradead.org>
Acked-by: NWill Deacon <will.deacon@arm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Michael Neuling <mikey@neuling.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Victor Kaplansky <VICTORK@il.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Link: http://lkml.kernel.org/r/20131213150640.908486364@infradead.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Disabling compiler optimizations can be fragile, since a new
optimization could be added to -O0 or -Os that breaks the assumptions
the code is making.

Instead of disabling compiler optimizations, use a dummy inline assembly
(based on RELOC_HIDE) to block the problematic kinds of optimization,
while still allowing other optimizations to be applied to the code.

The dummy inline assembly is added after every OR, and has the
accumulator variable as its input and output. The compiler is forced to
assume that the dummy inline assembly could both depend on the
accumulator variable and change the accumulator variable, so it is
forced to compute the value correctly before the inline assembly, and
cannot assume anything about its value after the inline assembly.

This change should be enough to make crypto_memneq work correctly (with
data-independent timing) even if it is inlined at its call sites. That
can be done later in a followup patch.

Compile-tested on x86_64.
Signed-off-by: NCesar Eduardo Barros <cesarb@cesarb.eti.br>
Acked-by: NDaniel Borkmann <dborkman@redhat.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

Currently, __kprobes is defined in linux/kprobes.h which
is too big to be included in small or basic headers
that want to make use of this simple attribute.

So move __kprobes definition into linux/compiler.h
in which other compiler attributes are defined.
Signed-off-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Timo Juhani Lindfors <timo.lindfors@iki.fi>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Nadia Yvette Chambers <nyc@holomorphy.com>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20130404104049.21071.20908.stgit@mhiramat-M0-7522
[ Improved the attribute explanation a bit. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Introduce compiletime_assert to compiler.h, which moves the details of
how to break a build and emit an error message for a specific compiler
to the headers where these details should be.  Following in the
tradition of the POSIX assert macro, compiletime_assert creates a
build-time error when the supplied condition is *false*.

Next, we add BUILD_BUG_ON_MSG to bug.h which simply wraps
compiletime_assert, inverting the logic, so that it fails when the
condition is *true*, consistent with the language "build bug on." This
macro allows you to specify the error message you want emitted when the
supplied condition is true.

Finally, we remove all other code from bug.h that mucks with these
details (BUILD_BUG & BUILD_BUG_ON), and have them all call
BUILD_BUG_ON_MSG.  This not only reduces source code bloat, but also
prevents the possibility of code being changed for one macro and not for
the other (which was previously the case for BUILD_BUG and
BUILD_BUG_ON).

Since __compiletime_error_fallback is now only used in compiler.h, I'm
considering it a private macro and removing the double negation that's
now extraneous.

[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: NDaniel Santos <daniel.santos@pobox.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Prior to the introduction of __attribute__((error("msg"))) in gcc 4.3,
creating compile-time errors required a little trickery.
BUILD_BUG{,_ON} uses this attribute when available to generate
compile-time errors, but also uses the negative-sized array trick for
older compilers, resulting in two error messages in some cases.  The
reason it's "some" cases is that as of gcc 4.4, the negative-sized array
will not create an error in some situations, like inline functions.

This patch replaces the negative-sized array code with the new
__compiletime_error_fallback() macro which expands to the same thing
unless the the error attribute is available, in which case it expands to
do{}while(0), resulting in exactly one compile-time error on all
versions of gcc.

Note that we are not changing the negative-sized array code for the
unoptimized version of BUILD_BUG_ON, since it has the potential to catch
problems that would be disabled in later versions of gcc were
__compiletime_error_fallback used.  The reason is that that an
unoptimized build can't always remove calls to an error-attributed
function call (like we are using) that should effectively become dead
code if it were optimized.  However, using a negative-sized array with a
similar value will not result in an false-positive (error).  The only
caveat being that it will also fail to catch valid conditions, which we
should be expecting in an unoptimized build anyway.
Signed-off-by: NDaniel Santos <daniel.santos@pobox.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

