Kernel: Rewrite i386 boot code + linker script
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@ -1,61 +1,98 @@
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# Declare constants for the multiboot header
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.set ALIGN, 1<<0 # align loaded modules on page boundaries
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.set MEMINFO, 1<<1 # provide memory map
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.set VIDEOINFO, 1<<2 # provide video info
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.set MB_FLAGS, ALIGN | MEMINFO | VIDEOINFO # this is the Multiboot 'flag' field
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.set MB_MAGIC, 0x1BADB002 # 'magic number' lets bootloader find the header
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.set MB_CHECKSUM, -(MB_MAGIC + MB_FLAGS) #checksum of above, to prove we are multiboot
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.set PG_PRESENT, 1<<0
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.set PG_READ_WRITE, 1<<1
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.set PG_PAGE_SIZE, 1<<7
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# Multiboot header
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.set FB_WIDTH, 800
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.set FB_HEIGHT, 600
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.set FB_BPP, 32
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#define KERNEL_OFFSET 0xC0000000
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#define V2P(vaddr) ((vaddr) - KERNEL_OFFSET)
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.code32
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# multiboot2 header
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.section .multiboot, "aw"
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.align 4
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.long MB_MAGIC
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.long MB_FLAGS
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.long MB_CHECKSUM
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.skip 20
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.align 8
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multiboot2_start:
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.long 0xE85250D6
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.long 0
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.long 800
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.long 600
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.long 32
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.long multiboot2_end - multiboot2_start
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.long -(0xE85250D6 + (multiboot2_end - multiboot2_start))
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# framebuffer tag
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.align 8
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.short 5
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.short 0
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.long 20
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.long FB_WIDTH
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.long FB_HEIGHT
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.long FB_BPP
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# legacy start
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.align 8
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.short 3
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.short 0
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.long 12
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.long V2P(_start)
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.align 8
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.short 0
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.short 0
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.long 8
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multiboot2_end:
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.section .bananboot, "aw"
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.align 8
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bananboot_start:
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.long 0xBABAB007
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.long -(0xBABAB007 + FB_WIDTH + FB_HEIGHT + FB_BPP)
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.long FB_WIDTH
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.long FB_HEIGHT
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.long FB_BPP
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bananboot_end:
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.section .bss, "aw", @nobits
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# Create stack
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.global g_boot_stack_bottom
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g_boot_stack_bottom:
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.skip 16384
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.global g_boot_stack_top
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g_boot_stack_top:
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boot_stack_bottom:
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.skip 4096 * 4
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boot_stack_top:
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# 0 MiB -> 1 MiB: bootloader stuff
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# 1 MiB -> : kernel
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.align 32
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boot_page_directory_pointer_table:
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.skip 4 * 8
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.align 4096
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boot_page_directory1:
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.skip 512 * 8
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.global g_kernel_cmdline
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g_kernel_cmdline:
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.global g_kernel_cmdline
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g_kernel_cmdline:
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.skip 4096
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.global g_multiboot_info
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g_multiboot_info:
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.skip 4
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.global g_multiboot_magic
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g_multiboot_magic:
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.skip 4
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bootloader_magic:
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.skip 8
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bootloader_info:
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.skip 8
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.section .text
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.section .data
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.align 4096
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boot_pml4:
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boot_pdpt_lo:
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boot_pdpt_hi:
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boot_pd:
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boot_gdt:
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.quad 0x0000000000000000 # null
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.quad 0x0000000000000000 # null descriptor
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.quad 0x00CF9A000000FFFF # kernel code
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.quad 0x00CF92000000FFFF # kernel data
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boot_gdtr:
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.short . - boot_gdt - 1
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.long boot_gdt
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.long V2P(boot_gdt)
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.global g_ap_startup_done
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g_ap_startup_done:
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.byte 0
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.global g_ap_running_count
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g_ap_running_count:
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.byte 0
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.global g_ap_stack_loaded
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g_ap_stack_loaded:
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.byte 0
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.section .text
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has_cpuid:
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pushfl
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@ -69,42 +106,13 @@ has_cpuid:
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testl $0x00200000, %eax
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ret
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has_pae:
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movl $0, %eax
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cpuid
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testl $(1 << 6), %edx
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ret
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has_sse:
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movl $1, %eax
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cpuid
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testl $(1 << 25), %edx
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ret
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check_requirements:
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call has_cpuid
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jz .exit
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call has_pae
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jz .exit
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call has_sse
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jz .exit
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ret
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.exit:
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jmp system_halt
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copy_kernel_commandline:
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pushl %esi
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pushl %edi
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movl g_multiboot_info, %esi
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addl $16, %esi
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movl (%esi), %esi
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movl $1024, %ecx
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movl $g_kernel_cmdline, %edi
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rep movsl
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popl %edi
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popl %esi
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ret
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enable_sse:
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movl %cr0, %eax
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andw $0xFFFB, %ax
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@ -116,19 +124,13 @@ enable_sse:
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ret
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initialize_paging:
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# identity map first 6 MiB
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movl $(0x00000000 + 0x83), boot_page_directory1 + 0
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movl $(0x00200000 + 0x83), boot_page_directory1 + 8
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movl $(0x00400000 + 0x83), boot_page_directory1 + 16
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movl $(boot_page_directory1 + 0x01), boot_page_directory_pointer_table
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# enable PAE
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movl %cr4, %ecx
