x86/asm/xen: Create stack frames in xen-asm.S

xen_irq_enable_direct(), xen_restore_fl_direct(), and check_events() are
callable non-leaf functions which don't honor CONFIG_FRAME_POINTER,
which can result in bad stack traces.

Create stack frames for them when CONFIG_FRAME_POINTER is enabled.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/a8340ad3fc72ba9ed34da9b3af9cdd6f1a896e17.1453405861.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/xen/xen-asm.S

@@ -14,6 +14,7 @@
 #include <asm/asm-offsets.h>
 #include <asm/percpu.h>
 #include <asm/processor-flags.h>
+#include <asm/frame.h>
 
 #include "xen-asm.h"
 
@@ -23,6 +24,7 @@
  * then enter the hypervisor to get them handled.
  */
 ENTRY(xen_irq_enable_direct)
+	FRAME_BEGIN
 	/* Unmask events */
 	movb $0, PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
 
@@ -39,6 +41,7 @@ ENTRY(xen_irq_enable_direct)
 2:	call check_events
 1:
 ENDPATCH(xen_irq_enable_direct)
+	FRAME_END
 	ret
 	ENDPROC(xen_irq_enable_direct)
 	RELOC(xen_irq_enable_direct, 2b+1)
@@ -82,6 +85,7 @@ ENDPATCH(xen_save_fl_direct)
  * enters the hypervisor to get them delivered if so.
  */
 ENTRY(xen_restore_fl_direct)
+	FRAME_BEGIN
 #ifdef CONFIG_X86_64
 	testw $X86_EFLAGS_IF, %di
 #else
@@ -100,6 +104,7 @@ ENTRY(xen_restore_fl_direct)
 2:	call check_events
 1:
 ENDPATCH(xen_restore_fl_direct)
+	FRAME_END
 	ret
 	ENDPROC(xen_restore_fl_direct)
 	RELOC(xen_restore_fl_direct, 2b+1)
@@ -109,7 +114,8 @@ ENDPATCH(xen_restore_fl_direct)
  * Force an event check by making a hypercall, but preserve regs
  * before making the call.
  */
-check_events:
+ENTRY(check_events)
+	FRAME_BEGIN
 #ifdef CONFIG_X86_32
 	push %eax
 	push %ecx
@@ -139,4 +145,6 @@ check_events:
 	pop %rcx
 	pop %rax
 #endif
+	FRAME_END
 	ret
+ENDPROC(check_events)