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diff --git a/community/gsoc/project_ideas/mtab/discussion.mdwn b/community/gsoc/project_ideas/mtab/discussion.mdwn deleted file mode 100644 index 716fb492..00000000 --- a/community/gsoc/project_ideas/mtab/discussion.mdwn +++ /dev/null @@ -1,2072 +0,0 @@ -[[!meta copyright="Copyright © 2013 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_hurd]] - -# IRC, freenode, #hurd, 2013-04-17 - - <kuldeepdhaka> thinking how to get the listing. traversing would be - ineffecient, trying to come up with something better - <braunr> what listing ? - <braunr> and traversing what ? - <kuldeepdhaka> mtab - <braunr> well i assumed so - <braunr> be more precise please - <kuldeepdhaka> when the translator is done initalized <translation - info> are written to /etc/mtab <translation info> will be provided - by the translator, and when some one want to read the info just read it - this way if their is some credentials like ftp sites pass username can be - masked by the translator - <kuldeepdhaka> if some trans dont want to list them, no need to write to - file | while unmounting (sorry i couldnt find the right word) , it - will pass the mount node address | <translation info> will have special - structure to remove/add mounts example "a /mount-to /mount-from" = add - , "r /mount-to" = remove here "/mount-to" will be unique for every - mount - <kuldeepdhaka> this have a draw back , we would have to trust trans for the - listed data | also "/mount-to" + "/mount-from" could be used a - combination for making sure that other trans unable remove others trans - mount data - <kuldeepdhaka> sorry but "also "/mount-to" + "/mount-from" could be used a - combination for making sure that other trans unable remove others trans - mount data" this is a bad idea if we had to print the whole thing - <kuldeepdhaka> braunr, whats ur opinion? - <pinotree> you don't need a mtab to "unmount" things on hurd - <braunr> kuldeepdhaka: hum, have you read the project idea ? - <braunr> - http://darnassus.sceen.net/~hurd-web/community/gsoc/project_ideas/mtab/ - <braunr> A more promising approach is to have mtab exported by a special - translator, which gathers the necessary information on demand. This could - work by traversing the tree of translators, asking each one for mount - points attached to it. - <kuldeepdhaka> pinotree, not to unmount, i mean is to remove the - <translation data> - <braunr> for a first implementation, i'd suggest a recursive traversal of - root-owned translators - <kuldeepdhaka> braunr, hum, but it did stated it as inefficient - <braunr> where ? - <kuldeepdhaka> para 5 , line 3 - <kuldeepdhaka> and line 6 - <braunr> no - <braunr> traversing "all" nodes would be inefficient - <braunr> translators which host the nodes of other translators could - maintain a simple list of active translators - <braunr> ext2fs, e.g. (if that's not already the case) could keep the list - of the translators it started - <braunr> we can already see that list with pstree for example - <braunr> but this new list would only retain those relevant for mtab - <braunr> i.e. root-owned ones - <pinotree> i would not limit to those though - <braunr> and then filter on their type (e.g. file system ones) - <braunr> pinotree: why ? - <pinotree> this way you could have proper per-user /proc/$pid/mounts info - <braunr> we could also very easily have a denial of service - <kuldeepdhaka> but how will the mount point and source point will be - listed? - <braunr> they're returned by the translator - <kuldeepdhaka> k - <braunr> you ask /, it returns its store and its options, and asks its - children recursively - <braunr> a /home translator would return its store and its options - <braunr> etc.. - <braunr> each translator would build the complete path before returning it - <braunr> sort of, it's very basic - <braunr> but that would be a very hurdish way to do it - <kuldeepdhaka> shall /etc/mtab should be made seek-able and what should be - the filesize? content are generated on demand so, it could arise problem - (fsize:0 , seek-able:no), ur opinions? - <braunr> kuldeepdhaka: it should have all the properties of a regular file - <braunr> the filesize would be determined after it's generated - <braunr> being empty doesn't imply it's not seekable - <kuldeepdhaka> content is generated on demand so, could cause problem while - seeking and filesize, shall i still program as regular file? - <kuldeepdhaka> in two different read, it could generate different content, - though same seek pos is used... - <braunr> what ? - <braunr> the content is generated on open - <kuldeepdhaka> ooh, ok - - -# IRC, freenode, #hurd, 2013-06-04 - - <safinaskar> how to see list of all connected translators? - <braunr> you can't directly - <braunr> you can use ps to list processes and guess which are translators - <braunr> (e.g. everything starting with /hurd/) - <braunr> a recursive call to obtain such a list would be useful - <braunr> similar to what's needed to implement /proc/mounts - - -# IRC, freenode, #hurd, 2013-06-25 - -In context of [[open_issues/mig_portable_rpc_declarations]]. - - <teythoon> should I go for an iterator like interface instead? - <teythoon> btw, what's the expected roundtrip time? - <braunr> don't think that way - <braunr> consider the round trip delay as varying - <teythoon> y, is it that bad? - <braunr> no - <braunr> but the less there is the better - <braunr> we think the same with system calls even if they're faster - <braunr> the delay itself isn't the real issue - <braunr> look at how proc provides information - <braunr> (in procfs for example) - - -## IRC, freenode, #hurd, 2013-06-26 - - <teythoon> so tell me about the more hurdish way of dealing with that issue - <teythoon> creating a specialized translator for this? - <braunr> 11:45 < pinotree> there's also - http://darnassus.sceen.net/~hurd-web/community/gsoc/project_ideas/mtab/ - about that topic - <braunr> you need to avoid thinking with centralization in mind - <braunr> the hurd is a distributed system in practice - <braunr> i think proc is the only centralized component in there - <teythoon> braunr: would having an mtab translator and having fs - translators register to thae be acceptable? - <teythoon> that* - <braunr> teythoon: why do you want to centralize it ? - <braunr> translators already register themselves when they get attached to - a node - <braunr> we don't want an additional registration - <braunr> have you read the link we gave you ? - <teythoon> I did and I got the message, but isn't the concept of - /proc/mounts or a mtab file already a centralized one? - <braunr> that doesn't mean the implementation has to be - <braunr> and no, i don't think it's centralized actually - <braunr> it's just a file - <braunr> you can build a file from many sources - <teythoon> or if we do it your way recursing on fs translators *but* - restricting this to root owned translators also suffering from - centralization wrt to the root user? I mean the concept of all mounted - filesystems does not apply cleanly to the hurd - <braunr> i don't understand - <braunr> restricting to the root user doesn't mean it's centralized - <braunr> trust has nothing to do with being centralized - <teythoon> I guess I'm not used to thinking this way - <braunr> teythoon: i guess that's the main reason why so few developers - work on the hurd - <teythoon> also the way fs notification is done is also centralized, that - could also be done recursively - <braunr> what doyou call fs notification ? - <teythoon> and the information I need could just be stuffed into the same - mechanism - <teythoon> fs translators being notified of system shutdown - <braunr> right - <braunr> that gets a bit complicated because the kernel is also a - centralized component - <braunr> it knows every memory object and their pagers - <braunr> it manages all virtual memory - <braunr> there are two different issues here - <braunr> syncing memory and shutting down file systems - <braunr> the latter could be done recursively, yes - <braunr> i wonder if the former could be delegated to external pagers as - well - <braunr> teythoon: but that's not the focus of your work aiui, it would - take much time - <teythoon> sure, but missing an mtab file or better yet /proc/mounts could - be an issue for me, at least a cosmetic one, if not a functional one - <braunr> i understand - <teythoon> and hacking up a quick solution for that seemed like a good - exercise - <braunr> i suggest you discuss it with your mentors - <braunr> they might agree to a temporary centralized solution - <braunr> although i don't think it's much simpler than the recursive one - <teythoon> braunr: would that be implemented in libdiskfs and friends? - <braunr> teythoon: i'm not sure, it might be a generic fs operation - <braunr> libnetfs etc.. are also mount points - <teythoon> so where would it go if it was generic? - <braunr> libfshelp perhaps - <teythoon> translator startup is handled in start-translator-long.c, so in - case a startup is successful, I'd add it to a list? - <braunr> i'd say so, yes - <teythoon> would that cover all cases, passive and active translators? - <braunr> that's another question - <braunr> do we consider passive translators as mounted ? - <teythoon> ah, that was not what i meant - <braunr> i know - <braunr> but it's related - <teythoon> start b/c of accessing a passive one vs. starting an active one - using settrans - <braunr> start_translator_xxx only spawn active translators - <braunr> it's the same - <teythoon> ok - <braunr> the definition of a passive translator is that it starts the - active translator on access - <teythoon> yeah I can see how that wouldn't be hard to implement - <braunr> i think we want to include passive translators in the mount table - <braunr> so registration must happen before starting the active one - <teythoon> so it's a) keeping a list of active translators and b) add an - interface to query fs translators for this list and c) an interface to - query mtab style information? - <braunr> keeping a list of all translators attached - <braunr> and yes - <braunr> well - <braunr> a is easy - <braunr> b is the real work - <braunr> c would be procfs using b - <teythoon> oh? I thought recursing on the translators and querying info - would be separate operations? - <braunr> why so ? - <braunr> the point is querying recursively :) - <braunr> and when i say recursively, it's only a logical view - <teythoon> ok, yes, it can be implemented this way, so we construct the - list while recursing on the translators - <braunr> i think it would be better to implement it the way looking up a - node is done - <teythoon> in a loop, using a stack? - <braunr> iteratively - <braunr> a translator would provide information about itself (if - supported), and referrences to translators locally registered to it - <teythoon> could you point me to the node lookup? - <teythoon> ah, yes - <braunr> eg., you ask /, it tells you it's on /dev/hd0, read-write, with - options, and send rights to /home, /proc, etc.. - <braunr> well rights, references - <braunr> it could be the path itself - <teythoon> rights as in a port to the translators? - <braunr> i think the path would be better but i'm not sure - <braunr> it would also allow you to check the permissions of the node - before querying - <teythoon> path would be nicer in the presence of stacked translators - <braunr> and obviously you'd have the path right away, no need to provide - it in the reply - <teythoon> true - - <teythoon> braunr: if we want to list passive translators (and I agree, we - should), it isn't sufficient to touch libfshelp, as setting a passive - translator is not handled there, only the startup - <braunr> teythoon: doesn't mean you can't add something there that other - libraries will use - <braunr> so yes, not sufficient - - -## IRC, freenode, #hurd, 2013-06-29 - - <teythoon> braunr: diskfs_S_fsys_set_options uses diskfs_node_iterate to - recurse on active translators if do_children is given - <teythoon> braunr: I wonder how fast that is in practice - <teythoon> braunr: if it's fast enough, there might not even be a need for - a new function in fsys.defs - <teythoon> and no need to keep a list of translators for that reason - <teythoon> braunr: if it's not fast enough, then diskfs_S_fsys_set_options - could use the list to speed this up - <braunr> teythoon: on all nodes ? - <teythoon> braunr: i believe so, yes, see libdiskfs/fsys-options.c - <braunr> teythoon: well, if it really is all node, you clearly don't want - that - - -## IRC, freenode, #hurd, 2013-07-01 - - <teythoon> I've ment to ask, the shiny new fsys_get_translators interface, - should it return the options for the queried translator or not? - <braunr> i don't think it should - <teythoon> ok - <braunr> let's walk through why it shouldn't - <teythoon> may I assume that the last argument returned by fsys_get_options - is the "source"? - <braunr> how would you know these options ? - <braunr> the source ? - <teythoon> I wouldn't actually - <braunr> yes, you wouldn't - <braunr> you'd have to ask the translators for that - <braunr> so the only thing you can do is point to them - <teythoon> well, the device to include in the mtab file - <braunr> and the client asks - <braunr> i don't know fsys_get_options tbh - <teythoon> well, both tmpfs and ext2fs print an appropriate value for - "device" as last argument - <braunr> looks like a bad interface to me - <braunr> options should be options - <braunr> there should be a specific call for the device - <braunr> but if everyone agrees with the options order, you can do it that - way for now i guess - <teythoon> one that could be used to recreate the "mount" using either - mount or settrans - <braunr> just comment it where appropriate - <teythoon> I thought that'd be the point? - <braunr> ? - <teythoon> % fsysopts tmp - <teythoon> /hurd/tmpfs --writable --no-inherit-dir-group --no-sync 48K - <braunr> where is the device ? - <teythoon> % settrans -ca tmp $(fsysopts tmp) - <braunr> 15:56 < teythoon> well, both tmpfs and ext2fs print an appropriate - value for "device" as last argument - <teythoon> 48K - <braunr> i don't see it - <braunr> really ? - <teythoon> yes - <braunr> what about ext2fs ? - <braunr> hm ok i see - <teythoon> % fsysopts / - <teythoon> ext2fs --writable --no-inherit-dir-group --sync=10 - --store-type=typed device:hd0s1 - <braunr> i don't think you should consider that as devices - <braunr> but really translator specific options - <pinotree> agree - <teythoon> I don't ;) - <teythoon> b/c the translator calling convention is hardcoded in the mount - utility - <braunr> ? - <teythoon> I think it's reasonable to assume that this mapping can be - reversed - <pinotree> theorically you can write a translator that takes no arguments, - but just options - <braunr> the 48K string for tmpfs is completely meaningless - <braunr> in fstab, it should be none - <pinotree> "tmpfs" - <braunr> the linux equivalent is the size option - <braunr> no, none - <braunr> it's totally ignored - <braunr> and it's recommended to set none rather than the type to avoid - confusion - <teythoon> u sure? - <teythoon> % settrans -cga tmp /hurd/tmpfs --mode=666 6M - <teythoon> % settrans -cga tmp /hurd/tmpfs --mode=666 6M - <teythoon> % fsysopts tmp - <teythoon> /hurd/tmpfs --writable --no-inherit-dir-group --no-sync 6M - <braunr> i've not explained myself clearly - <braunr> it's not ignored by the translator - <braunr> but in fstab, it should be in the options field - <braunr> it's not the source - <braunr> clearly not - <teythoon> ah - <braunr> now i'm talking about fstab, but iirc the format is similar in - mtab/mounts - <pinotree> close, but not the same - <braunr> yes, close - <teythoon> ok, so I'll put a method into libfshelp so that translators can - explicitly set a device and patch all existing translators to do so? - <braunr> teythoon: what i meant is that, for virtual vile systems (actually - file systems with no underlying devices), the device field is normally - ignored - <braunr> teythoon: why do you need that for exactly - <teythoon> right - <pinotree> do they even have a "device" field? - <braunr> (i can see why but i'd like more visibility) - <braunr> pinotree: not yet - <braunr> pinotree: that's what he wants to add - <braunr> but i'd like to see if there is another way to get the information - <braunr> 16:05 < braunr> teythoon: why do you need that for exactly - <teythoon> well if I'm constructing a mtab entry I need a value for the - device field - <braunr> do we actually need it to be valid ? - <teythoon> not necessarily I guess - <braunr> discuss it with your mentors then - <youpi> it has to be valid for e2fsck checks etc. - <braunr> doesn't e2fsck check fstab actually ? - <youpi> i.e. actually for the cases where it's trivial - <youpi> fstab doesn't tell it whether it's mounted - <youpi> I mean fsck checking whether it's mounted - <youpi> not fsck -a - <braunr> oh - <braunr> couldn't we ask the device instead ? - <braunr> looks twisted too - <youpi> that'd mean patching a lot of applications which do similar checks - <braunr> yes - <braunr> teythoon: propose an interface for that with your mentors then - <teythoon> yeah, but couldn't you lay it out a little, I mean would it be - one procedure or like three? - <braunr> 16:04 < teythoon> ok, so I'll put a method into libfshelp so that - translators can explicitly set a device and patch all existing - translators to do so? - <teythoon> ok - <braunr> why three ? - <teythoon> no, I mean when adding stuff to fsys.defs - <braunr> i understood that - <braunr> but why three ? :) - <teythoon> it'd be more generic - <braunr> really ? - <braunr> please show a quick example of what you have in mind - <teythoon> i honestly don't know, thus I'm asking ;) - <braunr> well first, this device thing bothers me - <braunr> when you look at how we set up our ext2fs translators, you can see - they use device:xxx - <braunr> and not /dev/xxx - <braunr> but ok, let's assume it's harmless - <teythoon> ok, but isn't the first way actually better? - <braunr> i think it ends up being the same - <braunr> ideally, that's what we want to use as device path - <teythoon> but you can recreate a storeio translator using the device:xxx - info, the node is useless for that - <braunr> so that we don't need to explicitely set it - <braunr> ? - <braunr> what do you mean ? - <teythoon> well, fsysopts / tells currently tells me device:hd0s1 - <braunr> for /, there isn't much choice - <braunr> /dev isn't there yet - <teythoon> ah, got it - <teythoon> that's why it differs... - <braunr> differs ? - <braunr> from what ? - <braunr> other ext2fs translators are set the same way by the debian - installer for example - <teythoon> % fsysopts /media/scratch - <teythoon> /hurd/ext2fs --writable --no-inherit-dir-group /dev/hd1s1 - <teythoon> here it uses the path to the node - <braunr> that's weird - <braunr> was that done by the debian installer ? - <teythoon> ah no, that was me - <braunr> :p - <braunr> $ fsysopts /home - <braunr> /hurd/ext2fs --writable --no-inherit-dir-group --store-type=device - hd0s6 - <braunr> so as you can see, it's not that simple to infer the device path - <teythoon> oho, yet another way ;) - <teythoon> right then - <pinotree> isn't device:hd0s1 as shortcut for specifying the store type, as - done with --store-type=device hd0s1? - <braunr> but perhaps we don't need to - <braunr> yes it is - <pinotree> iirc it's something libstore does, per-store prefixes - <braunr> ah that sucks - <braunr> teythoon: you may need to normalize those strings - <braunr> so that they match what's in fstab - <braunr> i.e. unix /dev paths - <braunr> otherwise e2fsck still won't be able to find the translators - mounting the device - <braunr> well, if it's mounted actually - <braunr> it just needs to find the matching line in mtab aiui - <braunr> so perhaps a libfshelp function for that, yes - <teythoon> braunr: so you suggest adding a normalizing function to - libfshelp that creates a /dev/path? - <braunr> yes - <braunr> used by the call you intend to add, which returns that device - string as found in fstab - <teythoon> found in fstab? so this would only work for translators managed - by