Michael Brown [Wed, 21 Mar 2018 12:39:18 +0000 (14:39 +0200)]
[librm] Provide symbols for inline code placed into other sections
Provide symbols constructed from the object name and line number for
code fragments placed into alternative sections, such as inline
REAL_CODE() assembly placed into .text16. This simplifies the
debugging task of finding the source code corresponding to a given
instruction pointer.
Note that we cannot use __FUNCTION__ since it is not a preprocessor
macro and so cannot be concatenated with string literals.
Michael Brown [Wed, 21 Mar 2018 08:28:05 +0000 (10:28 +0200)]
[undi] Treat invalid IRQ numbers as non-fatal errors
If the underlying PXE stack reports an invalid IRQ number (above
IRQ_MAX), treat this as equivalent to an empty IRQ number and fall
back to using polling mode.
Michael Brown [Tue, 20 Mar 2018 19:34:46 +0000 (21:34 +0200)]
[build] Prevent use of MMX and SSE registers
The existence of MMX and SSE is required by the System V x86_64 ABI
and so is assumed by gcc, but these registers are not preserved by our
own interrupt handlers and are unlikely to be preserved by other
context switch handlers in a boot firmware environment.
Explicitly prevent gcc from using MMX or SSE registers to avoid
potential problems due to silent register corruption.
We must remove the %xmm0-%xmm5 clobbers from the x86_64 version of
hv_call() since otherwise gcc will complain about unknown register
names. Theoretically, we should probably add code to explicitly
preserve the %xmm0-%xmm5 registers across a hypercall, in order to
guarantee to external code that these registers remain unchanged. In
practice this is difficult since SSE registers are disabled by
default: for background information see commits 71560d1 ("[librm]
Preserve FPU, MMX and SSE state across calls to virt_call()") and dd9a14d ("[librm] Conditionalize the workaround for the Tivoli VMM's
SSE garbling").
Michael Brown [Tue, 20 Mar 2018 18:42:39 +0000 (20:42 +0200)]
[rng] Use fixed-point calculations for min-entropy quantities
We currently perform various min-entropy calculations using build-time
floating-point arithmetic. No floating-point code ends up in the
final binary, since the results are eventually converted to integers
and asserted to be compile-time constants.
Though this mechanism is undoubtedly cute, it inhibits us from using
"-mno-sse" to prevent the use of SSE registers by the compiler.
Michael Brown [Tue, 20 Mar 2018 15:26:49 +0000 (17:26 +0200)]
[time] Add support for the ACPI power management timer
Allow the ACPI power management timer to be used if enabled via
TIMER_ACPI in config/timer.h. This provides an alternative timer on
systems where the standard 8254 PIT is unavailable or unreliable.
Michael Brown [Tue, 20 Mar 2018 11:22:30 +0000 (13:22 +0200)]
[efi] Provide Map_Mem() and associated UNDI callbacks
Some drivers are known to call the optional Map_Mem() callback without
first checking that the callback exists. Provide a usable basic
implementation of Map_Mem() along with the other callbacks that become
mandatory if Map_Mem() is provided.
Note that in theory the PCI I/O protocol is allowed to require
multiple calls to Map(), with each call handling only a subset of the
overall mapped range. However, the reference implementation in EDK2
assumes that a single Map() will always suffice, so we can probably
make the same simplifying assumption here.
Tested with the Intel E3522X2.EFI driver (which, incidentally, fails
to cleanly remove one of its mappings).
Originally-implemented-by: Maor Dickman <maord@mellanox.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Mon, 19 Mar 2018 13:47:39 +0000 (15:47 +0200)]
[lacp] Check the partner's own state when checking for blocked links
The blocked link test in eth_slow_lacp_rx() is performed before the
actor TLV is copied to the partner TLV, and so must test the actor
state field rather than the partner state field.
Michael Brown [Sun, 18 Mar 2018 20:27:49 +0000 (22:27 +0200)]
[ocsp] Allow OCSP checks to be disabled
Some CAs provide non-functional OCSP servers, and some clients are
forced to operate on networks without access to the OCSP servers.
