feat(grub): add multi-boot support and long mode swap
Signed-off-by: Julien CLEMENT <julien.clement@epita.fr>
This commit is contained in:
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b3edf35855
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30c103a6b3
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@ -4,6 +4,3 @@ target = "x86_64-julios.json"
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[unstable]
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build-std-features = ["compiler-builtins-mem"]
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build-std = ["core", "compiler_builtins"]
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[target.'cfg(target_os = "none")']
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runner = "bootimage runner"
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@ -1 +1,5 @@
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/target
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iso
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*.iso
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*.o
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julios
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@ -2,15 +2,6 @@
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# It is not intended for manual editing.
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version = 3
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[[package]]
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name = "bootloader"
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version = "0.9.19"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "b7c452074efc3c0bfb241fb7bc87df04741c7c85e926f6a07c05f8fbd6008240"
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[[package]]
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name = "julios"
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version = "0.1.0"
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dependencies = [
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"bootloader",
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]
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@ -5,5 +5,5 @@ edition = "2018"
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# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
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[dependencies]
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bootloader = "0.9.8"
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[lib]
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crate-type = ["staticlib"]
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@ -0,0 +1,39 @@
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KERNEL = julios
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ISO = julios.iso
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INSTALL_ROOT = iso
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ABS_INSTALL = $(abspath $(INSTALL_ROOT))
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LINKER_SCRIPT = src/linker.ld
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BOOT_OBJS = src/multiboot.o src/boot.o
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LIB_JULIOS = target/x86_64-julios/debug/libjulios.a
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GRUB_CFG = grub/grub.cfg
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all: $(ISO)
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$(ISO): install
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./tools/create-iso.sh $@ $(INSTALL_ROOT)
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install: $(KERNEL) $(GRUB_CFG)
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mkdir -p $(ABS_INSTALL)
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mkdir -p $(ABS_INSTALL)/boot/grub
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cp $(KERNEL) $(ABS_INSTALL)/boot
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cp grub/grub.cfg $(ABS_INSTALL)/boot/grub
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$(KERNEL): $(LIB_JULIOS) $(LINKER_SCRIPT) $(BOOT_OBJS)
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ld -n -T $(LINKER_SCRIPT) -o $(KERNEL) $(BOOT_OBJS) $(LIB_JULIOS)
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$(LIB_JULIOS):
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cargo build
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%.o: %.asm
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nasm -f elf64 $^ -o $@
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clean:
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$(RM) $(BOOT_OBJS)
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$(RM) $(KERNEL)
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$(RM) julios.iso
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$(RM) -r iso
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.PHONY: $(INSTALL_ROOT) install clean all
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@ -0,0 +1,4 @@
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menuentry "julios" {
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multiboot2 /boot/julios
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boot
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}
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@ -0,0 +1,190 @@
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section .rodata
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gdt64:
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dq 0
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.code: equ $ - gdt64
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dq (1<<43) | (1<<44) | (1<<47) | (1<<53)
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.pointer:
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dw $ - gdt64 - 1
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dq gdt64
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global _start
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section .text
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bits 32
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_start:
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mov esp, stack_top
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call check_multiboot
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call check_cpuid
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call check_long_mode
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call set_up_page_tables
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call enable_paging
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lgdt [gdt64.pointer]
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jmp gdt64.code:long_mode_start
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set_up_page_tables:
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; map first P4 entry to P3 table
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mov eax, p3_table
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or eax, 0b11 ; present + writable
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mov [p4_table], eax
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; map first P3 entry to P2 table
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mov eax, p2_table
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or eax, 0b11 ; present + writable
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mov [p3_table], eax
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; map each P2 entry to a huge 2MiB page
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mov ecx, 0 ; counter variable
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.map_p2_table:
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; map ecx-th P2 entry to a huge page that starts at address 2MiB*ecx
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mov eax, 0x200000 ; 2MiB
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mul ecx ; start address of ecx-th page
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or eax, 0b10000011 ; present + writable + huge
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mov [p2_table + ecx * 8], eax ; map ecx-th entry
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inc ecx ; increase counter
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cmp ecx, 512 ; if counter == 512, the whole P2 table is mapped
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jne .map_p2_table ; else map the next entry
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ret
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enable_paging:
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; load P4 to cr3 register (cpu uses this to access the P4 table)
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mov eax, p4_table
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mov cr3, eax
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; enable PAE-flag in cr4 (Physical Address Extension)
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mov eax, cr4
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or eax, 1 << 5
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mov cr4, eax
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; set the long mode bit in the EFER MSR (model specific register)
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mov ecx, 0xC0000080
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rdmsr
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or eax, 1 << 8
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wrmsr
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; enable paging in the cr0 register
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mov eax, cr0
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or eax, 1 << 31
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mov cr0, eax
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ret
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; Prints `ERR: ` and the given error code to screen and hangs.
