linux-toradex.git/include/linux/compiler-gcc4.h, branch v2.6.38.5

compiler-gcc.h: gcc-4.5 needs noclone and noinline on __naked functions

2010-06-29T22:29:31+00:00

A __naked function is defined in C but with a body completely implemented
by asm(), including any prologue and epilogue.  These asm() bodies expect
standard calling conventions for parameter passing.  Older GCCs implement
that correctly, but 4.[56] currently do not, see GCC PR44290.  In the
Linux kernel this breaks ARM, causing most arch/arm/mm/copypage-*.c
modules to get miscompiled, resulting in kernel crashes during bootup.

Part of the kernel fix is to augment the __naked function attribute to
also imply noinline and noclone.  This patch implements that, and has been
verified to fix boot failures with gcc-4.5 compiled 2.6.34 and 2.6.35-rc1
kernels.  The patch is a no-op with older GCCs.

Signed-off-by: Mikael Pettersson 
Signed-off-by: Khem Raj 
Cc: Russell King 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

2009-12-05T23:32:03+00:00

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  include/linux/compiler-gcc4.h: Fix build bug - gcc-4.0.2 doesn't understand __builtin_object_size
  x86/alternatives: No need for alternatives-asm.h to re-invent stuff already in asm.h
  x86/alternatives: Check replacementlen <= instrlen at build time
  x86, 64-bit: Set data segments to null after switching to 64-bit mode
  x86: Clean up the loadsegment() macro
  x86: Optimize loadsegment()
  x86: Add missing might_fault() checks to copy_{to,from}_user()
  x86-64: __copy_from_user_inatomic() adjustments
  x86: Remove unused thread_return label from switch_to()
  x86, 64-bit: Fix bstep_iret jump
  x86: Don't use the strict copy checks when branch profiling is in use
  x86, 64-bit: Move K8 B step iret fixup to fault entry asm
  x86: Generate cmpxchg build failures
  x86: Add a Kconfig option to turn the copy_from_user warnings into errors
  x86: Turn the copy_from_user check into an (optional) compile time warning
  x86: Use __builtin_memset and __builtin_memcpy for memset/memcpy
  x86: Use __builtin_object_size() to validate the buffer size for copy_from_user()

Add support for GCC-4.5's __builtin_unreachable() to compiler.h (v2)

2009-12-05T17:10:12+00:00

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: David Daney 
Acked-by: Ralf Baechle 
Signed-off-by: Linus Torvalds

include/linux/compiler-gcc4.h: Fix build bug - gcc-4.0.2 doesn't understand __builtin_object_size

2009-12-03T06:29:17+00:00

Maybe 4.1.0 doesn't too, but this fixed it for me.

Caused by:

 4a31276: x86: Turn the copy_from_user check into an (optional) compile time warning
 9f0cf4a: x86: Use __builtin_object_size() to validate the buffer size for copy_from_user()

Signed-off-by: Andrew Morton 
Cc: Arjan van de Ven 
LKML-Reference: <200910090724.n997OQl6013538@imap1.linux-foundation.org>
Signed-off-by: Ingo Molnar

x86: Add a Kconfig option to turn the copy_from_user warnings into errors

2009-10-02T17:01:42+00:00

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: Arjan van de Ven 
Cc: Linus Torvalds 
Cc: Andrew Morton 
LKML-Reference: <20091002075050.4e9f7641@infradead.org>
Signed-off-by: Ingo Molnar

x86: Turn the copy_from_user check into an (optional) compile time warning

2009-10-01T09:31:04+00:00

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: Arjan van de Ven 
Cc: Linus Torvalds 
Cc: "David S. Miller" 
Cc: James Morris 
Cc: Jan Beulich 
LKML-Reference: <20090930130523.348ae6c4@infradead.org>
Signed-off-by: Ingo Molnar

x86: Use __builtin_object_size() to validate the buffer size for copy_from_user()

2009-09-26T14:25:41+00:00

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: Arjan van de Ven 
LKML-Reference: <20090926143301.2c396b94@infradead.org>
Signed-off-by: Ingo Molnar

compiler-gcc4: conditionalize #error on KERNEL

2009-03-26T17:14:23+00:00

Impact: Fix for exported headers

We only want to error out on specific gcc versions if we are actually
building the kernel, so conditionalize the #if...#error on __KERNEL__.

Based on a patchset by Arnd Bergmann .

Cc: Arnd Bergmann 
Signed-off-by: H. Peter Anvin 
Signed-off-by: Ingo Molnar

Disallow gcc versions 4.1.{0,1}

2009-01-02T17:29:43+00:00

These compiler versions are known to miscompile __weak functions and
thus generate kernels that don't necessarily work correctly.  If a weak
function is int he same compilation unit as a caller, gcc may end up
inlining it, and thus binding the weak function too early.

See

    http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27781

for details.

Cc: Adrian Bunk 
Cc: Helge Deller 
Cc: Rusty Russell 
Cc: Ingo Molnar 
Signed-off-by: Linus Torvalds

Sanitize gcc version header includes

2009-01-02T17:23:03+00:00

 - 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: Linus Torvalds