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diff --git a/service_solahart_jakarta_selatan__082122541663/mig_portable_rpc_declarations.mdwn b/service_solahart_jakarta_selatan__082122541663/mig_portable_rpc_declarations.mdwn new file mode 100644 index 00000000..f5f18880 --- /dev/null +++ b/service_solahart_jakarta_selatan__082122541663/mig_portable_rpc_declarations.mdwn @@ -0,0 +1,291 @@ +[[!meta copyright="Copyright © 2011, 2012, 2013, 2014 Free Software Foundation, +Inc."]] + +[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] + +[[!tag open_issue_mig]] + +[[!toc]] + + +# 32-Bit vs. 64-Bit Interfaces + +## IRC, freenode, #hurd, 2011-10-16 + + <braunr> i guess it wouldn't be too hard to have a special mach kernel for + 64 bits processors, but 32 bits userland only + <youpi> well, it means tinkering with mig + <braunr> like old sparc systems :p + <youpi> to build the 32bit interface, not the 64bit one + <braunr> ah yes + <braunr> hm + <braunr> i'm not sure + <braunr> mig would assume a 32 bits kernel, like now + <youpi> and you'll have all kinds of discrepancies in vm_size_t & such + <braunr> yes + <braunr> the 64 bits type should be completely internal + <braunr> types* + <braunr> but it would be far less work than changing all the userspace bits + for 64 bit (ofc we'll do that some day but in the meanwhile ..) + <youpi> yes + <youpi> and it'd boost userland addrespace to 4GiB + <braunr> yes + <youpi> leaving time for a 64bit userland :) + + +## IRC, freenode, #hurd, 2011-11-14 + + <braunr> also, what's the best way to deal with types such as + <braunr> type cache_info_t = struct[23] of integer_t; + <braunr> whereas cache_info_t contains longs, which are obviously not + integer-wide on 64-bits processors + <braunr> ? + <youpi> you mean, to port mach to 64bit? + <braunr> no, to make the RPC declaration portable + <braunr> just in case :) + <youpi> refine integer_t into something more precise + <youpi> such as size_t, off_t, etc. + <braunr> i can't use a single line then + <braunr> struct cache_info contains ints, vm_size_t, longs + <braunr> should i just use the maximum size it can get ? + <braunr> or declare two sizes depending on the word size ? + <youpi> well, I'd say three + <braunr> youpi: three ? + <youpi> the ints, the vm_size_ts, and the longs + <braunr> youpi: i don't get it + <braunr> youpi: how would i write it in mig language ? + <youpi> I don't know the mig language + <braunr> me neither :) + <youpi> but I'd say don't lie + <braunr> i just see struct[23] of smething + <braunr> the original zone_info struct includes both integer_t and + vm_size_t, and declares it as + <braunr> type zone_info_t = struct[9] of integer_t; + <braunr> in its mig defs file + <braunr> i don't have a good example to reuse + <youpi> which is lying + <braunr> yes + <braunr> which is why i was wondering if mach architects themselves + actually solved that problem :) + <braunr> "There is no way to specify the fields of a + <braunr> C structure to MIG. The size and type-desc are just used to + give the size of + <braunr> the structure. + <braunr> " + <braunr> well, this sucks :/ + <braunr> well, i'll do what the rest of the code seems to do, and let it + rot until a viable solution is available + <antrik> braunr: we discussed the problem of expressing structs with MIG in + the libburn thread + <antrik> (which I still need to follow up on... [sigh]) + + +## IRC, freenode, #hurd, 2012-12-12 + +In context of [[microkernel/mach/gnumach/memory_management]]. + + <tschwinge> Or with a 64-bit one? ;-P + <braunr> tschwinge: i think we all had that idea in mind :) + <pinotree> tschwinge: patches welcome :P + <youpi> tschwinge: sure, please help us settle down with the mig stuff + <youpi> what was blocking me was just deciding how to do it + <braunr> hum, what's blocking x86_64, except time to work on it ? + <youpi> deciding the mig types & such things + <youpi> i.e. the RPC ABI + <braunr> ok + <braunr> easy answer: keep it the same + <youpi> sorry, let me rephrase + <youpi> decide what ABI is supposed to be on a 64bit system, so as to know + which way to rewrite the types of the kernel MIG part