x86, vdso: Add 32 bit VDSO time support for 64 bit kernel

This patch add the VDSO time support for the IA32 Emulation Layer.

Due the nature of the kernel headers and the LP64 compiler where the
size of a long and a pointer differs against a 32 bit compiler, there
is some type hacking necessary for optimal performance.

The vsyscall_gtod_data struture must be a rearranged to serve 32- and
64-bit code access at the same time:

- The seqcount_t was replaced by an unsigned, this makes the
  vsyscall_gtod_data intedepend of kernel configuration and internal functions.
- All kernel internal structures are replaced by fix size elements
  which works for 32- and 64-bit access
- The inner struct clock was removed to pack the whole struct.

The "unsigned seq" would be handled by functions derivated from seqcount_t.

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Link: http://lkml.kernel.org/r/1395094933-14252-11-git-send-email-stefani@seibold.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/x86/include/asm/vvar.h b/arch/x86/include/asm/vvar.h
index 52c79ffc31619..081d909bc4954 100644
--- a/arch/x86/include/asm/vvar.h
+++ b/arch/x86/include/asm/vvar.h
@@ -16,6 +16,9 @@
  * you mess up, the linker will catch it.)
  */
 
+#ifndef _ASM_X86_VVAR_H
+#define _ASM_X86_VVAR_H
+
 #if defined(__VVAR_KERNEL_LDS)
 
 /* The kernel linker script defines its own magic to put vvars in the
@@ -64,3 +67,5 @@ DECLARE_VVAR(16, int, vgetcpu_mode)
 DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data)
 
 #undef DECLARE_VVAR
+
+#endif