task1が動く

.clang-format

@@ -0,0 +1,2 @@
+BasedOnStyle: Google
+IndentWidth: 4

Makefile

@@ -4,7 +4,7 @@ LD=$(PREFIX)ld
 AS=$(PREFIX)as
 
 BASE_CFLAGS=-fno-stack-protector -fno-zero-initialized-in-bss -ffreestanding
-OPT_CFLAGS=-fno-builtin -nostdlib -nodefaultlibs -nostartfiles -mstrict-align
+OPT_CFLAGS=-fno-builtin -nostdlib -nodefaultlibs -nostartfiles -mstrict-align -g -O0
 WARN_CFLAGS=-Wall -Wextra
 ARCH_CFLAGS=-march=rv32im
 
@@ -16,19 +16,24 @@ C_SRC=$(wildcard kernel/*.c kernel/rv32/*.c)
 S_SRC=$(wildcard kernel/*.S kernel/rv32/*.S)
 OBJ_FILES=$(C_SRC:.c=.o) $(S_SRC:.S=.o)
 
+INCLUDES=-Ikernel -Ikernel/rv32
+
 kernel/kernel: $(OBJ_FILES)
 	$(LD) $(LDFLAGS) -o $@ $^
 
 %.o: %.c Makefile
-	$(CC) $(CFLAGS) -c -o $@ $<
+	$(CC) $(CFLAGS) $(INCLUDES) -c -o $@ $<
 
 %.o: %.S Makefile
-	$(AS) $(ASFLAGS) -c -o $@ $<
+	$(AS) $(ASFLAGS) $(INCLUDES) -c -o $@ $<
 
 clean:
 	rm -rf $(OBJ_FILES) kernel/kernel
 
 run: kernel/kernel
 	qemu-system-riscv32 -smp 1 -nographic -serial mon:stdio --no-reboot -m 128 -machine virt,aclint=on -bios none -kernel kernel/kernel
 
+debug: kernel/kernel
+	qemu-system-riscv32 -smp 1 -nographic -serial mon:stdio --no-reboot -m 128 -machine virt,aclint=on -bios none -kernel kernel/kernel -S -gdb tcp::1234
+
 .PHONY: clean run

kernel/main.c

@@ -1,21 +1,45 @@
-# define UARTADR 0x10000000
+#include "task.h"
+#include "switch.h"
+
+task_info task_list[2];
+
+#define UARTADR 0x10000000
 
 void print_int(int i) {
     i %= 10;
-    volatile unsigned int * const UART0DR = (unsigned int *)UARTADR;
+    volatile unsigned int *const UART0DR = (unsigned int *)UARTADR;
     *UART0DR = (unsigned int)(i + '0');
 }
 
 void print_uart0(const char *s) {
-    volatile unsigned int * const UART0DR = (unsigned int *)UARTADR;
+    volatile unsigned int *const UART0DR = (unsigned int *)UARTADR;
     while (*s != '\0') {
         *UART0DR = (unsigned int)(*s);
         s++;
     }
 }
 
-int main(){
+void clear_bss() {
+    extern unsigned int* __bss_start, __bss_end;
+    unsigned int start = (unsigned int)__bss_start;
+    unsigned int end = (unsigned int)__bss_end;
+    while (start < end) {
+        *(unsigned int*)start = 0;
+        start ++;
+    }
+}
+
+void task_1() {
+    while (1) {
+        print_uart0("task_1\n");
+    }
+}
+
+int main() {
+    clear_bss();
     print_uart0("Hello world!\n");
     print_int(1);
+    task_create(&task_list[0], task_1, 0);
+    task_load_rv32(&task_list[0].sp);
     return 0;
 }

kernel/rv32/link.ld

@@ -28,14 +28,14 @@ SECTIONS
         *(.sdata .sdata.*);
     }
     .bss : {
-      __bss = .;
+      __bss_start = .;
       *(.bss .bss.*);
       . = ALIGN(16);
       *(.sbss .sbss.*);
       __bss_end = .;
       . = ALIGN(4096);
-      stack_top = .;
       . = . + 16384;
+      stack_top = .;
     }
 
     . = ALIGN(4096);

kernel/rv32/switch.S

@@ -1,10 +1,11 @@
 .align 4
-.global task_switch
+.global task_switch_rv32
+.global task_load_rv32
 
 # a0には切り替え元のspアドレスが入っている
 # a1には切り替え先のspアドレスが入っている
 
-task_switch:
+task_switch_rv32:
 # レジスタを保存する分だけスタックを確保する
     addi sp,  sp, -13*4
 
@@ -49,3 +50,21 @@ task_switch:
 
 # 戻る
     ret
+
+task_load_rv32:
+    lw  sp,  (a0)
+    lw   ra,  0*4(sp)
+    lw   s0,  1*4(sp)
+    lw   s1,  2*4(sp)
+    lw   s2,  3*4(sp)
+    lw   s3,  4*4(sp)
+    lw   s4,  5*4(sp)
+    lw   s5,  6*4(sp)
+    lw   s6,  7*4(sp)
+    lw   s7,  8*4(sp)
+    lw   s8,  9*4(sp)
+    lw   s9,  10*4(sp)
+    lw   s10, 11*4(sp)
+    lw   s11, 12*4(sp)
+    addi sp,  sp, 13*4
+    ret

kernel/rv32/switch.h

@@ -0,0 +1,4 @@
+#pragma once
+
+void task_switch_rv32(unsigned int* old_sp, unsigned int new_sp);
+void task_load_rv32(unsigned int* sp);

kernel/task.c

@@ -0,0 +1,40 @@
+#include "switch.h"
+#include "task.h"
+
+void task_switch(task_info* current, task_info* next) {
+    task_switch_rv32(&current->sp, (unsigned int)&next->sp);
+}
+
+void task_create(task_info* task, void (*entry)(void), int pid) {
+    task->pid = pid;
+    //タスクのスタックポインタを設定
+    task->sp = (unsigned int)&(task->stack[4096]);
+    // stack pointerをずらしながら、レジスタの初期値を設定していく
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s11
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s10
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s9
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s8
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s7
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s6
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s5
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s4
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s3
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s2
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s1
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = 0; // s0
+    task->sp -= sizeof(unsigned int);
+    *((unsigned int*)(task->sp)) = (unsigned int)entry; // ra
+    return;
+}

kernel/task.h

@@ -0,0 +1,11 @@
+#pragma once
+
+typedef struct task_info {
+    int pid;
+    unsigned int stack[4096];
+    unsigned int sp;
+} task_info;
+
+void task_switch(task_info* current, task_info* next);
+
+void task_create(task_info* task, void (*entry)(void), int pid);