linux-kernel - [RFC PATCH 00/16] PTI support for x86-32

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Date:   Tue, 16 Jan 2018 17:36:43 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>, aliguori@...zon.com,
        daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <llong@...hat.com>, jroedel@...e.de,
        joro@...tes.org
Subject: [RFC PATCH 00/16] PTI support for x86-32

From: Joerg Roedel <jroedel@...e.de>

Hi,

here is my current WIP code to enable PTI on x86-32. It is
still in a pretty early state, but it successfully boots my
KVM guest with PAE and with legacy paging. The existing PTI
code for x86-64 already prepares a lot of the stuff needed
for 32 bit too, thanks for that to all the people involved
in its development :)

The patches are split as follows:

	- 1-3 contain the entry-code changes to enter and
	  exit the kernel via the sysenter trampoline stack.

	- 4-7 are fixes to get the code compile on 32 bit
	  with CONFIG_PAGE_TABLE_ISOLATION=y.

	- 8-14 adapt the existing PTI code to work properly
	  on 32 bit and add the needed parts to 32 bit
	  page-table code.

	- 15 switches PTI on by adding the CR3 switches to
	  kernel entry/exit.

	- 16 enables the Kconfig for all of X86

The code has not run on bare-metal yet, I'll test that in
the next days once I setup a 32 bit box again. I also havn't
tested Wine and DosEMU yet, so this might also be broken.

With that post I'd like to ask for all kinds of constructive
feedback on the approaches I have taken and of course the
many things I broke with it :)

One of the things that are surely broken is XEN_PV support.
I'd appreciate any help with testing and bugfixing on that
front.

So please review and let me know your thoughts.

Thanks,

	Joerg

Joerg Roedel (16):
  x86/entry/32: Rename TSS_sysenter_sp0 to TSS_sysenter_stack
  x86/entry/32: Enter the kernel via trampoline stack
  x86/entry/32: Leave the kernel via the trampoline stack
  x86/pti: Define X86_CR3_PTI_PCID_USER_BIT on x86_32
  x86/pgtable: Move pgdp kernel/user conversion functions to pgtable.h
  x86/mm/ldt: Reserve high address-space range for the LDT
  x86/mm: Move two more functions from pgtable_64.h to pgtable.h
  x86/pgtable/32: Allocate 8k page-tables when PTI is enabled
  x86/mm/pti: Clone CPU_ENTRY_AREA on PMD level on x86_32
  x86/mm/pti: Populate valid user pud entries
  x86/mm/pgtable: Move pti_set_user_pgd() to pgtable.h
  x86/mm/pae: Populate the user page-table with user pgd's
  x86/mm/pti: Add an overflow check to pti_clone_pmds()
  x86/mm/legacy: Populate the user page-table with user pgd's
  x86/entry/32: Switch between kernel and user cr3 on entry/exit
  x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32

 arch/x86/entry/entry_32.S               | 170 +++++++++++++++++++++++++++++---
 arch/x86/include/asm/pgtable-2level.h   |   3 +
 arch/x86/include/asm/pgtable-3level.h   |   3 +
 arch/x86/include/asm/pgtable.h          |  88 +++++++++++++++++
 arch/x86/include/asm/pgtable_32_types.h |   5 +-
 arch/x86/include/asm/pgtable_64.h       |  85 ----------------
 arch/x86/include/asm/processor-flags.h  |   8 +-
 arch/x86/include/asm/switch_to.h        |   6 +-
 arch/x86/kernel/asm-offsets_32.c        |   5 +-
 arch/x86/kernel/cpu/common.c            |   5 +-
 arch/x86/kernel/head_32.S               |  23 ++++-
 arch/x86/kernel/process.c               |   2 -
 arch/x86/kernel/process_32.c            |   6 ++
 arch/x86/mm/pgtable.c                   |  11 ++-
 arch/x86/mm/pti.c                       |  34 ++++++-
 security/Kconfig                        |   2 +-
 16 files changed, 333 insertions(+), 123 deletions(-)

-- 
2.13.6