fstab? - <braunr> no - <teythoon> ah - <teythoon> a string like the ones found in fstab? - <braunr> yes - <braunr> so that fsck and friends are able to know whether a device is - mounted or not - <braunr> i don't see any other purpose for that string in mtab - <braunr> you'd take regular paths as they are, convert device:xxx to - /dev/xxx, and return "none" for the rest i suppose - <teythoon> ok - <braunr> i'm not even sure it's right - <braunr> youpi: are you sure it's required ? - <teythoon> well it's a start and I think it's not too much work - <braunr> aiui, e2fsck may simply find the mount point in fstab, and ask the - translator if it's mounted - <teythoon> we can refine this later on maybe? - <braunr> or rather, init scripts, using mountpoint, before starting e2fsck - <braunr> teythoon: sure - <teythoon> there's this mountpoint issue... I need to run fsysopts / - --update early in the boot process - <teythoon> otherwise the device ids returned by stat(2)ing / are wrong and - mountpoint misbehaves - <teythoon> i guess b/c it's the rootfs - <braunr> device ids ? - <teythoon> % stat / | grep Device - <teythoon> Device: 3h/3d Inode: 2 Links: 22 - <braunr> do you mean the major/minor identifiers ? - <teythoon> I do. if I don't do the --update i get seemingly random values - <braunr> i guess that's expected - <braunr> we don't have major/minor values - <braunr> well, they're emulated - <teythoon> well, if that's fixable, that'd be really nice ;) - <braunr> we'll never have major/minor values - <teythoon> yeah, I understand that - <braunr> but they could be fixed by MAKEDEV when creating device nodes - <teythoon> but not having to call fsys_set_options on the rootfs to get the - emulation up to speed - <braunr> try doing it from grub - <braunr> not sure it's possible - <braunr> but worth checking - <teythoon> by means of an ext2fs flag? - <braunr> yes - <braunr> if there is one - <braunr> i don't know the --update flag, is it new from your work ? - <teythoon> braunr: no, it's been there before. -oremount gets mapped to - that - <braunr> it's documented by fsysopts, but not by the ext2fs translators - <teythoon> libdiskfs source says something about flushing buffers iirc - <braunr> -s - <braunr> what does it do ? - <braunr> teythoon: ok - <teythoon> braunr: so the plan is to automatically generate a device path - from the translators argz vector but to provide the functionality so - translators can set a more appropriate value? did I get the last part of - the discussion right? - <braunr> not set, return - <teythoon> yeah return from the procedure but settable using libfshelp? - <braunr> why settable ? - <braunr> you'd have a fsys call to obtain the dev string, and the server - side would call libfshelp on the fly to obtain a normalized value and - return it - <teythoon> ah, make a function overrideable that returns an appropriate - response? - <braunr> overrideable ? - <teythoon> like netfs_append_args - <braunr> you wouldn't change the command line, no - <teythoon> isn't that done using weak references or something? - <teythoon> no I know - <braunr> sorry i'm lost then - <teythoon> never mind, I'll propose a patch early to get your feedback - <youpi> braunr: am I sure that _what_ is required? - <youpi> the device? - <youpi> e2fsck surely needs it, yes - <braunr> a valid device path, yes - <youpi> it can't rely only on fstab - <braunr> yes - <youpi> since users may mount things by hand - <braunr> i've used strace on it and it does perform lookups there - <braunr> (although i also saw uuid magic that i guess wouldn't work yet on - the hurd) - - -## IRC, freenode, #hurd, 2013-07-03 - - <teythoon> I added a procedure to fsys.defs, added a server stub to my - tmpfs translator and wrote a simple client, but something hasn't picked - up the new message yet - <teythoon> % ./mtab tmp - <teythoon> ./mtab: get_translator_info: (ipc/mig) bad request message ID - <teythoon> I guess it's libhurduser.so from glibc, not sure though... - <braunr> glibc would only have the client calls - <braunr> what is "% ./mtab tmp" ? - <teythoon> mtab is my mtab tool/soon to be a translator testing thing, tmp - is an active tmpfs with the appropriate server stub - <braunr> so mtab has the client call, right ? - <teythoon> yes - <braunr> then tmpfs doesn't - <teythoon> so what to do about it? - <teythoon> i set LD_LIBRARY_PATH to my hurd builds lib dir, is that - preserved by settrans -a? - <pinotree> not really - <braunr> not at all - <braunr> there is a wiki entry about that iirc - <pinotree> http://darnassus.sceen.net/~hurd-web/hurd/debugging/translator/ - <teythoon> yeah, I read it too once - <teythoon> ah - <braunr> on the other hand, using export to set the environment should do - the work - <teythoon> yes, that did the trick, thanks :) - * teythoon got his EOPNOPSUPP... *nomnomnom - <braunr> ? - <braunr> same error ? - <teythoon> well I stubbed it out - <braunr> oh - <teythoon> no, that's what I've been expecting ;) - <pinotree> great - <braunr> :) - <braunr> yes that's better than "mig can't find it" - <teythoon> braunr: in that list of active and passive translators that will - have to be maintained, do you expect it should carry more information - other than the relative path to that translator? - <braunr> like what ? - <teythoon> dunno, maybe like a port to any active translator there - <teythoon> should we care if any active translator dies and remove the - entry if there's no passive translator that could restart it again? - <braunr> don't add anything until you see it's necessary or really useful - <braunr> yes - <braunr> think of something like sshfs - <braunr> when you kill it, it's not reported by mount any more - <teythoon> well, for a dynamically allocated list of strings I could use - the argz stuff, but if we'd ever add anything else, we'd need a linked - list or something, maybe a hash table - <teythoon> yes, I thought that'd be useful - <braunr> use libihash for no - <braunr> now - <teythoon> braunr: but what would I use as keys? the relative path should - be unique (unless translators are stacked... hmmm), but that's the value - I'd like to store and ihash keys are pointers - <teythoon> stacked translators are an kinda interesting case for mtab - anyways... - <braunr> why not store the string address ? - <braunr> i suppose that, for stacked translators, the code querying - information would only return the topmost translator - <braunr> since this is the one which matters for regular clients (if i'm - right) - <teythoon> wouldn't that map strings that are equal but stored at different - locations to different values? - <teythoon> that'd defeat the point - <teythoon> I suppose so, yes - <braunr> then add a layer that looks for existing strings before adding - <braunr> the list should normally be small so a linear lookup is fine - <teythoon> yeah sure, but then there's little advantage of using ihash in - the first place, isn't it? - <braunr> over what ? - <teythoon> over not using it at all - <braunr> how would you store the list then ? - <teythoon> it's either ll or ll+ihash - <braunr> uh no - <braunr> let me check - <braunr> there is ihash_iterate - <braunr> so you don't need a linked list - <teythoon> so how do I store my list of strings to deduplicate the keys? - <braunr> you store pointers - <braunr> and on addition, you iterate over all entries, making sure none - matches the new one - <braunr> and if it does, you replace it i guess - <braunr> depending on how you design the rest - <teythoon> in an dynamically allocated region of memory? - <braunr> i don't understand - <braunr> your strings should be dynmaically allocate, yes - <teythoon> no the array of char * - <braunr> your data structure being managed by libihash, you don't care - about allocation - <braunr> what array ? - <teythoon> ah, got it... - <teythoon> right. - <braunr> there is only one structure here, an ihash of char * - <teythoon> yes, I got the picture ;) - <braunr> goo - <braunr> d - <braunr> actually, the lookup wouldn't be linear since usually, hash tables - have stale entries - <teythoon> heh... what forest?!? - <braunr> but that's ok - <braunr> teythoon: ? - <teythoon> the one I couldn't make out b/c of all the trees... - <braunr> ? - <teythoon> ah, it's not important. there is this saying over here, not sure - if there's an english equivalent - <braunr> ok got it - <braunr> we have the same in french - <teythoon> I ran into a problem with my prototype - <teythoon> if an translator is set in e. g. diskfs_S_file_set_translator, - how do I get the path to that node? - <teythoon> I believe there cannot be a way to do that, b/c the mapping is - not bijective - <braunr> it doesn't have to be - <teythoon> ok, so how do I get *a* path for this node? - <braunr> that's another question - <braunr> do you see how the node is obtained ? - <braunr> np = cred->po->np; - <teythoon> yes - <braunr> the translation occurred earlier - <braunr> you need to find where - <braunr> then perhaps, you'll need to carry the path along - <braunr> or if you're lucky, it will still be there somewhere - <teythoon> the translation from path to node? - <braunr> yes - <teythoon> doesn't that happen in the client? and the client hands a file_t - to the file_set_translator routine? - <braunr> the relative lookup can't happen in the client - <braunr> the server can (and often does) retain information between two - RPCs - <teythoon> uh, I can access information from a previous rpc? is that - considered safe? - <braunr> think of open() then read() - <braunr> a simple int doesn't carry enough information - <braunr> that's why it's a descriptor - <teythoon> ah, the server retains some state, sure - <braunr> what it refers to is the state retained between several calls - <braunr> the object being invoked by clients - <braunr> teythoon: what is the "passive" parameter passed to - diskfs_S_file_set_translator ? - <teythoon> braunr: argz vector of the passive translator - <braunr> so it is a name - <braunr> but we also want active translators - <braunr> and what is active ? - <teythoon> not the name of the node though - <teythoon> active is the port (?) to the active translator - <teythoon> I guess - <braunr> fsys_t, looks that way yes - <braunr> i suppose you could add the path to the peropen structure - <teythoon> ok - <braunr> see diskfs_make_peropen - <teythoon> braunr: but translation happens in dir_lookup - <teythoon> in all places I've seen diskfs_make_peropen used, the path is - not available - <teythoon> why did you point me to diskfs_make_peropen? - <teythoon> s/dir_lookup/diskfs_lookup/ - <teythoon> diskfs_lookup operates on struct node, so the path would have to - be stored there, right? - <braunr> teythoon: dir_lookup should call diskfs_make_peropen - <braunr> at least diskfs_S_dir_lookup does - <braunr> and the path is present there - <teythoon> braunr: right - - <teythoon> hrm... I added a path field to struct peropen and initialize it - properly in diskfs_make_peropen, but some bogus values keep creeping in - :/ - <braunr> first of all, make it a dynamically allocated string - <teythoon> it is - <braunr> not a fixed sized embedded array - <braunr> good - <teythoon> yes - <braunr> if you really need help debugging what's happening, feel free to - post your current changes somewhere - <teythoon> there is a struct literal in fsys-getroot.c, but i fixed that as - well - <teythoon> % ./mtab tmp - <teythoon> none tmp ../tmpfs/tmpfs writable,no-inherit-dir-group,no-sync 0 - 0 - <teythoon> none tmp/bar ../tmpfs/tmpfs - writable,no-inherit-dir-group,no-sync 0 0 - <teythoon> none tmp/foo ../tmpfs/tmpfs - writable,no-inherit-dir-group,no-sync 0 0 - <teythoon> none tmp/foo/bar ../tmpfs/tmpfs - writable,no-inherit-dir-group,no-sync 0 0 - <teythoon> :) - - -## IRC, freenode, #hurd, 2013-07-10 - - <teythoon> btw, I read getcwd.c and got the idea - <teythoon> however this situation is different afaict - <teythoon> getcwd has a port to the current working directory, right? - <teythoon> so they can do open_dir with .. as relative path - <teythoon> but all I've got is a port referencing the node the translator - is being attached to - <teythoon> s/open_dir/dir_lookup/ - <teythoon> and that is not necessarily a directory, so dir_lookup fails - with not a directory - <teythoon> as far as I can see it is not possible to get the directory a - node is in from a port referencing that node - <teythoon> dir_lookup has to be handled by all nodes, not just directories - <teythoon> but file nodes only support "looking up" the empty string - <teythoon> not empty, but null: - <teythoon> This call is required to be supported by all files (even - non-directories) if the filename is null, and should function in that - case as a re-open of the file. */ - <braunr> why do you want the directory ? - <braunr> 10:40 < teythoon> as far as I can see it is not possible to get - the directory a node is in from a port referencing that node - <teythoon> to readdir(3) it and figure out the name of the node the - translator is bound to - <teythoon> similar to what getcwd does - <braunr> that's out of the question - <teythoon> wasn't that was youpi was suggesting? - <braunr> you may have a lot of nodes in there, such a lookup shouldn't be - done - <braunr> i didn't see that detail - <teythoon> "│ Concerning storing the path, it's a bit sad to have to do - that, and - <teythoon> │ it'll become wrong if one moves the mount points. Another - way would - <teythoon> │ be to make the client figure it out by itself from a port to - the mount - <teythoon> │ point, much like glibc/sysdeps/mach/hurd/getcwd.c. It'll be - slower, but - <teythoon> │ should be safer. The RPC would thus return an array of - ports to the - <teythoon> │ mount points instead of an array of strings. - <braunr> yes i remember that - <braunr> but i didn't understand well how getcwd work - <braunr> s - <braunr> another scalability issue - <braunr> not a big one though, we rarely have translators in directories - with thousands of nodes - <braunr> so why not - <braunr> teythoon: do it as youpi suggested - <braunr> well if you can - <braunr> eh - <braunr> if not, i don't know - <braunr> 10:47 < teythoon> │ it'll become wrong if one moves the mount - points. Another way would - <teythoon> yes, I know... :/ - <teythoon> well, I'm not even sure it is possible to get the directory a - node is in from the port referencing the node - <teythoon> as in, I'm not sure if the information is even there - <teythoon> b/c a filesystem is a tree, directories are nodes and files are - leafs - <teythoon> all non-leaf nodes reference their parent to allow traversing - the tree starting from any directory - <teythoon> but why would a leaf reference its parent(s - in case of - hardlinks)? - <braunr> uh, for the same reason ? - <teythoon> sure, it would be nice to do that, but I dont think this is - possible on unixy systems - <braunr> ? - <teythoon> you cannot say fchdir(2) to a fd that references a file - <braunr> do you mean /path/to/file/../ ? - <teythoon> yes - <teythoon> only that /path/to/file is given as fd or port - <braunr> when i pasted - <braunr> 10:49 < braunr> 10:47 < teythoon> │ it'll become wrong if one - moves