Re: [RFC PATCH v6 22/26] x86/cet/shstk: ELF header parsing of Shadow Stack

Yu-cheng Yu
2019-04-25T16:20:56Z

On Thu, 2019-04-25 at 16:35 +0100, Dave Martin wrote:
> On Thu, Apr 25, 2019 at 08:14:52AM -0700, Yu-cheng Yu wrote:
> > On Thu, 2019-04-25 at 12:02 +0100, Dave Martin wrote:
> > > [...]
> One other question: according to the draft spec at
> https://github.com/hjl-tools/linux-abi/wiki/Linux-Extensions-to-gABI, it
> looks like the .note.gnu.property section is supposed to be marked with
> SHF_ALLOC in object files.
>
> I think that means that the linker will map it with a PT_LOAD entry in
> the program header table in addition to the PT_NOTE that describes the
> location of the note. I need to check what the toolchain actually
> does.
>
> If so, can we simply rely on the notes being already mapped, rather than
> needing to do additional I/O on the ELF file to fetch the notes?

Assuming that is mapped and we do copy_from_user, it will trigger page faults.
I suspect in this case reading from the file is better?

Yu-cheng