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

1 files changed, 134 insertions, 0 deletions

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;
+                //         }
+                //     }
+                // }
+            }
+        }
+    }
+    
+}
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