wrote a shell but have an error will debug tomorrow

kernel.h

@@ -5,13 +5,14 @@
 #define PROC_UNUSED 0           // Unused processes control structure
 #define PROC_RUNNABLE 1         // Runnable proccess
 #define SATP_SV32 (1u << 31)
+#define SSTATUS_SPIE (1 << 5)
+#define SCAUSE_ECALL 8
 #define PAGE_V (1 << 0) // "Valid" bit (entry is allowed)
 #define PAGE_R (1 << 1) // Readable
 #define PAGE_W (1 << 2) // Writable
 #define PAGE_X (1 << 3) // Executable
 #define PAGE_U (1 << 4) // User (accessible in user mode)
 #define USER_BASE 0x1000000
-#define SSTATUS_SPIE (1 << 5)
 
 struct process {
     int pid;                    // ID of a process