IDT: Initialize IDT with a very basic exception handler that does nothing

11 files changed, 230 insertions, 14 deletions

diff --git a/kernel/CMakeLists.txt b/kernel/CMakeLists.txt
index cd9b187..bc4d5bb 100644
--- a/kernel/CMakeLists.txt
+++ b/kernel/CMakeLists.txt
@@ -6,6 +6,9 @@ set(SRC
   
   boot/gdt/gdt.cc
   boot/gdt/gdt.s
+  boot/idt/exceptions.cc
+  boot/idt/idt.cc
+  boot/idt/isr.s
   boot/init/boot.s
 
   drivers/serial.cc
@@ -61,6 +64,7 @@ set(CXX_COMPILE_OPTIONS
   -Wno-write-strings
   -Wno-missing-field-initializers
   -Wno-c++11-long-long
+  -Wno-c99-extensions
 )
 
 target_compile_options(kernel PRIVATE 
diff --git a/kernel/boot/gdt/gdt.cc b/kernel/boot/gdt/gdt.cc
index 360d9b8..708d399 100644
--- a/kernel/boot/gdt/gdt.cc
+++ b/kernel/boot/gdt/gdt.cc
@@ -17,7 +17,6 @@
  */
 
 #include <boot/gdt.h>
-#include <kernel/io.h>
 
 namespace GDT
 {
diff --git a/kernel/boot/idt/exceptions.cc b/kernel/boot/idt/exceptions.cc
new file mode 100644
index 0000000..79ffd68
--- /dev/null
+++ b/kernel/boot/idt/exceptions.cc
@@ -0,0 +1,36 @@
+/*
+ * bubbl
+ * Copyright (C) 2025  Raghuram Subramani <raghus2247@gmail.com>
+ *
+ * This program 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.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <boot/idt.h>
+#include <common.h>
+#include <kernel/halt.h>
+#include <libk/stdio.h>
+#include <stdbool.h>
+
+namespace IDT
+{
+
+void
+exception_handler(void)
+{
+  ASSERT_NOT_REACHED();
+  while (true)
+    __asm__ volatile("cli; hlt");
+}
+
+}
diff --git a/kernel/boot/idt/idt.cc b/kernel/boot/idt/idt.cc
new file mode 100644
index 0000000..e640fd5
--- /dev/null
+++ b/kernel/boot/idt/idt.cc
@@ -0,0 +1,46 @@
+/*
+ * bubbl
+ * Copyright (C) 2025  Raghuram Subramani <raghus2247@gmail.com>
+ *
+ * This program 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.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <boot/idt.h>
+#include <kernel/io.h>
+
+namespace IDT
+{
+
+extern "C" void *isr_stub_table[];
+
+entry_t l_entries[256];
+descriptor_t descriptor = { sizeof(l_entries) - 1, l_entries };
+
+void
+load(void)
+{
+  for (uint16_t i = 0; i < 256; i++)
+    l_entries[i] = (entry_t) { 0 };
+
+  /* The first 32 entries are exceptions */
+  for (uint8_t i = 0; i < 32; i++) {
+    entry_t idt_entry = IDT_ENTRY((uint32_t) isr_stub_table[i], 0x8E);
+    l_entries[i] = idt_entry;
+  }
+
+  __asm__ volatile("lidt %0" ::"m"(descriptor));
+  __asm__ volatile("sti");
+}
+
+}
diff --git a/kernel/boot/idt/isr.s b/kernel/boot/idt/isr.s
new file mode 100644
index 0000000..925bb27
--- /dev/null
+++ b/kernel/boot/idt/isr.s
@@ -0,0 +1,72 @@
+;;
+;; bubbl
+;; Copyright (C) 2025  Raghuram Subramani <raghus2247@gmail.com>
+;;
+;; This program 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.
+;;
+;; This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+;;
+
+extern exception_handler;
+
+global isr_stub_table
+isr_stub_table:
+%assign i 0
+%rep 32
+dd ISR_%+i
+%assign i i+1
+%endrep
+
+%macro ISR_WITH_ERROR 1
+ISR_%+%1:
+  call exception_handler
+  iret
+%endmacro
+
+%macro ISR_NO_ERROR 1
+ISR_%+%1:
+  call exception_handler
+  iret
+%endmacro
+
+ISR_NO_ERROR 0
+ISR_NO_ERROR 1
+ISR_NO_ERROR 2
+ISR_NO_ERROR 3
+ISR_NO_ERROR 4
+ISR_NO_ERROR 5
+ISR_NO_ERROR 6
+ISR_NO_ERROR 7
+ISR_WITH_ERROR 8
+ISR_NO_ERROR 9
+ISR_WITH_ERROR 10
+ISR_WITH_ERROR 11
+ISR_WITH_ERROR 12
+ISR_WITH_ERROR 13
+ISR_WITH_ERROR 14
+ISR_NO_ERROR 15
+ISR_NO_ERROR 16
+ISR_WITH_ERROR 17
+ISR_NO_ERROR 18
+ISR_NO_ERROR 19
+ISR_NO_ERROR 20
+ISR_NO_ERROR 21
+ISR_NO_ERROR 22
+ISR_NO_ERROR 23
+ISR_NO_ERROR 24
+ISR_NO_ERROR 25
+ISR_NO_ERROR 26
+ISR_NO_ERROR 27
+ISR_NO_ERROR 28
+ISR_NO_ERROR 29
+ISR_WITH_ERROR 30
+ISR_NO_ERROR 31
diff --git a/kernel/include/boot/gdt.h b/kernel/include/boot/gdt.h
index ff87981..237628c 100644
--- a/kernel/include/boot/gdt.h
+++ b/kernel/include/boot/gdt.h
@@ -78,13 +78,12 @@
 
