[mubios] Enable IRQ0

Signed-off-by: Richard Qin <richard.qin.x@gmail.com>

7 files changed, 112 insertions, 19 deletions

diff --git a/mubios/arch/mode_switch.S b/mubios/arch/mode_switch.S
index 575c78d..9b2643a 100644
--- a/mubios/arch/mode_switch.S
+++ b/mubios/arch/mode_switch.S
@@ -109,7 +109,7 @@ protected_mode_entry:
 	mov fs, ax
 	mov gs, ax
 
-	mov esp, 0x00008000
+	mov esp, 0x00007000
 
 	call post_main
 
@@ -165,7 +165,7 @@ protected16_return:
 
 	# Leave protected mode while already using a 16-bit code segment.
 	mov eax, cr0
-	and eax 0xFFFFFFFE
+	and eax, 0xFFFFFFFE
 	mov cr0, eax
 
 	# Jump to the prepared real-mode CS:IP pointer.
@@ -179,6 +179,8 @@ real_mode_return:
 	mov ds, ax
 	mov es, ax
 	mov ss, ax
+	mov fs, ax
+	mov gs, ax
 	mov sp, 0x7FFE
 
 	ret
diff --git a/mubios/arch/reset.S b/mubios/arch/reset.S
index 92dad17..0be8a05 100644
--- a/mubios/arch/reset.S
+++ b/mubios/arch/reset.S
@@ -40,8 +40,11 @@ reset_entry:
 	call enter_protected_mode
 
 reset_halt:
+	sti
+
+reset_halt_loop:
 	hlt
-	jmp reset_halt
+	jmp reset_halt_loop
 
 	.section .reset, "ax"
 	
diff --git a/mubios/core/post.c b/mubios/core/post.c
index 34ee715..a37f192 100644
--- a/mubios/core/post.c
+++ b/mubios/core/post.c
@@ -30,10 +30,11 @@ post_main (void)
   memory_init ();
   bda_init ();
 
-  ivt_init();
+  ivt_init ();
 
   pic_init ();
   pit_init ();
+  ioapic_init ();
 
   serial_write ("mubios: IVT/PIC/PIT initialized\r\n");
 }
diff --git a/mubios/drivers/ioapic.c b/mubios/drivers/ioapic.c
new file mode 100644
index 0000000..98f2210
--- /dev/null
+++ b/mubios/drivers/ioapic.c
@@ -0,0 +1,87 @@
+/*
+ RCC-Project
+
+ Copyright (C) 2026 Richard Qin
+
+ This file is part of RCC-Project.
+
+ RCC-Project is free software; you can redistribute it and/or modify it under
+ the terms of the GNU General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at your option) any
+ later version.
+
+ RCC-Project is distributed in the hope that it will be useful, but WITHOUT ANY
+ WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+ A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License along with
+ RCC-Project; see the file COPYING.  If not see
+ <http://www.gnu.org/licenses/>.
+ */
+
+#include "bios.h"
+#include "io.h"
+
+#define IOAPIC_INDEX 0xFEC00000u
+#define IOAPIC_DATA 0xFEC00010u
+
+#define IOAPIC_IRQ0_LOW 0x10u
+#define IOAPIC_IRQ0_HIGH 0x11u
+
+#define IOAPIC_IRQ0_EXTINT 0x00000700u
+
+#define IA32_APIC_BASE_MSR 0x0000001Bu
+#define APIC_BASE 0xFEE00000u
+#define APIC_SVR_OFFSET 0x000000F0u
+#define APIC_LVT0_OFFSET 0x00000350u
+
+static volatile u32 *const ioapic_index = (volatile u32 *)IOAPIC_INDEX;
+
+static volatile u32 *const ioapic_data = (volatile u32 *)IOAPIC_DATA;
+
+static inline void
+rdmsr (u32 msr, u32 *low, u32 *high)
+{
+  __asm__ volatile ("rdmsr" : "=a"(*low), "=d"(*high) : "c"(msr));
+}
+
+static inline void
+wrmsr (u32 msr, u32 low, u32 high)
+{
+  __asm__ volatile ("wrmsr" : : "a"(low), "d"(high), "c"(msr));
+}
+
+static void
+ioapic_write (u8 index, u32 value)
+{
+  *ioapic_index = index;
+  *ioapic_data = value;
+}
+
+void
+ioapic_init (void)
+{
+  u32 apic_base_low;
+  u32 apic_base_high;
+
+  rdmsr (IA32_APIC_BASE_MSR, &apic_base_low, &apic_base_high);
+
+  apic_base_low |= 0x00000800u;
+  wrmsr (IA32_APIC_BASE_MSR, apic_base_low, apic_base_high);
+
+  /*
+   * Enable the local APIC.
+   */
+  *(volatile u32 *)(APIC_BASE + APIC_SVR_OFFSET) = 0x000001FFu;
+
+  /*
+   * Route legacy PIC interrupts through LVT0.
+   */
+  *(volatile u32 *)(APIC_BASE + APIC_LVT0_OFFSET) = 0x00000700u;
+
+  /*
+   * Route IOAPIC pin 0 to the legacy PIC ExtINT path.
+   */
+  ioapic_write (IOAPIC_IRQ0_LOW, IOAPIC_IRQ0_EXTINT);
+  ioapic_write (IOAPIC_IRQ0_HIGH, 0x00000000u);
+}
diff --git a/mubios/drivers/pic.c b/mubios/drivers/pic.c
index 099cee8..2144b6b 100644
--- a/mubios/drivers/pic.c
+++ b/mubios/drivers/pic.c
@@ -23,9 +23,9 @@
 #include "io.h"
 
