x86, vdso: Patch alternatives in the 32-bit VDSO

We need the alternatives mechanism for rdtsc_barrier() to work.

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Link: http://lkml.kernel.org/r/1395094933-14252-9-git-send-email-stefani@seibold.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/vdso.h

@@ -28,4 +28,6 @@ extern const char vdso32_int80_start, vdso32_int80_end;
 extern const char vdso32_syscall_start, vdso32_syscall_end;
 extern const char vdso32_sysenter_start, vdso32_sysenter_end;
 
+void __init patch_vdso32(void *vdso, size_t len);
+
 #endif /* _ASM_X86_VDSO_H */