V2 [PATCH 04/12] x86/CET: Extend arch_prctl syscall for CET control

[Joseph Myers]

On Tue, 24 Jul 2018, H.J. Lu wrote:

> Note: sysdeps/unix/sysv/linux/x86/bits/prctl-internal.h should be
> renamed to sysdeps/unix/sysv/linux/x86/bits/prctl.h after the CET
> kernel interface has been committed into the public kernel.

bits/ should not be used for any internal headers; it's purely a naming 
convention for public headers.  So there should be no 
bits/prctl-internal.h header.

I don't think there should be bits/prctl.h at all either.  Not with this 
patch (because there isn't anything for it to do), and not once the 
interface is in the kernel (because existing practice is that we rely on 
the include of <linux/prctl.h> from <sys/prctl.h> to provide the values to 
users of glibc).

Rather, for the uses of these constants within glibc, to avoid relying on 
new kernel headers, provide an x86 include/sys/prctl.h that does 
#include_next <sys/prctl.h> and then defines these constants if not 
already defined.  And make sure that header gets a prominent comment 
naming the upstream kernel version with the constants (once they are 
upstream), so it's obvious at what point we can remove that header.

-- 
Joseph S. Myers
joseph@codesourcery.com