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; parameter: error code (in ascii) in al
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error:
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mov dword [0xb8000], 0x4f524f45
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mov dword [0xb8004], 0x4f3a4f52
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mov dword [0xb8008], 0x4f204f20
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mov byte [0xb800a], al
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hlt
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check_multiboot:
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cmp eax, 0x36d76289
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jne .no_multiboot
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ret
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.no_multiboot:
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mov al, "0"
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jmp error
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check_cpuid:
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; Check if CPUID is supported by attempting to flip the ID bit (bit 21)
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; in the FLAGS register. If we can flip it, CPUID is available.
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; Copy FLAGS in to EAX via stack
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pushfd
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pop eax
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; Copy to ECX as well for comparing later on
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mov ecx, eax
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; Flip the ID bit
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xor eax, 1 << 21
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; Copy EAX to FLAGS via the stack
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push eax
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popfd
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; Copy FLAGS back to EAX (with the flipped bit if CPUID is supported)
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pushfd
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pop eax
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; Restore FLAGS from the old version stored in ECX (i.e. flipping the
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; ID bit back if it was ever flipped).
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push ecx
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popfd
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; Compare EAX and ECX. If they are equal then that means the bit
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; wasn't flipped, and CPUID isn't supported.
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cmp eax, ecx
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je .no_cpuid
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ret
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.no_cpuid:
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mov al, "1"
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jmp error
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check_long_mode:
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; test if extended processor info in available
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mov eax, 0x80000000 ; implicit argument for cpuid
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cpuid ; get highest supported argument
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cmp eax, 0x80000001 ; it needs to be at least 0x80000001
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jb .no_long_mode ; if it's less, the CPU is too old for long mode
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; use extended info to test if long mode is available
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mov eax, 0x80000001 ; argument for extended processor info
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cpuid ; returns various feature bits in ecx and edx
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test edx, 1 << 29 ; test if the LM-bit is set in the D-register
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jz .no_long_mode ; If it's not set, there is no long mode
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ret
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.no_long_mode:
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mov al, "2"
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jmp error
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section .bss
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align 4096
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p4_table:
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resb 4096
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p3_table:
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resb 4096
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p2_table:
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resb 4096
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stack_bottom:
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resb 64
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stack_top:
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global long_mode_start
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section .text
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bits 64
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long_mode_start:
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; load 0 into all data segment registers
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mov ax, 0
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mov ss, ax
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mov ds, ax
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mov es, ax
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mov fs, ax
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mov gs, ax
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extern julios_main
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call julios_main
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mov rax, 0x2f592f412f4b2f4f
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mov qword [0xb8000], rax
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.loop:
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jmp .loop
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@ -10,7 +10,7 @@ fn panic(_info: &core::panic::PanicInfo) -> !
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static HELLO: &[u8] = b"Welcome to the JuliOS";
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#[no_mangle]
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pub extern "C" fn _start() -> !
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pub extern "C" fn julios_main() -> !
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{
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let vga_buffer: *mut u8 = 0xb8000 as *mut u8;
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@ -0,0 +1,16 @@
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ENTRY(_start)
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SECTIONS {
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. = 1M;
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.boot :
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{
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/* ensure that the multiboot header is at the beginning */
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*(.multiboot_header)
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}
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.text :
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{
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*(.text)
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}
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}
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@ -0,0 +1,15 @@
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section .multiboot_header
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header_start:
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dd 0xe85250d6 ; magic number (multiboot 2)
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dd 0 ; architecture 0 (protected mode i386)
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dd header_end - header_start ; header length
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; checksum
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dd 0x100000000 - (0xe85250d6 + 0 + (header_end - header_start))
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; insert optional multiboot tags here
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; required end tag
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dw 0 ; type
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dw 0 ; flags
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dd 8 ; size
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header_end:
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@ -0,0 +1,8 @@
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#!/bin/sh
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iso_filename=$1
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base_dir=$2
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unset MFLAGS MAKEFLAGS
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grub-mkrescue -o $iso_filename $base_dir
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