LibC: Write mostly functioning stdio

kernel/kernel/Process.cpp

@@ -304,6 +304,15 @@ namespace Kernel
 		return ret;
 	}
 
+	BAN::ErrorOr<void> Process::seek(int fd, size_t offset)
+	{
+		LockGuard _(m_lock);
+		TRY(validate_fd(fd));
+		auto& open_fd = open_file_description(fd);
+		open_fd.offset = offset;
+		return {};
+	}
+
 	BAN::ErrorOr<BAN::Vector<BAN::String>> Process::read_directory_entries(int fd)
 	{
 		OpenFileDescription open_fd_copy;
@@ -349,6 +358,14 @@ namespace Kernel
 		return {};
 	}
 
+	void Process::termid(char* buffer) const
+	{
+		if (m_tty == nullptr)
+			buffer[0] = '\0';
+		strcpy(buffer, "/dev/");
+		strcpy(buffer + 5, m_tty->name().data());
+	}
+
 	BAN::ErrorOr<BAN::String> Process::absolute_path_of(BAN::StringView path) const
 	{
 		if (path.empty())

kernel/kernel/Syscall.cpp

@@ -14,7 +14,7 @@ namespace Kernel
 	{
 		auto res = Process::current().read(fd, buffer, size);
 		if (res.is_error())
-			return res.error().get_error_code();
+			return -res.error().get_error_code();
 		return res.value();
 	}
 
@@ -22,7 +22,36 @@ namespace Kernel
 	{
 		auto res = Process::current().write(fd, buffer, size);
 		if (res.is_error())
-			return res.error().get_error_code();
+			return -res.error().get_error_code();
+		return res.value();
+	}
+
+	int sys_close(int fd)
+	{
+		auto res = Process::current().close(fd);
+		if (res.is_error())
+			return -res.error().get_error_code();
+		return 0;
+	}
+
+	int sys_seek(int fd, long offset)
+	{
+		auto res = Process::current().seek(fd, offset);
+		if (res.is_error())
+			return -res.error().get_error_code();
+		return 0;
+	}
+
+	void sys_termid(char* buffer)
+	{
+		Process::current().termid(buffer);
+	}
+
+	int sys_open(const char* path, int oflags)
+	{
+		auto res = Process::current().open(path, oflags);
+		if (res.is_error())
+			return -res.error().get_error_code();
 		return res.value();
 	}
 
@@ -44,10 +73,20 @@ namespace Kernel
 		case SYS_WRITE:
 			ret = sys_write((int)(uintptr_t)arg1, arg2, (size_t)(uintptr_t)arg3);
 			break;
-		default:
-			ret = -1;
-			dprintln("Unknown syscall");
+		case SYS_TERMID:
+			sys_termid((char*)arg1);
 			break;
+		case SYS_CLOSE:
+			ret = sys_close((int)(uintptr_t)arg1);
+			break;
+		case SYS_SEEK:
+			ret = sys_seek((int)(uintptr_t)arg1, (long)arg2);
+			break;
+		case SYS_OPEN:
+			ret = sys_open((const char*)arg1, (int)(uintptr_t)arg2);
+			break;
+		default:
+			Kernel::panic("Unknown syscall {}", syscall);
 		}
 
 		asm volatile("cli");