Allow the user to explicitly disable the use of OCSP checks by
undefining OCSP_CHECK in config/crypto.h.
Michael Brown [Sun, 18 Mar 2018 15:11:16 +0000 (17:11 +0200)]
[lacp] Mark link as blocked if partner is not yet up and running
Mark the link as blocked if the LACP partner is not reporting itself
as being in sync, collecting, and distributing.
This matches the behaviour for STP: we mark the link as blocked if we
detect that the switch is actively blocking traffic, in order to
extend the DHCP discovery period and so prevent boot failures on
switches that take an excessively long time to enable ports.
Michael Brown [Sun, 18 Mar 2018 12:54:57 +0000 (14:54 +0200)]
[librm] Add facility to provide register and stack dump for CPU exceptions
When DEBUG=librm_mgmt is enabled, intercept CPU exceptions and provide
a register and stack dump, then drop to an emergency shell. Exiting
from the shell will almost certainly not work, but this provides an
opportunity to view the register and stack dump and carry out some
basic debugging.
Note that we can intercept only the first 8 CPU exceptions, since a
PXE ROM is not permitted to rebase the PIC.
Michael Brown [Mon, 12 Mar 2018 10:55:28 +0000 (10:55 +0000)]
[efi] Drop to TPL_APPLICATION when gathering entropy
Commit c89a446 ("[efi] Run at TPL_CALLBACK to protect against UEFI
timers") introduced a regression in the EFI entropy gathering code.
When the EFI_RNG_PROTOCOL is not present, we fall back to using timer
interrupts (as for the BIOS build). Since timer interrupts are
disabled at TPL_CALLBACK, WaitForEvent() fails and no entropy can be
gathered.
Fix by dropping to TPL_APPLICATION while entropy gathering is enabled.
Reported-by: Andreas Hammarskjöld <junior@2PintSoftware.com> Tested-by: Andreas Hammarskjöld <junior@2PintSoftware.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Tue, 20 Feb 2018 10:56:31 +0000 (10:56 +0000)]
[efi] Run at TPL_CALLBACK to protect against UEFI timers
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.
Michael Brown [Mon, 19 Feb 2018 18:59:45 +0000 (18:59 +0000)]
[xhci] Consume event TRB before reporting completion to USB core
Reporting a completion via usb_complete() will pass control outside
the scope of xhci.c, and could potentially result in a further call to
xhci_event_poll() before returning from usb_complete(). Since we
currently update the event consumer counter only after calling
usb_complete(), this can result in duplicate completions and
consequent corruption of the submission TRB ring structures.
Fix by updating the event ring consumer counter before passing control
to usb_complete().
Reported-by: Andreas Hammarskjöld <junior@2PintSoftware.com> Tested-by: Andreas Hammarskjöld <junior@2PintSoftware.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Sat, 3 Feb 2018 19:21:54 +0000 (19:21 +0000)]
[intel] Work around broken reset mechanism in i219 devices
The i219 appears to have a seriously broken reset mechanism. After
any transmit or receive activity, resetting the card will break both
the transmit and receive datapaths until the next PCI bus reset.
The Linux and BSD drivers include a convoluted workaround authored by
Intel which involves setting a bit in the undocumented FEXTNVM11
register, then transmitting a dummy 512-byte packet containing garbage
data, then reconfiguring the receive descriptor prefetch thresholds
and temporarily reenabling the receive datapath. The comments in the
Intel fix do not even remotely match what the code actually does, and
the code accidentally leaves the transmitter enabled after use.
Experimentation suggests that an equivalent fix is to simply set the
undocumented bit in FEXTNVM11 before enabling the transmit or receive
descriptor rings.
Michael Brown [Mon, 29 Jan 2018 21:25:11 +0000 (21:25 +0000)]
[xhci] Assume an invalid PSI table if any invalid PSI value is observed
Invalid protocol speed ID tables appear to be increasingly common in
the wild, to the point that it is infeasible to apply an explicit
XHCI_BAD_PSIV flag for each offending PCI device ID.
