add files from learning repo

.gitignore

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+out/*
+nimcache/
+nimblecache/
+htmldocs/
+
+# General
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+# out
+*.o
+*.elf

Makefile

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+SHELL = /bin/bash
+.DEFAULT_GOAL := build
+BUILDDIR = build
+BINDIR = bin
+OBJECT_FILES = boot.o 
+
+build: clean-objects assemble-stub compile copy-o link
+
+assemble-stub:
+	mkdir -p $(BUILDDIR)/
+	aarch64-elf-as boot.s -o $(BUILDDIR)/boot.o
+
+compile:
+	mkdir -p $(BUILDDIR)/
+	nim c -d:release kernel.nim
+
+copy-o:
+	cp nimcache/*.o build/
+
+clear, clean:
+	rm -rf $(BUILDDIR) nimcache/ bin/
+
+clean-objects:
+	rm -rf $(BUILDDIR)/*.o nimcache/*.o
+
+link:
+	mkdir -p $(BINDIR) && \
+	aarch64-elf-ld -nostdlib -Tlinker.ld -o bin/kernel.elf -O2 $(wildcard build/*.o)
+
+boot:
+
+setup-macos:
+	brew install aarch64-elf-binutils aarch64-elf-gcc nim

boot.s

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+// QEMU Aarch64 Boot Stub
+
+.global _start
+_start:
+    ldr x30, =stack_top
+    mov sp, x30
+    bl kmain
+    b .

kernel.nim

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+import strutil
+
+proc kmain {.exportc.} =
+    printTxt(cast[seq[char]]("hello world\n"))

linker.ld

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+/* All this linker script does is allocate memory and */
+/* prepend the QEMU boot stub to our program */
+ENTRY(_start)
+SECTIONS {
+    . = 0x40000000;
+    .startup . : { build/boot.o(.text) }
+    .text : { *(.text) }
+    .data : { *(.data) }
+    .bss : { *(.bss COMMON) }
+    . = ALIGN(8);
+    . += 0x1000; /* 4kB of stack memory */
+    stack_top = .;
+}

nim.cfg

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+gcc.exe = "aarch64-elf-gcc"
+gcc.linkerexe = "aarch64-elf-ld"
+
+--os:standalone
+--cpu:arm64 
+-d:useMalloc 
+--mm:orc
+--cc:gcc
+--index:off
+--passC:"-w -I$lib -I$LIBRARY_PATH -ffreestanding -O2 -Wall -Wextra"
+# --passL:"-nostdlib -Tlinker.ld -o kernel.elf -O2"
+--boundChecks:on
+--noMain
+--noLinking
+--deadCodeElim:on
+--hints:on
+--listFullPaths:off
+--nimcache:"nimcache"

panicoverride.nim

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+import strutil
+
+func halt =
+    asm "wfi"
+
+proc panic*(str: string) =
+    halt()
+
+proc rawoutput*(str: string) =
+    printTxt(cast[seq[char]](str))

strutil.nim

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+var uart*: ptr uint8 = cast[ptr uint8](0x09000000)
+
+proc printTxt*(str: seq[char]) =
+    for i in 0..<len(str):
+        uart[] = cast[uint8](str[i])