x86/entry: Convert Divide Error to IDTENTRY

Convert #DE to IDTENTRY:
  - Implement the C entry point with DEFINE_IDTENTRY
  - Emit the ASM stub with DECLARE_IDTENTRY
  - Remove the ASM idtentry in 64bit
  - Remove the open coded ASM entry code in 32bit
  - Fixup the XEN/PV code

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505134904.663914713@linutronix.de

arch/x86/xen/enlighten_pv.c

@@ -604,6 +604,11 @@ struct trap_array_entry {
 	bool ist_okay;
 };
 
+#define TRAP_ENTRY(func, ist_ok) {			\
+	.orig		= asm_##func,			\
+	.xen		= xen_asm_##func,		\
+	.ist_okay	= ist_ok }
+
 static struct trap_array_entry trap_array[] = {
 	{ debug,                       xen_xendebug,                    true },
 	{ double_fault,                xen_double_fault,                true },
@@ -617,7 +622,7 @@ static struct trap_array_entry trap_array[] = {
 	{ entry_INT80_compat,          xen_entry_INT80_compat,          false },
 #endif
 	{ page_fault,                  xen_page_fault,                  false },
-	{ divide_error,                xen_divide_error,                false },
+	TRAP_ENTRY(exc_divide_error,			false ),
 	{ bounds,                      xen_bounds,                      false },
 	{ invalid_op,                  xen_invalid_op,                  false },
 	{ device_not_available,        xen_device_not_available,        false },

arch/x86/xen/xen-asm_64.S

@@ -28,7 +28,7 @@ SYM_CODE_END(xen_\name)
 _ASM_NOKPROBE(xen_\name)
 .endm
 
-xen_pv_trap divide_error
+xen_pv_trap asm_exc_divide_error
 xen_pv_trap debug
 xen_pv_trap xendebug
 xen_pv_trap int3