More EFI updates for v5.7

 - Incorporate a stable branch with the EFI pieces of Hans's work on
   loading device firmware from EFI boot service memory regions
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Just like with PCI options ROMs, which we save in the setup_efi_pci*
functions from arch/x86/boot/compressed/eboot.c, the EFI code / ROM itself
sometimes may contain data which is useful/necessary for peripheral drivers
to have access to.

Specifically the EFI code may contain an embedded copy of firmware which
needs to be (re)loaded into the peripheral. Normally such firmware would be
part of linux-firmware, but in some cases this is not feasible, for 2
reasons:

1) The firmware is customized for a specific use-case of the chipset / use
with a specific hardware model, so we cannot have a single firmware file
for the chipset. E.g. touchscreen controller firmwares are compiled
specifically for the hardware model they are used with, as they are
calibrated for a specific model digitizer.

2) Despite repeated attempts we have failed to get permission to
redistribute the firmware. This is especially a problem with customized
firmwares, these get created by the chip vendor for a specific ODM and the
copyright may partially belong with the ODM, so the chip vendor cannot
give a blanket permission to distribute these.

This commit adds support for finding peripheral firmware embedded in the
EFI code and makes the found firmware available through the new
efi_get_embedded_fw() function.

Support for loading these firmwares through the standard firmware loading
mechanism is added in a follow-up commit in this patch-series.

Note we check the EFI_BOOT_SERVICES_CODE for embedded firmware near the end
of start_kernel(), just before calling rest_init(), this is on purpose
because the typical EFI_BOOT_SERVICES_CODE memory-segment is too large for
early_memremap(), so the check must be done after mm_init(). This relies
on EFI_BOOT_SERVICES_CODE not being free-ed until efi_free_boot_services()
is called, which means that this will only work on x86 for now.
Reported-by: Dave Olsthoorn <dave@bewaar.me>
Suggested-by: Peter Jones <pjones@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20200115163554.101315-3-hdegoede@redhat.comSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

Sometimes it is useful to be able to dump the efi boot-services code and
data. This commit adds these as debugfs-blobs to /sys/kernel/debug/efi,
but only if efi=debug is passed on the kernel-commandline as this requires
not freeing those memory-regions, which costs 20+ MB of RAM.
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20200115163554.101315-2-hdegoede@redhat.comSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

The following commit:

  ef5a7b5e ("efi/x86: Remove GDT setup from efi_main")

introduced GDT setup into the 32-bit kernel's startup_32, and reloads
the GDTR after relocating the kernel for paranoia's sake.

A followup commit:

   32d00913 ("x86/boot: Reload GDTR after copying to the end of the buffer")

introduced a similar GDTR reload in the 64-bit kernel as well.

The GDTR is adjusted by (init_size-_end), however this may not be the
correct offset to apply if the kernel was loaded at a misaligned address
or below LOAD_PHYSICAL_ADDR, as in that case the decompression buffer
has an additional offset from the original load address.

This should never happen for a conformant bootloader, but we're being
paranoid anyway, so just store the new GDT address in there instead of
adding any offsets, which is simpler as well.

Fixes: ef5a7b5e ("efi/x86: Remove GDT setup from efi_main")
Fixes: 32d00913 ("x86/boot: Reload GDTR after copying to the end of the buffer")
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-efi@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Link: https://lore.kernel.org/r/20200226230031.3011645-2-nivedita@alum.mit.edu

Recent changes to the way we deal with EFI runtime services that
are marked as unsupported by the firmware resulted in a regression
for non-EFI boot. The problem is that all EFI runtime services are
marked as available by default, and any non-NULL checks on the EFI
service function pointers (which will be non-NULL even for runtime
services that are unsupported on an EFI boot) were replaced with
checks against the mask stored in efi.runtime_supported_mask.

When doing a non-EFI boot, this check against the mask will return
a false positive, given the fact that all runtime services are
marked as enabled by default. Since we dropped the non-NULL check
of the runtime service function pointer in favor of the mask check,
we will now unconditionally dereference the function pointer, even
if it is NULL, and go boom.

