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    Subject[RFC PATCH 00/16] PTI support for x86-32
    Date
    From: Joerg Roedel <jroedel@suse.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

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