interrupt separation between CPU exceptions and hardware IRQs by the PIC,

started to program the PICs for interrupt delivery

5 files changed, 72 insertions, 26 deletions

diff --git a/doc/LINKS.TODO b/doc/LINKS.TODO
index 15ea245..a7b3f15 100644
--- a/doc/LINKS.TODO
+++ b/doc/LINKS.TODO
@@ -37,3 +37,6 @@ longjmp:
 http://blog.reverberate.org/2013/05/deep-wizardry-stack-unwinding.html
 http://prettyos.de
 
+PIC:
+http://www.brokenthorn.com/Resources/OSDevPic.html
+
diff --git a/src/interrupts.asm b/src/interrupts.asm
index c21229c..9a05883 100644
--- a/src/interrupts.asm
+++ b/src/interrupts.asm
@@ -37,13 +37,27 @@ interrupts_ignore_request:
 	
 ; void interrupts_handle_request_0x00( );
 %macro exception_stub 1
-global interrupts_handle_request_%1
-interrupts_handle_request_%1:
+global interrupts_handle_exception_%1
+interrupts_handle_exception_%1:
 	mov [interrupt_no], byte %1
+	jmp int_entry
 %endmacro
 
 exception_stub 0x00
 
+; IRQs and exceptions would normally collidate, that's why the
+; hardware interrupts must be transposed by an offset
+IRQ_BASE equ 0x20
+
+%macro irq_stub 1
+global interrupts_handle_irq_%1
+interrupts_handle_irq_%1:
+	mov [interrupt_no], byte IRQ_BASE + %1
+	jmp int_entry
+%endmacro
+
+irq_stub 0x00
+
 int_entry:
 	; safe state of interrupted code
 	pusha
diff --git a/src/interrupts.c b/src/interrupts.c
index 810f105..59f38b8 100644
--- a/src/interrupts.c
+++ b/src/interrupts.c
@@ -17,6 +17,16 @@
 // types of IDT entries
 #define IDT_TYPE_INTERRUPT_GATE 0xE
 
+// offset for hardware interrupts
+#define IRQ_BASE 0x20
+#define IRQ_BASE_MASTER IRQ_BASE
+#define IRQ_BASE_SLAVE IRQ_BASE_MASTER + 8
+
+// PIC constants
+
+#define ICW1_ICW4 0x01 // support a 4th initialization word (ICW4)
+#define ICW1_INIT 0x10 // bit indicating initialization of chip
+
 void interrupts_init( interrupt_t *interrupt )
 {
 	memset( interrupt, 0, sizeof( interrupt_t ) );
@@ -28,16 +38,34 @@ void interrupts_init( interrupt_t *interrupt )
 
 	// divide-by-zero exception 0x00
 	interrupts_register_interrupt( interrupt, 0x00, GDT_CODE_SEGMENT_SELECTOR,
-			&interrupts_handle_request_0x00, KERNEL_RING, IDT_TYPE_INTERRUPT_GATE );
+		&interrupts_handle_exception_0x00, KERNEL_RING, IDT_TYPE_INTERRUPT_GATE );
 
-	interrupt->idt_pointer.size = 256 * sizeof( interrupt_gate_descriptor_t ) - 1;
-	interrupt->idt_pointer.base = (uint32_t)interrupt->descriptor_table;
-		
-	interrupts_load_idt( &interrupt->idt_pointer );
+	// IRQ 0 - PIT - programmable interrupt timer
+	interrupts_register_interrupt( interrupt, IRQ_BASE + 0x00, GDT_CODE_SEGMENT_SELECTOR,
+		&interrupts_handle_irq_0x00, KERNEL_RING, IDT_TYPE_INTERRUPT_GATE );
 
+	// IRQ 1 - keyboard
+	interrupts_register_interrupt( interrupt, IRQ_BASE + 0x00, GDT_CODE_SEGMENT_SELECTOR,
+		&interrupts_handle_irq_0x00, KERNEL_RING, IDT_TYPE_INTERRUPT_GATE );
+	
 	port8_init( &interrupt->PIC_master_control, 0x20 );
 	port8_init( &interrupt->PIC_master_data, 0x21 );
+	port8_init( &interrupt->PIC_slave_control, 0xA0 );
+	port8_init( &interrupt->PIC_slave_data, 0xA1 );
+
+	// initialize hardware management PICs (ICW1)
+	port8_write( &interrupt->PIC_master_control, ICW1_ICW4 | ICW1_INIT );
+	port8_write( &interrupt->PIC_slave_control, ICW1_ICW4 | ICW1_INIT );
 	
