x86/idt: Move early IDT setup out of 32-bit asm

The early IDT setup can be done in C code like it's done on 64-bit kernels.
Reuse the 64-bit version.

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/20170828064958.757980775@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/segment.h

@@ -238,6 +238,7 @@
 #ifndef __ASSEMBLY__
 
 extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];
+extern void early_ignore_irq(void);
 
 /*
  * Load a segment. Fall back on loading the zero segment if something goes

arch/x86/kernel/head32.c

@@ -10,6 +10,7 @@
 #include <linux/mm.h>
 #include <linux/memblock.h>
 
+#include <asm/desc.h>
 #include <asm/setup.h>
 #include <asm/sections.h>
 #include <asm/e820/api.h>
@@ -30,6 +31,9 @@ static void __init i386_default_early_setup(void)
 asmlinkage __visible void __init i386_start_kernel(void)
 {
 	cr4_init_shadow();
+
+	idt_setup_early_handler();
+
 	sanitize_boot_params(&boot_params);
 
 	x86_early_init_platform_quirks();

arch/x86/kernel/head_32.S

@@ -345,7 +345,6 @@ ENTRY(startup_32_smp)
 	movl %eax,%cr0
 
 	lgdt early_gdt_descr
-	lidt idt_descr
 	ljmp $(__KERNEL_CS),$1f
 1:	movl $(__KERNEL_DS),%eax	# reload all the segment registers
 	movl %eax,%ss			# after changing gdt.
@@ -378,37 +377,6 @@ ENDPROC(startup_32_smp)
  */
 __INIT
 setup_once:
-	/*
-	 * Set up a idt with 256 interrupt gates that push zero if there
-	 * is no error code and then jump to early_idt_handler_common.
-	 * It doesn't actually load the idt - that needs to be done on
-	 * each CPU. Interrupts are enabled elsewhere, when we can be
-	 * relatively sure everything is ok.
-	 */
-
-	movl $idt_table,%edi
-	movl $early_idt_handler_array,%eax
-	movl $NUM_EXCEPTION_VECTORS,%ecx
-1:
-	movl %eax,(%edi)
-	movl %eax,4(%edi)
-	/* interrupt gate, dpl=0, present */
-	movl $(0x8E000000 + __KERNEL_CS),2(%edi)
-	addl $EARLY_IDT_HANDLER_SIZE,%eax
-	addl $8,%edi
-	loop 1b
-
-	movl $256 - NUM_EXCEPTION_VECTORS,%ecx
-	movl $ignore_int,%edx
-	movl $(__KERNEL_CS << 16),%eax
-	movw %dx,%ax		/* selector = 0x0010 = cs */
-	movw $0x8E00,%dx	/* interrupt gate - dpl=0, present */
-2:
-	movl %eax,(%edi)
-	movl %edx,4(%edi)
-	addl $8,%edi
-	loop 2b
-
 #ifdef CONFIG_CC_STACKPROTECTOR
 	/*
 	 * Configure the stack canary. The linker can't handle this by
@@ -498,7 +466,7 @@ ENDPROC(early_idt_handler_common)
 
 /* This is the default interrupt "handler" :-) */
 	ALIGN
-ignore_int:
+ENTRY(early_ignore_irq)
 	cld
 #ifdef CONFIG_PRINTK
 	pushl %eax
@@ -533,7 +501,7 @@ ignore_int:
 hlt_loop:
 	hlt
 	jmp hlt_loop
-ENDPROC(ignore_int)
+ENDPROC(early_ignore_irq)
 __INITDATA
 	.align 4
 GLOBAL(early_recursion_flag)

arch/x86/kernel/idt.c

@@ -34,6 +34,10 @@ void __init idt_setup_early_handler(void)
 
 	for (i = 0; i < NUM_EXCEPTION_VECTORS; i++)
 		set_intr_gate(i, early_idt_handler_array[i]);
+#ifdef CONFIG_X86_32
+	for ( ; i < NR_VECTORS; i++)
+		set_intr_gate(i, early_ignore_irq);
+#endif
 	load_idt(&idt_descr);
 }