So let's ensure that the mask reflects reality on a non-EFI boot,
which is that all EFI runtime services are unsupported.
Reported-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-efi@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20200228121408.9075-7-ardb@kernel.org

Commit 9f922377 ("efi/libstub/arm: Make efi_entry() an ordinary PE/COFF
entrypoint") modified the handover code written in assembler, and for
maintainability, aligned the logic with the logic used in the 32-bit ARM
version, which is to avoid cache maintenance on the remaining instructions
in the subroutine that will be executed with the MMU and caches off, and
instead, branch into the relocated copy of the kernel image.

However, this assumes that this copy is executable, and this means we
expect EFI_LOADER_DATA regions to be executable as well, which is not
a reasonable assumption to make, even if this is true for most UEFI
implementations today.

So change this back, and add a __clean_dcache_area_poc() call to cover
the remaining code in the subroutine. While at it, switch the other
call site over to __clean_dcache_area_poc() as well, and clean up the
terminology in comments to avoid using 'flush' in the context of cache
maintenance. Also, let's switch to the new style asm annotations.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-efi@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20200228121408.9075-6-ardb@kernel.org

The following commit:

  c7225494 ("efi/arm: Work around missing cache maintenance in decompressor handover")

modified the EFI handover code written in assembler to work around the
missing cache maintenance of the piece of code that is executed after the
MMU and caches are turned off.

Due to the fact that this sequence incorporates a subroutine call, cleaning
that code from the cache is not a matter of simply passing the start and end of
the currently running subroutine into cache_clean_flush(), which is why
instead, the code jumps across into the cleaned copy of the image.

However, this assumes that this copy is executable, and this means we
expect EFI_LOADER_DATA regions to be executable as well, which is not
a reasonable assumption to make, even if this is true for most UEFI
implementations today.

So change this back, and add a cache_clean_flush() call to cover the
remaining code in the subroutine, and any code it may execute in the
context of cache_off().
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-efi@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20200228121408.9075-5-ardb@kernel.org

Shadowing variables is generally frowned upon.

Let's simply reuse the existing loop counter 'i' instead of shadowing it.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-efi@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/r/20200223221324.156086-1-xypron.glpk@gmx.de
Link: https://lore.kernel.org/r/20200228121408.9075-4-ardb@kernel.org

When booting with SME active, EFI tables must be mapped unencrypted since
they were built by UEFI in unencrypted memory. Update the list of tables
to be checked during early_memremap() processing to account for the EFI
RNG seed table.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-efi@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Link: https://lore.kernel.org/r/b64385fc13e5d7ad4b459216524f138e7879234f.1582662842.git.thomas.lendacky@amd.com
Link: https://lore.kernel.org/r/20200228121408.9075-3-ardb@kernel.org

When booting with SME active, EFI tables must be mapped unencrypted since
they were built by UEFI in unencrypted memory. Update the list of tables
to be checked during early_memremap() processing to account for the EFI
TPM tables.

This fixes a bug where an EFI TPM log table has been created by UEFI, but
it lives in memory that has been marked as usable rather than reserved.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-efi@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: <stable@vger.kernel.org> # v5.4+
Link: https://lore.kernel.org/r/4144cd813f113c20cdfa511cf59500a64e6015be.1582662842.git.thomas.lendacky@amd.com
Link: https://lore.kernel.org/r/20200228121408.9075-2-ardb@kernel.org

Pull EFI updates for v5.7 from Ard Biesheuvel:

This time, the set of changes for the EFI subsystem is much larger than
usual. The main reasons are:

 - Get things cleaned up before EFI support for RISC-V arrives, which will
   increase the size of the validation matrix, and therefore the threshold to
   making drastic changes,

 - After years of defunct maintainership, the GRUB project has finally started
   to consider changes from the distros regarding UEFI boot, some of which are
   highly specific to the way x86 does UEFI secure boot and measured boot,
   based on knowledge of both shim internals and the layout of bootparams and
   the x86 setup header. Having this maintenance burden on other architectures
   (which don't need shim in the first place) is hard to justify, so instead,
   we are introducing a generic Linux/UEFI boot protocol.

Summary of changes:

 - Boot time GDT handling changes (Arvind)

 - Simplify handling of EFI properties table on arm64

 - Generic EFI stub cleanups, to improve command line handling, file I/O,
   memory allocation, etc.