__linktime_error() does the same thing as __compiletime_error() and is
only used in bug.h.  Since the macro defines a function attribute that
will cause a failure at compile-time (not link-time), it makes more sense
to keep __compiletime_error(), which is also neatly mated with
__compiletime_warning().
Signed-off-by: NDaniel Santos <daniel.santos@pobox.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NBorislav Petkov <bp@alien8.de>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

linux/compiler.h has macros to denote functions that acquire or release
locks, but not to denote functions called with a lock held that return
with the lock still held.  Add a __must_hold macro to cover that case.
Signed-off-by: NJosh Triplett <josh@joshtriplett.org>
Reported-by: NEd Cashin <ecashin@coraid.com>
Tested-by: NEd Cashin <ecashin@coraid.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Jan Beulich points out __COUNTER__ (gcc 4.3 and above), so let's use
that to create unique ids.  This is better than __LINE__ which we use
today, so provide a wrapper.

Stanislaw Gruszka <sgruszka@redhat.com> reported that some module parameters
start with a digit, so we need to prepend when we for the unique id.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Acked-by: NJan Beulich <jbeulich@suse.com>

gcc 4.6+ has support for a externally_visible attribute that prevents the
optimizer from optimizing unused symbols away.  Add a __visible macro to
use it with that compiler version or later.

This is used (at least) by the "Link Time Optimization" patchset.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAlexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

We can place this in definitions that we expect the compiler to remove by
dead code elimination.  If this assertion fails, we get a nice error
message at build time.

The GCC function attribute error("message") was added in version 4.3, so
we define a new macro __linktime_error(message) to expand to this for
GCC-4.3 and later.  This will give us an error diagnostic from the
compiler on the line that fails.  For other compilers
__linktime_error(message) expands to nothing, and we have to be content
with a link time error, but at least we will still get a build error.

BUILD_BUG() expands to the undefined function __build_bug_failed() and
will fail at link time if the compiler ever emits code for it.  On GCC-4.3
and later, attribute((error())) is used so that the failure will be noted
at compile time instead.
Signed-off-by: NDavid Daney <david.daney@cavium.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: DM <dm.n9107@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Acked-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This commit provides definitions for the __rcu annotation defined earlier.
This annotation permits sparse to check for correct use of RCU-protected
pointers.  If a pointer that is annotated with __rcu is accessed
directly (as opposed to via rcu_dereference(), rcu_assign_pointer(),
or one of their variants), sparse can be made to complain.  To enable
such complaints, use the new default-disabled CONFIG_SPARSE_RCU_POINTER
kernel configuration option.  Please note that these sparse complaints are
intended to be a debugging aid, -not- a code-style-enforcement mechanism.

There are special rcu_dereference_protected() and rcu_access_pointer()
accessors for use when RCU read-side protection is not required, for
example, when no other CPU has access to the data structure in question
or while the current CPU hold the update-side lock.

This patch also updates a number of docbook comments that were showing
their age.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Christopher Li <sparse@chrisli.org>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

This commit defines an __rcu API, but provides only vacuous definitions
for it.  This breaks dependencies among most of the subsequent patches,
allowing them to reach mainline asynchronously via whatever trees are
appropriate.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Christopher Li <sparse@chrisli.org>
Cc: Josh Triplett <josh@joshtriplett.org>

This is to make the annotation of percpu variables during the next merge
window less painfull.

Extracted from a patch by Rusty Russell.
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Starting with version 4.5, GCC has a new built-in function
__builtin_unreachable() that can be used in places like the kernel's
BUG() where inline assembly is used to transfer control flow.  This
eliminated the need for an endless loop in these places.

The patch adds a new macro 'unreachable()' that will expand to either
__builtin_unreachable() or an endless loop depending on the compiler
version.

Change from v1: Simplify unreachable() for non-GCC 4.5 case.
Signed-off-by: NDavid Daney <ddaney@caviumnetworks.com>
Acked-by: NRalf Baechle <ralf@linux-mips.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

I wrote some code which is used as compile-time checker, and the
code should be elided after compile.

