Hi Dave, On 9 December 2015 at 16:48, Dave Hansen <dave@xxxxxxxx> wrote: > Hi Michael, > > Thanks for all the comments! I'll fix most of it when I post a new > version of the manpage, but I have a few general questions. > > On 12/09/2015 03:08 AM, Michael Kerrisk (man-pages) wrote: >>> >>> +is the protection or storage key to assign to the memory. >> >> Why "protection or storage key" here? This phrasing seems a >> little ambiguous to me, given that we also have a 'prot' >> argument. I think it would be clearer just to say >> "protection key". But maybe I'm missing something. > > x86 calls it a "protection key" while powerpc calls it a "storage key". > They're called "protection keys" consistently inside the kernel. > > Should we just stick to one name in the manpages? Yes. But perhaps you could note the alternate name in the pkey(7) page. >> * A general overview of why this functionality is useful. > > Any preference on a central spot to do the general overview? Does it go > in one of the manpages I'm already modifying, or a new one? How about we add one more page, pkey(7) that gives the overview and also summarizes the APIs. >> * A note on which architectures support/will support >> this functionality. > > x86 only for now. We might get powerpc support down the road somewhere. Supported architectures can be listed in pkey(7). >> * Explanation of what a protection domain is. > > A protection domain is a unique view of memory and is represented by the > value in the PKRU register. Out something about this in pkey(7), but explain what you mean by a "unique view of memory". >> * Explanation of how a process (thread?) changes its >> protection domain. > > Changing protection domains is done by pkey_set() system call, or by > using the WRPKRU instruction. The system call is preferred and less > error-prone since it enforces that a protection is allocated before its > access protection can be modified. Details (perhaps not the WRPKRU bit) that should go in pkey(7). >> * Explanation of the relationship between page permission >> bits (PROT_READ/PROT_WRITE/PROTE_EXEC) and >> PKEY_DISABLE_ACCESS and PKEY_DISABLE_WRITE. >> It's still not clear to me. Do the PKEY_* bits >> override the PROT_* bits. Or, something else? > > Protection keys add access restrictions in addition to existing page > permissions. They can only take away access; they never grant > additional access. This belongs in pkey(7) :-). Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>