 - Introduce a generic initrd loading method based on calling back into
   the firmware, instead of relying on the x86 EFI handover protocol or
   device tree.

 - Introduce a mixed mode boot method that does not rely on the x86 EFI
   handover protocol either, and could potentially be adopted by other
   architectures (if another one ever surfaces where one execution mode
   is a superset of another)

 - Clean up the contents of struct efi, and move out everything that
   doesn't need to be stored there.

 - Incorporate support for UEFI spec v2.8A changes that permit firmware
   implementations to return EFI_UNSUPPORTED from UEFI runtime services at
   OS runtime, and expose a mask of which ones are supported or unsupported
   via a configuration table.

 - Various documentation updates and minor code cleanups (Heinrich)

 - Partial fix for the lack of by-VA cache maintenance in the decompressor
   on 32-bit ARM. Note that these patches were deliberately put at the
   beginning so they can be used as a stable branch that will be shared with
   a PR containing the complete fix, which I will send to the ARM tree.
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Pull RISC-V fixes from Palmer Dabbelt:
 "This contains a handful of RISC-V related fixes that I've collected
  and would like to target for 5.6-rc4:

   - A fix to set up the PMPs on boot, which allows the kernel to access
     memory on systems that don't set up permissive PMPs before getting
     to Linux. This only effects machine-mode kernels, which currently
     means only NOMMU kernels.

   - A fix to avoid enabling supervisor-mode interrupts when running in
     machine-mode, also only for NOMMU kernels.

   - A pair of fixes to our KASAN support to avoid corrupting memory.

   - A gitignore fix.

  This boots on QEMU's virt board for me"

* tag 'riscv-for-linux-5.6-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: adjust the indent
  riscv: allocate a complete page size for each page table
  riscv: Fix gitignore
  RISC-V: Don't enable all interrupts in trap_init()
  riscv: set pmp configuration if kernel is running in M-mode

Pull MIPS fixes from Paul Burton:
 "Here are a few MIPS fixes, and a MAINTAINERS update to hand over MIPS
  maintenance to Thomas Bogendoerfer - this will be my final pull
  request as MIPS maintainer.

  Thanks for your helpful comments, useful corrections & responsiveness
  during the time I've fulfilled the role, and I'm sure I'll pop up
  elsewhere in the tree somewhere down the line"

* 'mips-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
  MAINTAINERS: Hand MIPS over to Thomas
  MIPS: ingenic: DTS: Fix watchdog nodes
  MIPS: X1000: Fix clock of watchdog node.
  MIPS: vdso: Wrap -mexplicit-relocs in cc-option
  MIPS: VPE: Fix a double free and a memory leak in 'release_vpe()'
  MIPS: cavium_octeon: Fix syncw generation.
  mips: vdso: add build time check that no 'jalr t9' calls left
  MIPS: Disable VDSO time functionality on microMIPS
  mips: vdso: fix 'jalr t9' crash in vdso code

My time with MIPS the company has reached its end, and so at best I'll
have little time spend on maintaining arch/mips/.

Ralf last authored a patch over 2 years ago, the last time he committed
one is even further back & activity was sporadic for a while before
that. The reality is that he isn't active.

Having a new maintainer with time to do things properly will be
beneficial all round. Thomas Bogendoerfer has been involved in MIPS
development for a long time & has offered to step up as maintainer, so
add Thomas and remove myself & Ralf from the MIPS entry.

Ralf already has an entry in CREDITS to honor his contributions, so this
just adds one for me.
Signed-off-by: Paul Burton <paulburton@kernel.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@vger.kernel.org

Adjust the indent to match Linux coding style.
Signed-off-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

Each page table should be created by allocating a complete page size
for it. Otherwise, the content of the page table would be corrupted
somewhere through memory allocation which allocates the memory at the
middle of the page table for other use.
Signed-off-by: Zong Li <zong.li@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

