By adding a new 4th level of page table, give the possibility to 64bit
kernel to address 2^48 bytes of virtual address: in practice, that offers
128TB of virtual address space to userspace and allows up to 64TB of
physical memory.

If the underlying hardware does not support sv48, we will automatically
fallback to a standard 3-level page table by folding the new PUD level into
PGDIR level. In order to detect HW capabilities at runtime, we
use SATP feature that ignores writes with an unsupported mode.
Signed-off-by: NAlexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: NPalmer Dabbelt <palmer@rivosinc.com>

The EFI_RT_PROPERTIES_TABLE contains a mask of runtime services that are
available after ExitBootServices(). This mostly does not concern the EFI
stub at all, given that it runs before that. However, there is one call
that is made at runtime, which is the call to SetVirtualAddressMap()
(which is not even callable at boot time to begin with)

So add the missing handling of the RT_PROP table to ensure that we only
call SetVirtualAddressMap() if it is not being advertised as unsupported
by the firmware.

Cc: <stable@vger.kernel.org> # v5.10+
Tested-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

Now that ARM started following the example of arm64 and RISC-V, and
no longer imposes any restrictions on the placement of the FDT in
memory at boot, we no longer need per-arch implementations of
efi_get_max_fdt_addr() to factor out the differences. So get rid of
it.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Reviewed-by: NAtish Patra <atish.patra@wdc.com>
Link: https://lore.kernel.org/r/20201029134901.9773-1-ardb@kernel.org

This patch adds EFI runtime service support for RISC-V.
Signed-off-by: NAtish Patra <atish.patra@wdc.com>
[ardb: - Remove the page check]
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Acked-by: NArd Biesheuvel <ardb@kernel.org>
Signed-off-by: NPalmer Dabbelt <palmerdabbelt@google.com>

Before commit

  d0f9ca9b ("ARM: decompressor: run decompressor in place if loaded via UEFI")

we were rather limited in the choice of base address for the uncompressed
kernel, as we were relying on the logic in the decompressor that blindly
rounds down the decompressor execution address to the next multiple of 128
MiB, and decompresses the kernel there. For this reason, we have a lot of
complicated memory region handling code, to ensure that this memory window
is available, even though it could be occupied by reserved regions or
other allocations that may or may not collide with the uncompressed image.

Today, we simply pass the target address for the decompressed image to the
decompressor directly, and so we can choose a suitable window just by
finding a 16 MiB aligned region, while taking TEXT_OFFSET and the region
for the swapper page tables into account.

So let's get rid of the complicated logic, and instead, use the existing
bottom up allocation routine to allocate a suitable window as low as
possible, and carve out a memory region that has the right properties.

Note that this removes any dependencies on the 'dram_base' argument to
handle_kernel_image(), and so this is removed as well. Given that this
was the only remaining use of dram_base, the code that produces it is
removed entirely as well.
Reviewed-by: NMaxim Uvarov <maxim.uvarov@linaro.org>
Tested-by: NMaxim Uvarov <maxim.uvarov@linaro.org>
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

The way we use the base of DRAM in the EFI stub is problematic as it
is ill defined what the base of DRAM actually means. There are some
restrictions on the placement of FDT and initrd which are defined in
terms of dram_base, but given that the placement of the kernel in
memory is what defines these boundaries (as on ARM, this is where the
linear region starts), it is better to use the image address in these
cases, and disregard dram_base altogether.
Reviewed-by: NMaxim Uvarov <maxim.uvarov@linaro.org>
Tested-by: NMaxim Uvarov <maxim.uvarov@linaro.org>
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

The prototype of the functions handle_kernel_image & efi_enter_kernel
are defined in efi-stub.c which may result in a compiler warnings if
-Wmissing-prototypes is set in gcc compiler.

Move the prototype to efistub.h to make the compiler happy.
Signed-off-by: NAtish Patra <atish.patra@wdc.com>
Link: https://lore.kernel.org/r/20200706172609.25965-2-atish.patra@wdc.comSigned-off-by: NArd Biesheuvel <ardb@kernel.org>

On 32-bit ARM, we may boot at HYP mode, or with the MMU and caches off
(or both), even though the EFI spec does not actually support this.
While booting at HYP mode is something we might tolerate, fiddling
with the caches is a more serious issue, as disabling the caches is
tricky to do safely from C code, and running without the Dcache makes
it impossible to support unaligned memory accesses, which is another
explicit requirement imposed by the EFI spec.

