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Filename Latest commit message Latest commit date
Baoquan He 94133e46a0 x86/efi: Correct EFI identity mapping under 'efi=old_map' when KASLR is enabled
For EFI with the 'efi=old_map' kernel option specified, the kernel will panic
when KASLR is enabled:

  BUG: unable to handle kernel paging request at 000000007febd57e
  IP: 0x7febd57e
  PGD 1025a067
  PUD 0

  Oops: 0010 [#1] SMP
  Call Trace:
   efi_enter_virtual_mode()
   start_kernel()
   x86_64_start_reservations()
   x86_64_start_kernel()
   start_cpu()

The root cause is that the identity mapping is not built correctly
in the 'efi=old_map' case.

On 'nokaslr' kernels, PAGE_OFFSET is 0xffff880000000000 which is PGDIR_SIZE
aligned. We can borrow the PUD table from the direct mappings safely. Given a
physical address X, we have pud_index(X) == pud_index(__va(X)).

However, on KASLR kernels, PAGE_OFFSET is PUD_SIZE aligned. For a given physical
address X, pud_index(X) != pud_index(__va(X)). We can't just copy the PGD entry
from direct mapping to build identity mapping, instead we need to copy the
PUD entries one by one from the direct mapping.

Fix it.

Signed-off-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Young <dyoung@redhat.com>
Cc: Frank Ramsay <frank.ramsay@hpe.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russ Anderson <rja@sgi.com>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20170526113652.21339-5-matt@codeblueprint.co.uk
[ Fixed and reworded the changelog and code comments to be more readable. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-05-28 11:06:16 +02:00
arch x86/efi: Correct EFI identity mapping under 'efi=old_map' when KASLR is enabled 2017-05-28 11:06:16 +02:00
block Merge branch 'nvme-4.12' of git://git.infradead.org/nvme into for-linus 2017-05-26 09:11:19 -06:00
certs
crypto
Documentation Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2017-05-26 16:45:13 -07:00
drivers efi: Remove duplicate 'const' specifiers 2017-05-28 11:06:16 +02:00
firmware
fs Changed since last update: 2017-05-26 12:13:08 -07:00
include TTY/Serial fixes for 4.12-rc3 2017-05-27 09:39:09 -07:00
init
ipc
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-05-27 09:14:24 -07:00
lib test_bpf: Add a couple of tests for BPF_JSGE. 2017-05-25 14:37:56 -04:00
mm
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-05-26 13:51:01 -07:00
samples
scripts
security
sound sound fixes for 4.12-rc3 2017-05-26 09:03:09 -07:00
tools powerpc fixes for 4.12 #4 2017-05-27 09:28:34 -07:00
usr
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.get_maintainer.ignore
.gitattributes
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COPYING
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MAINTAINERS TTY/Serial fixes for 4.12-rc3 2017-05-27 09:39:09 -07:00
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README

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.