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

From: Joerg Roedel
Date: Tue Jan 16 2018 - 11:51:24 EST

From: Joerg Roedel <jroedel@xxxxxxx>


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

- 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

So please review and let me know your thoughts.



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(-)