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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [MirageOS-devel] [OCaml 0006167]: OCAMLPARAM Support for Disabling Position-Independent Code (PIC) Generation
> On 26 Jan 2015, at 11:14, Anil Madhavapeddy <anil@xxxxxxxxxx> wrote: > > Thanks to Gabor Pali, the upstream OCaml 4.03 tree now has support for > disabling PIC code, which was one of the features needed to compile kFreeBSD > kernel modules in Mirage. Thanks for pushing this through, Gabor! Awesome! Is there anything else still to upstream or is it all ready for use? :) Cheers, Dave > > -anil > >> Begin forwarded message: >> >> To: anil@xxxxxxxxxx >> Subject: [OCaml 0006167]: OCAMLPARAM Support for Disabling >> Position-Independent Code (PIC) Generation >> Date: 24 January 2015 16:36:12 GMT >> From: Mantis Bug Tracker <nouser@xxxxxxxx> >> >> >> The following issue has been RESOLVED. >> ====================================================================== >> http://caml.inria.fr/mantis/view.php?id=6167 >> ====================================================================== >> Reported By: pgj >> Assigned To: gasche >> ====================================================================== >> Project: OCaml >> Issue ID: 6167 >> Category: OCaml backend (code generation) >> Reproducibility: N/A >> Severity: feature >> Priority: normal >> Status: resolved >> Resolution: fixed >> Fixed in Version: 4.03.0+dev >> ====================================================================== >> Date Submitted: 2013-09-10 16:20 CEST >> Last Modified: 2015-01-24 17:36 CET >> ====================================================================== >> Summary: OCAMLPARAM Support for Disabling >> Position-Independent Code (PIC) Generation >> Description: >> Add support for disabling Position-Independent Code (PIC) generation through >> the >> OCAMLPARAM environment variable. This change would make it possible to >> specify >> a "nopic" token which, when set, instructs the native code generator to emit >> position-dependent code independently of what was requested at the command >> line. >> >> The rationale of this option is similar to the other flags already supported >> by >> OCAMLPARAM: Allow the user to force generation of position-dependent code >> without the need for modifying build system files or sources. >> >> This patch was directly motivated by the need for making cross-compilation >> possible of the Mirage unikernel [1] to the "kFreeBSD" backend. This backend >> basically compiles Mirage (OCaml) programs into FreeBSD kernel modules, where >> certain expectations must be satisfied. One of those expectations is that >> the >> generated code must not be position-independent as the FreeBSD kernel dynamic >> loader (kld(4)) does not support ELF relocations of that type. Hence PIC >> generation has to be disabled globally for all the compiled code, regardless >> what the original upstream packages were instructed for. The "nodynlink" >> flag >> is also used in this case. >> >> The attached patch implements this functionality by moving the `pic_code` >> variable to the `Clflags` module for both the AMD64 and the ARM native code >> generator backends, while it retains the default settings for both. I have >> tested it on FreeBSD/amd64, but it should work on the ARM platform and on >> other >> operating systems. >> >> >> [1] http://openmirage.org/ >> >> ====================================================================== >> >> ---------------------------------------------------------------------- >> (0011174) doligez (administrator) - 2014-04-02 17:11 >> http://caml.inria.fr/mantis/view.php?id=6167#c11174 >> ---------------------------------------------------------------------- >> One small remark: if we add a "nopic" flag we should also add a "pic" flag >> for >> symmetry (and because all the hard work is already done). >> >> ---------------------------------------------------------------------- >> (0012912) whitequark (developer) - 2014-12-21 14:19 >> http://caml.inria.fr/mantis/view.php?id=6167#c12912 >> ---------------------------------------------------------------------- >> @gasche, can you please take a look at the attached patch? >> >> ---------------------------------------------------------------------- >> (0012913) gasche (developer) - 2014-12-21 16:07 >> http://caml.inria.fr/mantis/view.php?id=6167#c12913 >> ---------------------------------------------------------------------- >> It would be more natural, I think, to use pic=0 and pic=1 to disable or >> disable >> position-independent code. Given the fact that the key-value-handling logic >> is >> already present in the OCAMLPARAM code, the current patch allows nopic=1 and >> nopic=0 to respectively disable and enable position-independent code (with >> "nopic" being a shortcut for "nopic=1"), which is a rather obscure >> interface. If >> people prefer using "nopic" to "pic=0", we could at least support both pic >> and >> nopic as keys as Damien suggests. >> >> The other issue I have with the patch is the default-setting logic: >> >> +let pic_code = ref (String.compare "amd64" Config.architecture == 0) >> + (* -fPIC (only true by default on amd64) *) >> >> if you allow me to nitpick (no pun intended), this code would not scale to >> the >> addition of other architectures. We should pattern-match on >> Config.architecture, >> with at least a case for each architecture on which the option makes sense >> (having a catch-all pattern with the default value for the others is >> reasonable). >> >> Is anyone willing to improve the patch on these two aspects? Given the >> non-stellar reaction time, I would assume that the original contributor pgj >> may >> not be willing to do the extra work. If nobody comes forward by the time of >> the >> release, I could do it myself. >> >> ---------------------------------------------------------------------- >> (0012914) pgj (reporter) - 2014-12-21 17:26 >> http://caml.inria.fr/mantis/view.php?id=6167#c12914 >> ---------------------------------------------------------------------- >> Sorry, folks, I was busy with other stuff and I did not come to respond to >> the >> notes. I think you are right, and yes, I think I could adapt the patch >> according to the recommendations. >> >> ---------------------------------------------------------------------- >> (0012915) gasche (developer) - 2014-12-21 17:39 >> http://caml.inria.fr/mantis/view.php?id=6167#c12915 >> ---------------------------------------------------------------------- >> Nice! I certainly implied no criticism of you, I find it natural to could >> drift >> a bit after 6 months with no reply. You can take your time to prepare a >> patch. >> >> ---------------------------------------------------------------------- >> (0012916) pgj (reporter) - 2014-12-21 17:48 >> http://caml.inria.fr/mantis/view.php?id=6167#c12916 >> ---------------------------------------------------------------------- >> Sure, no problem. Thanks for reminding me :-) I did not have time for the >> original project either (for which the patch was originally written) so it >> simply got slipped, indeed. >> >> >> >> ---------------------------------------------------------------------- >> (0013134) pgj (reporter) - 2015-01-17 11:03 >> http://caml.inria.fr/mantis/view.php?id=6167#c13134 >> ---------------------------------------------------------------------- >> Please find a revisited version attached. It is now adapted to the trunk >> version as of today and theoretically has also the requested changes. I >> tested >> it on FreeBSD/amd64, it builds and works for me. Sorry for the delay :-) >> >> ---------------------------------------------------------------------- >> (0013169) gasche (developer) - 2015-01-24 17:35 >> http://caml.inria.fr/mantis/view.php?id=6167#c13169 >> ---------------------------------------------------------------------- >> Merged in trunk, thanks! >> >> Issue History >> Date Modified Username Field Change >> >> ====================================================================== >> 2013-09-10 16:20 pgj New Issue >> 2013-09-10 16:20 pgj File Added: nopic.diff >> 2013-09-11 22:07 doligez Tag Attached: patch >> 2014-04-02 17:09 doligez Status new => confirmed >> 2014-04-02 17:09 doligez Target Version => 4.02.0+dev >> 2014-04-02 17:11 doligez Note Added: 0011174 >> 2014-08-21 12:02 doligez Target Version 4.02.0+dev => >> 2014-12-21 14:19 whitequark Note Added: 0012912 >> 2014-12-21 16:07 gasche Note Added: 0012913 >> 2014-12-21 16:07 gasche Tag Attached: junior_job >> 2014-12-21 17:26 pgj Note Added: 0012914 >> 2014-12-21 17:39 gasche Note Added: 0012915 >> 2014-12-21 17:48 pgj Note Added: 0012916 >> 2014-12-21 17:48 pgj Note Edited: 0012916 >> 2015-01-17 11:01 pgj File Added: ocamlparam_pic.diff >> >> >> 2015-01-17 11:03 pgj Note Added: 0013134 >> 2015-01-24 17:35 gasche Note Added: 0013169 >> 2015-01-24 17:36 gasche Status confirmed => >> resolved >> 2015-01-24 17:36 gasche Fixed in Version => 4.03.0+dev >> 2015-01-24 17:36 gasche Resolution open => fixed >> 2015-01-24 17:36 gasche Assigned To => gasche >> ====================================================================== >> > > > _______________________________________________ > MirageOS-devel mailing list > MirageOS-devel@xxxxxxxxxxxxxxxxxxxx > http://lists.xenproject.org/cgi-bin/mailman/listinfo/mirageos-devel _______________________________________________ MirageOS-devel mailing list MirageOS-devel@xxxxxxxxxxxxxxxxxxxx http://lists.xenproject.org/cgi-bin/mailman/listinfo/mirageos-devel
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