parse elf header of initrd and map it to its entry in vmem

Makefile

@@ -35,7 +35,7 @@ kernel: $(BUILDDIR)/$(KIMG)
 
 $(BUILDDIR)/$(ISO): kernel
 	rm -f $(BUILDDIR)/$(ISO) boot/initrd
-	nasm -fbin user/userinit.asm -o boot/initrd
+	nasm -felf32 user/userinit.asm -o boot/initrd
 	cp $(BUILDDIR)/$(KIMG) boot/$(KIMG)
 	grub-mkrescue -o  $(BUILDDIR)/$(ISO) .
 iso: $(BUILDDIR)/$(ISO)

include/kernel/kernel.h

@@ -7,6 +7,14 @@
 #define cpu_relax asm volatile ("pause" ::)
 #define CHECK_FLAG(x, n) (x & (1<<n))
 
+typedef struct {
+    uint32_t eip;
+    uint32_t esp;
+    uint32_t cr3;
+} task_t;
+
+#define KERNEL_VMA 0xC0000000
+
 typedef struct {
    multi_mmap_t *multi_mmap;
    uint32_t multi_mmap_size;
@@ -37,6 +45,14 @@ struct gdt_entry {
 } __attribute__((packed));
 typedef struct gdt_entry gdt_t;
 
+#define PAGE_PRESENT (1<<0)
+#define PAGE_RW (1<<1)
+#define PAGE_USER (1<<2)
+
+#define PAGE_DIR_INDEX(x) (((x) >> 22) & 0x3FF)
+#define PAGE_TAB_INDEX(x) (((x) >> 12) & 0x3FF)
+#define PAGE_OFFSET(x) ((x) & 0xFFF)
+
 struct tss_entry {
     uint32_t prev_tss;    // The previous TSS - with hardware task switching this is used
     uint32_t esp0;        // The stack pointer to load when we change to kernel mode
@@ -68,5 +84,42 @@ struct tss_entry {
 } __attribute__((packed));
 typedef struct tss_entry tss_t;
 
+#define EI_NIDENT 16
+
+typedef uint16_t Elf32_Half;
+typedef uint32_t Elf32_Addr;
+typedef uint32_t Elf32_Off;
+typedef uint32_t Elf32_Word;
+typedef int32_t  Elf32_Sword;
+
+typedef struct {
+        uint8_t e_ident[EI_NIDENT];
+        Elf32_Half      e_type;
+        Elf32_Half      e_machine;
+        Elf32_Word      e_version;
+        Elf32_Addr      e_entry;
+        Elf32_Off       e_phoff;
+        Elf32_Off       e_shoff;
+        Elf32_Word      e_flags;
+        Elf32_Half      e_ehsize;
+        Elf32_Half      e_phentsize;
+        Elf32_Half      e_phnum;
+        Elf32_Half      e_shentsize;
+        Elf32_Half      e_shnum;
+        Elf32_Half      e_shstrndx;
+} elf_t;
+
+typedef struct {
+	Elf32_Word	sh_name;
+	Elf32_Word	sh_type;
+	Elf32_Word	sh_flags;
+	Elf32_Addr	sh_addr;
+	Elf32_Off	sh_offset;
+	Elf32_Word	sh_size;
+	Elf32_Word	sh_link;
+	Elf32_Word	sh_info;
+	Elf32_Word	sh_addralign;
+	Elf32_Word	sh_entsize;
+} section_t;
 
 #endif

kernel/init.asm

@@ -222,8 +222,10 @@ gdtp:
     dw gdt_end - gdt - 1
     dd gdt
 
+global boot_page_dir
 align 0x1000
 boot_page_dir: times 1024 dd 0
+global boot_page_tab
 align 0x1000
 boot_page_tab: times 1024 dd 0
 

kernel/kernel.c

@@ -17,6 +17,8 @@ extern void pit_isr(void);
 extern void jmp_user_mode(uint32_t esp, uint32_t eip);
 extern void flush_tss(uint32_t segment_selector);
 extern gdt_t gdt[6];
+extern uint32_t boot_page_dir[1024];
+extern uint32_t boot_page_tab[1024];
 
 void exception_handler(int_stack_frame_t r) {
     LOG("Exception 0x%X (0x%X) has occurred\nEAX: 0x%08X\nECX: 0x%08X\nEDX: 0x%08X\nEBX: 0x%08X\nESI: 0x%08X\nEDI: 0x%08X\nEBP: 0x%08X\nESP: 0x%08X\n",
@@ -31,13 +33,13 @@ void sleep(int delay) {
 	cpu_relax;
 }
 
