xen: fix section usage in xen-head.S and setup.c

additional section for .init.text appending a number.

A side effect of this was a section mismatch warning because modpost did
not recognize a .init.text section named .init.text.1: WARNING:
vmlinux.o(.text.head+0x247): Section mismatch: reference to
.init.text.1:start_kernel (between 'is386' and 'check_x87')

Fix this by hardcoding the "ax" in the pushsection.  Thanks to Torlaf for
reporting this.

Alan Modra provided the hint that made me able to locate the root cause of
this warning.  And Mike Frysinger told me how to properly fix it using
__INIT/__FINIT.

Fix following Section mismatch warning in addition:
WARNING: vmlinux.o(.text+0x14c8): Section mismatch: reference to .init.data:vsyscall_int80_start (between 'fiddle_vdso' and 'xen_setup_features')

fiddle_vdso was only used from a __init function - so declare it __init.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Toralf Förster <toralf.foerster@gmx.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/xen/setup.c

@@ -60,7 +60,7 @@ static void xen_idle(void)
 /*
  * Set the bit indicating "nosegneg" library variants should be used.
  */
-static void fiddle_vdso(void)
+static void __init fiddle_vdso(void)
 {
 	extern const char vdso32_default_start;
 	u32 *mask = VDSO32_SYMBOL(&vdso32_default_start, NOTE_MASK);

arch/x86/xen/xen-head.S

@@ -4,16 +4,18 @@
 #ifdef CONFIG_XEN
 
 #include <linux/elfnote.h>
+#include <linux/init.h>
 #include <asm/boot.h>
 #include <xen/interface/elfnote.h>
 
-.pushsection .init.text
+	__INIT
 ENTRY(startup_xen)
 	movl %esi,xen_start_info
 	cld
 	movl $(init_thread_union+THREAD_SIZE),%esp
 	jmp xen_start_kernel
-.popsection
+
+	__FINIT
 
 .pushsection .bss.page_aligned
 	.align PAGE_SIZE_asm