to support 64/32 + conversion + <braunr> can't this be done in two steps ? + <youpi> well, it'd mean revamping the whole kernel twice + <youpi> as the types at stake are referenced in the whole RPC code + <braunr> the first step i imagine would simply imply having an x86_64 + kernel for 32-bits userspace, without any type change (unless restricting + to 32-bits when a type is automatically enlarged on 64-bits) + <youpi> it's not so simple + <youpi> the RPC code is tricky + <youpi> and there are alignments things that RPC code uses + <youpi> which become different when build with a 64bit compiler + <pinotree> there are also things like int[N] for io_stat_struct and so on + <braunr> i see + <youpi> making the code wrong for 32 + <youpi> thus having to change the types + <youpi> pinotree: yes + <pinotree> (doesn't mig support structs, or it is too clumsy to be used in + practice?) + <braunr> pinotree: what's the problem with that (i explcitely said changing + int to e.g. int32_t) + <youpi> that won't fly for some of the calls + <youpi> e.g. getting a thread state + <braunr> pinotree: no it doesn't support struct + <pinotree> braunr: that some types in struct stat are long, for instance + <braunr> pinotree: same thing with longs + <braunr> youpi: why wouldn't it ? + <youpi> that wouldn't work on a 64bit system + <youpi> so we can't make it int32_t in the interface definition + <braunr> i understand the alignment issues and that the mig code adjusts + the generated code, but not the content of what is transfered + <braunr> well of course + <braunr> i'm talking about the first step here + <braunr> which targets a 32-bits userspace only + <youpi> ok, so we agree + <youpi> the second step would have to revamp the whole RPC code again + <braunr> i imagine the first to be less costly + <braunr> well, actually no + <braunr> you're right, the mig stuff would be easy on the application side, + but more complicated on the kernel side, since it would really mean + dealing with 64-bits values there + <braunr> (unless we keep a 3/1 split instead of giving the full 4g to + applications) + +See also [[microkernel/mach/gnumach/memory_management]]. + + <youpi> (I don't see what that changes) + <braunr> if the kernel still runs with 32-bits addresses, everything it + recevies from or sends through mig can be stored with the user side + 32-bits types + <youpi> err, ok, but what's the point of the 64bit kernel then ? :) + <braunr> and it simply uses 64-bits addresses to deal with physical memory + <youpi> ok + <youpi> that could even be a 3.5/0.5 split then + <braunr> but the memory model forces us to run either at the low 2g or the + highest ones + <youpi> but linux has 3/1, so we don't need that + <braunr> otherwise we need an mcmodel=medium + <braunr> we could do with mcmodel=medium though, for a time + <braunr> hm actually no, it would require mcmodel=large + <braunr> hum, that's stupid, we can make the kernel run at -2g, and use 3g + up to the sign extension hole for the kernel map + + +## IRC, freenode, #hurd, 2013-12-03 + + <azeem> I believe the main issue is redoing the RPCs in 64bit, i.e. the + Mach/Hurd interface + <braunr> mach has always been 64-bits capable + <braunr> the problem is both mach and the hurd + <braunr> it's at the system interface (the .defs of the RPCs) + <braunr> azeem: ah, actually that's why you also say + <braunr> but i consider it to be a hurd problem + <braunr> the hurd itself is defined as being a set of interfaces and + servers implementing them, i wouldn't exclude the interfaces + <braunr> that's what* + + +# Structured Data + +## IRC, freenode, #hurd, 2013-06-25 + + <teythoon> is there a nice way to get structured data through mig that I + haven't found yet? + <teythoon> say an array of string triples + <braunr> no + <teythoon> :/ + <braunr> but you shouldn't need that + <teythoon> my use case is getting info about fs translators from init to + procfs + +[[hurd/translator/mtab]], [[hurd/translator/mtab/discussion]]. + + <teythoon> should I go for an iterator like interface instead? + <braunr> depends + <braunr> how many do you need ? + <braunr> you could go for a