On 3/23/2021 1:49 PM, Peter Zijlstra wrote:

On Fri, Mar 19, 2021 at 02:43:04PM -0700, Yu, Yu-cheng wrote:

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On 3/16/2021 2:15 PM, Peter Zijlstra wrote:

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On Tue, Mar 16, 2021 at 08:10:26AM -0700, Yu-cheng Yu wrote:

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Control-flow Enforcement (CET) is a new Intel processor feature that blocks
return/jump-oriented programming attacks.  Details are in "Intel 64 and
IA-32 Architectures Software Developer's Manual" [1].

CET can protect applications and the kernel.  This series enables only
application-level protection, and has three parts:

    - Shadow stack [2],
    - Indirect branch tracking [3], and
    - Selftests [4].

CET is marketing; afaict SS and IBT are 100% independent and there's no
reason what so ever to have them share any code, let alone a Kconfig
knob.

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In fact, I think all of this would improve is you remove the CET name

from all of this entirely. Put this series under CONFIG_X86_SHSTK (or
_SS) and use CONFIG_X86_IBT for the other one.

Similarly with the .c file.

All this CET business is just pure confusion.

What about this, we bring back CONFIG_X86_SHSTK and CONFIG_X86_IBT.
For the CET name itself, can we change it to CFE (Control Flow Enforcement),
or just CF?

Carry Flag :-)

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In signal handling, ELF header parsing and arch_prctl(), shadow stack and
IBT pretty much share the same code.  It is better not to split them into
two sets of files.

Aside from redoing the UAPI we're stuck with that I suppose :/ And since
I think the CET name is all over the UAPI, you might as well keep it for
the kernel part of it as well :-(

But if there's sufficient !UAPI bits it might still make sense to also
have ibt.c and shstk.c

I will move code around and separate it into shadow stack and ibt. 
Hopefully in the next iteration, things will be more organized.

Thanks,
Yu-cheng