Initiated
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commit
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.elf
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.o
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build/
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# Lion's Share License -> LSL
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# Löwenware Software Distribution -> LSD
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# Löwe OS
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Operating System for ARMv8 (aarch64) architecture.
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ASM=clang
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TARGET=aarch64-none-elf
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CPU=cortex-a57
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LD=ld.lld
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OBJCOPY=objcopy --target elf64-littleaarch64
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all: build/core.bin build/core.elf
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# compilation -----------------------------------------------------------------
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build/core.o: core/core.s
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$(ASM) -c -triple --target=$(TARGET) -mcpu=$(CPU) -O0 -g $< -o $@
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build/uart.o: core/uart.s
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$(ASM) -c --target=$(TARGET) -mcpu=$(CPU) -O0 -g $< -o $@
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# ELF -------------------------------------------------------------------------
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build/core.elf: build/core.o build/uart.o
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$(LD) -Tcore/core.ld $^ -o $@
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# BIN -------------------------------------------------------------------------
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build/core.bin: build/core.elf
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$(OBJCOPY) -O binary $< $@
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build/core.sym: build/core.elf
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$(OBJCOPY) --only-keep-debug $< $@
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$(OBJCOPY) --strip-debug build/core.elf
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# Clean -----------------------------------------------------------------------
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clean:
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rm -f build/*
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ENTRY(_core_init)
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SECTIONS
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{
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. = 0x40000000;
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.text : { *(.text) }
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.data : { *(.text) }
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.bss : { *(.bss COMMON) }
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. = ALIGN(10);
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. = . + 0x1000;
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stack_ptr = . ;
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}
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# file: core.s
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# project: Löwe OS
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# authors: Elias Löwe <elias@lowenware.com>
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# -----------------------------------------------------------------------------
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.global _core_init
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.extern _uart_puts
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# -----------------------------------------------------------------------------
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.text
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_core_init:
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# set up stack pointer using x30 register
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LDR x30, =0x40001000
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MOV sp, x30
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bl 1f
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1:
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LDR x0, =some_int
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BL _uart_putx
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LDR x0, =greeting
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BL _uart_puts
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2:
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B 2b
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# -----------------------------------------------------------------------------
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.data
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greeting:
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.asciz "\nStarting Lowe OS\n"
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.equ some_int, 0x1234567890ABCDEF
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# -----------------------------------------------------------------------------
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# file : uart.s
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# project : Löwe OS
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# authors : Elias Löwe <elias@lowenware.com>
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# address of UART for virt device in qemu
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# -----------------------------------------------------------------------------
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.global _uart_putc # print single character uart
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.global _uart_putx # print integer in HEX format to uart
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.global _uart_puts # print null-terminated string to uart
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# -----------------------------------------------------------------------------
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.text
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# helper to avoid extra data moving
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# @x1 character print
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uart_putc:
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STP x2, lr, [sp, -16]!
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MOV x2, 0x09000000 # set UART address
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STRB w1, [x2] # put character out
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LDP x2, lr, [sp], 16
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RET
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# -----------------------------------------------------------------------------
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# print character to uart
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# @x0 character print
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_uart_putc:
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STR lr, [sp, -16]!
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MOV x1, x0 # set arguments
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BL uart_putc # put character out
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LDR lr, [sp], 16
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RET
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# -----------------------------------------------------------------------------
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# @x0 integer to print
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_uart_putx:
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STP lr, x3, [sp, -32]!
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STP x0, x1, [sp, 16]
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LDR x3, =60 # init bits counter 64-4
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1:
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LSR x1, x0, x3 # shift to digit
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AND x1, x1, 0xF # keep only digit
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CMP x1, 9 # compare it to 9
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BLS 2f # less or equal
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ADD x1, x1, 0x37 # turn into ASCII HEX char
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B 3f # continue to output
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2:
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ADD x1, x1, 0x30 # turn into ASCII num char
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3:
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BL uart_putc # output carachter
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CBZ x3, 0f # if counter == 0 return
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SUB x3, x3, 4 # otherwise subtract counter by 4
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B 1b # repeat
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0:
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LDP lr, x3, [sp], 16
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LDP x0, x1, [sp], 16
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RET
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# -----------------------------------------------------------------------------
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# @x0 pointer to string
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_uart_puts:
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STR lr, [sp, -16]!
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STP x0, x1, [sp, -16]!
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1:
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LDRB w1, [x0], 1 # load byte of string from address in x0
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CBZ w1, 0f # return if zero
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BL uart_putc # put charcter out
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B 1b # loop
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0:
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LDP x0, x1, [sp], 16
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LDR lr, [sp], 16
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RET
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# -----------------------------------------------------------------------------
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