-typedef struct {
+int strcmp(const char *str1, const char *str2) {
-    uint32_t eip;
+    while (*str1 && (*str1 == *str2)) {
-    uint32_t esp;
+        str1++;
-    uint32_t cr3;
+        str2++;
-} task_t;
+    }
-
+    return *(uint8_t *)str1 - *(uint8_t *)str2;
-#define KERNEL_VMA 0xC0000000
+}
 
 void kernel(multiboot_info_t *info) {
     if (!CHECK_FLAG(info->flags, 3)) goto halt;  // Modules
@@ -62,10 +64,10 @@ void kernel(multiboot_info_t *info) {
 
     asm volatile ("lidt %0" :: "m"(idtr));
     pic_remap(PIC_1_START, PIC_2_START);
-    asm volatile ("sti" ::);
+    //asm volatile ("sti" ::);
 
-    ctx.ticks = 0;
+    //ctx.ticks = 0;
-    pit_init();
+    //pit_init();
 
     uint32_t base = (uint32_t)&tss;
     uint32_t limit = base + sizeof(tss_t);
@@ -84,19 +86,34 @@ void kernel(multiboot_info_t *info) {
     tss.ss = tss.ds = tss.es = tss.fs = tss.gs = GDT_SEGMENT_SELECTOR(4, RING3);
     flush_tss(GDT_SEGMENT_SELECTOR(5, RING3));
 
-#define PAGE_PRESENT (1<<0)
+    multi_mod_t *init = (multi_mod_t *)(info->moduleaddress + KERNEL_VMA);
-#define PAGE_RW (1<<1)
+    elf_t *elf = (elf_t *)(init->mod_start+KERNEL_VMA);
-#define PAGE_USER (1<<2)
+    section_t *str = (section_t *)((uint32_t)elf + elf->e_shoff + elf->e_shstrndx*elf->e_shentsize);
+    section_t *text = 0;
+    for (int i = 0; i < elf->e_shnum; i++) {
+	section_t *sec = (section_t *)((uint32_t)elf + elf->e_shoff + i*elf->e_shentsize);
+	//LOG("Pingas: %d\n", elf->e_shstrndx);
+	const char *name = (char *)((uint32_t)elf + str->sh_offset + sec->sh_name);
+	if (!strcmp(name, ".text")) {
+	    text = sec;
+	}
+    }
 
-#define PAGE_DIR_INDEX(x) (((x) >> 22) & 0x3FF)
+    uint32_t elf_phys = (uint32_t)elf - KERNEL_VMA;
-#define PAGE_TAB_INDEX(x) (((x) >> 12) & 0x3FF)
+    LOG("0x%08X\n", elf_phys);
-#define PAGE_OFFSET(x) ((x) & 0xFFF)
+    uint32_t *elf_page_dir = mmap_find_first_free_block();
+    uint32_t *elf_page_tab = mmap_find_first_free_block();
+    elf_page_dir[768] = ((uint32_t)boot_page_tab - KERNEL_VMA) | 3;
+    elf_page_dir[PAGE_DIR_INDEX(elf->e_entry)] = ((uint32_t)elf_page_tab - KERNEL_VMA) | 7;
+    for (int i = 0; i < 1024; i++) {
+	elf_page_tab[i] = (elf_phys + 0x1000*i) | 7;
+    }
+
+    asm volatile ("mov %0, %%cr3" :: "r"((uint32_t)elf_page_dir - KERNEL_VMA));
 
     uint32_t stack = (uint32_t)mmap_find_first_free_block();
-    multi_mod_t *init = (multi_mod_t *)(info->moduleaddress + KERNEL_VMA);
+    LOG("Switching to ring 3... EIP: 0x%08X ESP: 0x%08X\n", elf->e_entry+text->sh_offset, stack+0x1000);
-    LOG("Switching to ring 3... EIP: 0x%08X ESP: 0x%08X\n", init->mod_start+KERNEL_VMA, stack+0x1000);
+    jmp_user_mode(stack+0x1000, elf->e_entry+text->sh_offset); 
-
-    jmp_user_mode(stack+0x1000, init->mod_start+KERNEL_VMA); 
 
 halt:
     for (;;) {}