kernel+libc: Implement getpgid()

kernel/src/sys/id.cpp

@@ -128,6 +128,20 @@ Result<u64> sys_setpgid(Registers*, SyscallArgs args)
     return 0;
 }
 
+Result<u64> sys_getpgid(Registers*, SyscallArgs args)
+{
+    pid_t pid = (pid_t)args[0];
+
+    auto* current = Scheduler::current();
+    if (pid == 0) pid = (pid_t)current->id;
+
+    if (pid < 0) return err(EINVAL);
+
+    auto* thread = TRY(Result<Thread*>::from_option(Scheduler::find_by_pid(pid), ESRCH));
+
+    return (u64)thread->pgid;
+}
+
 Result<u64> sys_fchmodat(Registers*, SyscallArgs args)
 {
     int dirfd = (int)args[0];

libc/include/unistd.h

@@ -45,6 +45,9 @@ extern "C"
     /* Return the current process' effective group ID. */
     gid_t getegid(void);
 
+    /* Return a process' process group ID. */
+    pid_t getpgid(pid_t pid);
+
     /* Set the current process' user IDs. */
     int setuid(uid_t uid);
 

libc/src/unistd.cpp

@@ -120,6 +120,12 @@ extern "C"
         return (gid_t)syscall(SYS_getegid);
     }
 
+    pid_t getpgid(pid_t pid)
+    {
+        long rc = syscall(SYS_getpgid, pid);
+        __errno_return(rc, pid_t);
+    }
+
     int setuid(uid_t uid)
     {
         long rc = syscall(SYS_setuid, uid);

libluna/include/luna/Syscall.h

@@ -6,7 +6,8 @@
             _e(getgid) _e(getegid) _e(setuid) _e(setgid) _e(seteuid) _e(setegid) _e(fchmodat) _e(fchownat) _e(ioctl)   \
                 _e(fstatat) _e(chdir) _e(getcwd) _e(unlinkat) _e(uname) _e(sethostname) _e(dup2) _e(pipe) _e(mount)    \
                     _e(umount) _e(pstat) _e(getrusage) _e(symlinkat) _e(readlinkat) _e(umask) _e(linkat) _e(faccessat) \
-                        _e(pivot_root) _e(sigreturn) _e(sigaction) _e(kill) _e(sigprocmask) _e(setpgid) _e(isatty)
+                        _e(pivot_root) _e(sigreturn) _e(sigaction) _e(kill) _e(sigprocmask) _e(setpgid) _e(isatty)     \
+                            _e(getpgid)
 
 enum Syscalls
 {