Pull kvm fixes from Paolo Bonzini:
 "Bugfixes, including the fix for CVE-2020-2732 and a few issues found
  by 'make W=1'"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: s390: rstify new ioctls in api.rst
  KVM: nVMX: Check IO instruction VM-exit conditions
  KVM: nVMX: Refactor IO bitmap checks into helper function
  KVM: nVMX: Don't emulate instructions in guest mode
  KVM: nVMX: Emulate MTF when performing instruction emulation
  KVM: fix error handling in svm_hardware_setup
  KVM: SVM: Fix potential memory leak in svm_cpu_init()
  KVM: apic: avoid calculating pending eoi from an uninitialized val
  KVM: nVMX: clear PIN_BASED_POSTED_INTR from nested pinbased_ctls only when apicv is globally disabled
  KVM: nVMX: handle nested posted interrupts when apicv is disabled for L1
  kvm: x86: svm: Fix NULL pointer dereference when AVIC not enabled
  KVM: VMX: Add VMX_FEATURE_USR_WAIT_PAUSE
  KVM: nVMX: Hold KVM's srcu lock when syncing vmcs12->shadow
  KVM: x86: don't notify userspace IOAPIC on edge-triggered interrupt EOI
  kvm/emulate: fix a -Werror=cast-function-type
  KVM: x86: fix incorrect comparison in trace event
  KVM: nVMX: Fix some obsolete comments and grammar error
  KVM: x86: fix missing prototypes
  KVM: x86: enable -Werror

Pull crypto fixes from Herbert Xu:
 "This fixes a Kconfig-related build error and an integer overflow in
  chacha20poly1305"

* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6:
  crypto: chacha20poly1305 - prevent integer overflow on large input
  tee: amdtee: amdtee depends on CRYPTO_DEV_CCP_DD

Pull tmpfs fix from Al Viro:
 "Regression from fs_parse series this cycle..."

* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  tmpfs: deny and force are not huge mount options

Jordy Zomer reported a KASAN out-of-bounds read in the floppy driver in
wait_til_ready().

Which on the face of it can't happen, since as Willy Tarreau points out,
the function does no particular memory access.  Except through the FDCS
macro, which just indexes a static allocation through teh current fdc,
which is always checked against N_FDC.

Except the checking happens after we've already assigned the value.

The floppy driver is a disgrace (a lot of it going back to my original
horrd "design"), and has no real maintainer.  Nobody has the hardware,
and nobody really cares.  But it still gets used in virtual environment
because it's one of those things that everybody supports.

The whole thing should be re-written, or at least parts of it should be
seriously cleaned up.  The 'current fdc' index, which is used by the
FDCS macro, and which is often shadowed by a local 'fdc' variable, is a
prime example of how not to write code.

But because nobody has the hardware or the motivation, let's just fix up
the immediate problem with a nasty band-aid: test the fdc index before
actually assigning it to the static 'fdc' variable.
Reported-by: Jordy Zomer <jordy@simplyhacker.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We also need to rstify the new ioctls that we added in parallel to the
rstification of the kvm docs.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Now that we have introduced new, generic ways for the OS loader to
interface with Linux kernels during boot, we need to record this
fact in a way that allows loaders to discover this information, and
fall back to the existing methods for older kernels.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Now that we have added new ways to load the initrd or the mixed mode
kernel, we will also need a way to tell the loader about this. Add
symbolic constants for the PE/COFF major/minor version numbers (which
fortunately have always been 0x0 for all architectures), so that we
can bump them later to document the capabilities of the stub.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Replace bare numbers in the PE/COFF header structure with symbolic
constants so they become self documenting.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Testing the value of the efi.get_variable function pointer is not
the right way to establish whether the platform supports EFI
variables at runtime. Instead, use the newly added granular check
that can test for the presence of each EFI runtime service
individually.
Acked-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Replace the EFI runtime services check with one that tells us whether
EFI GetVariable() is implemented by the firmware.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Do not attempt to call EFI ResetSystem if the runtime supported mask tells
us it is no longer functional at OS runtime.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Replace the EFI runtime services check with one that tells us whether
EFI GetVariable() is implemented by the firmware.

Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Replace the EFI runtime services check with one that tells us whether
EFI GetVariable() is implemented by the firmware.

