Kernel/LibC: add SYS_{SET,GET}_PWD and chdir, getpwd

kernel/include/kernel/Process.h

@@ -58,6 +58,9 @@ namespace Kernel
 
 		BAN::ErrorOr<void> setenvp(char** envp);
 
+		BAN::ErrorOr<void> set_pwd(const char* path);
+		BAN::ErrorOr<char*> get_pwd(char* buffer, size_t size);
+
 		BAN::ErrorOr<void> set_uid(uid_t);
 		BAN::ErrorOr<void> set_gid(gid_t);
 		BAN::ErrorOr<void> set_euid(uid_t);

kernel/kernel/Process.cpp

@@ -667,6 +667,38 @@ namespace Kernel
 		return {};
 	}
 
+	BAN::ErrorOr<void> Process::set_pwd(const char* path)
+	{
+		BAN::String absolute_path;
+
+		{
+			LockGuard _(m_lock);
+			absolute_path = TRY(absolute_path_of(path));
+		}
+
+		auto file = TRY(VirtualFileSystem::get().file_from_absolute_path(m_credentials, absolute_path, O_SEARCH));
+		if (!file.inode->mode().ifdir())
+			return BAN::Error::from_errno(ENOTDIR);
+
+		LockGuard _(m_lock);
+		m_working_directory = BAN::move(file.canonical_path);
+
+		return {};
+	}
+
+	BAN::ErrorOr<char*> Process::get_pwd(char* buffer, size_t size)
+	{
+		LockGuard _(m_lock);
+
+		if (size < m_working_directory.size() + 1)
+			return BAN::Error::from_errno(ERANGE);
+		
+		memcpy(buffer, m_working_directory.data(), m_working_directory.size());
+		buffer[m_working_directory.size()] = '\0';
+
+		return buffer;
+	}
+
 	BAN::ErrorOr<BAN::String> Process::working_directory() const
 	{
 		BAN::String result;

kernel/kernel/Syscall.cpp

@@ -228,6 +228,22 @@ namespace Kernel
 		return Process::current().get_egid();
 	}
 
+	long sys_get_pwd(char* buffer, size_t size)
+	{
+		auto ret = Process::current().get_pwd(buffer, size);
+		if (ret.is_error())
+			return -ret.error().get_error_code();
+		return (long)ret.value();
+	}
+
+	long sys_set_pwd(const char* path)
+	{
+		auto ret = Process::current().set_pwd(path);
+		if (ret.is_error())
+			return -ret.error().get_error_code();
+		return 0;
+	}
+
 	extern "C" long sys_fork_trampoline();
 
 	extern "C" long cpp_syscall_handler(int syscall, uintptr_t arg1, uintptr_t arg2, uintptr_t arg3, uintptr_t arg4, uintptr_t arg5)
@@ -335,6 +351,12 @@ namespace Kernel
 		case SYS_GET_EGID:
 			ret = sys_get_egid();
 			break;
+		case SYS_GET_PWD:
+			ret = sys_get_pwd((char*)arg1, (size_t)arg2);
+			break;
+		case SYS_SET_PWD:
+			ret = sys_set_pwd((const char*)arg1);
+			break;
 		default:
 			dwarnln("Unknown syscall {}", syscall);
 			ret = -ENOSYS;

libc/include/sys/syscall.h

@@ -36,6 +36,8 @@ __BEGIN_DECLS
 #define SYS_GET_GID 29
 #define SYS_GET_EUID 30
 #define SYS_GET_EGID 31
+#define SYS_GET_PWD 32
+#define SYS_SET_PWD 33
 
 __END_DECLS
 

libc/unistd.cpp

@@ -233,6 +233,19 @@ long syscall(long syscall, ...)
 			ret = Kernel::syscall(SYS_GET_EGID);
 			break;
 		}
+		case SYS_GET_PWD:
+		{
+			char* buffer = va_arg(args, char*);
+			size_t size = va_arg(args, size_t);
+			ret = Kernel::syscall(SYS_GET_PWD, (uintptr_t)buffer, size);
+			break;
+		}
+		case SYS_SET_PWD:
+		{
+			const char* path = va_arg(args, const char*);
+			ret = Kernel::syscall(SYS_SET_PWD, (uintptr_t)path);
+			break;
+		}
 		default:
 			puts("LibC: Unhandeled syscall");
 			ret = -ENOSYS;
@@ -342,6 +355,26 @@ unsigned int sleep(unsigned int seconds)
 	return syscall(SYS_SLEEP, seconds);
 }
 
+char* getcwd(char* buf, size_t size)
+{
+	if (size == 0)
+	{
+		errno = EINVAL;
+		return nullptr;
+	}
+
+	if ((char*)syscall(SYS_GET_PWD, buf, size) == nullptr)
+		return nullptr;
+
+	setenv("PWD", buf, 1);
+	return buf;
+}
+
+int chdir(const char* path)
+{
+	return syscall(SYS_SET_PWD, path);
+}
+
 uid_t getuid(void)
 {
 	return syscall(SYS_GET_UID);