x86: reduce static IRQ stub size

All of these stubs at the end pop the stack and tell the LOAPIC
that we are at EOI. Put this in common code which falls through to
_IntExit(). Saves 8 bytes per static IRQ stub. There is also small
constant savings in the common code for dynamic IRQs.

Change-Id: If17e9f105928a4251a2cb3fc0d192649c1c4d84b
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

arch/x86/core/i386_sysV_abi/intstub.S

@@ -30,12 +30,13 @@
 #include <arch/x86/asm.h>
 #include <offsets.h>	/* nanokernel structure offset definitions */
 #include <arch/cpu.h>	/* _NANO_ERR_SPURIOUS_INT */
-
+#include <drivers/loapic.h> /* LOAPIC_EOI */
 
 
 	/* exports (internal APIs) */
 
 	GTEXT(_IntEnt)
+	GTEXT(_IntExitWithEoi)
 	GTEXT(_IntExit)
 	GTEXT(_SpuriousIntNoErrCodeHandler)
 	GTEXT(_SpuriousIntHandler)
@@ -224,6 +225,29 @@ BRANCH_LABEL(_HandleIdle)
 	jmp	*%eax		/* "return" back to stub */
 #endif /* CONFIG_ADVANCED_POWER_MANAGEMENT */
 
+/**
+ * @brief Perform EOI, clean up stack, and do interrupt exit
+ *
+ * This is used by the interrupt stubs, which all leave the stack in
+ * a particular state and need to poke the interrupt controller.
+ * Prior to running the logic in _IntExit, the ISR parameter is popped off
+ * the stack and EOI is set to the LOAPIC.
+ */
+SECTION_FUNC(TEXT, _IntExitWithEoi)
+	popl %eax			/* Pushed onto stack by stub */
+#if CONFIG_EOI_FORWARDING_BUG
+	call	_lakemont_eoi
+#endif
+	xorl %eax, %eax			/* zeroes eax */
+	/* TODO not great to have hard-coded LOAPIC stuff here. When
+	 * we get around to introducing the interrupt controller abstraction
+	 * layer, the in-use IRQ controller code will define an ASM macro
+	 * with a specific name which does the correct thing for the particular
+	 * controller.
+	 */
+	loapic_eoi_reg = (CONFIG_LOAPIC_BASE_ADDRESS + LOAPIC_EOI)
+	movl %eax, loapic_eoi_reg	/* tell LOAPIC the IRQ is handled */
+	/* fall through to _IntExit */
 
 /**
  *
@@ -247,7 +271,7 @@ BRANCH_LABEL(_HandleIdle)
  *
  * void _IntExit (void);
  */
-SECTION_FUNC(TEXT, _IntExit)
+BRANCH_LABEL(_IntExit)
 
 	cli			/* disable interrupts */
 #ifdef CONFIG_INT_LATENCY_BENCHMARK
@@ -456,10 +480,8 @@ BRANCH_LABEL(callFatalHandler)
 #if ALL_DYN_IRQ_STUBS > 0
 BRANCH_LABEL(_DynIntStubCommon)
 	call _common_dynamic_irq_handler
-	/* Cleanse the stack of stub_num */
-	pop %eax
 	/* Clean up and call IRET */
-	jmp _IntExit
+	jmp _IntExitWithEoi
 
 /* Create all the dynamic IRQ stubs
  *

arch/x86/core/intconnect.c

@@ -43,7 +43,6 @@
 #include <arch/cpu.h>
 #include <nano_private.h>
 #include <misc/__assert.h>
-#include <drivers/loapic.h>
 #include <idtEnt.h>
 
 extern void _SpuriousIntHandler(void *);
@@ -260,11 +259,6 @@ int irq_connect(unsigned int irq, unsigned int priority,
 void _common_dynamic_irq_handler(uint32_t stub_idx)
 {
 	dyn_irq_list[stub_idx].handler(dyn_irq_list[stub_idx].param);
-	/*
-	 * Tell the APIC we're done servicing the interrupt.LOAPIC will notify
-	 * the IOAPIC if necessary
-	 */
-	_loapic_eoi();
 }
 
 /**

include/drivers/loapic.h

@@ -64,13 +64,7 @@ SECTION_FUNC(TEXT, _\()\device\()_\()\isr\()_stub)
 	call    _IntEnt          /* Inform kernel interrupt has begun */
 	pushl   \context         /* Push context parameter */
 	call    \isr             /* Call actual interrupt handler */
-	popl    %eax		 /* Clean-up stack from push above */
-#if CONFIG_EOI_FORWARDING_BUG
-	call	_lakemont_eoi
-#endif
-	xorl	%eax, %eax
-	movl	%eax, loapic_eoi /* Inform loapic interrupt is done */
-	jmp     _IntExit         /* Inform kernel interrupt is done */
+	jmp     _IntExitWithEoi  /* Inform kernel interrupt is done */
 .endm
 
 #else /* _ASMLANGUAGE */