Kernel/LibC: Implement `fchdir`, cleanup `chdir` and `getcwd`

kernel/include/kernel/Process.h

@@ -72,8 +72,9 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_nanosleep(const timespec* rqtp, timespec* rmtp);
 		BAN::ErrorOr<long> sys_setitimer(int which, const itimerval* value, itimerval* ovalue);
 
-		BAN::ErrorOr<long> sys_setpwd(const char* path);
+		BAN::ErrorOr<long> sys_getcwd(char* buffer, size_t size);
-		BAN::ErrorOr<long> sys_getpwd(char* buffer, size_t size);
+		BAN::ErrorOr<long> sys_chdir(const char* path);
+		BAN::ErrorOr<long> sys_fchdir(int fildes);
 
 		BAN::ErrorOr<long> sys_setuid(uid_t);
 		BAN::ErrorOr<long> sys_setgid(gid_t);

kernel/kernel/Process.cpp

@@ -1648,17 +1648,7 @@ namespace Kernel
 		return TRY(m_open_file_descriptors.read_dir_entries(fd, list, list_len));
 	}
 
-	BAN::ErrorOr<long> Process::sys_setpwd(const char* path)
+	BAN::ErrorOr<long> Process::sys_getcwd(char* buffer, size_t size)
-	{
-		LockGuard _(m_process_lock);
-
-		auto file = TRY(find_file(AT_FDCWD, path, O_SEARCH));
-		m_working_directory = BAN::move(file);
-
-		return 0;
-	}
-
-	BAN::ErrorOr<long> Process::sys_getpwd(char* buffer, size_t size)
 	{
 		LockGuard _(m_process_lock);
 
@@ -1673,6 +1663,28 @@ namespace Kernel
 		return (long)buffer;
 	}
 
+	BAN::ErrorOr<long> Process::sys_chdir(const char* path)
+	{
+		LockGuard _(m_process_lock);
+
+		TRY(validate_string_access(path));
+
+		auto file = TRY(find_file(AT_FDCWD, path, O_SEARCH));
+		m_working_directory = BAN::move(file);
+
+		return 0;
+	}
+
+	BAN::ErrorOr<long> Process::sys_fchdir(int fildes)
+	{
+		LockGuard _(m_process_lock);
+
+		auto file = TRY(m_open_file_descriptors.file_of(fildes));
+		m_working_directory = BAN::move(file);
+
+		return 0;
+	}
+
 	BAN::ErrorOr<long> Process::sys_mmap(const sys_mmap_t* args)
 	{
 		{

userspace/libraries/LibC/include/sys/syscall.h

@@ -32,8 +32,9 @@ __BEGIN_DECLS
 	O(SYS_GET_GID,			getgid)			\
 	O(SYS_GET_EUID,			geteuid)		\
 	O(SYS_GET_EGID,			getegid)		\
-	O(SYS_GET_PWD,			getpwd)			\
+	O(SYS_GETCWD,			getcwd)			\
-	O(SYS_SET_PWD,			setpwd)			\
+	O(SYS_CHDIR,			chdir)			\
+	O(SYS_FCHDIR,			fchdir)			\
 	O(SYS_CLOCK_GETTIME,	clock_gettime)	\
 	O(SYS_PIPE,				pipe)			\
 	O(SYS_DUP2,				dup2)			\

userspace/libraries/LibC/unistd.cpp

@@ -426,7 +426,7 @@ char* getcwd(char* buf, size_t size)
 		return nullptr;
 	}
 
-	if (syscall(SYS_GET_PWD, buf, size) == 0)
+	if (syscall(SYS_GETCWD, buf, size) == 0)
 		return nullptr;
 
 	return buf;
@@ -434,7 +434,12 @@ char* getcwd(char* buf, size_t size)
 
 int chdir(const char* path)
 {
-	return syscall(SYS_SET_PWD, path);
+	return syscall(SYS_CHDIR, path);
+}
+
+int fchdir(int fildes)
+{
+	return syscall(SYS_FCHDIR, fildes);
 }
 
 int chown(const char* path, uid_t owner, gid_t group)