iPXE will currently drop to TPL_APPLICATION whenever the current
system time is obtained via currticks(), since the system time
mechanism relies on a timer that can fire only when the TPL is below
TPL_CALLBACK.
This can cause unexpected behaviour if the system time is obtained in
the middle of an API call into iPXE by external code. For example,
MnpDxe sets up a 10ms periodic timer running at TPL_CALLBACK to poll
the underling EFI_SIMPLE_NETWORK_PROTOCOL device for received packets.
If the resulting poll within iPXE happens to hit a code path that
requires obtaining the current system time (e.g. due to reception of
an STP packet, which affects iPXE's blocked link timer), then iPXE
will end up temporarily dropping to TPL_APPLICATION. This can
potentially result in retriggering the MnpDxe periodic timer, causing
code to be unexpectedly re-entered.
Fix by recording the external TPL at any entry point into iPXE and
dropping only as far as this external TPL, rather than dropping
unconditionally to TPL_APPLICATION.
The side effect of this change is that iPXE's view of the current
system time will be frozen for the duration of any API calls made into
iPXE by external code at TPL_CALLBACK or above. Since any such
external code is already responsible for allowing execution at
TPL_APPLICATION to occur, then this should not cause a problem in
practice.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
iPXE will often have multiple drivers available for a USB device. For
example: some USB network devices will support both RNDIS and CDC-ECM,
and any device may be consumed by the fallback "usbio" driver under
UEFI in order to expose an EFI_USB_IO_PROTOCOL instance.
The driver scoring mechanism is used to select a device configuration
based on the availability of drivers for the interfaces exposed in
each configuration.
For the case of RNDIS versus CDC-ECM, this mechanism will always
produce the correct result since RNDIS and CDC-ECM will not exist
within the same configuration and so each configuration will receive a
score based on the relevant driver.
This guarantee does not hold for the "usbio" driver, which will match
against any device. It is a surprising coincidence that the "usbio"
driver seems to usually end up at the tail end of the USB drivers
list, thereby resulting in the expected behaviour.
Guarantee the expected behaviour by explicitly placing the "usbio"
driver at the end of the USB drivers list.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The length as returned by UsbGetSupportedLanguages() should not
include the length of the descriptor header itself.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The call to UninstallMultipleProtocolInterfaces() will implicitly
disconnect any relevant controllers, and there is no specified
requirement to explicitly call DisconnectController() prior to
callling UninstallMultipleProtocolInterfaces().
However, some UEFI implementations (observed with the USB keyboard
driver on a Microsoft Surface Go) will fail to implicitly disconnect
the controller and will consequently fail to uninstall the protocols.
The net effect is that unplugging and replugging a USB keyboard may
leave the keyboard in a non-functional state.
Work around these broken UEFI implementations by including an
unnecessary call to DisconnectController() before the call to
UninstallMultipleProtocolInterfaces().
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some UEFI USB drivers (e.g. the UsbKbDxe driver in EDK2) will react to
a reported EFI_USB_ERR_STALL by attempting to clear the endpoint halt.
This is redundant with iPXE's EFI_USB_IO_PROTOCOL implementation,
since endpoint stalls are cleared automatically by the USB core as
needed.
The UEFI USB driver's attempt to clear the endpoint halt can introduce
an unwanted 5 second delay per endpoint if the USB error was the
result of a device being physically removed, since the control
transfer will always time out.
Fix by reporting all USB errors as EFI_USB_ERR_SYSTEM instead of
EFI_USB_ERR_STALL.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Some UEFI USB drivers (observed with the keyboard driver on a
Microsoft Surface Go) will react to an asynchronous USB transfer
failure by terminating the transfer from within the completion
handler. This closes the USB endpoint and, in the current
implementation, frees the containing structure.
This can lead to use-after-free bugs after the UEFI USB driver's
completion handler returns, since the calling code in iPXE expects
that a completion handler will not perform a control-flow action such
as terminating the transfer.
Fix by leaving the USB endpoint structure allocated until the device
is finally removed, as is already done (as an optimisation) for
control and bulk transfers.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
The various USB specifications all use one-based numbering for ports.
This scheme is applied consistently across the various relevant
specifications, covering both port numbers that appear on the wire
(i.e. downstream hub port numbers) and port numbers that exist only
logically (i.e. root hub port numbers).
The UEFI specification is ambiguous about the port numbers as used for
the ParentPortNumber field within a USB_DEVICE_PATH structure. As of
UEFI specification version 2.8 errata B:
- section 10.3.4.5 just states "USB Parent Port Number" with no
indication of being zero-based or one-based
- section 17.1.1 notes that for the EFI_USB2_HC_PROTOCOL, references
to PortNumber parameters are zero-based for root hub ports
- section 17.1.1 also mentions a TranslatorPortNumber used by
EFI_USB2_HC_PROTOCOL, with no indication of being zero-based or
one-based
- there are no other mentions of USB port numbering schemes.
Experimentation and inspection of the EDK2 codebase reveals that at
least the EDK2 reference implementation will use zero-based numbering
for both root and non-root hub ports when populating a USB_DEVICE_PATH
structure (though will inconsistently use one-based numbering for the
TranslatorPortNumber parameter).
Use zero-based numbering for both root and non-root hub ports when
constructing a USB_DEVICE_PATH in order to match the behaviour of the
EDK2 implementation.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
As noted in the comments, UEFI manages to combines the all of the
worst aspects of both a polling design (inefficiency and inability to
sleep until something interesting happens) and of an interrupt-driven
design (the complexity of code that could be preempted at any time,
thanks to UEFI timers).
This causes problems in particular for UEFI USB keyboards: the
keyboard driver calls UsbAsyncInterruptTransfer() to set up a periodic
timer which is used to poll the USB bus. This poll may interrupt a
critical section within iPXE, typically resulting in list corruption
and either a hang or reboot.
Work around this problem by mirroring the BIOS design, in which we run
with interrupts disabled almost all of the time.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Allow the UEFI platform firmware to provide drivers for unrecognised
devices, by exposing our own implementation of EFI_USB_IO_PROTOCOL.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
