#4328: New APIs added to POSIX Standard (2021)

Matthew Joyce mfjoyce2004 at gmail.com
Thu Mar 25 15:51:09 UTC 2021 

Oh wow. That makes so much more sense now! Thanks very much for the
clarification!

Sincerely,

Matt

On Thu, Mar 25, 2021 at 2:18 PM Joel Sherrill <joel at rtems.org> wrote:
>
>
>
> On Thu, Mar 25, 2021 at 7:14 AM Matthew Joyce <mfjoyce2004 at gmail.com> wrote:
>>
>> Hi Dr. Joel,
>>
>> Thanks very much, that's a big help!  Correct, I've been updating the
>> spreadsheet as I go along. Ok, now I see that strlcat/strlcpy are used
>> in rtems/cpukit and implemented in Newlib.
>>
>> One additional question, please: I haven't yet looked into the source
>> of NetBSD or FreeBSD, but I do see that Newlib already implements
>> ppoll (poll.cc), dladdr (dlfcn.cc), pselect (select.cc), and
>> sockatmark (net.cc). None of them are defined in the rtems environment
>> yet. Is there any reason why the NetBSD/FreeBSD version would be
>> preferable to Newlib for these? Or is it just a matter of testing
>> what's out there to find what works well in the rtems environment?
>
>
> Without looking at the newlib git repo, I can tell you that the files
> you cite are the implementation of those methods for Cygwin. Just
> because they are in C++. :)
>
> The parts of the newlib repo RTEMS uses are under the newlib/
> subdirectory not the cygwin one. Within that, there is a libc/sys and
> only libc/sys/rtems is used for RTEMS. The others are for different
> operating systems. There are a few places with "machine" directory
> structures. Only the ones for the architecture you are building for
> is used.
>
> As to why NetBSD for libdl, that is because portions of the code
> originated there.
>
> And rtems-libbsd is based on FreeBSD. It is as close to the FreeBSD
> source as we can keep it.
>
>>
>>
>> In my proposal I'll take your advice and work on some of the easier
>> ones first in order to get the experience and process down.
>
>
> There are tickets for a lot of methods. The rtems-docs repo has the
> csv file (e.g. spreadsheet) which tracks RTEMS support against
> various standards. The RTEMS POSIX Compliance Guide is generated
> from that csv file. Between those, you can find other methods to ask
> about. In general, if it is required by the Software Communications
> Architecture (SCA) or FACE Technical Standard, then it is a method
> someone expected to possibly be used in an embedded system.
> SCA is a set of POSIX profiles focused on software defined radios and
> the FACE Technical Standard was developed with avionics in mind.
>
> But any are fair game if they are actually implementable. I don;t think
> the Compliance Guide says it yet, but we decided last year that
> wordexp() is likely not supportable on RTEMS. The newlib
> implementation assumes the presence of a shell with wildcard expansion
> and ability to fork a process.
>
> --joel
>
>>
>>
>> Thank you again for your time!
>>
>> Matt
>>
>> On Wed, Mar 24, 2021 at 5:03 PM Joel Sherrill <joel at rtems.org> wrote:
>> >
>> > Wow! Good work. There is a lot to digest here. Comments interspersed.
>> >
>> > I assume the spreadsheet is updated.
>> >
>> > On Wed, Mar 24, 2021 at 7:38 AM Matthew Joyce <mfjoyce2004 at gmail.com> wrote:
>> >>
>> >> Hi Dr. Joel,
>> >>
>> >> I've gone over the list a few times now and see a few categories shaping up:
>> >>
>> >> 1) Already done (In Newlib source, defined in libc.a):
>> >> a) reallocarray
>> >> b) qsort_r
>> >> c) memmem
>> >> d) strlcat / strlcpy
>> >> d) wcslcat / wcslcpy
>> >> *Out of this group, strlcat and strlcpy also show up in
>> >> src/rtems/cpukit. Why is that?
>> >
>> >
>> > The good news is that we support these. :)
>> >
>> > It looks to me that strlcat and strlcpy are used in cpukit but not implemented
>> > there. Where do you think they are implemented.
>> >
>> > This is a good example where a source code browser is helpful. grep can
>> > often answer the question but a source code browser can be easier. Personally,
>> > I use cscope but that is exceedingly old school. Any modern IDE should be
>> > helpful.
>> >
>> >>
>> >> 2) Not done yet (Do not show up in Newlib source or RTEMS):
>> >> a) getlocalename_l
>> >> b) posix_getdents
>> >> c) sem_clockwait
>> >> d) sig2str / str2sig
>> >>
>> >> 3) Not in Newlib; Referenced in RTEMS but hidden behind #ifdef:
>> >> a) pthread_cond_clockwait
>> >> (rtems/6/lib/gcc/sparc-rtems6/10.2.1/include/c++/condition_variable)
>> >> b) pthread_mutex_clocklock
>> >> (rtems/6/lib/gcc/sparc-rtems6/10.2.1/include/c++/mutex)
>> >> c) pthread_rwlock_clockrdlock
>> >> (rtems/6/lib/gcc/sparc-rtems6/10.2.1/include/c++/shared_mutex)
>> >> c) pthread_rwlock_clockwrlock
>> >> (rtems/6/lib/gcc/sparc-rtems6/10.2.1/include/c++/shared_mutex)
>> >> *It looks like some groundwork was done, but the methods are not yet supported.
>> >
>> >
>> > The paths you point to are C++ files that would implement C++ features
>> > using the available POSIX services. So they are users, not providers.
>> >
>> > All of the pthread services related to these are implemented in
>> > cpukit/posix/src. I think you can configure a clock for all these now
>> > to be used by detailed on wait and timedwait calls. My understanding
>> > is that these would let you use a specific clock on a per blocking call
>> > basis.
>> >
>> > First question is which clocks are intended to be supported.
>> >
>> > Second is the pattern of picking which timeout queue to go on when
>> > now it is coded to let you pick one which is used for the life of the object.
>> >
>> >>
>> >> 4) Misc (In Newlib source, not defined in libc.a, appear in RTEMS in
>> >> various ways)
>> >> a) getentropy (an alternate version is defined in RTEMS librtemsbsd.a,
>> >> in src/rtems/bsps/shared/dev/getentropy/getentropy-cpucounter.c. The
>> >> comments note that it is not cryptographically secure, so it may not
>> >> fit the bill for the getentropy() mentioned in the Open Group
>> >> document)
>> >
>> >
>> > I am far from a cryptography expert but this looks like a case where
>> > this method would be considered supported with the disclaimer that
>> > the quality of the entropy value depends on the BSP. If the user has
>> > specific requirements, they will need to verify the implementation
>> > used by the BSP by default is appropriate.
>> >
>> >>
>> >> b) ppoll (appears in rtems/6/share/gdb/syscalls)
>> >
>> >
>> > You need to be more careful with the grep. These again are in the
>> > installed tools and in this case, they appear in an XML file. Referenced
>> > but not implemented.
>> >
>> > ppoll() will need to come from rtems-libbsd. The required system call
>> > is included but disabled currently. AFAIK this means it is possible to
>> > provide this but that would require a more detailed discussion in case
>> > some underlying capability is missing. Chris Johns and Sebastian
>> > Huber would be the ones to guide here.
>> >
>> > Ruling: Likely possible.
>> >
>> >>
>> >> c) dladdr (appears in rtems/cpukit but not defined)
>> >
>> >
>> > I think this can be implemented in libdl but I am not sure if the
>> > code from NetBSD from this would directly work or just be a guide.
>> >
>> >>
>> >>
>> >> 5) Others?
>> >> It looks like there was work done on methods like sockatmark and
>> >> pselect, but I don't see them supported as yet. Should those be added
>> >> to the list or are they still being worked on?
>> >
>> >
>> > These would come from rtems-libbsd.
>> >
>> > I think sockatmark.c is implemented in freebsd/lib/libc/net/sockatmark.c
>> > but I don't know if the ioctl() is implemented. I expect it is but this would
>> > at least require a test. It may just work.
>> >
>> > pselect() looks to be missing and would have to be ported from FreeBSD.
