Interrupt Handling and Context Switching

- isr.c - Modified interrupt handler logic.
- sched.c - Updated task switching for initial boot.
- paging.c - Expanded kernel memory mapping.
- interrupts.h - Corrected stack frame definition.
- isr.s - Cleaned up interrupt return.

Author: PythonPlumber

include/interrupts.h

@@ -4,7 +4,7 @@
 #include "types.h"
 
 typedef struct {
-    uint32_t ds;
+    uint32_t gs, fs, es, ds;
     uint32_t edi, esi, ebp, esp, ebx, edx, ecx, eax;
     uint32_t int_no, err_code;
     uint32_t eip, cs, eflags, useresp, ss;

src/cpu/isr.c

@@ -63,15 +63,6 @@ static void vga_write_hex32(uint32_t value, uint8_t color) {
     }
 }
 
-static void vga_write_hex64(uint64_t value, uint8_t color) {
-    static const char hex[] = "0123456789ABCDEF";
-    vga_write_string("0x", color);
-    for (int i = 15; i >= 0; --i) {
-        uint8_t nibble = (uint8_t)((value >> (i * 4)) & 0xF);
-        vga_put_char((uint8_t)hex[nibble], color);
-    }
-}
-
 static void vga_write_label_hex(const char* label, uint32_t value, uint8_t color) {
     vga_write_string(label, color);
     vga_write_hex32(value, color);
@@ -202,11 +193,14 @@ static registers_t* irq0_handler(registers_t* regs) {
     if (!previous || !next || next == previous) {
         return regs;
     }
+
+    previous->esp = (uint32_t)regs;
+
     if (next->page_directory) {
         load_cr3(next->page_directory);
     }
-    context_switch(previous, next, regs);
-    return regs;
+    
+    return (registers_t*)next->esp;
 }
 
 void register_interrupt_handler(uint8_t n, isr_t handler) {
@@ -231,10 +225,11 @@ registers_t* isr_handler(registers_t* regs) {
 }
 
 registers_t* irq_handler(registers_t* regs) {
-    if (interrupt_handlers[regs->int_no]) {
-        regs = interrupt_handlers[regs->int_no](regs);
+    uint32_t int_no = regs->int_no;
+    if (interrupt_handlers[int_no]) {
+        regs = interrupt_handlers[int_no](regs);
     }
-    if (regs->int_no >= 40) {
+    if (int_no >= 40) {
         outb(0xA0, 0x20);
     }
     outb(0x20, 0x20);

src/cpu/isr.s

@@ -111,7 +111,6 @@ isr_common_stub:
 
     popa
     add esp, 8
-    sti
     iret
 
 irq_common_stub:
@@ -145,5 +144,4 @@ irq_common_stub:
 
     popa
     add esp, 8
-    sti
     iret

src/kernel.c

@@ -388,8 +388,8 @@ void kernel_main(unsigned int multiboot_magic, unsigned int multiboot_info_addr)
         }
     }
 
-    paging_init();
     acpi_scan();
+    paging_init();
     apex_intc_init();
     msgi_init();
     smp_rally_init();

src/kernel/sched.c

@@ -305,16 +305,8 @@ static process_t* process_create_ex(void (*entry)(void), uint32_t* page_director
     list_append(proc);
 
     if (start_immediately) {
-        process_t* current = scheduler_current();
-        if (!current) {
-            uint32_t cpu = get_cpu_id();
-            current_process[cpu] = proc;
-            proc->current_cpu = cpu;
-            proc->state = PROCESS_RUNNING;
-        } else {
-            proc->state = PROCESS_READY;
-            enqueue_task(proc);
-        }
+        proc->state = PROCESS_READY;
+        enqueue_task(proc);
     }
 
     spin_unlock(&sched_lock);
@@ -646,7 +638,23 @@ process_t* switch_task(registers_t* saved_stack, process_t** previous) {
     scheduler_wake_sleepers(now);
     scheduler_account_tick();
 
-    if (!current || !process_list) {
+    if (!current) {
+        process_t* best = scheduler_pick_best_ready();
+        if (best) {
+            dequeue_task(best);
+            current_process[cpu] = best;
+            best->state = PROCESS_RUNNING;
+            best->time_remaining = best->time_slice;
+            if (previous) *previous = 0;
+            spin_unlock(&sched_lock);
+            return best;
+        }
+        if (previous) *previous = 0;
+        spin_unlock(&sched_lock);
+        return 0;
+    }
+
+    if (!process_list) {
         if (previous) *previous = current;
         spin_unlock(&sched_lock);
         return current;

src/mem/paging.c

@@ -1,5 +1,6 @@
 #include "paging.h"
 #include "heap.h"
+#include "kernel.h"
 #include "pmm.h"
 #include "types.h"
 #include "util.h"
@@ -112,11 +113,35 @@ void paging_init(void) {
         page_directory[i] = PAGE_RW;
     }
 
-    uint32_t* first_table = alloc_table();
-    for (uint32_t i = 0; i < 1024; ++i) {
-        first_table[i] = (i * 0x1000) | PAGE_PRESENT | PAGE_RW;
+    for (uint32_t t = 0; t < 4; ++t) {
+        uint32_t* table = alloc_table();
+        for (uint32_t i = 0; i < 1024; ++i) {
+            table[i] = (t * 0x400000 + i * 0x1000) | PAGE_PRESENT | PAGE_RW;
+        }
+        page_directory[t] = ((uint32_t)table) | PAGE_PRESENT | PAGE_RW;
+    }
+
+    // Identity map LAPIC and IOAPIC regions (0xFE000000 - 0xFFFFFFFF)
+    // We use 4MB pages for simplicity since PSE is enabled
+    map_page_4mb(0xFEC00000, 0xFEC00000, PAGE_PRESENT | PAGE_RW);
+    map_page_4mb(0xFF000000, 0xFF000000, PAGE_PRESENT | PAGE_RW);
+
+    // Identity map ACPI tables
+    uint32_t rsdt = acpi_rsdt_addr();
+    if (rsdt) {
+        for (uint32_t i = 0; i < 4; i++) {
+            map_page(rsdt + i * 4096, rsdt + i * 4096, PAGE_PRESENT | PAGE_RW);
+        }
+        uint32_t count = acpi_rsdt_entries();
+        for (uint32_t i = 0; i < count; i++) {
+            uint32_t entry = acpi_rsdt_entry(i);
+            if (entry) {
+                for (uint32_t j = 0; j < 4; j++) {
+                    map_page(entry + j * 4096, entry + j * 4096, PAGE_PRESENT | PAGE_RW);
+                }
+            }
+        }
     }
-    page_directory[0] = ((uint32_t)first_table) | PAGE_PRESENT | PAGE_RW;
 
     load_cr3(page_directory);
     enable_pse();

src/video/framebuffer.c

@@ -1,4 +1,5 @@
 #include "framebuffer.h"
+#include "paging.h"
 #include "vga.h"
 #include "font.h"
 #include "multiboot.h"
@@ -157,6 +158,12 @@ void fb_init(void* multiboot_info) {
             framebuffer.pitch = mode->pitch;
             framebuffer.bpp = mode->bpp;
             framebuffer.type = FB_TYPE_LINEAR;
+
+            // Map the framebuffer memory
+            uint32_t fb_size = framebuffer.height * framebuffer.pitch;
+            for (uint32_t i = 0; i < fb_size; i += 4 * 1024 * 1024) {
+                map_page_4mb((uint32_t)framebuffer.address + i, (uint32_t)framebuffer.address + i, 0x03); // Present | RW
+            }
         }
     }
 }