So take note of the CPU mode and MMU state in the EFI stub diagnostic
output so that we can easily diagnose any issues that may arise from
this. E.g.,

  EFI stub: Entering in SVC mode with MMU enabled

Also, capture the CPSR and SCTLR system register values at EFI stub
entry, and after ExitBootServices() returns, and check whether the
MMU and Dcache were disabled at any point. If this is the case, a
diagnostic message like the following will be emitted:

  efi: [Firmware Bug]: EFI stub was entered with MMU and Dcache disabled, please fix your firmware!
  efi: CPSR at EFI stub entry        : 0x600001d3
  efi: SCTLR at EFI stub entry       : 0x00c51838
  efi: CPSR after ExitBootServices() : 0x600001d3
  efi: SCTLR after ExitBootServices(): 0x00c50838
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Reviewed-by: NLeif Lindholm <leif@nuviainc.com>

Fix a missing prototype warning by adding a forward declaration
for the PE/COFF entrypoint, and while at it, align the function
name between the x86 and ARM versions of the stub.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

Now that we removed the memory limit for the allocation of the
command line, there is no longer a need to use the page based
allocator so switch to a pool allocation instead.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

efi_parse_options can fail if it is unable to allocate space for a copy
of the command line. Check the return value to make sure it succeeded.
Signed-off-by: NArvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200430182843.2510180-12-nivedita@alum.mit.eduSigned-off-by: NArd Biesheuvel <ardb@kernel.org>

Factor out the initrd loading into a common function that can be called
both from the generic efi-stub.c and the x86-specific x86-stub.c.
Signed-off-by: NArvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200430182843.2510180-10-nivedita@alum.mit.eduSigned-off-by: NArd Biesheuvel <ardb@kernel.org>

Use efi_err if we ignore a command-line dtb= argument, so that it shows
up even on a quiet boot.
Signed-off-by: NArvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200430182843.2510180-8-nivedita@alum.mit.eduSigned-off-by: NArd Biesheuvel <ardb@kernel.org>

Rename pr_efi to efi_info and pr_efi_err to efi_err to make it more
obvious that they are part of the EFI stub and not generic printk infra.
Suggested-by: NJoe Perches <joe@perches.com>
Signed-off-by: NArvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200430182843.2510180-4-nivedita@alum.mit.eduSigned-off-by: NArd Biesheuvel <ardb@kernel.org>

The practice of using __pure getter functions to access global
variables in the EFI stub dates back to the time when we had to
carefully prevent GOT entries from being emitted, because we
could not rely on the toolchain to do this for us.

Today, we use the hidden visibility pragma for all EFI stub source
files, which now all live in the same subdirectory, and we apply a
sanity check on the objects, so we can get rid of these getter
functions and simply refer to global data objects directly.

So switch over the remaining boolean variables carrying options set
on the kernel command line.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

The practice of using __pure getter functions to access global
variables in the EFI stub dates back to the time when we had to
carefully prevent GOT entries from being emitted, because we
could not rely on the toolchain to do this for us.

Today, we use the hidden visibility pragma for all EFI stub source
files, which now all live in the same subdirectory, and we apply a
sanity check on the objects, so we can get rid of these getter
functions and simply refer to global data objects directly.

Start with efi_system_table(), and convert it into a global variable.
While at it, make it a pointer-to-const, because we can.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

Now that both arm and x86 are using the linker script to place the EFI
stub's global variables in the correct section, remove __efistub_global.
Signed-off-by: NArvind Sankar <nivedita@alum.mit.edu>
Reviewed-by: NArd Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20200416151227.3360778-4-nivedita@alum.mit.eduSigned-off-by: NArd Biesheuvel <ardb@kernel.org>

Fix the following sparse warning:

drivers/firmware/efi/libstub/arm-stub.c:68:6: warning:
symbol 'install_memreserve_table' was not declared. Should it be static?
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NZou Wei <zou_wei@huawei.com>
Link: https://lore.kernel.org/r/1587643713-28169-1-git-send-email-zou_wei@huawei.comSigned-off-by: NArd Biesheuvel <ardb@kernel.org>

Most of the arm-stub code is written in an architecture independent manner.
As a result, RISC-V can reuse most of the arm-stub code.

