linux-toradex.git/include/linux/bug.h, branch v4.6-rc6

mm: Some arch may want to use HPAGE_PMD related values as variables

2016-03-03T10:18:29+00:00

With next generation power processor, we are having a new mmu model
[1] that require us to maintain a different linux page table format.

Inorder to support both current and future ppc64 systems with a single
kernel we need to make sure kernel can select between different page
table format at runtime. With the new MMU (radix MMU) added, we will
have two different pmd hugepage size 16MB for hash model and 2MB for
Radix model. Hence make HPAGE_PMD related values as a variable.

Actual conversion of HPAGE_PMD to a variable for ppc64 happens in a
followup patch.

[1] http://ibm.biz/power-isa3 (Needs registration).

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Aneesh Kumar K.V 
Signed-off-by: Michael Ellerman

bug.h, compiler.h: introduce compiletime_assert & BUILD_BUG_ON_MSG

2013-02-22T01:22:16+00:00

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: Daniel Santos 
Cc: Andi Kleen 
Cc: Borislav Petkov 
Cc: David Rientjes 
Cc: Joe Perches 
Cc: Josh Triplett 
Cc: Paul Gortmaker 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

compiler.h, bug.h: prevent double error messages with BUILD_BUG{,_ON}

2013-02-22T01:22:16+00:00

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: Daniel Santos 
Cc: Andi Kleen 
Cc: Borislav Petkov 
Cc: David Rientjes 
Cc: Joe Perches 
Cc: Josh Triplett 
Cc: Paul Gortmaker 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug.h: make BUILD_BUG_ON generate compile-time error

2013-02-22T01:22:16+00:00

Negative sized arrays wont create a compile-time error in some cases
starting with gcc 4.4 (e.g., inlined functions), but gcc 4.3 introduced
the error function attribute that will.

This patch modifies BUILD_BUG_ON to behave like BUILD_BUG already does,
using the error function attribute so that you don't have to build the
entire kernel to discover that you have a problem, and then enjoy trying
to track it down from a link-time error.

Also, we are only including asm/bug.h and then expecting that
linux/compiler.h will eventually be included to define __linktime_error
(used in BUILD_BUG_ON).  This patch includes it directly for clarity and
to avoid the possibility of changes in /*/include/asm/bug.h being
changed or not including linux/compiler.h for some reason.

Signed-off-by: Daniel Santos 
Acked-by: Borislav Petkov 
Cc: Andi Kleen 
Cc: David Rientjes 
Cc: Joe Perches 
Cc: Josh Triplett 
Cc: Paul Gortmaker 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug.h: prevent double evaulation of `condition' in BUILD_BUG_ON

2013-02-22T01:22:16+00:00

When calling BUILD_BUG_ON in an optimized build using gcc 4.3 and later,
the condition will be evaulated twice, possibily with side-effects.  This
patch eliminates that error.

[akpm@linux-foundation.org: tweak code layout]
Signed-off-by: Daniel Santos 
Cc: Andi Kleen 
Cc: Borislav Petkov 
Cc: David Rientjes 
Cc: Joe Perches 
Cc: Josh Triplett 
Cc: Paul Gortmaker 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug.h: fix BUILD_BUG_ON macro in CHECKER

2013-02-22T01:22:15+00:00

When __CHECKER__ is defined, we disable all of the BUILD_BUG.* macros.
However, both BUILD_BUG_ON_NOT_POWER_OF_2 and BUILD_BUG_ON was evaluating
to nothing in this case, and we want (0) since this is a function-like
macro that will be followed by a semicolon.

Signed-off-by: Daniel Santos 
Acked-by: Borislav Petkov 
Cc: Andi Kleen 
Cc: David Rientjes 
Cc: Joe Perches 
Cc: Josh Triplett 
Cc: Paul Gortmaker 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

compiler{,-gcc4}.h, bug.h: Remove duplicate macros

2013-02-22T01:22:15+00:00

__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: Daniel Santos 
Acked-by: David Rientjes 
Acked-by: Borislav Petkov 
Cc: Andi Kleen 
Cc: Joe Perches 
Cc: Josh Triplett 
Cc: Paul Gortmaker 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

include/linux/bug.h: fix sparse warning related to BUILD_BUG_ON_INVALID

2012-11-27T01:41:24+00:00

Commit baf05aa9271b ("bug: introduce BUILD_BUG_ON_INVALID() macro")
introduces this macro only when _CHECKER_ is not defined.  Define a
silent macro in the else condition to fix following sparse warning:

  mm/filemap.c:395:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  mm/filemap.c:396:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  mm/filemap.c:397:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  include/linux/mm.h:419:9: error: undefined identifier 'BUILD_BUG_ON_INVALID'
  include/linux/mm.h:419:9: error: not a function 

Signed-off-by: Tushar Behera 
Acked-by: Konstantin Khlebnikov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug: introduce BUILD_BUG_ON_INVALID() macro

2012-05-29T23:22:20+00:00

Sometimes we want to check some expressions correctness at compile time.
"(void)(e);" or "if (e);" can be dangerous if the expression has
side-effects, and gcc sometimes generates a lot of code, even if the
expression has no effect.

This patch introduces macro BUILD_BUG_ON_INVALID() for such checks, it
forces a compilation error if expression is invalid without any extra
code.

[Cast to "long" required because sizeof does not work for bit-fields.]

Signed-off-by: Konstantin Khlebnikov 
Cc: Linus Torvalds 
Cc: Geert Uytterhoeven 
Cc: "H. Peter Anvin" 
Cc: Cong Wang 
Cc: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

bug: consolidate BUILD_BUG_ON with other bug code

2012-03-04T22:54:35+00:00

The support for BUILD_BUG in linux/kernel.h predates the
addition of linux/bug.h -- with this chunk off separate,
you can run into situations where a person gets a compile
fail even when they've included linux/bug.h, like this:

    CC      lib/string.o
  lib/string.c: In function 'strlcat':
  lib/string.c:225:2: error: implicit declaration of function 'BUILD_BUG_ON'
  make[2]: *** [lib/string.o] Error 1
  $
  $ grep linux/bug.h lib/string.c
  #include 
  $

Since the above violates the principle of least surprise, move
the BUG chunks from kernel.h to bug.h so it is all together.

Signed-off-by: Paul Gortmaker

linux-toradex.git/include/linux/bug.h, branch v4.6-rc6

mm: Some arch may want to use HPAGE_PMD related values as variables

bug.h, compiler.h: introduce compiletime_assert & BUILD_BUG_ON_MSG

compiler.h, bug.h: prevent double error messages with BUILD_BUG{,_ON}

bug.h: make BUILD_BUG_ON generate compile-time error

bug.h: prevent double evaulation of `condition' in BUILD_BUG_ON

bug.h: fix BUILD_BUG_ON macro in __CHECKER__

compiler{,-gcc4}.h, bug.h: Remove duplicate macros

include/linux/bug.h: fix sparse warning related to BUILD_BUG_ON_INVALID

bug: introduce BUILD_BUG_ON_INVALID() macro

bug: consolidate BUILD_BUG_ON with other bug code

bug.h: fix BUILD_BUG_ON macro in CHECKER