x86 vDSO: consolidate vdso32

This makes x86_64's ia32 emulation support share the sources used in the
32-bit kernel for the 32-bit vDSO and much of its setup code.

The 32-bit vDSO mapping now behaves the same on x86_64 as on native 32-bit.
The abi.syscall32 sysctl on x86_64 now takes the same values that
vm.vdso_enabled takes on the 32-bit kernel.  That is, 1 means a randomized
vDSO location, 2 means the fixed old address.  The CONFIG_COMPAT_VDSO
option is now available to make this the default setting, the same meaning
it has for the 32-bit kernel.  (This does not affect the 64-bit vDSO.)

The argument vdso32=[012] can be used on both 32-bit and 64-bit kernels to
set this paramter at boot time.  The vdso=[012] argument still does this
same thing on the 32-bit kernel.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 80b7ba4056db..2f4d88babd36 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1191,9 +1191,9 @@ config HOTPLUG_CPU
 config COMPAT_VDSO
         bool "Compat VDSO support"
         default y
-        depends on X86_32
+        depends on X86_32 || IA32_EMULATION
         help
-          Map the VDSO to the predictable old-style address too.
+          Map the 32-bit VDSO to the predictable old-style address too.
         ---help---
           Say N here if you are running a sufficiently recent glibc
           version (2.3.3 or later), to remove the high-mapped