Implement "Hello, world!" demo

.gitignore

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+*.o
+*.elf

Makefile

@@ -1,2 +1,36 @@
+BUILDDIR = build
+
+all: githooks $(BUILDDIR)/kernel.elf
+
 githooks: | hooks
 	@git config core.hooksPath hooks/
+
+$(BUILDDIR):
+	@mkdir $(BUILDDIR)
+
+clean:
+	@$(RM) -rf $(BUILDDIR)
+
+CC = $(CROSS_PREFIX)gcc
+
+SRCS = $(wildcard src/*.S src/*.c)
+OBJS = $(patsubst src/%.S,$(BUILDDIR)/%.o,$(SRCS))
+OBJS := $(patsubst src/%.c,$(BUILDDIR)/%.o,$(OBJS))
+
+CFLAGS = -I include/ -mcmodel=medany
+LDFLAGS = -ffreestanding -nostdlib
+
+$(BUILDDIR)/%.o: src/%.S | $(BUILDDIR)
+	@printf "  CCAS\t$(@F)\n"
+	@$(CC) $< -c -o $@ $(CFLAGS)
+
+$(BUILDDIR)/%.o: src/%.c | $(BUILDDIR)
+	@printf "  CC\t$(@F)\n"
+	@$(CC) $< -c -o $@ $(CFLAGS)
+
+$(BUILDDIR)/kernel.elf: $(OBJS) kernel.ld | $(BUILDDIR)
+	@printf "  CCLD\t$(@F)\n"
+	@$(CC) $(OBJS) -o $@ -T kernel.ld $(LDFLAGS)
+
+run: $(BUILDDIR)/kernel.elf
+	@qemu-system-riscv64 -M virt -nographic -kernel $<

include/attribs.h

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+#pragma once
+
+#include <stdnoreturn.h>

include/config.h

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+#pragma once
+
+#define KSTACK_BASE 0x88000000

include/types.h

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+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+
+typedef uint8_t u8;
+typedef uint16_t u16;
+typedef uint32_t u32;
+typedef uint64_t u64;
+
+typedef int8_t i8;
+typedef int16_t i16;
+typedef int32_t i32;
+typedef int64_t i64;
+
+typedef uintptr_t usize;
+typedef intptr_t ssize;

kernel.ld

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+ENTRY(_start)
+
+SECTIONS {
+    . = 0x80200000;
+
+    .init : {
+        *(.init .init.*)
+    }
+
+    .text : {
+        *(.text .text.*)
+    }
+
+    .rodata : {
+        *(.rodata .rodata.*)
+    }
+
+    .data : {
+        *(.data .data.*)
+    }
+
+    .sdata : {
+        *(.sdata .sdata.*)
+    }
+
+    .sbss : {
+        *(.sbss .sbss.*)
+    }
+
+    .bss : {
+        *(.bss .bss.*)
+    }
+}

src/entry.S

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+#include <config.h>
+
+    .section .init
+
+    .global _start
+_start:
+    li sp, KSTACK_BASE
+    tail kmain

src/kmain.c

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+#include <attribs.h>
+#include <types.h>
+
+noreturn void kmain(void) {
+    volatile u8 *uart = (volatile u8 *) 0x10000000;
+    const char *s = "Hello, world!\n";
+
+    for (int i = 0; s[i] != '\0'; i++)
+        *uart = s[i];
+
+    while (true)
+        ;
+}