first commit

rv_tests/hello_world/Makefile

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+# RISC-V toolchain
+CC = riscv64-unknown-elf-gcc
+AS = riscv64-unknown-elf-as
+LD = riscv64-unknown-elf-ld
+OBJCOPY = riscv64-unknown-elf-objcopy
+QEMU = qemu-system-riscv64
+
+# Compilation flags
+ARCH_FLAGS = -march=rv64imac -mabi=lp64
+LDSCRIPT = linker.ld
+
+# Output files
+ELF = hello.elf
+BIN = hello.bin
+OBJ = hello.o
+SRC = hello.S
+
+# Default rule
+all: $(BIN)
+
+# Assemble and link to ELF
+$(ELF): $(SRC) $(LDSCRIPT)
+	$(AS) $(ARCH_FLAGS) -o $(OBJ) $(SRC)
+	$(LD) -T $(LDSCRIPT) -o $(ELF) $(OBJ)
+
+# Convert ELF to raw binary
+$(BIN): $(ELF)
+	$(OBJCOPY) -O binary $(ELF) $(BIN)
+
+# Run in QEMU
+run: $(BIN)
+	echo "Press CTRL+A then X to exit QEMU"
+	$(QEMU) -machine virt -nographic -bios none -kernel $(BIN) -device loader,file=$(BIN),addr=0x80000000
+
+# Clean up generated files
+clean:
+	rm -f $(OBJ) $(ELF) $(BIN)

rv_tests/hello_world/build.sh

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+# Assemble the code
+riscv64-unknown-elf-as -march=rv64imac -mabi=lp64 -o hello.o hello.S
+
+# Link with our linker script to create an ELF file
+riscv64-unknown-elf-ld -T linker.ld -o hello.elf hello.o
+
+# Convert ELF to a raw binary
+riscv64-unknown-elf-objcopy -O binary hello.elf hello.bin

rv_tests/hello_world/hello.S

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+.section .text.init
+.global _start
+
+.equ UART_BASE, 0x10000000  # QEMU's UART base address
+
+_start:
+    # Load address of the string into a1
+    la a1, message
+
+loop:
+    lbu a0, 0(a1)            # Load a byte from the string
+    beqz a0, exit            # If null terminator, exit
+    li t0, UART_BASE         # Load UART address
+    sb a0, 0(t0)             # Store character to UART (8-bit write)
+    addi a1, a1, 1           # Move to next character
+    j loop                   # Repeat
+
+exit:
+    j exit                   # Infinite loop
+
+.section .rodata
+message:
+    .asciz "Hello, world!\n"

rv_tests/hello_world/linker.ld

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+OUTPUT_ARCH(riscv)
+ENTRY(_start)
+
+SECTIONS
+{
+    /* Start execution at 0x80000000 */
+    . = 0x80000000;
+
+    .text : {
+        *(.text.init)
+        *(.text)
+    }
+
+    .rodata : {
+        *(.rodata)
+    }
+
+    .data : {
+        *(.data)
+    }
+
+    .bss : {
+        *(.bss)
+    }
+}