syscall lab need to finish

kernel/syscall.c

@@ -7,6 +7,11 @@
 #include "syscall.h"
 #include "defs.h"
 
+// 保留系统调用别名
+char* syscalls_name[24] = {"", "fork", "exit", "wait", "pipe", "read", "kill", "exec",
+                      "fstat", "chdir", "dup", "getpid", "sbrk", "sleep", "uptime",
+                      "open", "write", "mknod", "unlink", "link", "mkdir", "close", "trace"};
+
 // Fetch the uint64 at addr from the current process.
 int
 fetchaddr(uint64 addr, uint64 *ip)
@@ -101,6 +106,7 @@ extern uint64 sys_unlink(void);
 extern uint64 sys_link(void);
 extern uint64 sys_mkdir(void);
 extern uint64 sys_close(void);
+extern uint64 sys_trace(void);
 
 // An array mapping syscall numbers from syscall.h
 // to the function that handles the system call.
@@ -126,6 +132,7 @@ static uint64 (*syscalls[])(void) = {
 [SYS_link]    sys_link,
 [SYS_mkdir]   sys_mkdir,
 [SYS_close]   sys_close,
+[SYS_trace]   sys_trace,
 };
 
 void
@@ -139,6 +146,9 @@ syscall(void)
     // Use num to lookup the system call function for num, call it,
     // and store its return value in p->trapframe->a0
     p->trapframe->a0 = syscalls[num]();
+    if (p->tracemask & (1 << num)) {
+       printf("%d: syscall %s -> %d\n",p->pid, syscalls_name[num], p->trapframe->a0);
+    }
   } else {
     printf("%d %s: unknown sys call %d\n",
             p->pid, p->name, num);