[comboot] Use built-in interrupt reflector

We now have the ability to handle interrupts while in protected mode,
and so no longer need to set up a dedicated interrupt descriptor table
while running COM32 executables.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/arch/i386/interface/syslinux/com32_call.c

@@ -189,20 +189,3 @@ int __asmcall com32_cfarcall ( uint32_t proc, physaddr_t stack, size_t stacksz )
 
 	return eax;
 }
-
-/**
- * IRQ handler
- */
-void __asmcall com32_irq ( uint32_t vector ) {
-	uint32_t *ivt_entry = phys_to_virt( vector * 4 );
-
-	__asm__ __volatile__ (
-		REAL_CODE ( "pushfw\n\t"
-			    "pushw %%cs\n\t"
-			    "pushw $com32_irq_return\n\t"
-			    "pushl %0\n\t"
-			    "lret\n"
-			    "com32_irq_return:\n\t" )
-		: /* no outputs */
-		: "r" ( *ivt_entry ) );
-}

src/arch/i386/interface/syslinux/com32_wrapper.S

@@ -23,26 +23,6 @@ FILE_LICENCE ( GPL2_OR_LATER )
 	.arch i386
 	.code32
 
-	/*
-	 * This code is entered after running the following sequence out of
-	 * the interrupt jump buffer:
-	 *
-	 * pushal
-	 * movb $vector, %al
-	 * jmp com32_irq_wrapper
-	 */
-
-	.globl com32_irq_wrapper
-com32_irq_wrapper:
-
-	movzbl %al,%eax
-	pushl %eax
-	movl $com32_irq, %eax
-	call com32_wrapper
-	popl %eax
-	popal
-	iret
-
 	.globl com32_farcall_wrapper
 com32_farcall_wrapper:
 
@@ -69,9 +49,6 @@ com32_wrapper:
 	/* Switch to internal virtual address space */
 	call _phys_to_virt
 
-	/* Switch to internal IDT (if we have one for debugging) */
-	lidt com32_internal_idtr
-
 	mov %eax, (com32_helper_function)
 
 	/* Save external COM32 stack pointer */
@@ -99,9 +76,6 @@ com32_wrapper:
 	movl %esp, (com32_internal_esp)
 	movl (com32_external_esp), %esp
 
-	/* Switch to com32 IDT */
-	lidt com32_external_idtr
-
 	/* Switch to external flat physical address space */
 	call _virt_to_phys