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

Pull x86 iopl updates from Ingo Molnar:
 "This implements a nice simplification of the iopl and ioperm code that
  Thomas Gleixner discovered: we can implement the IO privilege features
  of the iopl system call by using the IO permission bitmap in
  permissive mode, while trapping CLI/STI/POPF/PUSHF uses in user-space
  if they change the interrupt flag.

  This implements that feature, with testing facilities and related
  cleanups"

[ "Simplification" may be an over-statement. The main goal is to avoid
  the cli/sti of iopl by effectively implementing the IO port access
  parts of iopl in terms of ioperm.

  This may end up not workign well in case people actually depend on
  cli/sti being available, or if there are mixed uses of iopl and
  ioperm. We will see..       - Linus ]

* 'x86-iopl-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (22 commits)
  x86/ioperm: Fix use of deprecated config option
  x86/entry/32: Clarify register saving in __switch_to_asm()
  selftests/x86/iopl: Extend test to cover IOPL emulation
  x86/ioperm: Extend IOPL config to control ioperm() as well
  x86/iopl: Remove legacy IOPL option
  x86/iopl: Restrict iopl() permission scope
  x86/iopl: Fixup misleading comment
  selftests/x86/ioperm: Extend testing so the shared bitmap is exercised
  x86/ioperm: Share I/O bitmap if identical
  x86/ioperm: Remove bitmap if all permissions dropped
  x86/ioperm: Move TSS bitmap update to exit to user work
  x86/ioperm: Add bitmap sequence number
  x86/ioperm: Move iobitmap data into a struct
  x86/tss: Move I/O bitmap data into a seperate struct
  x86/io: Speedup schedule out of I/O bitmap user
  x86/ioperm: Avoid bitmap allocation if no permissions are set
  x86/ioperm: Simplify first ioperm() invocation logic
  x86/iopl: Cleanup include maze
  x86/tss: Fix and move VMX BUILD_BUG_ON()
  x86/cpu: Unify cpu_init()
  ...

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b89eb1f0c0d2..d936174f9d49 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1224,6 +1224,24 @@ config X86_VSYSCALL_EMULATION
 	 Disabling this option saves about 7K of kernel size and
 	 possibly 4K of additional runtime pagetable memory.
 
+config X86_IOPL_IOPERM
+	bool "IOPERM and IOPL Emulation"
+	default y
+	---help---
+	  This enables the ioperm() and iopl() syscalls which are necessary
+	  for legacy applications.
+
+	  Legacy IOPL support is an overbroad mechanism which allows user
+	  space aside of accessing all 65536 I/O ports also to disable
+	  interrupts. To gain this access the caller needs CAP_SYS_RAWIO
+	  capabilities and permission from potentially active security
+	  modules.
+
+	  The emulation restricts the functionality of the syscall to
+	  only allowing the full range I/O port access, but prevents the
+	  ability to disable interrupts from user space which would be
+	  granted if the hardware IOPL mechanism would be used.
+
 config TOSHIBA
 	tristate "Toshiba Laptop support"
 	depends on X86_32