Fix by assuming an invalid PSI table as soon as any invalid value is
reported by the hardware.
Michael Brown [Wed, 17 Jan 2018 14:09:56 +0000 (14:09 +0000)]
[ena] Fix spurious uninitialised variable warning on older versions of gcc
Some older versions of gcc (observed with gcc 4.7.2) report a spurious
uninitialised variable warning in ena_get_device_attributes(). Work
around this warning by manually inlining the relevant code (which has
only a single call site).
Reported-by: xbgmsharp <xbgmsharp@gmail.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Martin Habets [Wed, 10 Jan 2018 15:32:34 +0000 (15:32 +0000)]
[netdevice] Make netdev_irq_enabled() independent of netdev_irq_supported()
The UNDI layer uses the NETDEV_IRQ_ENABLED flag to choose whether to
return PXENV_UNDI_ISR_OUT_OURS or PXENV_UNDI_ISR_OUT_NOT_OURS for a
given interrupt. For a network device that does not support
interrupts, the flag will never be set and so pxenv_undi_isr() will
always return PXENV_UNDI_ISR_OUT_NOT_OURS. This causes some NBPs
(such as lpxelinux.0) to hang.
Redefine NETDEV_IRQ_ENABLED as a simple administrative flag which can
be set even on network devices that do not support interrupts. This
allows pxenv_undi_isr() (which is the sole user of NETDEV_IRQ_ENABLED)
to function as expected by lpxelinux.0.
Signed-off-by: Martin Habets <mhabets@solarflare.com> Modified-by: Michael Brown <mcb30@ipxe.org> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Tue, 2 Jan 2018 20:26:40 +0000 (21:26 +0100)]
[build] Avoid use of "ld --oformat binary"
Using "ld --oformat binary" for mbr.bin and usbdisk.bin seems to cause
segmentation faults on some versions of binutils (observed on Fedora
27). Work around this problem by using ld to create an intermediate
ELF object, followed by objcopy (via the existing %.tmp -> %.bin rule)
to create the final binary.
Note that we cannot simply use a single-stage "objcopy -O binary"
since this will not process the relocation records for x86_64: see
commit 1afcccd ("[build] Do not use "objcopy -O binary" for objects
with relocation records").
Reported-by: Brent S <bts@square-r00t.net> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Fri, 29 Dec 2017 11:57:00 +0000 (11:57 +0000)]
[legal] Add missing FILE_LICENCE declarations
Add missing FILE_LICENCE declarations to x86_64 headers based on the
corresponding i386 headers (from which the x86_64 headers were
originally derived).
Michael Brown [Thu, 28 Dec 2017 13:38:50 +0000 (13:38 +0000)]
[image] Omit URI query string and fragment from download progress messages
The URIs printed as part of download progress messages are intended to
provide a quick visual progress indication to the user. Very long
query strings can render this visual indication useless in practice,
since the most important information (generally the URI host and path)
is drowned out by multiple lines of human-illegible URI-encoded data.
Omit the query string entirely from the download progress message.
For consistency and brevity, also omit the URI fragment along with the
username and password (which was previously redacted anyway).
Michael Brown [Thu, 28 Dec 2017 13:04:59 +0000 (13:04 +0000)]
[http] Report unsuccessful response status lines at DBGVL_LOG
The precise HTTP response status code is currently visible only at
DBGLVL_EXTRA. Allow for easier debugging by reporting the whole
status line at DBGLVL_LOG for any unsuccessful responses.
Michael Brown [Thu, 28 Dec 2017 12:09:27 +0000 (12:09 +0000)]
[xen] Skip probing of any unsupported device types
Xen 4.4 includes the device "device/suspend/event-channel" which does
not have a "backend" key. This currently causes the entire XenBus
device tree probe to fail.
Fix by skipping probe attempts for device types for which there is no
iPXE driver.
Debugged-by: Eytan Heidingsfeld <eytanh@gmail.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Tue, 7 Nov 2017 11:33:13 +0000 (11:33 +0000)]
[http] Gracefully handle offers of multiple authentication schemes
Servers may provide multiple WWW-Authenticate headers, each offering a
different authentication scheme. We currently fail the request as
soon as we encounter an unrecognised scheme, which prevents subsequent
offers from succeeding.