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orl $0x20, %ecx
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movl %ecx, %cr4
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# set address of paging structures
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movl $boot_page_directory_pointer_table, %ecx
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movl $V2P(boot_pml4), %ecx
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movl %ecx, %cr3
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# enable paging
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@ -138,41 +140,52 @@ initialize_paging:
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ret
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initialize_gdt:
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lgdt boot_gdtr
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# flush gdt
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movw $0x10, %ax
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movw %ax, %ds
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movw %ax, %es
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movw %ax, %fs
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movw %ax, %gs
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movw %ax, %ss
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jmp $0x08, $flush
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flush:
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ret
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.global _start
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.type _start, @function
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_start:
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# Initialize stack and multiboot info
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movl $g_boot_stack_top, %esp
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movl %eax, g_multiboot_magic
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movl %ebx, g_multiboot_info
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cli; cld
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# Initialize stack and multiboot info
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movl %eax, V2P(bootloader_magic)
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movl %ebx, V2P(bootloader_info)
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movl $V2P(boot_stack_top), %esp
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call copy_kernel_commandline
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call check_requirements
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call enable_sse
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call initialize_paging
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call initialize_gdt
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# flush gdt
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lgdt V2P(boot_gdtr)
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ljmpl $0x08, $V2P(gdt_flush)
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gdt_flush:
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movw $0x10, %ax
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movw %ax, %ds
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movw %ax, %ss
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movw %ax, %es
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# move stack pointer to higher half
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movl %esp, %esp
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addl $KERNEL_OFFSET, %esp
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# jump to higher half
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leal higher_half, %ecx
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jmp *%ecx
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higher_half:
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# call global constuctors
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call _init
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# call to the kernel itself (clear ebp for stacktrace)
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xorl %ebp, %ebp
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movl V2P(bootloader_magic), %edi
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movl V2P(bootloader_info), %esi
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call kernel_main
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# call global destructors
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call _fini
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system_halt:
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@ -180,3 +193,76 @@ system_halt:
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cli
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1: hlt
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jmp 1b
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.section .ap_init, "ax"
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.code16
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.global ap_trampoline
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ap_trampoline:
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jmp 1f
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.align 8
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ap_stack_ptr:
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.skip 4
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1:
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cli; cld
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ljmpl $0x00, $ap_cs_clear
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ap_cs_clear:
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xorw %ax, %ax
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movw %ax, %ds
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# load ap gdt and enter protected mode
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lgdt ap_gdtr
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movl %cr0, %eax
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orb $1, %al
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movl %eax, %cr0
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ljmpl $0x08, $ap_protected_mode
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.code32
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ap_protected_mode:
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movw $0x10, %ax
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movw %ax, %ds
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movw %ax, %ss
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movw %ax, %es
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movl ap_stack_ptr, %esp
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movb $1, V2P(g_ap_stack_loaded)
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call V2P(enable_sse)
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call V2P(initialize_paging)
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# load boot gdt and enter long mode
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lgdt V2P(boot_gdtr)
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ljmpl $0x08, $ap_flush_gdt
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ap_flush_gdt:
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# move stack pointer to higher half
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movl %esp, %esp
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addl $KERNEL_OFFSET, %esp
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# jump to higher half
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leal ap_higher_half, %ecx
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jmp *%ecx
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ap_higher_half:
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# clear rbp for stacktrace
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xorl %ebp, %ebp
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1: pause
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cmpb $0, g_ap_startup_done
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jz 1b
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lock incb g_ap_running_count
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call ap_main
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jmp system_halt
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ap_gdt:
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.quad 0x0000000000000000 # null descriptor
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.quad 0x00CF9A000000FFFF # 32 bit code
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.quad 0x00CF92000000FFFF # 32 bit data
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ap_gdtr:
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.short . - ap_gdt - 1
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.long ap_gdt
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@ -1,28 +1,45 @@
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ENTRY (_start)
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KERNEL_OFFSET = 0xC0000000;
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SECTIONS
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{
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. = 0x00100000;
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. = 0xF000;
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.ap_init ALIGN(4K) : AT(ADDR(.ap_init))
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{
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g_ap_init_addr = .;
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*(.ap_init)
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}
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. = 0x00100000 + KERNEL_OFFSET;
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g_kernel_start = .;
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.text BLOCK(4K) : ALIGN(4K)
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.text ALIGN(4K) : AT(ADDR(.text) - KERNEL_OFFSET)
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{
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g_kernel_execute_start = .;
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*(.multiboot)
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*(.text)
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*(.bananboot)
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*(.text.*)
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}
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.rodata BLOCK(4K) : ALIGN(4K)
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.userspace ALIGN(4K) : AT(ADDR(.userspace) - KERNEL_OFFSET)
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{
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g_userspace_start = .;
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*(.userspace)
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g_userspace_end = .;
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g_kernel_execute_end = .;
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}
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.rodata ALIGN(4K) : AT(ADDR(.rodata) - KERNEL_OFFSET)
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{
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*(.rodata.*)
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}
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.data BLOCK(4K) : ALIGN(4K)
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.data ALIGN(4K) : AT(ADDR(.data) - KERNEL_OFFSET)
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{
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*(.data)
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}
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.bss BLOCK(4K) : ALIGN(4K)
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.bss ALIGN(4K) : AT(ADDR(.bss) - KERNEL_OFFSET)
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{
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*(COMMON)
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*(.bss)
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}
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g_kernel_end = .;
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}
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