On Thu, Apr 21, 2016 at 06:27:13PM +0200, Gabriel Laskar wrote: > On Thu, 21 Apr 2016 14:04:33 +0100 > "Dr. David Alan Gilbert" <dgilb...@redhat.com> wrote: > > > Hi, > > Please find below a decoder for the UFFDIO_COPY ioctl > > on the userfaultfd fd; but there are a few other ioctls > > in the set to decode and I thought I'd ask before doing those: > > > > 1) Is it basically on the right lines; I'm not that confident > > I understand the return flags on the ioctl decoder function. > > The return flags are the same as for the syscalls in general, it is > written in defs.h around line 378. It allows to type the return value > if it is not an int. > > For the ioctl decoding function, on entering there is: > > * 0 if nothing has been decoded, (and it will be probably done on > exiting()) > * 1 parameter have been parsed, and printed > * RVAL_DECODED if there is nothing else to do. > * 1 | RVAL_DECODED : parameter have been parsed, but there is some kind > of error/nothing has been printed, so this allow the ioctl decoder to > write a default value. > > and on exiting, there is only 0 or 1.
You can find the result of my attempt to explain this semantics in the mailing list archive, e.g. at https://sourceforge.net/p/strace/mailman/message/34451172/ -- ldv
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