So I need to annotate the code as "always unused", compared to
"maybe unused".
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <4AEE2CEC.8040206@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

We have to make __kernel "__attribute__((address_space(0)))" so we can
cast to it.

tj: * put_cpu_var() update.

    * Annotations added to dynamic allocator interface.
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NTejun Heo <tj@kernel.org>

For automated testing it is useful to have the option to turn
the warnings on copy_from_user() etc checks into errors:

 In function ‘copy_from_user’,
     inlined from ‘fd_copyin’ at drivers/block/floppy.c:3080,
     inlined from ‘fd_ioctl’ at drivers/block/floppy.c:3503:
   linux/arch/x86/include/asm/uaccess_32.h:213:
  error: call to ‘copy_from_user_overflow’ declared with attribute error:
  copy_from_user buffer size is not provably correct
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <20091002075050.4e9f7641@infradead.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

A previous patch added the buffer size check to copy_from_user().

One of the things learned from analyzing the result of the previous
patch is that in general, gcc is really good at proving that the
code contains sufficient security checks to not need to do a
runtime check. But that for those cases where gcc could not prove
this, there was a relatively high percentage of real security
issues.

This patch turns the case of "gcc cannot prove" into a compile time
warning, as long as a sufficiently new gcc is in use that supports
this. The objective is that these warnings will trigger developers
checking new cases out before a security hole enters a linux kernel
release.
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: James Morris <jmorris@namei.org>
Cc: Jan Beulich <jbeulich@novell.com>
LKML-Reference: <20090930130523.348ae6c4@infradead.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

gcc (4.x) supports the __builtin_object_size() builtin, which
reports the size of an object that a pointer point to, when known
at compile time. If the buffer size is not known at compile time, a
constant -1 is returned.

This patch uses this feature to add a sanity check to
copy_from_user(); if the target buffer is known to be smaller than
the copy size, the copy is aborted and a WARNing is emitted in
memory debug mode.

These extra checks compile away when the object size is not known,
or if both the buffer size and the copy length are constants.
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
LKML-Reference: <20090926143301.2c396b94@infradead.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new API

__builtin_types_compatible_p() is a little awkward to use: it takes two
types rather than types or variables, and it's just damn long.

(typeof(type) == type, so this works on types as well as vars).
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

The code that enables branch tracing for all (non-constant) branches
plays games with the preprocessor and #define's the C 'if ()' construct
to do tracing.

That's all fine, but it fails for some unusual but valid C code that is
sometimes used in macros, notably by the intel-iommu code:

	if (i=drhd->iommu, drhd->ignored) ..

because now the preprocessor complains about multiple arguments to the
'if' macro.

So make the macro expansion of this particularly horrid trick use
varargs, and handle the case of comma-expressions in if-statements.  Use
another macro to do it cleanly in just one place.

This replaces a patch by David (and acked by Steven) that did this all
inside that one already-too-horrid macro.
Tested-by: NIngo Molnar <mingo@elte.hu>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix the branch tracer barfing on comma statements within if ()
statements.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

One of the changes between kernels 2.6.28 and 2.6.29 is that a branch profiler
has been added for if() statements. Unfortunately this patch makes the sparse
output unusable with CONFIG_TRACE_BRANCH_PROFILING=y: when branch profiling is
enabled, sparse prints so much false positives that the real issues are no
longer visible. This behavior can be reproduced as follows:
* enable CONFIG_TRACE_BRANCH_PROFILING, e.g. by running make allyesconfig or
  make allmodconfig.
* run make C=2

Result: a huge number of the following sparse warnings.
...
include/linux/cpumask.h:547:2: warning: symbol '______r' shadows an earlier one
include/linux/cpumask.h:547:2: originally declared here
...

The patch below fixes this by disabling branch profiling while analyzing the
kernel code with sparse.

