Re: [Qemu-devel] [PATCH v4 2/4] linux-user: Set PAGE_TARGET_1 for TARGET_PROT_BTI

[Peter Maydell]

On Mon, 29 Apr 2019 at 21:13, Richard Henderson
<address@hidden> wrote:
>
> On 4/29/19 9:21 AM, Peter Maydell wrote:
> > This looks ok code-wise, but we'd need to hide it behind
> > a defaults-to-off x-something property if we wanted to
> > commit it before the kernel ABI is fixed.
>
> I'm not intending to change the user-level abi, only the
> internal abi within qemu, for handling of the elf notes.

You're changing target_mmap(), which is used by the
guest mmap syscall, though, right?

> You think this should be done differently, so that there's
> zero possibility of a user-level setting the relevant bit?

I think that we shouldn't allow guest binaries written
to the ad-hoc TARGET_PROT_BTI ABI to work without an
explicit x-something command line argument to QEMU, to
indicate that the user knows they're doing something
odd and that these binaries won't always continue to work
in future QEMU versions.

thanks
-- PMM