Cc: Mike Marciniszyn <mike.marciniszyn@intel.com>
Cc: Dennis Dalessandro <dennis.dalessandro@intel.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-rdma@vger.kernel.org
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Drop the separate driver that registers the EFI rtc on all EFI
systems that have runtime services available, and instead, move
the registration into the core EFI code, and make it conditional
on whether the actual time related services are available.
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

The UEFI spec rev 2.8 permits firmware implementations to support only
a subset of EFI runtime services at OS runtime (i.e., after the call to
ExitBootServices()), so let's take this into account in the drivers that
rely specifically on the availability of the EFI variable services.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Take the newly introduced EFI_RT_PROPERTIES_TABLE configuration table
into account, which carries a mask of which EFI runtime services are
still functional after ExitBootServices() has been called by the OS.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Revision 2.8 of the UEFI spec introduces provisions for firmware to
advertise lack of support for certain runtime services at OS runtime.
Let's store this mask in struct efi for easy access.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

The efi_get_fdt_params() routine uses the early OF device tree
traversal helpers, that iterate over each node in the DT and invoke
a caller provided callback that can inspect the node's contents and
look for the required data. This requires a special param struct to
be passed around, with pointers into param enumeration structs that
contain (and duplicate) property names and offsets into yet another
struct that carries the collected data.

Since we know the data we look for is either under /hypervisor/uefi
or under /chosen, it is much simpler to use the libfdt routines, and
just try to grab a reference to either node directly, and read each
property in sequence.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Push the FDT params specific types and definition into fdtparams.c,
and instead, pass a reference to the memory map data structure and
populate it directly, and return the system table address as the
return value.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

On ARM systems, we discover the UEFI system table address and memory
map address from the /chosen node in the device tree, or in the Xen
case, from a similar node under /hypervisor.

Before making some functional changes to that code, move it into its
own file that only gets built if CONFIG_EFI_PARAMS_FROM_FDT=y.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Currently, mixed mode is closely tied to the EFI handover protocol
and relies on intimate knowledge of the bootparams structure, setup
header etc, all of which are rather byzantine and entirely specific
to x86.

Even though no other EFI supported architectures are currently known
that could support something like mixed mode, it still makes sense to
abstract a bit from this, and make it part of a generic Linux on EFI
boot protocol.

To that end, add a .compat section to the mixed mode binary, and populate
it with the PE machine type and entry point address, allowing firmware
implementations to match it to their native machine type, and invoke
non-native binaries using a secondary entry point.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Add support for booting 64-bit x86 kernels from 32-bit firmware running
on 64-bit capable CPUs without requiring the bootloader to implement
the EFI handover protocol or allocate the setup block, etc etc, all of
which can be done by the stub itself, using code that already exists.

Instead, create an ordinary EFI application entrypoint but implemented
in 32-bit code [so that it can be invoked by 32-bit firmware], and stash
the address of this 32-bit entrypoint in the .compat section where the
bootloader can find it.

Note that we use the setup block embedded in the binary to go through
startup_32(), but it gets reallocated and copied in efi_pe_entry(),
using the same code that runs when the x86 kernel is booted in EFI
mode from native firmware. This requires the loaded image protocol to
be installed on the kernel image's EFI handle, and point to the kernel
image itself and not to its loader. This, in turn, requires the
bootloader to use the LoadImage() boot service to load the 64-bit
image from 32-bit firmware, which is in fact supported by firmware
based on EDK2. (Only StartImage() will fail, and instead, the newly
added entrypoint needs to be invoked)
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Currently, we either return with an error [from efi_pe_entry()] or
enter a deadloop [in efi_main()] if any fatal errors occur during
execution of the EFI stub. Let's switch to calling the Exit() EFI boot
service instead in both cases, so that we
a) can get rid of the deadloop, and simply return to the boot manager
   if any errors occur during execution of the stub, including during
   the call to ExitBootServices(),
b) can also return cleanly from efi_pe_entry() or efi_main() in mixed
   mode, once we introduce support for LoadImage/StartImage based mixed
   mode in the next patch.

Note that on systems running downstream GRUBs [which do not use LoadImage
or StartImage to boot the kernel, and instead, pass their own image
handle as the loaded image handle], calling Exit() will exit from GRUB
rather than from the kernel, but this is a tolerable side effect.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>