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SubjectRe: [RFC PATCH 00/16] PTI support for x86-32
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Please ignore my previous email. I got it working… Sorry for the spam.


Nadav Amit <nadav.amit@gmail.com> wrote:

> I am looking on PTI on x86-32, but I did not mange to get the PoC to work on
> this setup (kaslr disabled, similar setup works on 64-bit).
>
> Did you use any PoC to “test” the protection?
>
> Thanks,
> Nadav
>
>
> Joerg Roedel <joro@8bytes.org> wrote:
>
>> 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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