feat: add preemptive scheduling, SBI timer support and FDT parser.

7 files changed, 220 insertions, 34 deletions

diff --git a/src/kernel/config.cc b/src/kernel/config.cc
new file mode 100644
index 0000000..47f7a3e
--- /dev/null
+++ b/src/kernel/config.cc
@@ -0,0 +1,9 @@
+#include "common/types.h"
+
+uint64 g_uart_base = 0;
+// uint64 g_clint_base = 0;
+uint64 g_plic_base = 0;
+uint64 g_ram_start = 0;
+uint64 g_ram_size = 0;
+
+extern "C" uint64 g_dtb_addr;
\ No newline at end of file
diff --git a/src/kernel/fdt.cc b/src/kernel/fdt.cc
new file mode 100644
index 0000000..93922a7
--- /dev/null
+++ b/src/kernel/fdt.cc
@@ -0,0 +1,134 @@
+#include "common/types.h"
+#include "drivers/uart.h"
+#include "kernel/config.h"
+
+inline uint32_t bswap(uint32_t x)
+{
+    return ((x & 0xFF) << 24) | ((x & 0xFF00) << 8) |
+           ((x & 0xFF0000) >> 8) | ((x >> 24) & 0xFF);
+}
+
+struct fdt_header
+{
+    uint32 magic;
+    uint32 totalsize;
+    uint32 off_dt_struct;
+    uint32 off_dt_strings;
+    uint32 off_mem_rsvmap;
+    uint32 version;
+    uint32 last_comp_version;
+    uint32 boot_cpuid_phys;
+    uint32 size_dt_strings;
+    uint32 size_dt_struct;
+};
+
+#define FDT_MAGIC 0xd00dfeed
+#define FDT_BEGIN_NODE 1
+#define FDT_END_NODE 2
+#define FDT_PROP 3
+#define FDT_NOP 4
+#define FDT_END 9
+
+int strcmp(const char* s1, const char* s2)
+{
+    while (*s1 && (*s1 == *s2))
+    {
+        s1++;
+        s2++;
+    }
+    return *(const unsigned char*)s1 - *(const unsigned char*)s2;
+}
+
+int memcmp(const void *ptr1, const void *ptr2, uint32 num)
+{
+    const unsigned char *p1 = (const unsigned char *)ptr1;
+    const unsigned char *p2 = (const unsigned char *)ptr2;
+    for (uint32 i = 0; i < num; i++)
+    {
+        if (p1[i] != p2[i])
+            return p1[i] - p2[i];
+    }
+    return 0;
+}
+
+void fdt_init(uint64 dtb)
+{
+    if (dtb == 0) return;
+
+    struct fdt_header* header = (struct fdt_header*)dtb;
+    if (bswap(header->magic) != FDT_MAGIC)
+        return;
+    
+    uint8* struct_ptr = (uint8*)(dtb + bswap(header->off_dt_struct));
+    char* strings_ptr = (char *)(dtb + bswap(header->off_dt_strings));
+
+    uint64 current_reg_addr = 0;
+
+    while (1)
+    {
+        uint32 token = bswap(*(uint32*)struct_ptr);
+        struct_ptr += 4;
+
+        if(token == FDT_END)break;
+        if(token == FDT_NOP)continue;
+
+        if(token == FDT_BEGIN_NODE)
+        {
+            while (*struct_ptr != 0)struct_ptr++;
+            struct_ptr++;
+            struct_ptr = (uint8*)(((uint64)struct_ptr + 3) & ~3);
+        }
+        else if(token == FDT_END_NODE)
+        {
+            
+        }
+        else if (token == FDT_PROP)
+        {
+            uint32 len = bswap(*(uint32*)struct_ptr);
+            struct_ptr += 4;
+            uint32 nameoff = bswap(*(uint32*)struct_ptr);
+            struct_ptr += 4;
+
+            char* name = strings_ptr + nameoff;
+            uint8* data = struct_ptr;
+
+            struct_ptr += len;
+            struct_ptr = (uint8*)(((uint64)struct_ptr + 3) & ~3);
+
+            if(strcmp(name, "reg") == 0 && len >= 8)
+            {
+                uint32 hi = bswap(*(uint32*)data);
+                uint32 lo = bswap(*(uint32*)(data + 4));
+                current_reg_addr = ((uint64)hi << 32) | lo;
+            }
+
+            if(strcmp(name, "compatible") == 0)
+            {
+                if (g_uart_base == 0)
+                {
+                    for(uint32 i = 0; i < len; i++)
+                    {
+                        if (data[i] == 'n' && data[i + 1] == 's' && data[i + 2] == '1')
+                        {
+                            g_uart_base = current_reg_addr;
+                            break;
+                        }
+                    }
+                }
+
+                // if (g_clint_base == 0)
+                // {
+                //     for (uint32 i = 0; i < len; i++)
+                //     {
+                //         if (data[i] == 'c' && data[i + 1] == 'l' && data[i + 2] == 'i' && data[i + 3] == 'n')
+                //         {
+                //             g_clint_base = current_reg_addr;
+                //             break;
+                //         }
+                //     }
+                // }
+            }
+        }
+    }
+    
+}
\ No newline at end of file
diff --git a/src/kernel/main.cc b/src/kernel/main.cc
index 5dfba9b..68c0974 100644
--- a/src/kernel/main.cc
+++ b/src/kernel/main.cc
@@ -4,6 +4,9 @@
 #include "kernel/trap.h"
 #include "kernel/proc.h"
 #include "kernel/timer.h"
+#include "kernel/config.h"
+
+void fdt_init(uint64 dtb);
 
