On 12/18/2015 01:04 PM, Linus Torvalds wrote: > On Fri, Dec 18, 2015 at 12:49 PM, Andy Lutomirski <l...@amacapital.net> wrote: >> >> IOW, I like my idea in which signal delivery always sets PKRU to the >> application-requested-by-syscall values and sigreturn restores it. > > So I don't mind that, as long as the whole "sigreturn restores it" is > part of things. > > Your original email with the suggestion to *not* resture PKRU I didn't > like. Setting it and restoring it is fine. > > I do wonder if you need an explicit value, though. I think it's > reasonable to say that PKRU value 0 is special. It's what we'd start > processes with, and why not just say that it's what we run signal > handlers in? > > Would any other value ever make sense, really?
Having a PKRU with the execute-only permissions set is the only one I can think of. For a system with a _dedicated_ PKEY for execute-only, this is easy and could even be made a part of init_fpstate with no other code changes. But, if we are picking out an execute-only pkey more dynamically, we've got to keep the default value for the entire process somewhere. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
