Function SysSelect

Kernel/src/arch/x86_64/syscalls.cpp:2090–2216

//////////////////////// \brief SysSelect(nfds, readfds, writefds, exceptfds, timeout) Set a file handle's mode/status flags \param nfds (int) number of file descriptors \param readfds (fd_set) check for readable fds \param writefds (fd_set) check for writable fds \param exceptfds (fd_set) check for exceptions on fds \param timeout (timespec) timeout period \return number of events on success, n

/// \return number of events on success, negative error code on failure
/////////////////////////////
long SysSelect(regs64_t* r){
	process_t* currentProcess = Scheduler::GetCurrentProcess();

	int nfds = static_cast<int>(SC_ARG0(r));
	fd_set_t* readFdsMask = reinterpret_cast<fd_set_t*>(SC_ARG1(r));
	fd_set_t* writeFdsMask = reinterpret_cast<fd_set_t*>(SC_ARG2(r));
	fd_set_t* exceptFdsMask = reinterpret_cast<fd_set_t*>(SC_ARG3(r));
	timespec_t* timeout = reinterpret_cast<timespec_t*>(SC_ARG4(r));

	if(!((!readFdsMask || Memory::CheckUsermodePointer(SC_ARG1(r), sizeof(fd_set_t), currentProcess->addressSpace))
		&& (!writeFdsMask || Memory::CheckUsermodePointer(SC_ARG2(r), sizeof(fd_set_t), currentProcess->addressSpace))
		&& (!exceptFdsMask || Memory::CheckUsermodePointer(SC_ARG3(r), sizeof(fd_set_t), currentProcess->addressSpace))
		&& Memory::CheckUsermodePointer(SC_ARG4(r), sizeof(timespec_t), currentProcess->addressSpace))){
		return -EFAULT; // Only return EFAULT if read/write/exceptfds is not null
	}

	List<Pair<fs_fd_t*, int>> readfds;
	List<Pair<fs_fd_t*, int>> writefds;
	List<Pair<fs_fd_t*, int>> exceptfds;

	auto getHandleSafe = [&](int fd) -> fs_fd_t* {
		if(static_cast<unsigned>(fd) > currentProcess->fileDescriptors.get_length()){
			return nullptr;
		}
		return currentProcess->fileDescriptors[fd]; // If fd is null then this will return null as if out of range
	};

	for(int i = 0; i < 128 && i * 8 < nfds; i++){
		char read = 0, write = 0, except = 0;
		if(readFdsMask) {
			read = readFdsMask->fds_bits[i];
			readFdsMask->fds_bits[i] = 0; // With select the fds are cleared to 0 unless they are ready
		}

		if(writeFdsMask){
			write = writeFdsMask->fds_bits[i];
			writeFdsMask->fds_bits[i] = 0;
		}
		
		if(exceptFdsMask){
			except = exceptFdsMask->fds_bits[i];
			exceptFdsMask->fds_bits[i] = 0;
		}

		for(int j = 0; j < 8 && (i * 8 + j) < nfds; j++){
			if((read >> j) & 0x1){
				fs_fd_t* h = getHandleSafe(i * 8 + j);
				if(!h){
					return -EBADF;
				}

				readfds.add_back(Pair<fs_fd_t*, int>(h, i * 8 + j));
			}
			
			if((write >> j) & 0x1){
				fs_fd_t* h = getHandleSafe(i * 8 + j);
				if(!h){
					return -EBADF;