lkml.org 
[lkml]   [2022]   [Feb]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 05/39] x86: Base IBT bits
On Thu, Feb 24, 2022 at 04:35:51PM -0800, Kees Cook wrote:
> On Thu, Feb 24, 2022 at 03:51:43PM +0100, Peter Zijlstra wrote:
> > Add Kconfig, Makefile and basic instruction support for x86 IBT.
> >
> > XXX clang is not playing ball, probably lld being 'funny', I'm having
> > problems with .plt entries appearing all over after linking.
>
> I'll try to look into this; I know you've been chatting with Nathan
> about it. Is there an open bug for it? (And any kind of reproducer
> smaller than a 39 patch series we can show the linker folks?) :)

I should be able to create a reproducer with cvise and file a bug on
GitHub around this tomorrow, I should have done it after Peter's
comments on IRC.

Cheers,
Nathan

> > [...]
> > +config X86_KERNEL_IBT
> > + prompt "Indirect Branch Tracking"
> > + bool
> > + depends on X86_64 && CC_HAS_IBT
> > + help
> > + Build the kernel with support for Indirect Branch Tracking, a
> > + hardware supported CFI scheme. Any indirect call must land on
>
> hardware support course-grain forward-edge Control Flow Integrity
> protection. It enforces that all indirect calls must land on
>
> > + an ENDBR instruction, as such, the compiler will litter the
> > + code with them to make this happen.
>
> "litter the code" -> "instrument the machine code".
>
>
> > +
> > config X86_INTEL_MEMORY_PROTECTION_KEYS
> > prompt "Memory Protection Keys"
> > def_bool y
> > --- a/arch/x86/Makefile
> > +++ b/arch/x86/Makefile
> > @@ -36,7 +36,7 @@ endif
> >
> > # How to compile the 16-bit code. Note we always compile for -march=i386;
> > # that way we can complain to the user if the CPU is insufficient.
> > -REALMODE_CFLAGS := -m16 -g -Os -DDISABLE_BRANCH_PROFILING \
> > +REALMODE_CFLAGS := -m16 -g -Os -DDISABLE_BRANCH_PROFILING -D__DISABLE_EXPORTS \
> > -Wall -Wstrict-prototypes -march=i386 -mregparm=3 \
> > -fno-strict-aliasing -fomit-frame-pointer -fno-pic \
> > -mno-mmx -mno-sse $(call cc-option,-fcf-protection=none)
>
> This change seems important separately from this patch, yes? (Or at
> least a specific call-out in the commit log.)
>
> Otherwise, looks good.
>
> --
> Kees Cook

\
 
 \ /
  Last update: 2022-02-25 01:48    [W:0.295 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site