Red Bear OS
260003331e
Three bugs in the xHCI endpoint-restart path used by all error recovery (stall hard reset, transaction-error soft retry, resource retry, split/babble hard reset): 1. Latent deadlock: restart_endpoint held the port_states write guard across set_tr_deque_ptr(), which internally re-acquires a read guard on the same key (std RwLock read-while-write on one thread). Unobserved because error injection is not yet exercised at runtime (P8-C). Fixed by scoping phase-1 ring priming so the guard drops before the async command. 2. Doorbell ordering violated xHCI spec 4.6.8/4.6.10: after Reset Endpoint the TR Dequeue Pointer is undefined, so Set TR Dequeue Pointer must complete BEFORE the doorbell transitions the endpoint Stopped->Running. The old order (doorbell first) ran the endpoint with an undefined dequeue pointer — undefined xHC behavior on real hardware. Linux rings the doorbell from the Set TR Dequeue command completion path (xhci_handle_cmd_set_deq, ring.c:1416-1554); xhcid now issues Set TR Dequeue, awaits completion, then rings. 3. Priming NoOp never executed: ring.register() was captured after ring.next() advanced the enqueue index, so the dequeue pointed past the NoOp (dead TRB). Now captured before next(), priming the hardware dequeue AT the NoOp so the xHC executes it on restart — same semantics as Linux xhci_move_dequeue_past_td pointing at the first valid TRB. Verified: cargo check clean (138 warnings, unchanged), 43/43 tests pass.
Drivers
- Libraries
- Services
- Hardware Interfaces
- Devices
- System Interfaces
- System Calls
- Schemes
- Contribution Details
Libraries
- amlserde - Library to provide serialization/deserialization of the AML symbol table from ACPI
- common - Library with shared driver code
- executor - Library to run Rust futures and integrate the executor in an interrupt+queue model without a separated reactor thread
- graphics/console-draw - Library with shared terminal drawing code
- graphics/driver-graphics - Library with shared graphics code
- graphics/graphics-ipc - Library with graphics IPC shared code
- net/driver-network - Library with shared networking code
- storage/partitionlib - Library with MBR and GPT code
- storage/driver-block - Library with shared storage code
- virtio-core - VirtIO driver library
Services
- graphics/fbbootlogd - Daemon for boot log drawing
- graphics/fbcond - Terminal daemon
- hwd - Daemon that handle the ACPI and DeviceTree booting
- inputd - Multiplexes input from multiple input drivers and provides that to Orbital
- pcid-spawner - Daemon for PCI-based device driver spawn
- storage/lived - Daemon for live disk
- redoxerd - Daemon that send/receive terminal text between the host system and QEMU
Hardware Interfaces
- acpid - ACPI interface driver
- pcid - PCI and PCI Express driver
Devices
CPU
- rtcd - x86 Real Time Clock driver
Controllers
- usb/xhcid - xHCI USB controller driver
Storage
- storage/ahcid - AHCI (SATA) driver
- storage/bcm2835-sdhcid - BCM2835 storage driver
- storage/ided - PATA (IDE) driver
- storage/nvmed - NVMe driver
- storage/virtio-blkd - VirtIO block device driver
- storage/usbscsid - USB SCSI driver
Graphics
- graphics/ihdgd - Intel graphics driver
- graphics/vesad - VESA video driver
- graphics/virtio-gpud - VirtIO-GPU device driver
Input
- input/ps2d - PS/2 interface driver
- input/usbhidd - USB HID driver
- usb/usbhubd - USB Hub driver
- usb/usbctl - TODO
Sound
- audio/ac97d - AC'97 codec driver
- audio/ihdad - Intel HD Audio chipset driver
- audio/sb16d - Sound Blaster sound card driver
Networking
- net/e1000d - Intel Gigabit ethernet driver
- net/ixgbed - Intel 10 Gigabit ethernet driver
- net/rtl8139d, net/rtl8168d - Realtek ethernet drivers
- net/virtio-netd - VirtIO network device driver
Virtualization
- vboxd - VirtualBox driver
Some drivers are work-in-progress and incomplete, read this tracking issue to verify.
System Interfaces
This section explain the system interfaces used by drivers.
System Calls
iopl: system call that sets the I/O privilege level. x86 has four privilege rings (0/1/2/3), of which the kernel runs in ring 0 and userspace in ring 3. IOPL can only be changed by the kernel, for obvious security reasons, and therefore the Redox kernel needs root to set it. It is unique for each process. Processes with IOPL=3 can access I/O ports, and the kernel can access them as well.
Schemes
/scheme/memory/physical: Allows mapping physical memory frames to driver-accessible virtual memory pages, with various available memory types:/scheme/memory/physical: Default memory type (currently writeback)/scheme/memory/physical@wbWriteback cached memory/scheme/memory/physical@uc: Uncacheable memory/scheme/memory/physical@wc: Write-combining memory
/scheme/irq: Allows getting events from interrupts. It is used primarily by listening for its file descriptors using the/scheme/eventscheme.
Contribution Details
Driver Design
A device driver on Redox is an user-space daemon that use system calls and schemes to work, while operating systems with monolithic kernels drivers use internal kernel APIs instead of common program APIs.
If you want to port a driver from a monolithic operating system to Redox you will need to rewrite the driver with reverse enginnering of the code logic, because the logic is adapted to internal kernel APIs (it's a hard task if the device is complex, datasheets are much more easy).
Write a Driver
Datasheets are preferable (much more easy depending on device complexity), when they are freely available. Be aware that datasheets are often provided under a Non-Disclosure Agreement from hardware vendors, which can affect the ability to create an MIT-licensed driver.
If datasheets aren't available you need to do reverse-engineering of BSD or Linux drivers (if you want use a Linux driver as reference for your Redox driver please ask in the Chat before the implementation to know/satisfy the license requirements and not waste your time, also if you use a BSD driver not licensed as BSD as reference).
Libraries
You should use the redox-scheme and redox_event libraries to create your drivers, you can also read the example driver or read the code of other drivers with the same type of your device.
Before testing your changes be aware of this.
References
If you want to reverse enginner the existing drivers, you can access the BSD code using these links:
How To Contribute
To learn how to contribute to this system component you need to read the following document:
Development
To learn how to do development with this system component inside the Redox build system you need to read the Build System and Coding and Building pages.
How To Build
To build this system component you need to download the Redox build system, you can learn how to do it on the Building Redox page.
This is necessary because they only work with cross-compilation to a Redox virtual machine or real hardware, but you can do some testing from Linux.