blindly implemented exit system call

common.h

@@ -22,6 +22,7 @@ typedef uint32_t vaddr_t;
 #define PAGE_SIZE 4096
 #define SYS_PUTCHAR 1
 #define SYS_GETCHAR 2
+#define SYS_EXIT    3
 
 void *memset(void *buf, char c, size_t n);
 void *memcpy(void *dst, const void *src, size_t n);

kernel.c

@@ -315,6 +315,11 @@ void proc_b_entry(void) {
 
 void handle_syscall(struct trap_frame *f) {
     switch (f->a3) {
+        case SYS_EXIT:
+            printf("process %d exited\n", current_proc->pid);
+            current_proc->state = PROC_EXITED;
+            yield();
+            PANIC("unreachable");
         case SYS_GETCHAR:
             while (1) {
                 long ch = getchar();

kernel.h

@@ -4,6 +4,7 @@
 #define PROCS_MAX 8             // Maximum ammount of processes
 #define PROC_UNUSED 0           // Unused processes control structure
 #define PROC_RUNNABLE 1         // Runnable proccess
+#define PROC_EXITED   2
 #define SATP_SV32 (1u << 31)
 #define SSTATUS_SPIE (1 << 5)
 #define SCAUSE_ECALL 8

shell.c

@@ -22,6 +22,8 @@ prompt:
 
         if (strcmp(cmdline, "hello") == 0)
             printf("Hellow :3\n");
+        else if (strcmp(cmdline, "exit") == 0)
+            exit();
         else
             printf("I don't know what is %s yet :(\n", cmdline);
     }

user.c

@@ -18,7 +18,8 @@ int syscall(int sysno, int arg0, int arg1, int arg2) {
 }
 
 __attribute__((noreturn)) void exit(void) {
-    for(;;);
+    syscall(SYS_EXIT, 0, 0, 0);
+    for (;;); // just in case
 }
 
 void putchar(char ch) {