See also:
* http://lkml.org/lkml/2008/11/21/18
* http://bugzilla.kernel.org/show_bug.cgi?id=12925Signed-off-by: NBart Van Assche <bart.vanassche@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Steven Rostedt <srostedt@redhat.com>
LKML-Reference: <200904051620.02311.bart.vanassche@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: better performance for if branch tracer

Use an array to count the hit and misses of a conditional instead
of using another conditional. This cuts down on saturation of branch
predictions and increases performance of modern pipelined architectures.
Signed-off-by: NWitold Baryluk <baryluk@smp.if.uj.edu.pl>
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>

 - include the gcc version-dependent header files from the generic gcc
   header file, rather than the other way around (iow: don't make the
   non-gcc header file have to know about gcc versions)

 - don't include compiler-gcc4.h for gcc 5 (for whenever it gets
   released).  That's just confusing and made us do odd things in the
   gcc4 header file (testing that we really had version 4!)

 - generate the name from the __GNUC__ version directly, rather than
   having a mess of #if conditionals.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Impact: feature to profile if statements

This patch adds a branch profiler for all if () statements.
The results will be found in:

  /debugfs/tracing/profile_branch

For example:

   miss      hit    %        Function                  File              Line
 ------- ---------  -        --------                  ----              ----
       0        1 100 x86_64_start_reservations      head64.c             127
       0        1 100 copy_bootdata                  head64.c             69
       1        0   0 x86_64_start_kernel            head64.c             111
      32        0   0 set_intr_gate                  desc.h               319
       1        0   0 reserve_ebda_region            head.c               51
       1        0   0 reserve_ebda_region            head.c               47
       0        1 100 reserve_ebda_region            head.c               42
       0        0   X maxcpus                        main.c               165

Miss means the branch was not taken. Hit means the branch was taken.
The percent is the percentage the branch was taken.

This adds a significant amount of overhead and should only be used
by those analyzing their system.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: clean up to make one profiler of like and unlikely tracer

The likely and unlikely profiler prints out the file and line numbers
of the annotated branches that it is profiling. It shows the number
of times it was correct or incorrect in its guess. Having two
different files or sections for that matter to tell us if it was a
likely or unlikely is pretty pointless. We really only care if
it was correct or not.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: clean up of branch check

The unlikely/likely profiler does an extra assign of the f.line.
This is not needed since it is already calculated at compile time.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: name change of unlikely tracer and profiler

Ingo Molnar suggested changing the config from UNLIKELY_PROFILE
to BRANCH_PROFILING. I never did like the "unlikely" name so I
went one step farther, and renamed all the unlikely configurations
to a "BRANCH" variant.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix bootup crash

the branch tracer missed arch/x86/vdso/vclock_gettime.c from
disabling tracing, which caused such bootup crashes:

  [  201.840097] init[1]: segfault at 7fffed3fe7c0 ip 00007fffed3fea2e sp 000077

also clean up the ugly ifdefs in arch/x86/kernel/vsyscall_64.c by
creating DISABLE_UNLIKELY_PROFILE facility for code to turn off
instrumentation on a per file basis.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new unlikely/likely profiler

Andrew Morton recently suggested having an in-kernel way to profile
likely and unlikely macros. This patch achieves that goal.

When configured, every(*) likely and unlikely macro gets a counter attached
to it. When the condition is hit, the hit and misses of that condition
are recorded. These numbers can later be retrieved by:

  /debugfs/tracing/profile_likely    - All likely markers
  /debugfs/tracing/profile_unlikely  - All unlikely markers.

# cat /debug/tracing/profile_unlikely | head
 correct incorrect  %        Function                  File              Line
 ------- ---------  -        --------                  ----              ----
    2167        0   0 do_arch_prctl                  process_64.c         832
       0        0   0 do_arch_prctl                  process_64.c         804
    2670        0   0 IS_ERR                         err.h                34
   71230     5693   7 __switch_to                    process_64.c         673
   76919        0   0 __switch_to                    process_64.c         639
   43184    33743  43 __switch_to                    process_64.c         624
   12740    64181  83 __switch_to                    process_64.c         594
   12740    64174  83 __switch_to                    process_64.c         590