variable sized array too + <braunr> have a look at what already exists + <teythoon> records, maybe 10-15, depends on many fs translators are running + <braunr> a variable sized array is ok if the size isn't too big (and when i + say too big, i mean hundreds of MiB) + <braunr> an iterator is ok too if there aren't too many items + <braunr> you may want to combine both (i think that's what proc does) + <braunr> be aware that the maximum size of a message is limited to 512 MiB + <teythoon> yeah I saw the array[] of stuff stuff, but array[] of string_t + does not work, I guess b/c string_t is also an array + <teythoon> how would I send an array of variable length strings? + <braunr> i'm not sure you can + <braunr> or maybe out of line + <teythoon> somehow I expected mig to serialize arbitrary data structures, + maybe it's to old for that? + <teythoon> yeah, I read about uot of line, but that seems overkill + <braunr> it is old yes + <braunr> and not very user friendly in the end + <braunr> let me check + <teythoon> we could stuff json into mig... + <braunr> see proc_getallpids for example + <braunr> we could get rid of low level serialization altogether :p + <teythoon> hah, exactly what I was looking at + <braunr> (which is what i'll do in x15) + <braunr> type pidarray_t = array[] of pid_t; + <teythoon> but that is trivial b/c its array[] of pid_t + <braunr> and always have the server writing guide near you + <teythoon> yes + <braunr> well, make one big string and an array of lengths :p + <teythoon> thought about that and said to myself, there must be a better + way that I haven't found yet + <braunr> or one big string filled with real null-terminated c strings that + you keep parsing until you ate all input bytes + <braunr> i'm almost certain there isn't + <braunr> type string_t = c_string[1024]; /* XXX */ + <teythoon> yes + <braunr> even that isn't really variable sized + <teythoon> you think anyone would object to me putting a json encoder in + /hurd/init? it is probably better than me at serializing stuff... + <braunr> try with mig anyway + <braunr> the less dependencies we have for core stuff, the simpler it is + <braunr> but i agree, mig is painful + <teythoon> would it be too hacky if I abused the argz functions? they do + exactly what I'd need + + +## IRC, freenode, #hurd, 2013-06-26 + + <teythoon> there is https://code.google.com/p/protobuf-c/ and it has a rpc + mechanism and I believe one could plug arbitrary transports easily + <braunr> please don't think about it + <braunr> we really don't want to add another layer of serialization + <braunr> it's better to completely redesign mach ipc anyway + <braunr> and there is a project for that :p + <teythoon> ive seen x15 + <teythoon> just food for thought + <braunr> i've studied google protocol buffers + <braunr> and fyi, no, it wouldn't be easy to plug arbitrary transports on + top of mach + <braunr> there is a lot of knowledge about mach ports in mig + +[[hurd/translator/mtab]], [[hurd/translator/mtab/discussion]]. + + <teythoon> but again I face the challenge of serializing a arbitrary sized + list of arbitrary sized strings + <braunr> yes + <teythoon> list of ports is easier ;) but I think its worthwile + <teythoon> so what about abusing argz* for this? you think it's too bad a + hack? + <braunr> no since it's in glibc + <teythoon> awesome :) + <braunr> but i don't remember the details well and i'm not sure the way you + use it is safe + <teythoon> yeah, I might have got the details wrong, I hadn't had the + chance to test it ;) + + <braunr> about this dynamic size problem + <braunr> a "simple" varying size array should do + <braunr> you can easily put all your strings in there + <teythoon> seperated by 0? + <braunr> yes + <teythoon> that's exactly what the argz stuff does + <braunr> you'll get the size of the array anyway, and consume it until + there is no byte left + <braunr> good + <braunr> but be careful with this too + <braunr> since translators can be run by users, they somtimes can't be + trusted + <braunr> and even a translator running as root may behave badly + <braunr> so careful with parsing + <teythoon> noted |