Re: [PATCH v4 1/6] x86/elf: Add table to document READ_IMPLIES_EXEC

[Kees Cook]

On Wed, Mar 11, 2020 at 08:44:46PM +0100, Borislav Petkov wrote:
> Ozenn Mon, Feb 24, 2020 at 09:13:02PM -0800, Kees Cook wrote:
> > Add a table to document the current behavior of READ_IMPLIES_EXEC in
> > preparation for changing the behavior.
> > 
> > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
> > ---
> >  arch/x86/include/asm/elf.h | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> > 
> > diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
> > index 69c0f892e310..733f69c2b053 100644
> > --- a/arch/x86/include/asm/elf.h
> > +++ b/arch/x86/include/asm/elf.h
> > @@ -281,6 +281,25 @@ extern u32 elf_hwcap2;
> >  /*
> >   * An executable for which elf_read_implies_exec() returns TRUE will
> >   * have the READ_IMPLIES_EXEC personality flag set automatically.
> > + *
> > + * The decision process for determining the results are:
> > + *
> > + *              CPU: | lacks NX*  | has NX, ia32     | has NX, x86_64 |
> > + * ELF:              |            |                  |                |
> > + * -------------------------------|------------------|----------------|
> > + * missing GNU_STACK | exec-all   | exec-all         | exec-all       |
> > + * GNU_STACK == RWX  | exec-all   | exec-all         | exec-all       |
> > + * GNU_STACK == RW   | exec-none  | exec-none        | exec-none      |
> 
> In all those tables, you wanna do:
> 
> s/GNU_STACK/PT_GNU_STACK/g
> 
> so that it is clear what this define is.

Fair enough. :) I think I was trying to save 3 characters from earlier
tables that were wider. I'll send a v5.

Thanks!

-Kees

-- 
Kees Cook