 void delay()
 {
@@ -19,7 +22,7 @@ void task_a()
     {
         Drivers::uart_putc('A');
         delay();
-        ProcManager::yield();
+        // ProcManager::yield();
     }
 }
 
@@ -29,7 +32,7 @@ void task_b()
     {
         Drivers::uart_putc('B');
         delay();
-        ProcManager::yield();
+        // ProcManager::yield();
     }
     
 }
@@ -37,6 +40,7 @@ void task_b()
 extern "C" void kernel_main()
 {
 
+    fdt_init(g_dtb_addr);
     Drivers::uart_init();
     Drivers::uart_puts("\n[Modern DOS Kernel] Booted in S-Mode.\n");
     Drivers::uart_puts("2025 Richard Qin\n");
@@ -58,26 +62,14 @@ extern "C" void kernel_main()
     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("[Boot] ProcManager Initialized.\n");
 
+    void task_a();
+    void task_b();
     ProcManager::create_kernel_thread(task_a, "Task A");
     ProcManager::create_kernel_thread(task_b, "Task B");
 
+    Drivers::uart_puts("[Kernel] Scheduler Starting...\n");
     ProcManager::scheduler();
-
-    while (1)
-    {
-
-    }
 }
\ No newline at end of file
diff --git a/src/kernel/mm/vm.cc b/src/kernel/mm/vm.cc
index 8696fdb..8a7068e 100644
--- a/src/kernel/mm/vm.cc
+++ b/src/kernel/mm/vm.cc
@@ -2,6 +2,7 @@
 #include "kernel/pmm.h"
 #include "drivers/uart.h"
 #include "common/types.h"
+#include "kernel/config.h"
 
 extern "C" char text_start[];
 extern "C" char text_end[];
@@ -76,9 +77,20 @@ namespace VM
     {
         kernel_pagetable = (pagetable_t)PMM::alloc_page();
 
