From 02c0816e413926a8269ff5ab91c56a28ef861e5f Mon Sep 17 00:00:00 2001
From: Ali Mashtizadeh <mashti@cs.stanford.edu>
Date: Sun, 18 Jan 2015 15:08:12 -0800
Subject: [PATCH] Adding wait system call

---
 bin/shell/shell.c     | 25 +++++++++++++++++++++++--
 include/syscall.h     |  3 ++-
 lib/libc/syscall.c    |  6 ++++++
 sys/include/syscall.h |  7 ++++---
 sys/kern/syscall.c    | 19 ++++++++++++++-----
 5 files changed, 49 insertions(+), 11 deletions(-)

diff --git a/bin/shell/shell.c b/bin/shell/shell.c
index f113315..f50698a 100644
--- a/bin/shell/shell.c
+++ b/bin/shell/shell.c
@@ -19,6 +19,7 @@ main(int argc, const char *argv[])
     char buf[256];
 
     printf("System Shell\n");
+
     while (1) {
 	fputs("Shell> ", stdout);
 	fgets(buf, sizeof(buf), stdin);
@@ -31,12 +32,13 @@ void
 Cmd_Help(int argc, const char *argv[])
 {
     printf("cat        Print file\n");
+    printf("bkpt       Trigger a kernel breakpoint\n");
+    printf("date       Print current date and time\n");
     printf("echo       Echo arguments\n");
     printf("exit       Exit shell\n");
     printf("help       Display the list of commands\n");
     printf("ls         List files in a directory\n");
-    printf("date       Print current date and time\n");
-    printf("bkpt       Trigger a kernel breakpoint\n");
+    printf("spawn      Spawn a process\n");
 }
 
 void
@@ -124,6 +126,23 @@ Cmd_Hexdump(int argc, const char *argv[])
 {
 }
 
+void
+Cmd_Spawn(int argc, const char *argv[])
+{
+    int fd;
+    uint64_t status;
+    uintptr_t offset = 0;
+
+    if (argc != 2) {
+	fputs("Requires an argument\n", stdout);
+	return;
+    }
+
+    status = OSSpawn(argv[1]);
+    // XXX: check errors
+    OSWait(status);
+}
+
 void
 DispatchCommand(char *buf)
 {
@@ -168,6 +187,8 @@ DispatchCommand(char *buf)
 	exit(0);
     } else if (strcmp(argv[0], "ls") == 0) {
 	Cmd_List(argc, (const char **)argv);
+    } else if (strcmp(argv[0], "spawn") == 0) {
+	Cmd_Spawn(argc, (const char **)argv);
     } else if (strcmp(argv[0], "#") == 0) {
 	// Ignore comments
     } else if (buf[0] != '\0') {
diff --git a/include/syscall.h b/include/syscall.h
index 4421aec..720bc73 100644
--- a/include/syscall.h
+++ b/include/syscall.h
@@ -5,9 +5,10 @@
 #include <sys/stat.h>
 
 uint64_t OSTime();
-void OSExit(int status);
 uint64_t OSGetPID();
+void OSExit(int status);
 uint64_t OSSpawn(const char *path);
+uint64_t OSWait(uint64_t pid);
 
 // Memory
 void *OSMemMap(void *addr, uint64_t len, int flags);
diff --git a/lib/libc/syscall.c b/lib/libc/syscall.c
index bd153c4..761bdd1 100644
--- a/lib/libc/syscall.c
+++ b/lib/libc/syscall.c
@@ -31,6 +31,12 @@ OSSpawn(const char *path)
     return syscall(SYSCALL_SPAWN, path);
 }
 
+uint64_t
+OSWait(uint64_t pid)
+{
+    return syscall(SYSCALL_WAIT, pid);
+}
+
 void *
 OSMemMap(void *addr, uint64_t len, int flags)
 {
diff --git a/sys/include/syscall.h b/sys/include/syscall.h
index 005f3c5..26f3ddd 100644
--- a/sys/include/syscall.h
+++ b/sys/include/syscall.h
@@ -4,9 +4,10 @@
 
 #define SYSCALL_NULL		0x00
 #define SYSCALL_TIME		0x01
-#define SYSCALL_EXIT		0x02
-#define SYSCALL_SPAWN		0x03
-#define SYSCALL_GETPID		0x04
+#define SYSCALL_GETPID		0x02
+#define SYSCALL_EXIT		0x03
+#define SYSCALL_SPAWN		0x04
+#define SYSCALL_WAIT		0x05
 
 // Memory
 #define SYSCALL_MMAP		0x08
diff --git a/sys/kern/syscall.c b/sys/kern/syscall.c
index d8649b7..aabdf9b 100644
--- a/sys/kern/syscall.c
+++ b/sys/kern/syscall.c
@@ -24,6 +24,13 @@ Syscall_Time()
     return KTime_GetEpochNS();
 }
 
+uint64_t
+Syscall_GetPID()
+{
+    Thread *cur = Thread_Current();
+    return cur->tid;
+}
+
 void
 Syscall_Exit(uint64_t status)
 {
@@ -101,10 +108,10 @@ Syscall_Spawn(uint64_t user_path)
 }
 
 uint64_t
-Syscall_GetPID()
+Syscall_Wait(uint64_t pid)
 {
-    Thread *cur = Thread_Current();
-    return cur->tid;
+    NOT_IMPLEMENTED();
+    return 0;
 }
 
 uint64_t
@@ -379,13 +386,15 @@ Syscall_Entry(uint64_t syscall, uint64_t a1, uint64_t a2,
 	    return 0;
 	case SYSCALL_TIME:
 	    return Syscall_Time();
+	case SYSCALL_GETPID:
+	    return Syscall_GetPID();
 	case SYSCALL_EXIT:
 	    Syscall_Exit(a1);
 	    return 0; // To eliminate warning
 	case SYSCALL_SPAWN:
 	    return Syscall_Spawn(a1);
-	case SYSCALL_GETPID:
-	    return Syscall_GetPID();
+	case SYSCALL_WAIT:
+	    return Syscall_Wait(a1);
 	case SYSCALL_MMAP:
 	    return Syscall_MMap(a1, a2, a3);
 	case SYSCALL_MUNMAP: