Hi Mike, On Tue, Apr 24, 2012 at 4:24 PM, Mike Frysinger <vapier@xxxxxxxxxx> wrote: > On Saturday 14 April 2012 17:22:06 Michael Kerrisk (man-pages) wrote: >> The count arguments and >> .IR local_iov >> are checked before doing any transfers. >> If the counts are too big, or >> .I local_iov >> is invalid, >> or the addresses refer to regions that are inaccessible to the local >> process, none of the vectors will be processed >> and an error will be returned immediately. > > to be clear, the arrays themselves are checked to see if they point to valid > memory, as are the count values, before the transfer takes place. so if > local_iov/remote_iov are NULL or similarly invalid, nothing happens. in > practice, this generally equates to the same thing, but there is a slight edge > case -- if the remote_iov array is mostly valid, but the remote count value > causes it to spill into invalid memory, nothing will be processed. note that > i'm talking about the storage of the elements themselves and not the memory > they point to. but maybe being super pedantic here isn't necessary ... > >> Note, however, that these system calls do not check the memory regions >> in the remote process until just before doing the read/write. >> Consequently, a partial read/write may result if one of the > > any mention of a partial read/write should point to the text clarifying what > that means (perhaps something as simple as "see RETURN VALUE for more info". I added a reference to RETURN VALUE there. >> Does that not make better sense? > > it does Good. >> Perhaps I'm too clogged up with a cold, but I couldn't draw an answer >> to the question " does "a single iovec element" here apply to the >> remote iovec elements, the local iovec elements, or both?" from your >> reply. > > wrt partial transfers, remote only afaict. this is by virtue of nothing being > transferred at all if any of the local elements are invalid. Okay -- I added the word "remote". Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
