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

* '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()

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 7d0b681a132b..731318e5ac1d 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -296,4 +296,18 @@ config OPTIMIZE_INLINING
 
           If unsure, say N.
 
+config DEBUG_STRICT_USER_COPY_CHECKS
+        bool "Strict copy size checks"
+        depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
+        ---help---
+          Enabling this option turns a certain set of sanity checks for user
+          copy operations into compile time failures.
+
+          The copy_from_user() etc checks are there to help test if there
+          are sufficient security checks on the length argument of
+          the copy operation, by having gcc prove that the argument is
+          within bounds.
+
+          If unsure, or if you run an older (pre 4.4) gcc, say N.
+
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