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

Pull x86 vdso updates from Ingo Molnar:
 "Various vDSO updates from Andy Lutomirski, mostly cleanups and
  reorganization to improve maintainability, but also some
  micro-optimizations and robustization changes"

* 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86_64/vsyscall: Restore orig_ax after vsyscall seccomp
  x86_64: Add a comment explaining the TASK_SIZE_MAX guard page
  x86_64,vsyscall: Make vsyscall emulation configurable
  x86_64, vsyscall: Rewrite comment and clean up headers in vsyscall code
  x86_64, vsyscall: Turn vsyscalls all the way off when vsyscall==none
  x86,vdso: Use LSL unconditionally for vgetcpu
  x86: vdso: Fix build with older gcc
  x86_64/vdso: Clean up vgetcpu init and merge the vdso initcalls
  x86_64/vdso: Remove jiffies from the vvar page
  x86/vdso: Make the PER_CPU segment 32 bits
  x86/vdso: Make the PER_CPU segment start out accessed
  x86/vdso: Change the PER_CPU segment to use struct desc_struct
  x86_64/vdso: Move getcpu code from vsyscall_64.c to vdso/vma.c
  x86_64/vsyscall: Move all of the gate_area code to vsyscall_64.c

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 666ac6651c17..bea3a0159496 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -992,6 +992,24 @@ config X86_ESPFIX64
         def_bool y
         depends on X86_16BIT && X86_64
 
+config X86_VSYSCALL_EMULATION
+       bool "Enable vsyscall emulation" if EXPERT
+       default y
+       depends on X86_64
+       ---help---
+         This enables emulation of the legacy vsyscall page.  Disabling
+         it is roughly equivalent to booting with vsyscall=none, except
+         that it will also disable the helpful warning if a program
+         tries to use a vsyscall.  With this option set to N, offending
+         programs will just segfault, citing addresses of the form
+         0xffffffffff600?00.
+
+         This option is required by many programs built before 2013, and
+         care should be used even with newer programs if set to N.
+
+         Disabling this option saves about 7K of kernel size and
+         possibly 4K of additional runtime pagetable memory.
+
 config TOSHIBA
         tristate "Toshiba Laptop support"
         depends on X86_32