[Init]

Author: Artem Lisnevskiy

.gdbinit.tmpl-riscv

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+set confirm off
+set architecture riscv:rv64
+target remote 127.0.0.1:1234
+symbol-file kernel_img
+set disassemble-next-line auto
+set riscv use-compressed-breakpoints yes

.gitirnore

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+*~
+_*
+*.o
+*.d
+*.asm
+*.sym
+*.img
+vectors.S
+bootblock
+entryother
+initcode
+initcode.out
+kernelmemfs
+mkfs
+kernel/kernel
+user/usys.S
+debug/
+target/
+Cargo.lock
+**/*.rs.bk
+*.pdb

Makefile

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+# riscv64-unknown-elf- or riscv64-linux-gnu-
+# perhaps in /opt/riscv/bin
+TOOLPREFIX = riscv64-unknown-elf-
+
+QEMU = qemu-system-riscv64
+
+CC = $(TOOLPREFIX)gcc
+AS = $(TOOLPREFIX)as
+LD = $(TOOLPREFIX)ld
+OBJCOPY = $(TOOLPREFIX)objcopy
+OBJDUMP = $(TOOLPREFIX)objdump
+
+CFLAGS = -Wall -Werror -O -fno-omit-frame-pointer -ggdb -gdwarf-2
+CFLAGS += -MD
+CFLAGS += -Wl,--gc-sections -mcmodel=medany -march=rv64gc
+CFLAGS += -Wl,--no-warn-rwx-segments
+CFLAGS += -ffreestanding -nostartfiles -nostdlib -nodefaultlibs -fno-common -mno-relax
+CFLAGS += -I.
+CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
+
+ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]no-pie'),)
+CFLAGS += -fno-pie -no-pie
+endif
+ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]nopie'),)
+CFLAGS += -fno-pie -nopie
+endif
+
+LDFLAGS = -z max-page-size=4096
+
+OBJS = \
+  entry.o \
+  start.o \
+  main.o
+
+kernel_img: $(OBJS) kernel.ld
+	$(LD) $(LDFLAGS) -T kernel.ld -o kernel_img $(OBJS)
+	$(OBJDUMP) -S kernel_img > kernel.asm
+	$(OBJDUMP) -t kernel_img | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym
+
+tags: $(OBJS) _init
+	etags *.S *.c
+
+# Prevent deletion of intermediate files, e.g. cat.o, after first build, so
+# that disk image changes after first build are persistent until clean.  More
+# details:
+# http://www.gnu.org/software/make/manual/html_node/Chained-Rules.html
+.PRECIOUS: %.o
+
+-include *.d
+
+clean: 
+	rm -f *.tex *.dvi *.idx *.aux *.log *.ind *.ilg \
+	*.o */*.o *.d */*.d *.asm */*.asm *.sym */*.sym \
+	kernel_img
+
+# try to generate a unique GDB port
+GDBPORT = 1234
+
+# QEMU's gdb stub command line changed in 0.11
+QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
+	then echo "-gdb tcp::$(GDBPORT)"; \
+	else echo "-s -p $(GDBPORT)"; fi)
+
+QEMUOPTS = \
+	-machine virt \
+	-bios none \
+	-kernel kernel_img \
+	-m 128M \
+	-cpu rv64 \
+	-smp 1 \
+	-serial mon:stdio \
+	-device virtio-rng-device \
+	-device virtio-gpu-device \
+	-device virtio-net-device \
+	-device virtio-tablet-device \
+	-device virtio-keyboard-device
+
+qemu: kernel_img
+	$(QEMU) $(QEMUOPTS)
+
+qemu-gdb: kernel_img .gdbinit.tmpl-riscv
+	@echo "*** Now run 'gdb' in another window." 1>&2
+	$(QEMU) $(QEMUOPTS) -S $(QEMUGDB)
+

entry.s

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+.option norvc
+.section .text._entry
+.type _entry, @function
+.global	_entry
+_entry:
+
+    /* Отключение всех прерываний */
+    csrw sie, zero
+	csrw sscratch, zero
+	mv tp, zero
+
+    csrw mideleg, zero
+    csrw medeleg, zero
+    csrw mie, zero
+    csrw mip, zero
+
+    la t5, stack0
+    lui t6, 2
+    add t5, t5, t6
+    mv sp, t5
+
+.option push
+.option norelax
+	la gp, __global_pointer$
+.option pop
+
+    csrw satp, zero
+
+    la t5, bss_start
+	la t6, bss_end
+bss_clear:
+	sd zero, (t5)
+	addi t5, t5, 8
+	bltu t5, t6, bss_clear
+
+    la t0, kmain
+	csrw mepc, t0
+
+    call kmain
+
+finish:
+    j finish
+
+debug_message:
+    .string "[DEBUG]\n\r"
+
+.size _entry, . - _entry

kernel.ld

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+OUTPUT_ARCH( "riscv" )
+ENTRY( _entry )
+
+SECTIONS
+{
+  /*
+   * ensure that entry.S / _entry is at 0x80000000,
+   * where qemu's -kernel jumps.
+   */
+  . = 0x80000000;
+
+  .text : {
+    *(.text .text.*)
+    . = ALIGN(0x1000);
+    _trampoline = .;
+    *(trampsec)
+    . = ALIGN(0x1000);
+    PROVIDE(etext = .);
+  }
+
+  .rodata : {
+    . = ALIGN(16);
+    *(.srodata .srodata.*) /* do not need to distinguish this from .rodata */
+    . = ALIGN(16);
+    *(.rodata .rodata.*)
+  }
+
+  .data : {
+    . = ALIGN(16);
+    *(.sdata .sdata.*) /* do not need to distinguish this from .data */
+    . = ALIGN(16);
+    *(.data .data.*)
+  }
+
+  .bss : {
+    PROVIDE(bss_start = .);
+    . = ALIGN(16);
+    *(.sbss .sbss.*) /* do not need to distinguish this from .bss */
+    . = ALIGN(16);
+    *(.bss .bss.*)
+    PROVIDE(__global_pointer$ = .);
+    PROVIDE(bss_end = .);
+  }
+
+  PROVIDE(end = .);
+}

main.c

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+unsigned char * uart = (unsigned char *)0x10000000; 
+
+void putchar(unsigned char c) {
+	*uart = c;
+	return;
+}
+
+void print(const char * str) {
+	while(*str != '\0') {
+		putchar(*str);
+		str++;
+	}
+	return;
+}
+ 
+void kmain(void) {
+	print("Hello world!\r\n");
+	while(1) {
+		// Read input from the UART
+		putchar(*uart);
+	}
+	return;
+}

start.c

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+__attribute__ ((aligned (16))) char stack0[4096];