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>
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 active timer (providing udelay() and currticks()) to be
selected at runtime based on probing during the INIT_EARLY stage of
initialisation.
TICKS_PER_SEC is now a fixed compile-time constant for all builds, and
is independent of the underlying clock tick rate. We choose the value
1024 to allow multiplications and divisions on seconds to be converted
to bit shifts.
TICKS_PER_MS is defined as 1, allowing multiplications and divisions
on milliseconds to be omitted entirely. The 2% inaccuracy in this
definition is negligible when using the standard BIOS timer (running
at around 18.2Hz).
TIMER_RDTSC now checks for a constant TSC before claiming to be a
usable timer. (This timer can be tested in KVM via the command-line
option "-cpu host,+invtsc".)
Signed-off-by: Michael Brown <mcb30@ipxe.org>
EFI provides no clean way for device drivers to shut down in
preparation for handover to a booted operating system. The platform
firmware simply doesn't bother to call the drivers' Stop() methods.
Instead, drivers must register an EVT_SIGNAL_EXIT_BOOT_SERVICES event
to be signalled when ExitBootServices() is called, and clean up
without any reference to the EFI driver model.
Unfortunately, all timers silently stop working when ExitBootServices()
is called. Even more unfortunately, and for no discernible reason,
this happens before any EVT_SIGNAL_EXIT_BOOT_SERVICES events are
signalled. The net effect of this entertaining design choice is that
any timeout loops on the shutdown path (e.g. for gracefully closing
outstanding TCP connections) may wait indefinitely.
There is no way to report failure from currticks(), since the API
lazily assumes that the host system continues to travel through time
in the usual direction. Work around EFI's violation of this
assumption by falling back to a simple free-running monotonic counter.
Debugged-by: Maor Dickman <maord@mellanox.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
We currently use the EFI_CPU_ARCH_PROTOCOL's GetTimerValue() method to
generate the currticks() timer, calibrated against a 1ms delay from
the boot services Stall() method.
This does not work on ARM platforms, where GetTimerValue() is an empty
stub which just returns EFI_UNSUPPORTED.
Fix by instead creating a periodic timer event, and using this event
to increment a current tick counter.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Exploit the redefinition of iPXE error codes to include a "platform
error code" to allow for meaningful conversion of EFI_STATUS values to
iPXE errors and vice versa.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
Access to the gpxe.org and etherboot.org domains and associated
resources has been revoked by the registrant of the domain. Work
around this problem by renaming project from gPXE to iPXE, and
updating URLs to match.
Also update README, LOG and COPYRIGHTS to remove obsolete information.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
EFI_STATUS is defined as an INTN, which maps to UINT32 (i.e. unsigned
int) on i386 and UINT64 (i.e. unsigned long) on x86_64. This would
require a cast each time the error status is printed.
Add efi_strerror() to avoid this ickiness and simultaneously enable
prettier reporting of EFI status codes.
This brings us in to line with Linux definitions, and also simplifies
adding x86_64 support since both platforms have 2-byte shorts, 4-byte
ints and 8-byte long longs.
We have EFI APIs for CPU I/O, PCI I/O, timers, console I/O, user
access and user memory allocation.
EFI executables are created using the vanilla GNU toolchain, with the
EXE header handcrafted in assembly and relocations generated by a
custom efilink utility.
Michael Brown
Michael Brown