# cat /debug/tracing/profile_unlikely | \
  awk '{ if ($3 > 25) print $0; }' |head -20
   44963    35259  43 __switch_to                    process_64.c         624
   12762    67454  84 __switch_to                    process_64.c         594
   12762    67447  84 __switch_to                    process_64.c         590
    1478      595  28 syscall_get_error              syscall.h            51
       0     2821 100 syscall_trace_leave            ptrace.c             1567
       0        1 100 native_smp_prepare_cpus        smpboot.c            1237
   86338   265881  75 calc_delta_fair                sched_fair.c         408
  210410   108540  34 calc_delta_mine                sched.c              1267
       0    54550 100 sched_info_queued              sched_stats.h        222
   51899    66435  56 pick_next_task_fair            sched_fair.c         1422
       6       10  62 yield_task_fair                sched_fair.c         982
    7325     2692  26 rt_policy                      sched.c              144
       0     1270 100 pre_schedule_rt                sched_rt.c           1261
    1268    48073  97 pick_next_task_rt              sched_rt.c           884
       0    45181 100 sched_info_dequeued            sched_stats.h        177
       0       15 100 sched_move_task                sched.c              8700
       0       15 100 sched_move_task                sched.c              8690
   53167    33217  38 schedule                       sched.c              4457
       0    80208 100 sched_info_switch              sched_stats.h        270
   30585    49631  61 context_switch                 sched.c              2619

# cat /debug/tracing/profile_likely | awk '{ if ($3 > 25) print $0; }'
   39900    36577  47 pick_next_task                 sched.c              4397
   20824    15233  42 switch_mm                      mmu_context_64.h     18
       0        7 100 __cancel_work_timer            workqueue.c          560
     617    66484  99 clocksource_adjust             timekeeping.c        456
       0   346340 100 audit_syscall_exit             auditsc.c            1570
      38   347350  99 audit_get_context              auditsc.c            732
       0   345244 100 audit_syscall_entry            auditsc.c            1541
      38     1017  96 audit_free                     auditsc.c            1446
       0     1090 100 audit_alloc                    auditsc.c            862
    2618     1090  29 audit_alloc                    auditsc.c            858
       0        6 100 move_masked_irq                migration.c          9
       1      198  99 probe_sched_wakeup             trace_sched_switch.c 58
       2        2  50 probe_wakeup                   trace_sched_wakeup.c 227
       0        2 100 probe_wakeup_sched_switch      trace_sched_wakeup.c 144
    4514     2090  31 __grab_cache_page              filemap.c            2149
   12882   228786  94 mapping_unevictable            pagemap.h            50
       4       11  73 __flush_cpu_slab               slub.c               1466
  627757   330451  34 slab_free                      slub.c               1731
    2959    61245  95 dentry_lru_del_init            dcache.c             153
     946     1217  56 load_elf_binary                binfmt_elf.c         904
     102       82  44 disk_put_part                  genhd.h              206
       1        1  50 dst_gc_task                    dst.c                82
       0       19 100 tcp_mss_split_point            tcp_output.c         1126

As you can see by the above, there's a bit of work to do in rethinking
the use of some unlikelys and likelys. Note: the unlikely case had 71 hits
that were more than 25%.

Note:  After submitting my first version of this patch, Andrew Morton
  showed me a version written by Daniel Walker, where I picked up
  the following ideas from:

  1)  Using __builtin_constant_p to avoid profiling fixed values.
  2)  Using __FILE__ instead of instruction pointers.
  3)  Using the preprocessor to stop all profiling of likely
       annotations from vsyscall_64.c.

Thanks to Andrew Morton, Arjan van de Ven, Theodore Tso and Ingo Molnar
for their feed back on this patch.

(*) Not ever unlikely is recorded, those that are used by vsyscalls
 (a few of them) had to have profiling disabled.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The notrace define belongs in compiler.h so that it can be used in
init.h
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Remove the redundant definition of ACCESS_ONCE() from rcupreempt.c in
favor of the one in compiler.h.  Also merge the comment header from
rcupreempt.c's definition into that in compiler.h.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>