higher half kernel

bochsrc

@@ -2,4 +2,4 @@ ata0-slave: type=cdrom, path=./build/Hazel.iso, status=inserted
 magic_break: enabled=1
 boot: cdrom
 
-display_library: sdl2
+display_library: x

kernel/init.asm

@@ -4,7 +4,7 @@
 %define VID   1<<2
 %define FLAGS (ALIGN | MMAP | VID)
 
-section .multiboot
+section .multiboot.data
 dd MAGIC
 dd FLAGS 
 dd -(MAGIC + FLAGS)
@@ -19,7 +19,7 @@ dd 80 ; width
 dd 25 ; height
 dd 0 ; depth
 
-section .text
+section .multiboot.text
 global _start
 _start:
     cli
@@ -28,6 +28,37 @@ _start:
     cmp eax, 0x2BADB002
     jne halt
 
+    ; Setup table
+    ; Identity page 0-4 mib
+    mov eax, 0
+    mov edx, 0
+.fill_table:
+    mov ecx, edx
+    or ecx, 3
+    mov [boot_page_tab-0xC0000000+eax*4], ecx
+    add edx, 0x1000
+    inc eax
+    cmp eax, 1024
+    jne .fill_table
+
+    mov ecx, boot_page_tab
+    sub ecx, 0xC0000000
+    or ecx, 3
+    mov [boot_page_dir-0xC0000000], ecx
+    mov [boot_page_dir-0xC0000000+768*4], ecx
+
+    ; Enable paging
+    mov eax, boot_page_dir
+    sub eax, 0xC0000000
+    mov cr3, eax
+    mov eax, cr0
+    or eax, (1<<31)
+    mov cr0, eax
+
+    jmp higher_half
+
+section .text
+higher_half:
     ; Load GDT
     lgdt [gdtp]
     ; Offset to kernel data descriptor
@@ -52,7 +83,6 @@ halt:
 
 global pit_isr
 pit_isr:
-    cli
     extern pit_handler
     call pit_handler
     iret
@@ -187,6 +217,11 @@ gdtp:
     dw gdt_end - gdt - 1
     dd gdt
 
+align 0x1000
+boot_page_dir: times 1024 dd 0
+align 0x1000
+boot_page_tab: times 1024 dd 0
+
 section .bss
 align 16
 stack_top:

kernel/kernel.c

@@ -37,9 +37,6 @@ typedef struct {
     uint32_t cr3;
 } task_t;
 
-__attribute__((aligned(4096))) uint32_t page_dir[1024];
-__attribute__((aligned(4096))) uint32_t page_tab[1024];
-
 void kernel(multiboot_info_t *info) {
     if (!CHECK_FLAG(info->flags, 3)) goto halt;  // Modules
     if (!CHECK_FLAG(info->flags, 6)) goto halt;  // Memory map
@@ -93,31 +90,11 @@ void kernel(multiboot_info_t *info) {
 #define PAGE_TAB_INDEX(x) (((x) >> 12) & 0x3FF)
 #define PAGE_OFFSET(x) ((x) & 0xFFF)
 
-    for (int i = 0; i < 1024; i++) {
-        page_tab[i] = (i * 0x1000) | PAGE_PRESENT | PAGE_RW | PAGE_USER;
-    }
-
-    for (int i = 0; i < 1024; i++) {
-        page_dir[i] = ((uint32_t)page_tab) | PAGE_PRESENT | PAGE_RW | PAGE_USER;
-    }
-
-    //enable_paging(page_dir);
-    asm volatile("mov %0, %%cr3" :: "r" (page_dir));
-
-    asm volatile(
-        "mov %%cr0, %%eax;"
-        "or $0x80000000, %%eax;"
-        "mov %%eax, %%cr0;"
-        :
-        :
-        : "%eax"
-    );
-
     uint32_t stack = (uint32_t)mmap_find_first_free_block();
     multi_mod_t *init = (multi_mod_t *)info->moduleaddress;
     LOG("Switching to ring 3... EIP: 0x%08X ESP: 0x%08X\n", init->mod_start, stack+0x1000);
 
-    jmp_user_mode(stack+0x1000, init->mod_start); 
+    //jmp_user_mode(stack+0x1000, init->mod_start); 
 
 halt:
     for (;;) {}

kernel/kernel.ld

@@ -1,52 +1,36 @@
-/* The bootloader will look at this image and start execution at the symbol
-   designated as the entry point. */
 ENTRY(_start)
 
-/* Tell where the various sections of the object files will be put in the final
-   kernel image. */
 SECTIONS
 {
-	/* It used to be universally recommended to use 1M as a start offset,
-	   as it was effectively guaranteed to be available under BIOS systems.
-	   However, UEFI has made things more complicated, and experimental data
-	   strongly suggests that 2M is a safer place to load. In 2016, a new
-	   feature was introduced to the multiboot2 spec to inform bootloaders
-	   that a kernel can be loaded anywhere within a range of addresses and
-	   will be able to relocate itself to run from such a loader-selected
-	   address, in order to give the loader freedom in selecting a span of
-	   memory which is verified to be available by the firmware, in order to
-	   work around this issue. This does not use that feature, so 2M was
-	   chosen as a safer option than the traditional 1M. */
 	. = 1M;
-
+	_kernel_start = .;
-	/* First put the multiboot header, as it is required to be put very early
+	.multiboot.data : {
-	   in the image or the bootloader won't recognize the file format.
+	    *(.multiboot.data)
-	   Next we'll put the .text section. */
+	}
-	.text BLOCK(4K) : ALIGN(4K)
+	.multiboot.text : {
-	{
+	    *(.multiboot.text)
-		*(.multiboot)
-		*(.text)
 	}
 
-	/* Read-only data. */
+	. += 0xC0000000;
-	.rodata BLOCK(4K) : ALIGN(4K)
+
+	.text ALIGN (4K) : AT (ADDR (.text) - 0xC0000000)
+	{
+		*(.text)
+	}
+	.rodata ALIGN (4K) : AT (ADDR (.rodata) - 0xC0000000)
 	{
 		*(.rodata)
 	}
-
+	.data ALIGN (4K) : AT (ADDR (.data) - 0xC0000000)
-	/* Read-write data (initialized) */
-	.data BLOCK(4K) : ALIGN(4K)
 	{
 		*(.data)
 	}
-
+	.bss ALIGN (4K) : AT (ADDR (.bss) - 0xC0000000)
-	/* Read-write data (uninitialized) and stack */
-	.bss BLOCK(4K) : ALIGN(4K)
 	{
 		*(COMMON)
 		*(.bss)
+		*(.bootstrap_stack)
 	}
 
-	/* The compiler may produce other sections, by default it will put them in
+	_kernel_end = .;
-	   a segment with the same name. Simply add stuff here as needed. */
 }