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Implementing a virtual serial port using DriverKit/SerialDriverKit
I'm trying to implement a virtual serial port driver for my ham radio projects which require emulating some serial port devices and I need to have a "backend" to translate the commands received by the virtual serial port into some network-based communications. I think the best way to do that is to subclass IOUserSerial? Based on the available docs on this class (https://developer.apple.com/documentation/serialdriverkit/iouserserial), I've done the basic implementation below. When the driver gets loaded, I can see sth like tty.serial-1000008DD in /dev and I can use picocom to do I/O on the virtual serial port. And I see TxDataAvailable() gets called every time I type a character in picocom. The problems are however, firstly, when TxDataAvailable() is called, the TX buffer is all-zero so although the driver knows there is some incoming data received from picocom, it cannot actually see the data in neither Tx/Rx buffers. Secondly, I couldn't figure out how to notify the system that there are data available for sending back to picocom. I call RxDataAvailable(), but nothing appears on picocom, and RxFreeSpaceAvailable() never gets called back. So I think I must be doing something wrong somewhere. Really appreciate it if anyone could point out how should I fix it, many thanks! VirtualSerialPortDriver.cpp: constexpr int bufferSize = 2048; using SerialPortInterface = driverkit::serial::SerialPortInterface; struct VirtualSerialPortDriver_IVars {     IOBufferMemoryDescriptor *ifmd, *rxq, *txq;     SerialPortInterface *interface;     uint64_t rx_buf, tx_buf;     bool dtr, rts; }; bool VirtualSerialPortDriver::init() {     bool result = false;     result = super::init();     if (result != true)     {         goto Exit;     }     ivars = IONewZero(VirtualSerialPortDriver_IVars, 1);     if (ivars == nullptr)     {         goto Exit;     }     kern_return_t ret;     ret = ivars->rxq->Create(kIOMemoryDirectionInOut, bufferSize, 0, &ivars->rxq);     if (ret != kIOReturnSuccess) {         goto Exit;     }     ret = ivars->txq->Create(kIOMemoryDirectionInOut, bufferSize, 0, &ivars->txq);     if (ret != kIOReturnSuccess) {         goto Exit;     }     IOAddressSegment ioaddrseg;     ivars->rxq->GetAddressRange(&ioaddrseg);     ivars->rx_buf = ioaddrseg.address;     ivars->txq->GetAddressRange(&ioaddrseg);     ivars->tx_buf = ioaddrseg.address;     return true; Exit:     return false; } kern_return_t IMPL(VirtualSerialPortDriver, HwActivate) {     kern_return_t ret;     ret = HwActivate(SUPERDISPATCH);     if (ret != kIOReturnSuccess) {         goto Exit;     }     // Loopback, set CTS to RTS, set DSR and DCD to DTR     ret = SetModemStatus(ivars->rts, ivars->dtr, false, ivars->dtr);     if (ret != kIOReturnSuccess) {         goto Exit;     } Exit:     return ret; } kern_return_t IMPL(VirtualSerialPortDriver, HwDeactivate) {     kern_return_t ret;     ret = HwDeactivate(SUPERDISPATCH);     if (ret != kIOReturnSuccess) {         goto Exit;     } Exit:     return ret; } kern_return_t IMPL(VirtualSerialPortDriver, Start) {     kern_return_t ret;   ret = Start(provider, SUPERDISPATCH);     if (ret != kIOReturnSuccess) {         return ret;     }     IOMemoryDescriptor *rxq_, *txq_;     ret = ConnectQueues(&ivars->ifmd, &rxq_, &txq_, ivars->rxq, ivars->txq, 0, 0, 11, 11);     if (ret != kIOReturnSuccess) {         return ret;     }     IOAddressSegment ioaddrseg;     ivars->ifmd->GetAddressRange(&ioaddrseg);     ivars->interface = reinterpret_cast<SerialPortInterface*>(ioaddrseg.address);     SerialPortInterface &intf = *ivars->interface;     ret = RegisterService();     if (ret != kIOReturnSuccess) {         goto Exit;     }     TxFreeSpaceAvailable(); Exit:     return ret; } void IMPL(VirtualSerialPortDriver, TxDataAvailable) {     SerialPortInterface &intf = *ivars->interface;     // Loopback     // FIXME consider wrapped case     size_t tx_buf_sz = intf.txPI - intf.txCI;     void *src = reinterpret_cast<void *>(ivars->tx_buf + intf.txCI); //    char src[] = "Hello, World!";     void *dest = reinterpret_cast<void *>(ivars->rx_buf + intf.rxPI);     memcpy(dest, src, tx_buf_sz);     intf.rxPI += tx_buf_sz;     RxDataAvailable();     intf.txCI = intf.txPI;     TxFreeSpaceAvailable();     Log("[TX Buf]: %{public}s", reinterpret_cast<char *>(ivars->tx_buf));     Log("[RX Buf]: %{public}s", reinterpret_cast<char *>(ivars->rx_buf)); // dmesg confirms both buffers are all-zero     Log("[TX] txPI: %d, txCI: %d, rxPI: %d, rxCI: %d, txqoffset: %d, rxqoffset: %d, txlogsz: %d, rxlogsz: %d",         intf.txPI, intf.txCI, intf.rxPI, intf.rxCI, intf.txqoffset, intf.rxqoffset, intf.txqlogsz, intf.rxqlogsz); } void IMPL(VirtualSerialPortDriver, RxFreeSpaceAvailable) {     Log("RxFreeSpaceAvailable() called!"); } kern_return_t   IMPL(VirtualSerialPortDriver,HwResetFIFO){     Log("HwResetFIFO() called with tx: %d, rx: %d!", tx, rx);     kern_return_t ret = kIOReturnSuccess;     return ret; } kern_return_t   IMPL(VirtualSerialPortDriver,HwSendBreak){     Log("HwSendBreak() called!");     kern_return_t ret = kIOReturnSuccess;     return ret; } kern_return_t   IMPL(VirtualSerialPortDriver,HwProgramUART){     Log("HwProgramUART() called, BaudRate: %u, nD: %d, nS: %d, P: %d!", baudRate, nDataBits, nHalfStopBits, parity);     kern_return_t ret = kIOReturnSuccess;     return ret; }      kern_return_t   IMPL(VirtualSerialPortDriver,HwProgramBaudRate){     Log("HwProgramBaudRate() called, BaudRate = %d!", baudRate);     kern_return_t ret = kIOReturnSuccess;     return ret; } kern_return_t   IMPL(VirtualSerialPortDriver,HwProgramMCR){     Log("HwProgramMCR() called, DTR: %d, RTS: %d!", dtr, rts);     ivars->dtr = dtr;     ivars->rts = rts;     kern_return_t ret = kIOReturnSuccess; Exit:     return ret; } kern_return_t  IMPL(VirtualSerialPortDriver, HwGetModemStatus){     *cts = ivars->rts;     *dsr = ivars->dtr;     *ri = false;     *dcd = ivars->dtr;     Log("HwGetModemStatus() called, returning CTS=%d, DSR=%d, RI=%d, DCD=%d!", *cts, *dsr, *ri, *dcd);     kern_return_t ret = kIOReturnSuccess;     return ret; } kern_return_t   IMPL(VirtualSerialPortDriver,HwProgramLatencyTimer){     Log("HwProgramLatencyTimer() called!");     kern_return_t ret = kIOReturnSuccess;     return ret; } kern_return_t   IMPL(VirtualSerialPortDriver,HwProgramFlowControl){     Log("HwProgramFlowControl() called! arg: %u, xon: %d, xoff: %d", arg, xon, xoff);     kern_return_t ret = kIOReturnSuccess; Exit:     return ret; }
1
0
2.1k
Feb ’25
Looking for USBSerialDriver sample code
I would like to write a driver that supports our custom USB-C connected device, which provides a serial port interface. USBSerialDriverKit looks like the solution I need. Unfortunately, without a decent sample, I'm not sure how to accomplish this. The DriverKit documentation does a good job of telling me what APIs exist but it is very light on semantic information and details about how to use all of these API elements. A function call with five unexplained parameters just is that useful to me. Does anyone have or know of a resource that can help me figure out how to get started?
1
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717
Feb ’25
iphone mirroring
Hi Team , I want to create a system where i can mirror the iPhone screen connected through USB and control it from the web browser. can anyone help me ? Thanks , Mukta
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0
379
Jan ’25
Crash in IOService::Create
I am getting an unexpected crash from IOService::Create() when attempting to create a new user-client. The crash is a nullptr exception in OSCopyInObjects(). The last call from my code was IOService::Create(). As far as I can tell, all the input parameters to Create() are correct, and the Info.plist is has the correct key and class information - indeed, if I corrupt these I get an error status return rather than a crash. Any suggestions as to what could be causing this? I suspect that the problem may be related from a change in the underlying application that is creating the user client. This was modified from a standard app to a daemon, following the advice here: https://developer.apple.com/documentation/xcode/signing-a-daemon-with-a-restricted-entitlement. However, it is the driver that crashes - not the host opening the user client.