Rename the arm-stub.c to efi-stub.c so that ARM, ARM64 and RISC-V can use it.
This patch doesn't introduce any functional changes.
Signed-off-by: NAtish Patra <atish.patra@wdc.com>
Reviewed-by: NPalmer Dabbelt <palmerdabbelt@google.com>
Link: https://lore.kernel.org/r/20200415195422.19866-2-atish.patra@wdc.comSigned-off-by: NArd Biesheuvel <ardb@kernel.org>

Commit:

  ec93fc37 ("efi/libstub: Add support for loading the initrd from a device path")

added a diagnostic print to the ARM version of the EFI stub that
reports whether an initrd has been loaded that was passed
via the command line using initrd=.

However, it failed to take into account that, for historical reasons,
the file loading routines return EFI_SUCCESS when no file was found,
and the only way to decide whether a file was loaded is to inspect
the 'size' argument that is passed by reference. So let's inspect
this returned size, to prevent the print from being emitted even if
no initrd was loaded at all.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Signed-off-by: NIngo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-efi@vger.kernel.org

One of the advantages of using what basically amounts to a callback
interface into the bootloader for loading the initrd is that it provides
a natural place for the bootloader or firmware to measure the initrd
contents while they are being passed to the kernel.

Unfortunately, this is not a guarantee that the initrd will in fact be
loaded and its /init invoked by the kernel, since the command line may
contain the 'noinitrd' option, in which case the initrd is ignored, but
this will not be reflected in the PCR that covers the initrd measurement.

This could be addressed by measuring the command line as well, and
including that PCR in the attestation policy, but this locks down the
command line completely, which may be too restrictive.

So let's take the noinitrd argument into account in the stub, too. This
forces any PCR that covers the initrd to assume a different value when
noinitrd is passed, allowing an attestation policy to disregard the
command line if there is no need to take its measurement into account
for other reasons.

As Peter points out, this would still require the agent that takes the
measurements to measure a separator event into the PCR in question at
ExitBootServices() time, to prevent replay attacks using the known
measurement from the TPM log.

Cc: Peter Jones <pjones@redhat.com>
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

There are currently two ways to specify the initrd to be passed to the
Linux kernel when booting via the EFI stub:
- it can be passed as a initrd= command line option when doing a pure PE
  boot (as opposed to the EFI handover protocol that exists for x86)
- otherwise, the bootloader or firmware can load the initrd into memory,
  and pass the address and size via the bootparams struct (x86) or
  device tree (ARM)

In the first case, we are limited to loading from the same file system
that the kernel was loaded from, and it is also problematic in a trusted
boot context, given that we cannot easily protect the command line from
tampering without either adding complicated white/blacklisting of boot
arguments or locking down the command line altogether.

In the second case, we force the bootloader to duplicate knowledge about
the boot protocol which is already encoded in the stub, and which may be
subject to change over time, e.g., bootparams struct definitions, memory
allocation/alignment requirements for the placement of the initrd etc etc.
In the ARM case, it also requires the bootloader to modify the hardware
description provided by the firmware, as it is passed in the same file.
On systems where the initrd is measured after loading, it creates a time
window where the initrd contents might be manipulated in memory before
handing over to the kernel.

Address these concerns by adding support for loading the initrd into
memory by invoking the EFI LoadFile2 protocol installed on a vendor
GUIDed device path that specifically designates a Linux initrd.
This addresses the above concerns, by putting the EFI stub in charge of
placement in memory and of passing the base and size to the kernel proper
(via whatever means it desires) while still leaving it up to the firmware
or bootloader to obtain the file contents, potentially from other file
systems than the one the kernel itself was loaded from. On platforms that
implement measured boot, it permits the firmware to take the measurement
right before the kernel actually consumes the contents.
Acked-by: NLaszlo Ersek <lersek@redhat.com>
Tested-by: NIlias Apalodimas <ilias.apalodimas@linaro.org>
Acked-by: NIlias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

On x86, the preferred load address of the initrd is still below 4 GB,
even though in some cases, we can cope with an initrd that is loaded
above that.

