x86: prevent IRQs from firing during init

arch/x86/sys/i386/irq.S

@@ -12,15 +12,16 @@
 	.extern irq_table
 
 	/* there is probably a fancy CPU feature for this, but idk */
-_in_irq:
+irq_count:
 	.byte 0
 
 	.text
 
-	/* bool in_irq(void); */
+/* bool in_irq(void); */
 ASM_ENTRY(in_irq)
 	xor	%eax, %eax
-	movb	_in_irq, %al
+	cmpb	$0, irq_count
+	setne	%al
 	ret
 ASM_END(in_irq)
 
@@ -29,7 +30,7 @@ ASM_ENTRY(_x86_isr_irq\num )
 	push	%eax
 	push	%ecx
 	push	%edx
-	movb	$1, _in_irq
+	incb	irq_count
 #if CFG_DEBUG_IRQ
 	pushl	$\num
 #endif
@@ -37,12 +38,7 @@ ASM_ENTRY(_x86_isr_irq\num )
 #if CFG_DEBUG_IRQ
 	add	$4, %esp
 #endif
-	movb	$0x20, %al		/* PIC End Of Interrupt command code */
-.if \num >= 8
-	jmp	leave_irq_pic2
-.else
-	jmp	leave_irq_pic1
-.endif
+	jmp	leave_irq
 ASM_END(_x86_isr_irq\num )
 .endm
 
@@ -63,16 +59,16 @@ ASM_END(_x86_isr_irq\num )
 	gen_irq 14
 	gen_irq 15
 
-leave_irq_pic2:
-	outb	%al, $X86_PORT_PIC2_CMD	/* send End Of Interrupt to PIC2 */
-leave_irq_pic1:
-	outb	%al, $X86_PORT_PIC1_CMD	/* send End Of Interrupt to PIC1 */
-	movb	$0, _in_irq
+	.align 4
+leave_irq:
+	decb	irq_count
 	pop	%edx
 	pop	%ecx
 	pop	%eax
 	iret
 
+	.size leave_irq, . - leave_irq
+
 /*
  * This file is part of GayBSD.
  * Copyright (c) 2021 fef <owo@fef.moe>.

arch/x86/sys/irq.c

@@ -39,6 +39,13 @@ void arch_irq_init(void)
 	x86_set_intr_gate(X86_VECT_IRQ(14), _x86_isr_irq14);
 	x86_set_intr_gate(X86_VECT_IRQ(15), _x86_isr_irq15);
 
+	/*
+	 * disable interrupts to prevent IRQs from being fired
+	 * immediately after the initialization sequence is complete
+	 * (we need time to mask all IRQs again first)
+	 */
+	disable_intr();
+
 	/* begin initialization sequence in cascade mode */
 	x86_outb_wait(X86_PORT_PIC1_CMD, ICW1_INIT | ICW1_ICW4);
 	x86_outb_wait(X86_PORT_PIC2_CMD, ICW1_INIT | ICW1_ICW4);
@@ -57,9 +64,15 @@ void arch_irq_init(void)
 	x86_outb_wait(X86_PORT_PIC1_DATA, ICW4_8086);
 	x86_outb_wait(X86_PORT_PIC2_DATA, ICW4_8086);
 
-	/* mask all IRQs */
+	/*
+	 * The initialization sequence is finished now, meaning all IRQ masks
+	 * have been cleared (they are all enabled).  Disable them again.
+	 */
 	x86_outb_wait(X86_PORT_PIC1_DATA, 0xff);
-	x86_outb(X86_PORT_PIC2_DATA, 0xff);
+	x86_outb_wait(X86_PORT_PIC2_DATA, 0xff);
+
+	/* it's safe to turn interrupts back on now */
+	enable_intr();
 }
 
 void arch_irq_enable(unsigned int number)
@@ -92,6 +105,13 @@ void arch_irq_disable(unsigned int number)
 	x86_outb(port, mask);
 }
 
+void x86_irq_ack(unsigned int number)
+{
+	if (number >= 8)
+		x86_outb(X86_PORT_PIC2_CMD, 0x20);
+	x86_outb(X86_PORT_PIC1_CMD, 0x20);
+}
+
 /*
  * This file is part of GayBSD.
  * Copyright (c) 2021 fef <owo@fef.moe>.