x86/idt: Move 32-bit idt_descr to C code

32-bit kernels have the idt_descr defined in the low level assembly entry code,
but there is no good reason for that.

Move it into the C file and use the 64-bit version of it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064958.445862201@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/head_32.S

@@ -622,7 +622,6 @@ int_msg:
 
 	.data
 .globl boot_gdt_descr
-.globl idt_descr
 
 	ALIGN
 # early boot GDT descriptor (must use 1:1 address mapping)
@@ -631,11 +630,6 @@ boot_gdt_descr:
 	.word __BOOT_DS+7
 	.long boot_gdt - __PAGE_OFFSET
 
-	.word 0				# 32-bit align idt_desc.address
-idt_descr:
-	.word IDT_ENTRIES*8-1		# idt contains 256 entries
-	.long idt_table
-
 # boot GDT descriptor (later on used by CPU#0):
 	.word 0				# 32 bit align gdt_desc.address
 ENTRY(early_gdt_descr)

arch/x86/kernel/idt.c

@@ -10,15 +10,15 @@
 /* Must be page-aligned because the real IDT is used in a fixmap. */
 gate_desc idt_table[IDT_ENTRIES] __page_aligned_bss;
 
-#ifdef CONFIG_X86_64
-/* No need to be aligned, but done to keep all IDTs defined the same way. */
-gate_desc debug_idt_table[IDT_ENTRIES] __page_aligned_bss;
-
 struct desc_ptr idt_descr __ro_after_init = {
-	.size		= IDT_ENTRIES * 16 - 1,
+	.size		= (IDT_ENTRIES * 2 * sizeof(unsigned long)) - 1,
 	.address	= (unsigned long) idt_table,
 };
 
+#ifdef CONFIG_X86_64
+/* No need to be aligned, but done to keep all IDTs defined the same way. */
+gate_desc debug_idt_table[IDT_ENTRIES] __page_aligned_bss;
+
 const struct desc_ptr debug_idt_descr = {
 	.size		= IDT_ENTRIES * 16 - 1,
 	.address	= (unsigned long) debug_idt_table,