diff --git a/Makefile b/Makefile
index ded5bc2..2628613 100644
--- a/Makefile
+++ b/Makefile
@@ -188,6 +188,7 @@ UPROGS=\
 	$U/_grind\
 	$U/_wc\
 	$U/_zombie\
+	$U/_alarmtest\
 
 
 
diff --git a/kernel/proc.c b/kernel/proc.c
index 959b778..2f0feac 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -131,6 +131,11 @@ found:
     release(&p->lock);
     return 0;
   }
+  if((p->trapframe1 = (struct trapframe *)kalloc()) == 0){
+    freeproc(p);
+    release(&p->lock);
+    return 0;
+  }
 
   // An empty user page table.
   p->pagetable = proc_pagetable(p);
@@ -145,6 +150,8 @@ found:
   memset(&p->context, 0, sizeof(p->context));
   p->context.ra = (uint64)forkret;
   p->context.sp = p->kstack + PGSIZE;
+  p->alarm_hdlr = 0;
+  p->alarm_intrv = p->alarm_ticks = 0;
 
   return p;
 }
@@ -158,6 +165,9 @@ freeproc(struct proc *p)
   if(p->trapframe)
     kfree((void*)p->trapframe);
   p->trapframe = 0;
+  if(p->trapframe1)
+    kfree((void*)p->trapframe1);
+  p->trapframe1 = 0;
   if(p->pagetable)
     proc_freepagetable(p->pagetable, p->sz);
   p->pagetable = 0;
diff --git a/kernel/proc.h b/kernel/proc.h
index d021857..83da3f7 100644
--- a/kernel/proc.h
+++ b/kernel/proc.h
@@ -100,8 +100,12 @@ struct proc {
   uint64 sz;                   // Size of process memory (bytes)
   pagetable_t pagetable;       // User page table
   struct trapframe *trapframe; // data page for trampoline.S
+  struct trapframe *trapframe1; // data page for trampoline.S
   struct context context;      // swtch() here to run process
   struct file *ofile[NOFILE];  // Open files
   struct inode *cwd;           // Current directory
+  int alarm_intrv;             // alarm interval
+  uint64 alarm_hdlr;            // alarm handler
+  int alarm_ticks;             // ticks after last alarm
   char name[16];               // Process name (debugging)
 };
diff --git a/kernel/syscall.c b/kernel/syscall.c
index ed65409..e4f006a 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -101,6 +101,8 @@ extern uint64 sys_unlink(void);
 extern uint64 sys_link(void);
 extern uint64 sys_mkdir(void);
 extern uint64 sys_close(void);
+extern uint64 sys_sigalarm(void);
+extern uint64 sys_sigreturn(void);
 
 // An array mapping syscall numbers from syscall.h
 // to the function that handles the system call.
@@ -126,6 +128,8 @@ static uint64 (*syscalls[])(void) = {
 [SYS_link]    sys_link,
 [SYS_mkdir]   sys_mkdir,
 [SYS_close]   sys_close,
+[SYS_sigalarm]   sys_sigalarm,
+[SYS_sigreturn]   sys_sigreturn,
 };
 
 void
diff --git a/kernel/syscall.h b/kernel/syscall.h
index bc5f356..349ed72 100644
--- a/kernel/syscall.h
+++ b/kernel/syscall.h
@@ -20,3 +20,5 @@
 #define SYS_link   19
 #define SYS_mkdir  20
 #define SYS_close  21
+#define SYS_sigalarm    22
+#define SYS_sigreturn   23
diff --git a/kernel/sysproc.c b/kernel/sysproc.c
index fe64ad3..3d845ea 100644
--- a/kernel/sysproc.c
+++ b/kernel/sysproc.c
@@ -92,3 +92,28 @@ sys_uptime(void)
   release(&tickslock);
   return xticks;
 }
+
+uint64
+sys_sigalarm(void)
+{
+  int interval;
+  uint64 hdlr;
+  argint(0, &interval); 
+  argaddr(1, &hdlr);
+  struct proc* p = myproc();
+
+  p->alarm_ticks = 0;
+  p->alarm_intrv = interval;
+  p->alarm_hdlr = hdlr;
+
+  return 0;
+}
+
+uint64
+sys_sigreturn(void)
+{
+  struct proc* p = myproc();
+  memmove(p->trapframe, p->trapframe1, sizeof(struct trapframe));
+  p->alarm_ticks = 0;
+  return p->trapframe->a0;
+}
\ No newline at end of file
diff --git a/kernel/trap.c b/kernel/trap.c
index 512c850..518ee15 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -67,6 +67,18 @@ usertrap(void)
     syscall();
   } else if((which_dev = devintr()) != 0){
     // ok
+    if (which_dev == 2) {
+      acquire(&p->lock);
+      if (p->alarm_intrv) {
+        if (p->alarm_ticks <= p->alarm_intrv)
+          p->alarm_ticks ++;
+        if (p->alarm_intrv == p->alarm_ticks) {
+          memmove(p->trapframe1, p->trapframe, sizeof(struct trapframe));
+          p->trapframe->epc = p->alarm_hdlr;
+        }
+      }
+      release(&p->lock);
+    }
   } else {
     printf("usertrap(): unexpected scause %p pid=%d\n", r_scause(), p->pid);
     printf("            sepc=%p stval=%p\n", r_sepc(), r_stval());
diff --git a/time.txt b/time.txt
new file mode 100644
index 0000000..bf0d87a
--- /dev/null
+++ b/time.txt
@@ -0,0 +1 @@
+4
\ No newline at end of file
diff --git a/user/user.h b/user/user.h
index 4d398d5..9426153 100644
--- a/user/user.h
+++ b/user/user.h
@@ -22,6 +22,8 @@ int getpid(void);
 char* sbrk(int);
 int sleep(int);
 int uptime(void);
+int sigalarm(int ticks, void (*handler)());
+int sigreturn(void);
 
 // ulib.c
 int stat(const char*, struct stat*);
diff --git a/user/usys.pl b/user/usys.pl
index 01e426e..fa548b0 100755
--- a/user/usys.pl
+++ b/user/usys.pl
@@ -36,3 +36,5 @@ entry("getpid");
 entry("sbrk");
 entry("sleep");
 entry("uptime");
+entry("sigalarm");
+entry("sigreturn");