Process multiboot data

src/kernel/boot/boot.S

@@ -16,6 +16,9 @@ _start:
 
     cli
 
+    mov edi, eax
+    mov esi, ebx
+
     // Temporary stack for booting
     mov esp, offset V2P(BootStack)
 

src/kernel/boot/kmain.c

@@ -1,33 +1,39 @@
+#include <stdint.h>
 #include <memory.h>
 #include <vga.h>
 #include <debug.h>
+#include <multiboot.h>
 
-void clear_screen()
-{
-    unsigned char *vidmem = P2V(0xB8000);
-    for(int i=0; i < 80*24*2; i++)
-        *vidmem++ = 0;
-}
+struct kernel_boot_data_st kernel_boot_data;
 
-void print_string(char *str)
-{
-    unsigned char *vidmem = P2V(0xB8000);
-    while(*str)
-    {
-        *vidmem++ = *str++;
-        *vidmem++ = 0x7;
-    }
-}
-
-void kmain()
+void kmain(uint64_t multiboot_magic, void *multiboot_data)
 {
     vga_init();
+
+    debug("Started kernel\n");
+
+    debug("Multiboot magic: %x", multiboot_magic);
+    multiboot_init(multiboot_magic, P2V(multiboot_data));
+
+    debug_info("Multiboot v %d kernel loaded.\n", kernel_boot_data.multiboot_version);
+    debug_info("Bootloader: %s\n", kernel_boot_data.bootloader);
+
+    debug_info("Memory areas:\n");
+    size_t index = 0;
+    uintptr_t start, end;
+    uint32_t type;
+    while(!multiboot_get_memory_ara(index, &start, &end, &type))
+    {
+        debug_info("%d %x-%x\n", type, start, end);
+        index++;
+    }
+
     debug("Hello, world!");
     int value = 123;
     debug_info("dec: %d hex: %x, binary: %b", value, value, value);
 
     PANIC("End of kernel function!");
     
-    debug_info("Broke out of panic")
+    debug_info("Broke out of panic");
     for(;;);
 }

src/kernel/boot/multiboot.c

@@ -0,0 +1,98 @@
+#include <stdint.h>
+#include <multiboot.h>
+#include <memory.h>
+#include <debug.h>
+
+// https://www.gnu.org/software/grub/manual/multiboot2/multiboot.html
+
+struct taglist {
+    uint32_t total_size;
+    uint32_t reserved;
+}__attribute__((packed));
+
+struct tag {
+    uint32_t type;
+    uint32_t size;
+    uint8_t data[];
+}__attribute__((packed));
+
+struct mmap_entry {
+    uint64_t base;
+    uint64_t len;
+    uint32_t type;
+    uint32_t reserved;
+}__attribute__((packed));
+
+struct mmap {
+    uint32_t entry_size;
+    uint32_t entry_version;
+    struct mmap_entry entries[];
+}__attribute__((packed));
+
+struct fbinfo {
+    uint64_t framebuffer_addr;
+    uint32_t framebuffer_pitch;
+    uint32_t framebuffer_width;
+    uint32_t framebuffer_height;
+    uint8_t framebuffer_bpp;
+    uint8_t framebuffer_type;
+    uint8_t reserved;
+    uint8_t data[];
+}__attribute__((packed));
+
+int parse_multiboot2(struct taglist *tags)
+{
+    struct tag *tag = incptr(tags, sizeof(struct taglist));
+    struct mmap *mmap;
+    while(tag->type)
+    {
+        debug("Tag type: %d\n", tag->type);
+        switch(tag->type)
+        {
+            case MBOOT2_TAG_BOOTLOADER:
+                kernel_boot_data.bootloader = (char *)tag->data;
+                break;
+            case MBOOT2_TAG_CMDLINE:
+                kernel_boot_data.commandline = (char *)tag->data;
+                break;
+            case MBOOT2_TAG_MMAP:
+                mmap = kernel_boot_data.mmap = (void *)tag->data;
+                kernel_boot_data.mmap_len = (tag->size - 8)/mmap->entry_size;
+                kernel_boot_data.mmap_size = (tag->size - 8);
+                break;
+            case 8:
+                break;
+        }
+        
+        int padded_size = tag->size + ((tag->size % 8)?(8-(tag->size%8)):0);
+        tag = incptr(tag, padded_size);
+    }
+    return 0;
+}
+
+int multiboot_init(uint64_t magic, void *mboot_info)
+{
+    if(magic == MBOOT2_REPLY)
+    {
+        kernel_boot_data.multiboot_version = 2;
+        parse_multiboot2(mboot_info);
+    }
+    else
+        return 1;
+
+    return 0;
+}
+
+int multiboot_get_memory_ara(size_t index, uintptr_t *start, uintptr_t *end, uint32_t *type)
+{
+    if(index >= kernel_boot_data.mmap_len) return 1;
+
+    struct mmap *mmap = kernel_boot_data.mmap;
+    struct mmap_entry *entry = mmap->entries;
+    entry = incptr(entry, index*mmap->entry_size);
+
+    *start = entry->base;
+    *end = entry->base + entry->len;
+    *type = entry->type;
+    return 0;
+}

src/kernel/include/memory.h

@@ -9,6 +9,8 @@
 #include <stdint.h>
 #define V2P(a) ((uintptr_t)(a) &~KERNEL_OFFSET)
 #define P2V(a) ((void *)((uintptr_t)(a) | KERNEL_OFFSET))
+
+#define incptr(p, n) ((void *)(((uintptr_t)(p)) + (n)))
 #endif
 
 

src/kernel/include/multiboot.h

@@ -5,3 +5,25 @@
 #define MBOOT2_ARCH 0
 #define MBOOT2_LENGTH (Multiboot2HeaderEnd - Multiboot2Header)
 #define MBOOT2_CHECKSUM -(MBOOT2_MAGIC + MBOOT2_ARCH + MBOOT2_LENGTH)
+
+#define MBOOT2_TAG_CMDLINE 1
+#define MBOOT2_TAG_BOOTLOADER 2
+#define MBOOT2_TAG_MMAP 6
+#define MBOOT2_TAG_FBINFO 8
+
+#ifndef __ASSEMBLER__
+#include <stddef.h>
+struct kernel_boot_data_st{
+    int multiboot_version;
+    char *bootloader;
+    char *commandline;
+    size_t mmap_size;
+    unsigned int mmap_len;
+    void *mmap;
+};
+
+extern struct kernel_boot_data_st kernel_boot_data;
+
+int multiboot_init(uint64_t magic, void *mboot_info);
+int multiboot_get_memory_ara(size_t index, uintptr_t *start, uintptr_t *end, uint32_t *type);
+#endif