feat:Cooperative Multitasking

6 files changed, 232 insertions, 52 deletions

diff --git a/src/kernel/main.cc b/src/kernel/main.cc
index 2fa10a2..5dfba9b 100644
--- a/src/kernel/main.cc
+++ b/src/kernel/main.cc
@@ -2,20 +2,37 @@
 #include "kernel/pmm.h"
 #include "kernel/mm.h"
 #include "kernel/trap.h"
+#include "kernel/proc.h"
+#include "kernel/timer.h"
 
-// void print_hex(uint64_t val)
-// {
-//     char buf[17];
-//     buf[16] = 0;
-//     const char *digits = "0123456789ABCDEF";
-//     for (int i = 15; i >= 0; i--)
-//     {
-//         buf[i] = digits[val & 0xf];
-//         val >>= 4;
-//     }
-//     Drivers::uart_puts("0x");
-//     Drivers::uart_puts(buf);
-// }
+void delay()
+{
+    for(volatile int i = 0; i < 1000000; i++)
+    {
+
+    }
+}
+
+void task_a()
+{
+    while(1)
+    {
+        Drivers::uart_putc('A');
+        delay();
+        ProcManager::yield();
+    }
+}
+
+void task_b()
+{
+    while (1)
+    {
+        Drivers::uart_putc('B');
+        delay();
+        ProcManager::yield();
+    }
+    
+}
 
 extern "C" void kernel_main()
 {
@@ -24,39 +41,10 @@ extern "C" void kernel_main()
     Drivers::uart_puts("\n[Modern DOS Kernel] Booted in S-Mode.\n");
     Drivers::uart_puts("2025 Richard Qin\n");
     Drivers::uart_puts("\n");
+    Drivers::uart_puts("\n[Boot] Kernel started.\n");
 
-    Drivers::uart_puts("[Kernel] Initializing PMM...\n");
     PMM::init();
-    Drivers::uart_puts("[Kernel] PMM initialized.\n");
-
-    Drivers::uart_puts("[Kernel] Testing alloc_page...\n");
-    void *p1 = PMM::alloc_page();
-    void *p2 = PMM::alloc_page();
-
-    Drivers::uart_puts("Allocated Page 1: ");
-    Drivers::print_hex((uint64_t)p1);
-    Drivers::uart_puts("\n");
-
-    Drivers::uart_puts("Allocated Page 2: ");
-    Drivers::print_hex((uint64_t)p2);
-    Drivers::uart_puts("\n");
-
-    Drivers::uart_puts("[Kernel] Freeing Page 1...\n");
-    PMM::free_page(p1);
-
-    void *p3 = PMM::alloc_page();
-    Drivers::uart_puts("Allocated Page 3: ");
-    Drivers::print_hex((uint64_t)p3);
-    Drivers::uart_puts("\n");
-
-    if (p3 == p1)
-    {
-        Drivers::uart_puts("[Test Passed] Reuse freed memory successfully.\n");
-    }
-    else
-    {
-        Drivers::uart_puts("[Test Failed] Memory leak or logic error.\n");
-    }
+    Drivers::uart_puts("[Boot] PMM initialized.\n");
 
     VM::kvminit();
     Drivers::uart_puts("[Boot] Kernel page table created.\n");
@@ -67,15 +55,26 @@ extern "C" void kernel_main()
     Trap::init();
     Drivers::uart_puts("[Boot] Trap Handler Installed.\n");
 
-    Drivers::uart_puts("\n[Test] Triggering Page Fault by reading 0x0...\n");
-    volatile int *p = (int *)0x0;
-    int crash = *p;
-    (void)crash;
+    Timer::init();
+    Drivers::uart_puts("[Boot] Timer Interrupt Enabled.\n");
+
+    // Drivers::uart_puts("\n[Test] Triggering Page Fault by reading 0x0...\n");
+    // volatile int *p = (int *)0x0;
+    // int crash = *p;
+    // (void)crash;
+
+    // Drivers::uart_puts("[Test Failed] Shuold not reach here.\n");
+
+    // Drivers::uart_puts("\n[Test] Triggering Store Fault on Text Segment...\n");
+    // *(int*)0x80000000 = 1234;
+
+    ProcManager::init();
+    Drivers::uart_puts("[Boot] Process Manager initialized.\n");
 
-    Drivers::uart_puts("[Test Failed] Shuold not reach here.\n");
+    ProcManager::create_kernel_thread(task_a, "Task A");
+    ProcManager::create_kernel_thread(task_b, "Task B");
 
-    Drivers::uart_puts("\n[Test] Triggering Store Fault on Text Segment...\n");
-    *(int*)0x80000000 = 1234;
+    ProcManager::scheduler();
 
     while (1)
     {
diff --git a/src/kernel/mm/vm.cc b/src/kernel/mm/vm.cc
index 3c14d40..8696fdb 100644
--- a/src/kernel/mm/vm.cc
+++ b/src/kernel/mm/vm.cc
@@ -78,6 +78,8 @@ namespace VM
 
         mappages(kernel_pagetable, 0x10000000, 0x10000, 0x10000000, PTE_R | PTE_W);
 
