kernel+libc+init: Add getppid() and wait()

apps/init.c

@@ -47,5 +47,5 @@ int main()
         return 1;
     }
 
-    while (1) { waitpid(-1, NULL, 0); }
+    while (1) wait(NULL);
 }

kernel/src/sys/id.cpp

@@ -5,3 +5,8 @@ Result<u64> sys_getpid(Registers*, SyscallArgs)
 {
     return Scheduler::current()->id;
 }
+
+Result<u64> sys_getppid(Registers*, SyscallArgs)
+{
+    return Scheduler::current()->parent_id;
+}

libc/include/sys/wait.h

@@ -14,6 +14,9 @@ extern "C"
     /* Wait for a child process to exit. */
     pid_t waitpid(pid_t pid, int* status, int options);
 
+    /* Wait for any child process to exit. */
+    pid_t wait(int* status);
+
 #ifdef __cplusplus
 }
 #endif

libc/include/unistd.h

@@ -25,6 +25,9 @@ extern "C"
     /* Return the current process' process ID. */
     pid_t getpid(void);
 
+    /* Return the current process' parent process ID. */
+    pid_t getppid(void);
+
     /* Replace the current process with another one. On success, does not return. */
     int execv(const char* path, char* const* argv);
 

libc/src/sys/wait.cpp

@@ -10,4 +10,9 @@ extern "C"
         long rc = syscall(SYS_waitpid, pid, status, options);
         __errno_return(rc, pid_t);
     }
+
+    pid_t wait(int* status)
+    {
+        return waitpid(-1, status, 0);
+    }
 }

libc/src/unistd.cpp

@@ -19,6 +19,11 @@ extern "C"
         return (pid_t)syscall(SYS_getpid);
     }
 
+    pid_t getppid(void)
+    {
+        return (pid_t)syscall(SYS_getppid);
+    }
+
     int execv(const char* path, char* const* argv)
     {
         long rc = syscall(SYS_exec, path, argv);

libluna/include/luna/Syscall.h

@@ -2,7 +2,7 @@
 
 #define enumerate_syscalls(_e)                                                                                         \
     _e(exit) _e(clock_gettime) _e(mmap) _e(munmap) _e(usleep) _e(open) _e(close) _e(read) _e(getpid) _e(write)         \
-        _e(lseek) _e(mkdir) _e(exec) _e(mknod) _e(fork) _e(waitpid)
+        _e(lseek) _e(mkdir) _e(exec) _e(mknod) _e(fork) _e(waitpid) _e(getppid)
 
 enum Syscalls
 {