To simplify the code, and to make it more straightforward to introduce
other ways to load the initrd, pass the soft and hard memory limits at
the same time, and let the code handling the initrd= command line option
deal with this.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

The file I/O routine that is used to load initrd or dtb files from
the EFI system partition suffers from a few issues:
- it converts the u8[] command line back to a UTF-16 string, which is
  pointless since we only handle initrd or dtb arguments provided via
  the loaded image protocol anyway, which is where we got the UTF-16[]
  command line from in the first place when booting via the PE entry
  point,
- in the far majority of cases, only a single initrd= option is present,
  but it optimizes for multiple options, by going over the command line
  twice, allocating heap buffers for dynamically sized arrays, etc.
- the coding style is hard to follow, with few comments, and all logic
  including string parsing etc all combined in a single routine.

Let's fix this by rewriting most of it, based on the idea that in the
case of multiple initrds, we can just allocate a new, bigger buffer
and copy over the data before freeing the old one.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

get_dram_base() is only called from arm-stub.c so move it into
the same source file as its caller.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

We now support cmdline data that is located in memory that is not
32-bit addressable, so relax the allocation limit on systems where
this feature is enabled.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

The UEFI spec defines (and deprecates) a misguided and shortlived
memory protection feature that is based on splitting memory regions
covering PE/COFF executables into separate code and data regions,
without annotating them as belonging to the same executable image.
When the OS assigns the virtual addresses of these regions, it may
move them around arbitrarily, without taking into account that the
PE/COFF code sections may contain relative references into the data
sections, which means the relative placement of these segments has
to be preserved or the executable image will be corrupted.

The original workaround on arm64 was to ensure that adjacent regions
of the same type were mapped adjacently in the virtual mapping, but
this requires sorting of the memory map, which we would prefer to
avoid.

Considering that the native physical mapping of the PE/COFF images
does not suffer from this issue, let's preserve it at runtime, and
install it as the virtual mapping as well.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

Expose efi_entry() as the PE/COFF entrypoint directly, instead of
jumping into a wrapper that fiddles with stack buffers and other
stuff that the compiler is much better at. The only reason this
code exists is to obtain a pointer to the base of the image, but
we can get the same value from the loaded_image protocol, which
we already need for other reasons anyway.

Update the return type as well, to make it consistent with what
is required for a PE/COFF executable entrypoint.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

Drop leading underscores and use bool not int for true/false
variables set on the command line.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-25-ardb@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

The macros efi_call_early and efi_call_runtime are used to call EFI
boot services and runtime services, respectively. However, the naming
is confusing, given that the early vs runtime distinction may suggest
that these are used for calling the same set of services either early
or late (== at runtime), while in reality, the sets of services they
can be used with are completely disjoint, and efi_call_runtime is also
only usable in 'early' code.

So do a global sweep to replace all occurrences with efi_bs_call or
efi_rt_call, respectively, where BS and RT match the idiom used by
the UEFI spec to refer to boot time or runtime services.

While at it, use 'func' as the macro parameter name for the function
pointers, which is less likely to collide and cause weird build errors.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-24-ardb@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

We have a helper efi_system_table() that gives us the address of the
EFI system table in memory, so there is no longer point in passing
it around from each function to the next.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-20-ardb@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

As a first step towards getting rid of the need to pass around a function
parameter 'sys_table_arg' pointing to the EFI system table, remove the
references to it in the printing code, which is represents the majority
of the use cases.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-19-ardb@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Use a single implementation for efi_char16_printk() across all
architectures.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-17-ardb@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

The efi_call macros on ARM have a dependency on a variable 'sys_table_arg'
existing in the scope of the macro instantiation. Since this variable
always points to the same data structure, let's create a global getter
for it and use that instead.

Note that the use of a global variable with external linkage is avoided,
given the problems we had in the past with early processing of the GOT
tables.

While at it, drop the redundant casts in the efi_table_attr and
efi_call_proto macros.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-16-ardb@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

In preparation of moving to a native vs. mixed mode split rather than a
32 vs. 64 bit split when it comes to invoking EFI firmware services,
update all the native protocol definitions and redefine them as unions
containing an anonymous struct for the native view and a struct called
'mixed_mode' describing the 32-bit view of the protocol when called from
64-bit code.

While at it, flesh out some PCI I/O member definitions that we will be
needing shortly.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20191224151025.32482-9-ardb@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

Wire up the existing code for ARM that loads the TPM event log into
OS accessible buffers while running the EFI stub so that the kernel
proper can access it at runtime.
Tested-by: NZou Cao <zoucao@linux.alibaba.com>
Signed-off-by: NXinwei Kong <kong.kongxinwei@hisilicon.com>
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

Based on 1 normalized pattern(s):

  this file is part of the linux kernel and is made available under
  the terms of the gnu general public license version 2

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 28 file(s).
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NEnrico Weigelt <info@metux.net>
Reviewed-by: NAllison Randal <allison@lohutok.net>
Reviewed-by: NKate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.534229504@linutronix.deSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

This reverts commit eff89628, which
deferred the processing of persistent memory reservations to a point
where the memory may have already been allocated and overwritten,
defeating the purpose.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: NWill Deacon <will.deacon@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20190215123333.21209-3-ard.biesheuvel@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

The UEFI spec revision 2.7 errata A section 8.4 has the following to
say about the virtual memory runtime services:

  "This section contains function definitions for the virtual memory
  support that may be optionally used by an operating system at runtime.
  If an operating system chooses to make EFI runtime service calls in a
  virtual addressing mode instead of the flat physical mode, then the
  operating system must use the services in this section to switch the
  EFI runtime services from flat physical addressing to virtual
  addressing."

So it is pretty clear that calling SetVirtualAddressMap() is entirely
optional, and so there is no point in doing so unless it achieves
anything useful for us.

This is not the case for 64-bit ARM. The identity mapping used by the
firmware is arbitrarily converted into another permutation of userland
addresses (i.e., bits [63:48] cleared), and the runtime code could easily
deal with the original layout in exactly the same way as it deals with
the converted layout. However, due to constraints related to page size
differences if the OS is not running with 4k pages, and related to
systems that may expose the individual sections of PE/COFF runtime
modules as different memory regions, creating the virtual layout is a
bit fiddly, and requires us to sort the memory map and reason about
adjacent regions with identical memory types etc etc.

So the obvious fix is to stop calling SetVirtualAddressMap() altogether
on arm64 systems. However, to avoid surprises, which are notoriously
hard to diagnose when it comes to OS<->firmware interactions, let's
start by making it an opt-out feature, and implement support for the
'efi=novamap' kernel command line parameter on ARM and arm64 systems.

( Note that 32-bit ARM generally does require SetVirtualAddressMap() to be
  used, given that the physical memory map and the kernel virtual address
  map are not guaranteed to be non-overlapping like on arm64. However,
  having support for efi=novamap,noruntime on 32-bit ARM, combined with
  the recently proposed support for earlycon=efifb, is likely to be useful
  to diagnose boot issues on such systems if they have no accessible serial
  port. )
Tested-by: NJeffrey Hugo <jhugo@codeaurora.org>
Tested-by: NBjorn Andersson <bjorn.andersson@linaro.org>
Tested-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Alexander Graf <agraf@suse.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20190202094119.13230-8-ard.biesheuvel@linaro.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

We wish to introduce a 52-bit virtual address space for userspace but
maintain compatibility with software that assumes the maximum VA space
size is 48 bit.

In order to achieve this, on 52-bit VA systems, we make mmap behave as
if it were running on a 48-bit VA system (unless userspace explicitly
requests a VA where addr[51:48] != 0).

On a system running a 52-bit userspace we need TASK_SIZE to represent
the 52-bit limit as it is used in various places to distinguish between
kernelspace and userspace addresses.

Thus we need a new limit for mmap, stack, ELF loader and EFI (which uses
TTBR0) to represent the non-extended VA space.

This patch introduces DEFAULT_MAP_WINDOW and DEFAULT_MAP_WINDOW_64 and
switches the appropriate logic to use that instead of TASK_SIZE.
Signed-off-by: NSteve Capper <steve.capper@arm.com>
Reviewed-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>