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

Eshan Dhawan eshandhawan51 at gmail.com
Sun Mar 28 04:54:24 UTC 2021 

> On 27-Mar-2021, at 1:49 AM, Matthew Joyce <mfjoyce2004 at gmail.com> wrote:
> 
> Hi Dr. Joel,
> 
> I finally built rtems-libbsd and see that pselect and sockatmark are
> both defined there. I went ahead and added a "In rtems-libbsd" column
> in the spreadsheet to reflect that.
> 
> With those two defined, it looks like the only methods from the FACE
> 3.0 General Purpose Profile that aren't currently supported are
> confstr() and the <spawn.h> set. Could I ask, what is the thinking on
> those? The man page suggests that spawn was created with embedded
> systems in mind, but I'd guess a conscious decision was made to leave
> them out? How about confstr?
> 
> Thank you!
> 
> Matt
> 
Hi Matt
Confstr code is ready just under styling issues. 
So maybe you could count it as Present. 

Thanks 
- Eshan 
> 
>> 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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