 #define GDT_ENTRY(base, limit, access_flags, flags)                           \
   {                                                                           \
-    (limit & 0xffff),          /* limit_low */                                \
-        (base & 0xffff),       /* base_low */                                 \
-        ((base >> 16) & 0xff), /* base_mid */                                 \
-        access_flags,          /* access_flags */                             \
-        FLAGS_LIMIT_HIGH(flags,                                               \
-                         ((limit >> 16) & 0xff)), /* flags_limit_high */      \
-        ((base >> 24) & 0xff)                     /* base_high */             \
+    (limit & 0xffff),                                /* limit_low */          \
+    (base & 0xffff),                                 /* base_low */           \
+    ((base >> 16) & 0xff),                           /* base_mid */           \
+    access_flags,                                    /* access_flags */       \
+    FLAGS_LIMIT_HIGH(flags, ((limit >> 16) & 0xff)), /* flags_limit_high */   \
+    ((base >> 24) & 0xff)                            /* base_high */          \
   }
 
 namespace GDT
@@ -105,6 +104,8 @@ typedef struct {
 } PACKED descriptor_t;
 
 extern "C" void _GDT_flush(descriptor_t *descriptor);
+
+void initialize(void);
 void load(void);
 
 }
diff --git a/kernel/include/boot/idt.h b/kernel/include/boot/idt.h
new file mode 100644
index 0000000..2eda86c
--- /dev/null
+++ b/kernel/include/boot/idt.h
@@ -0,0 +1,55 @@
+/*
+ * bubbl
+ * Copyright (C) 2024-2025  Raghuram Subramani <raghus2247@gmail.com>
+ *
+ * This program 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.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __boot_idt_h
+#define __boot_idt_h
+
+#include <common.h>
+#include <stdint.h>
+
+#define IDT_ENTRY(isr, attributes)                                            \
+  {                                                                           \
+    (isr & 0xffff), /* isr_low */                                             \
+    0,              /* segment_selector */                                    \
+    0,              /* reserved */                                            \
+    attributes,     /* attributes */                                          \
+    (isr >> 16)     /* isr_high */                                            \
+  }
+
+namespace IDT
+{
+
+typedef struct {
+  uint16_t isr_low;
+  uint16_t segment_selector;
+  uint8_t reserved;
+  uint8_t attributes;
+  uint16_t isr_high;
+} PACKED entry_t;
+
+typedef struct {
+  uint16_t limit; /* sizeof(IDT) - 1 */
+  entry_t *ptr;   /* Address of IDT */
+} PACKED descriptor_t;
+
+void load(void);
+extern "C" NORETURN void exception_handler(void);
+
+}
+
+#endif
diff --git a/kernel/include/common.h b/kernel/include/common.h
index 7c5270a..ecda7b2 100644
--- a/kernel/include/common.h
+++ b/kernel/include/common.h
@@ -21,6 +21,7 @@
 
 #define ALWAYS_INLINE __attribute__((always_inline)) inline
 #define PACKED __attribute__((packed))
+#define NORETURN __attribute__((noreturn))
 #define ALIGNED(x) __attribute__((aligned(x)))
 
 #define KiB 1024
diff --git a/kernel/kernel/kernel.cc b/kernel/kernel/kernel.cc
index a4670a9..34a693b 100644
--- a/kernel/kernel/kernel.cc
+++ b/kernel/kernel/kernel.cc
@@ -17,6 +17,7 @@
  */
 
 #include <boot/gdt.h>
+#include <boot/idt.h>
 #include <drivers/serial.h>
 #include <drivers/vga_text_buffer.h>
 #include <kernel/halt.h>
@@ -44,6 +45,7 @@ kernel_main(uint32_t magic, multiboot_info_t *multiboot_info)
   MemoryMap::load(multiboot_info);
   PhysicalMM::initialize();
   VirtualMM::initialize();
+  IDT::load();
 
   printk("\nKernel", "Started.");
 
diff --git a/kernel/kernel/spinlock.cc b/kernel/kernel/spinlock.cc
index 3a9031c..a57206d 100644
--- a/kernel/kernel/spinlock.cc
+++ b/kernel/kernel/spinlock.cc
@@ -31,5 +31,5 @@ void
 Spinlock::release(void)
 {
   __sync_bool_compare_and_swap(&m_lock, 1, 0);
-  /* TODO: Enable interrupts here */
+  // __asm__ volatile("sti");
 }
diff --git a/kernel/mm/virtual_mm/virtual_mm.cc b/kernel/mm/virtual_mm/virtual_mm.cc
index 3ba0735..e1bef9d 100644
--- a/kernel/mm/virtual_mm/virtual_mm.cc
+++ b/kernel/mm/virtual_mm/virtual_mm.cc
@@ -50,7 +50,7 @@ get_page_directory(void)
 ALWAYS_INLINE void
 load_page_directory(uint32_t *page_directory)
 {
-  __asm__("movl %0, %%cr3" ::"r"(page_directory));
+  __asm__ volatile("movl %0, %%cr3" ::"r"(page_directory));
 }
 
 bool
@@ -67,10 +67,10 @@ switch_page_directory(uint32_t *page_directory)
 ALWAYS_INLINE static void
 enable_paging(void)
 {
-  __asm__("movl %%cr0, %%eax;"
-          "orl $0x80000000, %%eax;"
-          "movl %%eax, %%cr0" ::
-              : "eax");
+  __asm__ volatile("movl %%cr0, %%eax;"
+                   "orl $0x80000000, %%eax;"
+                   "movl %%eax, %%cr0" ::
+                       : "eax");
 }
 
 void