>> >
>> >>
>> >> As you suggested, I'll look into NetBSD for dladdr and do some digging
>> >> on the implementation of the other outstanding methods. You mentioned
>> >> that the "clock" ones have to be strictly added to rtems/cpukit, but
>> >> the references I found above are all in lib/gcc/sparc-rtems6/10.2.1.
>> >> Why is that the case and what is 10.2.1? Also, I'm not sure what to
>> >> make of getentropy and ppoll based on what I found above...at your
>> >> convenience could you please advise?
>> >
>> >
>> > Hopefully the above helped.
>> >
>> > You don't have to restrict your possible set to these new additions.
>> > There are others. I think Eshan has done the research for where to
>> > get implementations of the missing long double methods for newlib.
>> > And there are tickets for other missing methods or specific capabilities
>> > in methods that are supported. Those are quite possible to have
>> > some alternatives that are easier to approach.
>> >
>> > --joel
>> >
>> >
>> >>
>> >>
>> >> Thank you very much!
>> >>
>> >> Matt
>> >>
>> >>
>> >>
>> >>
>> >> On Sun, Mar 21, 2021 at 6:38 PM Joel Sherrill <joel at rtems.org> wrote:
>> >> >
>> >> >
>> >> >
>> >> > On Sun, Mar 21, 2021 at 2:28 AM Matthew Joyce <mfjoyce2004 at gmail.com> wrote:
>> >> >>
>> >> >> Gentlemen,
>> >> >>
>> >> >> Awesome, thanks!  I see how that works now...I'll give it a thorough
>> >> >> look tomorrow and will update the spreadsheet accordingly. I'll pipe
>> >> >> back up when I have a more accurate look of what's currently there.
>> >> >
>> >> >
>> >> > Knowing what doesn't have to be done is the first step. (rtems, newlib, and libbsd)
>> >> >
>> >> > I'd be prone to look for things that are easy to add first.
>> >> >
>> >> > Some may not be implementable on RTEMS due to only supporting a
>> >> > single process and no virtual memory. If you have doubts on whether it
>> >> > is possible to support a specific method, speak up and let's try to decide.
>> >> >
>> >> > Then find upstream places for an implementation where possible. I suspect
>> >> > all the new "clock" methods will require discussion on an implementation
>> >> > pattern but those must strictly be added to rtems/cpukit with tests and
>> >> > documentation. At least I can throw you that much. :)
>> >> >
>> >> >>
>> >> >> Thanks again and have a great Sunday!
>> >> >>
>> >> >> Matt
>> >> >>
>> >> >> On Fri, Mar 19, 2021 at 8:27 PM Joel Sherrill <joel at rtems.org> wrote:
>> >> >> >
>> >> >> >
>> >> >> >
>> >> >> > On Fri, Mar 19, 2021 at 1:08 PM Gedare Bloom <gedare at rtems.org> wrote:
>> >> >> >>
>> >> >> >> On Fri, Mar 19, 2021 at 11:16 AM Matthew Joyce <mfjoyce2004 at gmail.com> wrote:
>> >> >> >> >
>> >> >> >> > Dr. Joel,
>> >> >> >> >
>> >> >> >> > Thanks very much...I'll keep working to get a sense of what goes
>> >> >> >> > where! In the meantime, where can I look to get the ground truth of
>> >> >> >> > which methods are "in RTEMS" as opposed to those in newlib?
>> >> >> >> >
>> >> >> >> There is only one ground truth:
>> >> >> >> git://git.rtems.org/rtems.git
>> >> >> >>
>> >> >> >> And for newlib
>> >> >> >>
>> >> >> >> git://sourceware.org/git/newlib-cygwin.git
>> >> >> >>
>> >> >> >> That said, searching for the function name symbols in compiled
>> >> >> >> libraries is a good first step to rule out newlib. Then, you can
>> >> >> >> 'grep' the RTEMS source code for the function names to see if they
>> >> >> >> exist there.
>> >> >> >
>> >> >> >
>> >> >> > rtems/cpukit to be specitic. It won't be implemented anywhere else.
>> >> >> >
>> >> >> > And clearly we both have forgotten that networking APIs are in the
>> >> >> > rtems-libbsd repository.