Fix by silently ignoring headers for schemes that we do not recognise.
If no schemes are recognised then the request will eventually fail
anyway due to the 401 response code.
If multiple schemes are supported, arbitrarily choose the scheme
appearing first within the response headers.
Michael Brown [Fri, 22 Sep 2017 13:02:40 +0000 (14:02 +0100)]
[efi] Inhibit our driver Start() method during disconnection attempts
Some HP BIOSes (observed with a Z840) seem to attempt to connect our
drivers in the middle of our call to DisconnectController(). The
precise chain of events is unclear, but the symptom is that we see
several calls to our Supported() and Start() methods, followed by a
system lock-up.
Work around this dubious BIOS behaviour by explicitly failing calls to
our Start() method while we are in the middle of attempting to
disconnect drivers.
Reported-by: Jordan Wright <jordan.m.wright@disney.com> Debugged-by: Adrian Lucrèce Céleste <adrianlucrececeleste@airmail.cc> Debugged-by: Christian Nilsson <nikize@gmail.com> Tested-by: Jordan Wright <jordan.m.wright@disney.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Mon, 18 Sep 2017 12:32:39 +0000 (13:32 +0100)]
[build] Exclude selected directories from Secure Boot builds
When submitting binaries for UEFI Secure Boot signing, certain
known-dubious subsystems (such as 802.11 and NFS) must be excluded
from the build. Mark the directories containing these subsystems as
insecure, and allow the build target to include an explicit "security
flag" (a literal "-sb" appended to the build platform) to exclude
these source directories from the build process.
For example:
make bin-x86_64-efi-sb/ipxe.efi
will build iPXE with all code from the 802.11 and NFS subsystems
excluded from the build.
Michael Brown [Wed, 13 Sep 2017 07:07:55 +0000 (10:07 +0300)]
[efi] Continue to connect remaining handles after connection errors
Some UEFI BIOSes will deliberately break the implementation of
ConnectController() to return errors for devices that have been
"disabled" via the BIOS setup screen. (As an added bonus, such BIOSes
may return garbage EFI_STATUS values such as 0xff.)
Work around these broken UEFI BIOSes by ignoring failures and
continuing to attempt to connect any remaining handles.
Michael Brown [Wed, 6 Sep 2017 22:56:22 +0000 (23:56 +0100)]
[efi] Match behaviour of SnpDxe for truncated received packets
The UEFI specification does not state whether or not a return value of
EFI_BUFFER_TOO_SMALL from the SNP Receive() method should follow the
usual EFI API behaviour of allowing the caller to retry the request
with an increased buffer size.
Examination of the SnpDxe driver in EDK2 suggests that Receive() will
just return the truncated packet (complete with any requested
link-layer header fields), so match this behaviour.
Michael Brown [Wed, 6 Sep 2017 22:18:29 +0000 (23:18 +0100)]
[efi] Check buffer length for packets retrieved via our SNP protocol
We do not currently check the length of the caller's buffer for
received packets. This creates a potential buffer overrun when iPXE
is being used via the SNP or UNDI protocols.
Fix by checking the buffer length and correctly returning the required
length and an EFI_BUFFER_TOO_SMALL error.
Reported-by: Paul McMillan <paul.mcmillan@oracle.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Tue, 5 Sep 2017 21:55:05 +0000 (22:55 +0100)]
[peerdist] Gather and report peer statistics during download
Record and report the number of peers (calculated as the maximum
number of peers discovered for a block's segment at the time that the
block download is complete), and the percentage of blocks retrieved
from peers rather than from the origin server.
Michael Brown [Tue, 5 Sep 2017 22:21:34 +0000 (23:21 +0100)]
[monojob] Check for job progress only once per timer tick
Checking for job progress is essentially a user interface activity,
and can safely be performed only once per timer tick (as is already
done with checking for keypresses).