 #define PIC1_COMMAND 0x0020u
-#define PIC1_DATA    0x0021u
+#define PIC1_DATA 0x0021u
 #define PIC2_COMMAND 0x00A0u
-#define PIC2_DATA    0x00A1u
+#define PIC2_DATA 0x00A1u
 
 #define PIC_ICW1_INIT 0x11u
 #define PIC_ICW4_8086 0x01u
@@ -36,30 +36,28 @@
 #define PIC1_CASCADE_ID 0x04u
 #define PIC2_CASCADE_ID 0x02u
 
-#define PIC1_MASK_DEFAULT 0xFBu
+#define PIC1_MASK_DEFAULT 0xFAu
 #define PIC2_MASK_DEFAULT 0xFFu
 
 void
 pic_init (void)
 {
   io_out8 (PIC1_COMMAND, PIC_ICW1_INIT);
-  io_out8(PIC2_COMMAND, PIC_ICW1_INIT);
+  io_out8 (PIC2_COMMAND, PIC_ICW1_INIT);
 
-  io_out8(PIC1_DATA, PIC1_VECTOR_BASE);
+  io_out8 (PIC1_DATA, PIC1_VECTOR_BASE);
   io_out8 (PIC2_DATA, PIC2_VECTOR_BASE);
 
-  io_out8(PIC1_DATA, PIC1_CASCADE_ID);
+  io_out8 (PIC1_DATA, PIC1_CASCADE_ID);
   io_out8 (PIC2_DATA, PIC2_CASCADE_ID);
 
-  io_out8(PIC1_DATA, PIC_ICW4_8086);
+  io_out8 (PIC1_DATA, PIC_ICW4_8086);
   io_out8 (PIC2_DATA, PIC_ICW4_8086);
 
   /*
    * Keep the cascade line enabled.
    * All actual hardware IRQ lines remain masked.
    */
-  io_out8(PIC1_DATA, PIC1_MASK_DEFAULT);
+  io_out8 (PIC1_DATA, PIC1_MASK_DEFAULT);
   io_out8 (PIC2_DATA, PIC2_MASK_DEFAULT);
-  
 }
-
diff --git a/mubios/drivers/pit.c b/mubios/drivers/pit.c
index 4213940..69b3390 100644
--- a/mubios/drivers/pit.c
+++ b/mubios/drivers/pit.c
@@ -23,17 +23,18 @@
 #include "io.h"
 
 #define PIT_COUNTER0 0x0040u
-#define PIT_COMMAND  0x0043u
+#define PIT_COMMAND 0x0043u
 
 #define PIT_SELECT_CHANNEL0 0x00u
-#define PIT_ACCESS_WORD     0x30u
-#define PIT_MODE_2          0x04u
+#define PIT_ACCESS_WORD 0x30u
+#define PIT_MODE_2 0x04u
 #define PIT_BINARY 0x00u
 
 #define PIT_COMMAND_CHANNEL0_MODE2                                            \
   (PIT_SELECT_CHANNEL0 | PIT_ACCESS_WORD | PIT_MODE_2 | PIT_BINARY)
 
-void pit_init(void)
+void
+pit_init (void)
 {
   io_out8 (PIT_COMMAND, PIT_COMMAND_CHANNEL0_MODE2);
 
@@ -41,5 +42,5 @@ void pit_init(void)
    * A divisor of zero represents 65536.
    */
   io_out8 (PIT_COUNTER0, 0x00u);
-  io_out8 (PIT_COUNTER0, 0x00u);  
+  io_out8 (PIT_COUNTER0, 0x00u);
 }
diff --git a/mubios/include/bios.h b/mubios/include/bios.h
index e524682..eee22e8 100644
--- a/mubios/include/bios.h
+++ b/mubios/include/bios.h
@@ -46,6 +46,7 @@ void serial_write (const char *text);
 
 void pic_init (void);
 void pit_init (void);
+void ioapic_init (void);
 
 void ivt_init (void);