+        mappages(kernel_pagetable, 0x2000000, 0x10000, 0x2000000, PTE_R | PTE_W);
+
         mappages(kernel_pagetable, (uint64)text_start, (uint64)text_end - (uint64)text_start,
                  (uint64)text_start, PTE_R | PTE_X);
 
diff --git a/src/kernel/proc/proc.cc b/src/kernel/proc/proc.cc
new file mode 100644
index 0000000..469b7eb
--- /dev/null
+++ b/src/kernel/proc/proc.cc
@@ -0,0 +1,113 @@
+#include "kernel/proc.h"
+#include "kernel/pmm.h"
+#include "drivers/uart.h"
+
+#define NPROC 10
+
+void str_copy(char *dst, const char *src)
+{
+    while (*src)
+        *dst++ = *src++;
+    *dst = 0;
+}
+
+extern "C" void swtch(struct Context *old_ctx, struct Context *new_ctx);
+
+struct Proc procs[NPROC];
+struct Context main_context;
+
+namespace ProcManager
+{
+    void init()
+    {
+        for (int i = 0; i < NPROC; i++)
+        {
+            procs[i].state = UNUSED;
+        }
+    }
+
+    void create_kernel_thread(void (*func)(), const char *name)
+    {
+        struct Proc *p = nullptr;
+        for(int i = 0; i < NPROC; i++)
+        {
+            if(procs[i].state == UNUSED)
+            {
+                p = &procs[i];
+                p->pid = i + 1;
+                break;
+            }
+        }
+
+        if (!p)
+        {
+            Drivers::uart_puts("Error: No free process slots!\n");
+            return;
+        }
+
+        p->kstack = PMM::alloc_page();
+        if (!p->kstack)
+        {
+            Drivers::uart_puts("Error: Alloc kstack failed!\n");
+            return;
+        }
+
+        p->context.ra = (uint64)func;
+
+        p->context.sp = (uint64)p->kstack + 4096;
+
+        p->state = RUNNABLE;
+        str_copy(p->name, name);
+
+        Drivers::uart_puts("[Proc] Created thread: ");
+        Drivers::uart_puts(name);
+        Drivers::uart_puts("\n");
+    }
+
+    void yield()
+    {
+        struct Proc *p = nullptr;
+        for(int i = 0; i < NPROC; i++)
+        {
+            if (procs[i].state == RUNNING)
+            {
+                p = &procs[i];
+                break;
+            }
+        }
+        if(p)
+        {
+            p->state = RUNNABLE;
+            swtch(&p->context, &main_context);
+        }
+    }
+
+    void scheduler()
+    {
+        struct Proc *p = nullptr;
+        Drivers::uart_puts("[Proc] Scheduler started.\n");
+
+        for (;;)
+        {
+            // int nothing_to_run = 1;
+
+            intr_off();
+
+            for (p = procs; p < &procs[NPROC]; p++)
+            {
+                if (p->state == RUNNABLE)
+                {
+                    // nothing_to_run = 0;
+
+                    p->state = RUNNING;
+
+                    intr_on();
+
+                    swtch(&main_context, &p->context);
+
+                    intr_off();
+                }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/kernel/proc/swtch.S b/src/kernel/proc/swtch.S
new file mode 100644
index 0000000..f59de20
--- /dev/null
+++ b/src/kernel/proc/swtch.S
@@ -0,0 +1,34 @@
+.global swtch
+
+swtch:
+    sd ra, 0(a0)
+    sd sp, 8(a0)
+    sd s0, 16(a0)
+    sd s1, 24(a0)
+    sd s2, 32(a0)
+    sd s3, 40(a0)
+    sd s4, 48(a0)
+    sd s5, 56(a0)
+    sd s6, 64(a0)
+    sd s7, 72(a0)
+    sd s8, 80(a0)
+    sd s9, 88(a0)
+    sd s10, 96(a0)
+    sd s11, 104(a0)
+
+    ld ra, 0(a1)
+    ld sp, 8(a1)
+    ld s0, 16(a1)
+    ld s1, 24(a1)
+    ld s2, 32(a1)
+    ld s3, 40(a1)
+    ld s4, 48(a1)
+    ld s5, 56(a1)
+    ld s6, 64(a1)
+    ld s7, 72(a1)
+    ld s8, 80(a1)
+    ld s9, 88(a1)
+    ld s10, 96(a1)
+    ld s11, 104(a1)
+
+    ret
diff --git a/src/kernel/timer.cc b/src/kernel/timer.cc
new file mode 100644
index 0000000..8cb3b0f
--- /dev/null
+++ b/src/kernel/timer.cc
@@ -0,0 +1,28 @@
+#include "common/types.h"
+#include "kernel/timer.h"
+
+#define CLINT_BASE 0x2000000L
+#define CLINT_MTIMECMP(hartid) (CLINT_BASE + 0x4000 + 8 * (hartid))
+#define CLINT_MTIME (CLINT_BASE + 0xBFF8)
+
+#define INTERVAL 1000000
+
+namespace Timer{
+    uint64 get_time(){
+        return *(volatile uint64*)CLINT_MTIME;
+    }
+
+    void set_next_trigger(){
+        uint64 mtime = get_time();
+
+        *(volatile uint64 *)CLINT_MTIMECMP(0) = mtime + INTERVAL;
+    }
+
+    void init(){
+        set_next_trigger();
+        uint64 sie;
+        asm volatile("csrr %0, sie" : "=r"(sie));
+        sie |= (1L << 5);
+        asm volatile("csrw sie, %0" : : "r"(sie));
+    }
+}
\ No newline at end of file
diff --git a/src/kernel/trap/handler.cc b/src/kernel/trap/handler.cc
index 9cc19d1..ecb6652 100644
--- a/src/kernel/trap/handler.cc
+++ b/src/kernel/trap/handler.cc
@@ -1,6 +1,9 @@
 #include "kernel/trap.h"
 #include "common/types.h"
 #include "drivers/uart.h"
+#include "kernel/proc.h"
+#include "kernel/timer.h"
+
 
 void panic(const char *s)
 {
@@ -48,7 +51,8 @@ namespace Trap
 
             case 5:
                 Drivers::uart_puts("[IRQ] Timer Interrupt\n");
-
+                Timer::set_next_trigger();
+                ProcManager::yield();
                 break;
             
             case 9: