efi: Add support for a UEFI variable filesystem

The existing EFI variables code only supports variables of up to 1024
bytes. This limitation existed in version 0.99 of the EFI specification,
but was removed before any full releases. Since variables can now be
larger than a single page, sysfs isn't the best interface for this. So,
instead, let's add a filesystem. Variables can be read, written and
created, with the first 4 bytes of each variable representing its UEFI
attributes. The create() method doesn't actually commit to flash since
zero-length variables can't exist per-spec.

Updates from Jeremy Kerr <jeremy.kerr@canonical.com>.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efi: Handle deletions and size changes in efivarfs_write_file

A write to an efivarfs file will not always result in a variable of
'count' size after the EFI SetVariable() call. We may have appended to
the existing data (ie, with the EFI_VARIABLE_APPEND_WRITE attribute), or
even have deleted the variable (with an authenticated variable update,
with a zero datasize).

This change re-reads the updated variable from firmware, to check for
size changes and deletions. In the latter case, we need to drop the
dentry.

Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efi: add efivars kobject to efi sysfs folder

UEFI variable filesystem need a new mount point, so this patch add
efivars kobject to efi_kobj for create a /sys/firmware/efi/efivars
folder.

Cc: Matthew Garrett <mjg@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: Add documentation for the EFI variable filesystem

Signed-off-by: Matt Fleming <matt.fleming@intel.com>
x86, mm: Include the entire kernel memory map in trampoline_pgd

There are various pieces of code in arch/x86 that require a page table
with an identity mapping. Make trampoline_pgd a proper kernel page
table, it currently only includes the kernel text and module space
mapping.

One new feature of trampoline_pgd is that it now has mappings for the
physical I/O device addresses, which are inserted at ioremap()
time. Some broken implementations of EFI firmware require these
mappings to always be around.

Acked-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
x86, efi: 1:1 pagetable mapping for virtual EFI calls

Some firmware still needs a 1:1 (virt->phys) mapping even after we've
called SetVirtualAddressMap(). So install the mapping alongside our
existing kernel mapping whenever we make EFI calls in virtual mode.

This bug was discovered on ASUS machines where the firmware
implementation of GetTime() accesses the RTC device via physical
addresses, even though that's bogus per the UEFI spec since we've
informed the firmware via SetVirtualAddressMap() that the boottime
memory map is no longer valid.

This bug seems to be present in a lot of consumer devices, so there's
not a lot we can do about this spec violation apart from workaround
it.

Cc: JérômeCarretero <cJ-ko@zougloub.eu>
Cc: Vasco Dias <rafa.vasco@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
x86/kernel: remove tboot 1:1 page table creation code

For TXT boot, while Linux kernel trys to shutdown/S3/S4/reboot, it
need to jump back to tboot code and do TXT teardown work. Previously
kernel zapped all mem page identity mapping (va=pa) after booting, so
tboot code mem address was mapped again with identity mapping. Now
kernel didn't zap the identity mapping page table, so tboot related
code can remove the remapping code before trapping back now.

Signed-off-by: Xiaoyan Zhang <xiaoyan.zhang@intel.com>
Acked-by: Gang Wei <gang.wei@intel.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
x86-64/efi: Use EFI to deal with platform wall clock (again)

Other than ix86, x86-64 on EFI so far didn't set the
{g,s}et_wallclock accessors to the EFI routines, thus
incorrectly using raw RTC accesses instead.

Simply removing the #ifdef around the respective code isn't
enough, however: While so far early get-time calls were done in
physical mode, this doesn't work properly for x86-64, as virtual
addresses would still need to be set up for all runtime regions
(which wasn't the case on the system I have access to), so
instead the patch moves the call to efi_enter_virtual_mode()
ahead (which in turn allows to drop all code related to calling
efi-get-time in physical mode).

Additionally the earlier calling of efi_set_executable()
requires the CPA code to cope, i.e. during early boot it must be
avoided to call cpa_flush_array(), as the first thing this
function does is a BUG_ON(irqs_disabled()).

Also make the two EFI functions in question here static -
they're not being referenced elsewhere.

History:

    This commit was originally merged as bacef661acdb ("x86-64/efi:
    Use EFI to deal with platform wall clock") but it resulted in some
    ASUS machines no longer booting due to a firmware bug, and so was
    reverted in f026cfa82f62. A pre-emptive fix for the buggy ASUS
    firmware was merged in 03a1c254975e ("x86, efi: 1:1 pagetable
    mapping for virtual EFI calls") so now this patch can be
    reapplied.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Matt Fleming <matt.fleming@intel.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com> [added commit history]
efivarfs: efivarfs_file_read ensure we free data in error paths

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: efivarfs_create() ensure we drop our reference on inode on error

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: efivarfs_fill_super() fix inode reference counts

When d_make_root() fails it will automatically drop the reference
on the root inode.  We should not be doing so as well.

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: efivarfs_fill_super() ensure we free our temporary name

d_alloc_name() copies the passed name to new storage, once complete we
no longer need our name.

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: efivarfs_fill_super() ensure we clean up correctly on error

Ensure we free both the name and inode on error when building the
individual variables.

Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: Implement exclusive access for {get,set}_variable

Currently, efivarfs does not enforce exclusion over the get_variable and
set_variable operations. Section 7.1 of UEFI requires us to only allow a
single processor to enter {get,set}_variable services at once.

This change acquires the efivars->lock over calls to these operations
from the efivarfs paths.

Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efi: Clarify GUID length calculations

At present, the handling of GUIDs in efivar file names isn't consistent.
We use GUID_LEN in some places, and 38 in others (GUID_LEN plus
separator), and implicitly use the presence of the trailing NUL.

This change removes the trailing NUL from GUID_LEN, so that we're
explicitly adding it when required. We also replace magic numbers
with GUID_LEN, and clarify the comments where appropriate.

We also fix the allocation size in efivar_create_sysfs_entry, where
we're allocating one byte too much, due to counting the trailing NUL
twice - once when calculating short_name_size, and once in the kzalloc.

Signed-off-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: Return an error if we fail to read a variable

Instead of always returning 0 in efivarfs_file_read(), even when we
fail to successfully read the variable, convert the EFI status to
something meaningful and return that to the caller. This way the user
will have some hint as to why the read failed.

Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: Replace magic number with sizeof(attributes)

Seeing "+ 4" littered throughout the functions gets a bit
confusing. Use "sizeof(attributes)" which clearly explains what
quantity we're adding.

Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: Add unique magic number

Using pstore's superblock magic number is no doubt going to cause
problems in the future. Give efivarfs its own magic number.

Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: Make 'datasize' unsigned long

There's no reason to declare 'datasize' as an int, since the majority
of the functions it's passed to expect an unsigned long anyway. Plus,
this way we avoid any sign problems during arithmetic.

Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
efivarfs: Return a consistent error when efivarfs_get_inode() fails

Instead of returning -ENOSPC if efivarfs_get_inode() fails we should
be returning -ENOMEM, since running out of memory is the only reason
it can fail.  Furthermore, that's the error value used everywhere else
in this file. It's also less likely to confuse users that hit this
error case.

Acked-by: Jeremy Kerr <jeremy.kerr@canonical.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>