+	// set IRQ base of both PICS (ICW2)
+	port8_write( &interrupt->PIC_master_data, IRQ_BASE_MASTER );
+	port8_write( &interrupt->PIC_slave_data, IRQ_BASE_SLAVE );
+
+	// tell CPU where the IDT is
+	interrupt->idt_pointer.size = 256 * sizeof( interrupt_gate_descriptor_t ) - 1;
+	interrupt->idt_pointer.base = (uint32_t)interrupt->descriptor_table;
+
+	interrupts_load_idt( &interrupt->idt_pointer );
 }
 
 void interrupts_register_interrupt( interrupt_t *interrupts, 
diff --git a/src/interrupts.h b/src/interrupts.h
index 593a993..e90506f 100644
--- a/src/interrupts.h
+++ b/src/interrupts.h
@@ -46,6 +46,10 @@ typedef struct {
 	interrupt_gate_descriptor_t descriptor_table[NOF_INTERRUPT_GATES];
 	port8_t PIC_master_control;
 	port8_t PIC_master_data;
+	// since PC/AT we always have a slave PIC, we don't support the PC/XT architecture
+	// with just one PIC
+	port8_t PIC_slave_control;
+	port8_t PIC_slave_data;
 } interrupt_t;
 
 void interrupts_enable( void );
@@ -59,7 +63,8 @@ void interrupts_load_idt( interrupt_descriptor_table_pointer_t *idt_pointer );
 uint32_t interrupts_handle_interrupt( uint8_t interrupt_no, uint32_t esp );
 
 void interrupts_ignore_request( );
-void interrupts_handle_request_0x00( );
+void interrupts_handle_exception_0x00( );
+void interrupts_handle_irq_0x00( );
 
 // initialize IDT
 // handle gates
diff --git a/src/kernel.c b/src/kernel.c
index 355067a..e33d509 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -11,22 +11,17 @@
 
 static jmp_buf panic_jmp_buf;
 
-static vga_t vga;
-static console_t console;
-// static serial_t serial;
-
 void entry( void )
 {	
+	serial_t serial;
+	serial_init( &serial );
 
-//	serial_t serial;
-//	serial_init( &serial );
-
-//	vga_t vga;
+	vga_t vga;
 	vga_init( &vga );
 	vga_set_color( &vga, VGA_COLOR_LIGHT_GREY );
 	vga_set_background_color( &vga, VGA_COLOR_BLACK );
 
-//	console_t console;
+	console_t console;
 	console_init( &console );
 	console_add_vga_output( &console, &vga );
 //	console_add_serial_output( &console, &serial );
@@ -39,17 +34,18 @@ void entry( void )
 	puts( "Initializing interrupts" );
 	interrupt_t interrupt;
 	interrupts_init( &interrupt );
-	interrupts_enable( );
-		
-//~ vga_put_char_at( &vga, 81, 20, 'X' );
 
 	// exit point in case of kernel panic, do this as soon as
 	// possible
-	int v = setjmp( panic_jmp_buf );
-	printf( "setjmp returned %d\n", v );
-	if( v > 0 ) { 
+	if( setjmp( panic_jmp_buf ) > 0 ) {
 		goto TERMINATE;
 	}
+	
+	// TODO: initialize hardware here
+	
+	interrupts_enable( );
+		
+//~ vga_put_char_at( &vga, 81, 20, 'X' );
 
 	console_put_string( &console, "Running.." );
 	
@@ -62,9 +58,9 @@ void entry( void )
 			vga_put_char_at( &vga, x_pos, y_pos, '.' );
 			x_pos++;
 //			serial_put_char( &serial, '.' );
-int y = 0;
-int x = 12 / y;
-printf( "Hex number is 0x%X and string is '%s'\n", x, "abaos" );			
+//~ int y = 0;
+//~ int x = 12 / y;
+//~ printf( "Hex number is 0x%X and string is '%s'\n", x, "abaos" );			
 
 		}
 		vga_put_char_at( &vga, x_pos, y_pos, bar[i%4] );