Michael Brown [Tue, 5 Sep 2017 11:21:11 +0000 (12:21 +0100)]
[netdevice] Cancel all pending transmissions on any transmit error
Some external code (such as the UEFI UNDI driver for the Realtek USB
NIC on a Microsoft Surface Book) will block during transmission
attempts and can take several seconds to report a transmit error. If
there is a large queue of pending transmissions, then the accumulated
time from a series of such failures can easily exceed the EFI watchdog
timeout, resulting in what appears to be a system lockup followed by a
reboot.
Work around this problem by immediately cancelling any pending
transmissions as soon as any transmit error occurs.
The only expected transmit error under normal operation is ENOBUFS
arising when the hardware transmit queue is full. By definition, this
can happen only for drivers that do not utilise deferred
transmissions, and so this new behaviour will not affect these
drivers.
Michael Brown [Tue, 5 Sep 2017 09:48:41 +0000 (10:48 +0100)]
[efi] Raise TPL when calling UNDI entry point
The SnpDxe driver raises the task priority level to TPL_CALLBACK when
calling the UNDI entry point. This does not appear to be a documented
requirement, but we should probably match the behaviour of SnpDxe to
minimise surprises to third party code.
Michael Brown [Mon, 4 Sep 2017 13:00:32 +0000 (14:00 +0100)]
[malloc] Avoid false positive warnings from valgrind
Calling discard_cache() is likely to result in a call to
free_memblock(), which will call valgrind_make_blocks_noaccess()
before returning. This causes valgrind to report an invalid read on
the next iteration through the loop in alloc_memblock().
Fix by explicitly calling valgrind_make_blocks_defined() after
discard_cache() returns. Also call valgrind_make_blocks_noaccess()
before calling discard_cache(), to guard against free list corruption
while executing cache discarders.
Michael Brown [Wed, 30 Aug 2017 09:15:25 +0000 (10:15 +0100)]
[romprefix] Avoid unaligned accesses within ROM headers
Ensure that all headers (PCI, UNDI, PnP, iPXE) are aligned to at least
four bytes, so that all accesses to header fields will be correctly
aligned even when reading directly from the expansion ROM BAR.
Reported-by: Peter von Konigsmark <peter@exablaze.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Fri, 28 Jul 2017 20:19:45 +0000 (21:19 +0100)]
[hyperv] Do not steal ownership from the Gen 2 UEFI firmware
We must not steal ownership from the Gen 2 UEFI firmware, since doing
so will cause an immediate system crash (most likely in the form of a
reboot).
This problem was masked before commit a0f6e75 ("[hyperv] Do not fail
if guest OS ID MSR is already set"), since prior to that commit we
would always fail if we found any non-zero guest OS identity. We now
accept a non-zero previous guest OS identity in order to allow for
situations such as chainloading from iPXE to another iPXE, and as a
prerequisite for commit b91cc98 ("[hyperv] Cope with Windows Server
2016 enlightenments").
A proper fix would be to reverse engineer the UEFI protocols exposed
within the Hyper-V Gen 2 firmware and use these to bind to the VMBus
device representing the network connection, (with the native Hyper-V
driver moved to become a BIOS-only feature).
As an interim solution, fail to initialise the native Hyper-V driver
if we detect the guest OS identity known to be used by the Gen 2 UEFI
firmware. This will cause the standard all-drivers build (ipxe.efi)
to fall back to using the SNP driver.
Michael Brown [Fri, 28 Jul 2017 14:40:44 +0000 (15:40 +0100)]
[build] Fix ARM32 EFI builds with current EDK2 headers
EDK2 commit 6440385 ("MdePkg/Include: Add enumeration size checks to
Base.h") enforced the UEFI specification mandate that enums should
always be 32 bits. This revealed a latent bug in iPXE, which does not
build with -fno-short-enums.
Fix by adding -fno-short-enums to CFLAGS for ARM32 EFI builds.