>> >> >> >
>> >> >> > https://git.rtems.org/rtems-libbsd/
>> >> >> >
>> >> >> > I suspect ppoll() might already be in there. Or at least supported by
>> >> >> > FreeBSD.
>> >> >> >
>> >> >> > You should clone everything and grep the sources. newlib already has
>> >> >> > qsort_r. This is the nm I used:
>> >> >> >
>> >> >> > $ ~/rtems-work/tools/6/bin/sparc-rtems6-nm ~/rtems-work/tools/6/sparc-rtems6/lib/libc.a | grep qsort_r
>> >> >> > lib_a-bsd_qsort_r.o:
>> >> >> > 00000000 T __bsd_qsort_r
>> >> >> > lib_a-qsort_r.o:
>> >> >> > 00000000 T qsort_r
>> >> >> >
>> >> >> > Notice the last line has "T qsort_r" which says it is defined.
>> >> >> >
>> >> >> > grep -r in the newlib source shows it is in ./libc/search/qsort_r.c
>> >> >> >
>> >> >> > dladdr() looks to be prototyped in RTEMS but hidden behind an ifdef like it
>> >> >> > wasn't ported from NetBSD so that looks possible. It is in rtems.
>> >> >> >
>> >> >> > Those two examples should help you figure out why you missed
>> >> >> > finding some things that were implemented.
>> >> >> >
>> >> >> > I need to figure out what this next POSIX version is to be called
>> >> >> > so I can update the tracking spreadsheet that generates the RTEMS
>> >> >> > POSIX Compliance Guide, :)
>> >> >> >
>> >> >> > --joel
>> >> >> >>
>> >> >> >>
>> >> >> >> > Thanks again!
>> >> >> >> >
>> >> >> >> > Matt
>> >> >> >> >
>> >> >> >> > On Fri, Mar 19, 2021 at 1:58 PM Joel Sherrill <joel at rtems.org> wrote:
>> >> >> >> > >
>> >> >> >> > > Keep devel@ on the list. :)
>> >> >> >> > >
>> >> >> >> > > On Fri, Mar 19, 2021 at 7:51 AM Matthew Joyce <mfjoyce2004 at gmail.com> wrote:
>> >> >> >> > >>
>> >> >> >> > >> Sir,
>> >> >> >> > >>
>> >> >> >> > >> Thank you for the link! I see that you're right, those last four are
>> >> >> >> > >> in newlib, plus memmem(). I updated those in the Google Sheet.
>> >> >> >> > >>
>> >> >> >> > >> Now I see the newlib part, but where are you referring to specifically
>> >> >> >> > >> when you say RTEMS, as in "POSIX support comes from a mix of RTEMS and
>> >> >> >> > >> newlib"?
>> >> >> >> > >
>> >> >> >> > >
>> >> >> >> > > POSIX is a HUGE HUGE standard and references other standards. One
>> >> >> >> > > it references and pulls in is the C99 Standard C Library which is libc and
>> >> >> >> > > libm. RTEMS mostly does not implement this functionality and relies on
>> >> >> >> > > another open source project for those APIs. Newlib is an open source
>> >> >> >> > > C Library used by RTEMS, Cygwin, and most embedded systems GNU tools
>> >> >> >> > > chains.
>> >> >> >> > >
>> >> >> >> > > Most of the POSIX header files with RTEMS are actually in Newlib even
>> >> >> >> > > if they originated with RTEMS. Many are shared with Cygwin.
>> >> >> >> > >
>> >> >> >> > > So methods like the string, memory, and *printf come from Newlib since they
>> >> >> >> > > are in C99. We provide POSIX like threading, signals, core file access, and
>> >> >> >> > > much more.
>> >> >> >> > >
>> >> >> >> > > It's a complementary relationship but it takes a bit to figure out when
>> >> >> >> > > something should be in one or the other. The line gets blurred at times.
>> >> >> >> > >
>> >> >> >> > > Say you added a new CPU architecture implementation of a math
>> >> >> >> > > method (like Eshan did last year), then it goes in newlib. But he also
>> >> >> >> > > added some POSIX methods which go in RTEMS. In either case,
>> >> >> >> > > we like tests for them in RTEMS to show they work in our environment.