1
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515
Jan ’25
DriverKit CppUserClient Searching for dext service but Failed opening service with error: 0xe00002c7
Hi Everybody, Follow Communicating between a DriverKit extension and a client app to migrate our kext to dext. The dext might have been loaded successfully by using the command systemextensionsctl list, the dext is loaded and enabled. % sectl list 1 extension(s) --- com.apple.system_extension.driver_extension enabled active teamID bundleID (version) name [state] * * K3TDMD9Y6B com.accusys.scsidriver (1.0/1) com.accusys.scsidriver [activated enabled] We try to use the CppUserClient.cpp to communicate with the dext, but can not get the dext service. The debug message as below: Failed opening service with error: 0xe00002c7. Here is the part of CppUserClient.cpp static const char* dextIdentifier = "com.accusys.scsidriver"; kern_return_t ret = kIOReturnSuccess; io_iterator_t iterator = IO_OBJECT_NULL; io_service_t service = IO_OBJECT_NULL; ret = IOServiceGetMatchingServices(kIOMasterPortDefault, IOServiceMatching("IOUserServer"), &iterator); printf("dextIdentifier = %s\n", dextIdentifier); printf("IOServiceNameMatching return = %d\n", ret); if (ret != kIOReturnSuccess) { printf("Unable to find service for identifier with error: 0x%08x.\n", ret); PrintErrorDetails(ret); } printf("Searching for dext service...\n"); while ((service = IOIteratorNext(iterator)) != IO_OBJECT_NULL) { // Open a connection to this user client as a server to that client, and store the instance in "service" ret = IOServiceOpen(service, mach_task_self_, kIOHIDServerConnectType, &connection); if (ret == kIOReturnSuccess) { printf("\tOpened service.\n"); break; } else { printf("\tFailed opening service with error: 0x%08x.\n", ret); } IOObjectRelease(service); } IOObjectRelease(iterator); if (service == IO_OBJECT_NULL) { printf("Failed to match to device.\n"); return EXIT_FAILURE; } The console output message is dextIdentifier = com.accusys.scsidriver IOServiceNameMatching return = 0 Searching for dext service... Failed opening service with error: 0xe00002c7. Failed opening service with error: 0xe00002c7. Failed opening service with error: 0xe00002c7. Failed opening service with error: 0xe00002c7. Failed to match to device. Here is the log show message fredapp start UserInitializeController pcitest: fredapp pci vendorID: 14d6 deviceID: 626f fredapp nnnnnew configuaration read32 0x10 info: 1 fredapp nnnnnew configuaration read32 0x14 info: 80100004 fredapp new 128 before enable busmaster ReqMSGport_info 0x00000040 : fffff pcitest: fredapp 131 pci ConfigurationRead16 busmaster value 0 pcitest: fredapp 134 Enable BusMaster and IO space done...... locate 139 fredapp MemoryWrite32 function done...... fredapp new 143 after enable busmaster ReqMSGport_info 0x00000040 : 0 fredapp newwww before GetBARInfo memoryIndex1 info is: 5 fredapp GetBARInfo 1 kernel return status is: 0 fredapp GetBARInfo memoryIndex1 info is: 0 fredapp GetBARInfo barSize1 info is: 262144 fredapp GetBARInfo barType1 info is: 0 fredapp GetBARInfo result0 info is: 3758097136 fredapp GetBARInfo memoryIndex0 info is: 0 fredapp GetBARInfo barSize0 info is: 0 fredapp GetBARInfo barType0 info is: 0 pcitest: newwww fredapp againnnn test ReqMSGport info: 8 fredapp Start MPIO_Init_Prepare fredapp end MPIO_Init_Prepare. fredapp call 741 Total_memory_size: 1bb900 fredapp Start MemoryAllocationForAME_Module. fredapp IOBufferMemoryDescriptor create return status info is kIOReturnSuc fredapp IOBufferMemoryDescriptor virtualAddressSegment address info: 0x1 fredapp virtualAddressSegment length info: 0x00080000 fredapp end IOBufferMemoryDescriptor Create. fredapp dmaSpecification maxAddressBits: 0x00000000 fredapp dmaSpecification maxAddressBits: 0x00000027 fredapp IODMACommand create return status info is kIOReturnSuccess fredapp end IODMACommand Create. fredapp PrepareForDMA return status info is kIOReturnSuccess fredapp PrepareForDMA return status info is 0x00000000 fredapp Allocate memory PrepareforDMA return flags info: 0x00000003 fredapp Allocate memory PrepareforDMA return segmentsCount info: 0x00000 fredapp Allocate memory PrepareforDMA return physicalAddressSegment info: fredapp IOBufferMemoryDescriptor virtualAddressSegment address info-2: 0 fredapp verify data success init() - Finished. fredapp start UserGetDMASpecification fredapp end UserGetDMASpecification fredapp start UserMapHBAData fredapp end UserMapHBAData fredapp start UserStartController fredapp interruptType info is 0x00010000 fredapp PCI Dext interrupt final value return status info is 0x00000000 Any suggestions? Best Regards, Charles
6
0
804
Jan ’25