Reported-by: Benjamin S. Allen <bsallen@alcf.anl.gov> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Fri, 28 Jul 2017 12:50:35 +0000 (13:50 +0100)]
[build] Fix use of inline assembly on GCC 4.8 ARM64 builds
The inline assembly used in include/errno.h to generate the einfo
blocks requires the ability to generate an immediate constant with no
immediate-value prefix (such as the dollar sign for x86 assembly).
We currently achieve this via the undocumented "%c0" form of operand.
This causes an "invalid operand prefix" error on GCC 4.8 for ARM64
builds.
Fix by switching to the equally undocumented "%a0" form of operand,
which appears to work correctly on all tested versions of GCC.
Reported-by: Benjamin S. Allen <bsallen@alcf.anl.gov> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Fri, 21 Jul 2017 13:48:27 +0000 (14:48 +0100)]
[efi] Enumerate PCI BARs in same order as SnpDxe
The UEFI specification has an implicit and demonstrably incorrect
requirement (in the Mem_IO() calling convention) that any UNDI network
device has at most one memory BAR and one I/O BAR.
Some UEFI platforms have been observed to report the existence of
non-existent additional I/O BARs, causing iPXE to select the wrong
BAR. This problem does not affect the SnpDxe driver, since that
driver will always choose the lowest numbered existent BAR of each
type.
Adjust iPXE's behaviour to match that of SnpDxe, i.e. to always select
the lowest numbered BAR(s).
Debugged-by: Andreas Hammarskjöld <junior@2PintSoftware.com> Debugged-by: Adklei <adklei@realtek.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Fri, 7 Jul 2017 16:25:37 +0000 (17:25 +0100)]
[smsc75xx] Expose functionality shared with LAN78xx devices
The LAN78xx datapath is essentially identical to that of the SMSC75xx.
Expose the transmit, poll, and bulk IN endpoint operations to allow
for reuse by the LAN78xx driver.
Jason Wang [Mon, 10 Jul 2017 09:10:41 +0000 (17:10 +0800)]
[virtio] Support VIRTIO_NET_F_IOMMU_PLATFORM
Since we don't enable IOMMU at all, we can then simply enable the
IOMMU support by claiming the support of VIRITO_F_IOMMU_PLATFORM.
This fixes booting failure when iommu_platform is set from qemu cli.
Signed-off-by: Jason Wang <jasowang@redhat.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
Michael Brown [Thu, 6 Jul 2017 15:58:22 +0000 (16:58 +0100)]
[smscusb] Abstract out common SMSC USB device functionality
The smsc75xx and smsc95xx drivers include a substantial amount of
identical functionality, varying only in the base address of register
sets. Abstract out this common functionality to allow code to be
shared between the drivers.
Michael Brown [Mon, 3 Jul 2017 12:38:55 +0000 (13:38 +0100)]
[usb] Use non-zero language ID to retrieve strings
We currently use a zero language ID to retrieve strings such as the
ECM/NCM MAC address. This works on most hardware devices, but is
known to fail on some software emulated CDC-NCM devices.
Fix by using the first supported language ID, falling back to English
(0x0409) if any error occurs when fetching the list of supported
languages. This matches the behaviour of the Linux kernel.
Michael Brown [Tue, 13 Jun 2017 11:12:11 +0000 (12:12 +0100)]
[crypto] Provide asn1_built() to construct a cursor from a builder
Our ASN.1 parsing code uses a struct asn1_cursor, while the object
construction code uses a struct asn1_builder. These structures are
identical apart from the const modifier applied to the data pointer in
struct asn1_cursor.
Provide asn1_built() to safely typecast a struct asn1_builder to a
struct asn1_cursor, allowing constructed objects to be passed to
functions expecting a struct asn1_cursor.
Michael Brown [Thu, 15 Jun 2017 13:50:20 +0000 (14:50 +0100)]
[cpuid] Allow input %ecx value to be specified
For some CPUID leaves (e.g. %eax=0x00000004), the result depends on
the input value of %ecx. Allow this subfunction number to be
specified as a parameter to the cpuid() wrapper.
The subfunction number is exposed via the ${cpuid/...} settings
mechanism using the syntax
projects / thirdparty / ipxe.git / log