-        mappages(kernel_pagetable, 0x10000000, 0x10000, 0x10000000, PTE_R | PTE_W);
+        if (g_uart_base != 0)
+        {
+            mappages(kernel_pagetable, g_uart_base, PGSIZE, g_uart_base, PTE_R | PTE_W);
+        }
+
+        // if (g_clint_base != 0)
+        // {
+        //     mappages(kernel_pagetable, g_clint_base, 0x10000, g_clint_base, PTE_R | PTE_W);
+        // }
 
-        mappages(kernel_pagetable, 0x2000000, 0x10000, 0x2000000, PTE_R | PTE_W);
+        if (g_plic_base != 0)
+        {
+            mappages(kernel_pagetable, g_plic_base, 0x400000, g_plic_base, 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/sbi.cc b/src/kernel/sbi.cc
new file mode 100644
index 0000000..442d219
--- /dev/null
+++ b/src/kernel/sbi.cc
@@ -0,0 +1,34 @@
+#include "common/types.h"
+
+namespace SBI
+{
+    struct sbiret
+    {
+        long error;
+        long value;
+    };
+
+    struct sbiret sbi_call(int ext, int fid, uint64 arg0, uint64 arg1, uint64 arg2)
+    {
+        struct sbiret ret;
+        register uint64 a0 asm("a0") = arg0;
+        register uint64 a1 asm("a1") = arg1;
+        register uint64 a2 asm("a2") = arg2;
+        register uint64 a6 asm("a6") = fid;
+        register uint64 a7 asm("a7") = ext;
+
+        asm volatile(
+            "ecall"
+            : "=r"(a0), "=r"(a1)
+            : "r"(a0), "r"(a1), "r"(a2), "r"(a6), "r"(a7)
+            : "memory");
+        ret.error = a0;
+        ret.value = a1;
+        return ret;
+    }
+
+    void set_timer(uint64 stime_value)
+    {
+        sbi_call(0x54494D45, 0, stime_value, 0, 0);
+    }
+}
\ No newline at end of file
diff --git a/src/kernel/timer.cc b/src/kernel/timer.cc
index 8cb3b0f..fb871d5 100644
--- a/src/kernel/timer.cc
+++ b/src/kernel/timer.cc
@@ -1,25 +1,31 @@
 #include "common/types.h"
-#include "kernel/timer.h"
+#include "kernel/config.h"
 
-#define CLINT_BASE 0x2000000L
-#define CLINT_MTIMECMP(hartid) (CLINT_BASE + 0x4000 + 8 * (hartid))
-#define CLINT_MTIME (CLINT_BASE + 0xBFF8)
+namespace SBI
+{
+    void set_timer(uint64 stime_value);
+}
 
 #define INTERVAL 1000000
 
-namespace Timer{
-    uint64 get_time(){
-        return *(volatile uint64*)CLINT_MTIME;
+namespace Timer
+{
+    uint64 get_time()
+    {
+        uint64 time;
+        asm volatile("rdtime %0" : "=r"(time));
+        return time;
     }
 
-    void set_next_trigger(){
-        uint64 mtime = get_time();
-
-        *(volatile uint64 *)CLINT_MTIMECMP(0) = mtime + INTERVAL;
+    void set_next_trigger()
+    {
+        SBI::set_timer(get_time() + INTERVAL);
     }
 
-    void init(){
+    void init()
+    {
         set_next_trigger();
+
         uint64 sie;
         asm volatile("csrr %0, sie" : "=r"(sie));
         sie |= (1L << 5);
diff --git a/src/kernel/trap/handler.cc b/src/kernel/trap/handler.cc
index ecb6652..df4f202 100644
--- a/src/kernel/trap/handler.cc
+++ b/src/kernel/trap/handler.cc
@@ -45,8 +45,7 @@ namespace Trap
             switch (cause_code)
             {
             case 1:
-                Drivers::uart_puts("[IRQ] Software Interrupt\n");
-                asm volatile("csrc sip, %0" : : "r"(1 << 1));
+                Drivers::uart_puts("[IRQ] Software Interrupt (Unexpected)\n");
                 break;
 
             case 5: