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

[Nadav Amit]

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 âtestâ the protection?

Thanks,
Nadav


Joerg Roedel <joro@xxxxxxxxxx> wrote:

> From: Joerg Roedel <jroedel@xxxxxxx>
> 
> 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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