>> >> >> >> > >
>> >> >> >> > > --joel
>> >> >> >> > >
>> >> >> >> > >
>> >> >> >> > >
>> >> >> >> > >>
>> >> >> >> > >> Thanks again!
>> >> >> >> > >>
>> >> >> >> > >> Matt
>> >> >> >> > >>
>> >> >> >> > >> On Fri, Mar 19, 2021 at 1:13 PM Joel Sherrill <joel at rtems.org> wrote:
>> >> >> >> > >> >
>> >> >> >> > >> >
>> >> >> >> > >> >
>> >> >> >> > >> > On Fri, Mar 19, 2021, 6:40 AM Joel Sherrill <joel at rtems.org> wrote:
>> >> >> >> > >> >>
>> >> >> >> > >> >>
>> >> >> >> > >> >>
>> >> >> >> > >> >> On Fri, Mar 19, 2021, 5:48 AM Matthew Joyce <mfjoyce2004 at gmail.com> wrote:
>> >> >> >> > >> >>>
>> >> >> >> > >> >>> https://docs.google.com/spreadsheets/d/1reCNOIZC5JTwQENgl-hvG8THfQqNtlUDVy_07PYodic/edit?usp=sharing
>> >> >> >> > >> >>>
>> >> >> >> > >> >>> Hello,
>> >> >> >> > >> >>>
>> >> >> >> > >> >>> As suggested by Dr. Sherril, I've taken an initial look through this
>> >> >> >> > >> >>> document https://www.opengroup.org/austin/docs/austin_1110.pdf and
>> >> >> >> > >> >>> added the new methods  to a Googe Sheet, linked above.
>> >> >> >> > >> >>>
>> >> >> >> > >> >>> None of them appear to be in the RTEMS POSIX API Users Guide, but
>> >> >> >> > >> >>> maybe that's not the right place to look. I'll stand by for your
>> >> >> >> > >> >>> feedback regarding what's possible / desirable to add to RTEMS.
>> >> >> >> > >> >>
>> >> >> >> > >> >>
>> >> >> >> > >> >> It is possible they are in our C Library or Math Library.  Or just not in the manual. The POSIX manual tends to be sparse since you can always use man pages or the POSIX standard.
>> >> >> >> > >> >>
>> >> >> >> > >> >> Since you have RTEMS and tools built. Find one of the libc.a and libm.a files in the tools install and librtemscpu.a in the RTEMS build or install. Then try a command something like this:
>> >> >> >> > >> >>
>> >> >> >> > >> >> CPU-rtems6-nm LIBRARY | grep SYMBOL
>> >> >> >> > >> >>
>> >> >> >> > >> >> If you see it list with T then it is in the text section and there.
>> >> >> >> > >> >
>> >> >> >> > >> >
>> >> >> >> > >> > Following up, I initially answered from my phone and didn't look at source.  I am still on my phone but looked through the list and think the last four methods are probably the only ones currently supported.
>> >> >> >> > >> >
>> >> >> >> > >> > https://sourceware.org/git/?p=newlib-cygwin.git;a=tree;f=newlib/libc/string;h=ceeec602cdd0e6b5c6b002b741bda9b41da4e441;hb=HEAD
>> >> >> >> > >> >
>> >> >> >> > >> > POSIX support comes from a mix of RTEMS and newlib. That's key to this type of project.
>> >> >> >> > >> >
>> >> >> >> > >> > --joel
>> >> >> >> > >> >>
>> >> >> >> > >> >>
>> >> >> >> > >> >>
>> >> >> >> > >> >>>
>> >> >> >> > >> >>> Thanks very much for your time!
>> >> >> >> > >> >>>
>> >> >> >> > >> >>> Sincerely,
>> >> >> >> > >> >>>
>> >> >> >> > >> >>> Matt
>> >> >> >> > _______________________________________________
>> >> >> >> > devel mailing list
>> >> >> >> > devel at rtems.org
>> >> >> >> > http://lists.rtems.org/mailman/listinfo/devel

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