the mount points. Another way would - <braunr> i was actually wondering if it was true - <teythoon> ah - <braunr> why can't the path be updated at the same time ? - <braunr> it's a relative path anyway - <braunr> completely managed by the parent translator - <teythoon> ah - <teythoon> right - <teythoon> it's still kind of hacky, but I cannot see how to do this - properly - <braunr> hacky ? - <teythoon> but yes, updating the path should work I guess - <teythoon> or sad - <braunr> what i find hacky is to set translators in two passes - <braunr> otherwise we'd only keep the translator paths - <braunr> not all paths - <teythoon> true - <braunr> but then, it only concerns open nodes - <braunr> and again, there shouldn't be too many of them - <braunr> so actually it's ok - <teythoon> braunr: I understand the struct nodes are cached in libdiskfs, - so wouldn't it be easier to attach the path to that struct instead of - struct peropen so that all peropen objects reference the same node - object? - <teythoon> so that the path can be updated if anyone dir_renames it - <teythoon> *all peropen objects derived from the same file name that is - <braunr> teythoon: i'm not sure - <braunr> nodes could be real nodes (i.e. inodes) - <braunr> there can be several paths for the same inode - <teythoon> braunr: I'm aware of that, but didn't we agree the other day - that any path would do? - <braunr> i don't remember we did - <braunr> i don't know the details well, but i don't think setting a - translator on a hard link should set the translator at the inode level - <braunr> on the other hand, if a new inode is created to replace the - previous one (or stack over it), then storing the path there should be - fine - <teythoon> braunr: I don't think I can update the paths if they're stored - in the peropen struct - <teythoon> how would I get a reference to all those peropen objects? - <braunr> ? - <braunr> first, what's the context when you talkb about updating paths ? - <teythoon> well, youpi was concerned about renaming a mount point - <teythoon> and you implied that this could be managed - <braunr> can we actually do that btw ? - <teythoon> what? - <braunr> renaming a mount point - <teythoon> yep, just tried - <braunr> i mean, on a regular unix system like linux - <braunr> $ mv test blah - <braunr> mv: cannot move `test' to `blah': Device or resource busy - <braunr> (using sshfs so YMMV) - <pinotree> do you have anything (shells, open files, etc) inside it? - <braunr> no - <braunr> i'll try with an empty loop-mounted ext4 - <teythoon> I was testing on the Hurd, worked fine there even with a shell - inside - <braunr> same thing - <braunr> i consider it a bug - <braunr> we may want to check what posix says about it - <teythoon> o_O - <braunr> and decide not to support renaming - <teythoon> why? - <pinotree> start a discussion in ml, maybe roland can chime in - <braunr> it complicates things - <braunr> ah yes - <teythoon> sure, but I can move or rename a directory, why should it be - different with a mount point? - <braunr> because it's two of them - <braunr> they're stacked - <braunr> if we do want to support that, we must be very careful about - atomically updating all the stack - <teythoon> ok - <teythoon> braunr: I'm trying to detect dying translators to remove them - from the list of translators - <teythoon> what port can I use for that purpose? - <teythoon> if I use the bootstrap port, can I then use the same method as - init/init.c uses? just defining a do_mach_notify_dead_name function and - the multiplexer will call this? - <braunr> teythoon: possibly - <teythoon> braunr: we'll see shortly... - <teythoon> I get KERN_INVALID_CAPABILITY indicating that my bootstrap port - is invalid - <teythoon> when calling mach_port_request_notification to get the dead name - notification I mean - <braunr> is the translator already started when you do that ? - <teythoon> yes, at least I think so, I'm hooking into - diskfs_S_file_set_translator and that gets an active translators port - <teythoon> also the mach docs suggests that the notification port is - invalid, not the name port referencing the translator - <braunr> i guess it shouldn't - <braunr> oh - <braunr> please show the code - <braunr> but beware, if the translator is started, assume it could die - immediately - <teythoon> braunr: http://paste.debian.net/15371/ line 87 - <braunr> teythoon: notify can't be bootstrap - <braunr> what do you have in mind when writing this ? - <braunr> i'm not sure i follow - <teythoon> I want to be notified if an active translator goes away to - remove it from the list of translators - <braunr> ok but then - <braunr> create a send-once right - <braunr> and wait on it - <braunr> also, why do you want to be notified ? - <braunr> isn't this already done ? - <braunr> or can't do it lazily on access attempt ? - <braunr> +you - <teythoon> in the client? - <braunr> in the parent server - <braunr> what happens currently when a translator dies - <braunr> is the parent notified ? - <braunr> or does it give an invalid right ? - <teythoon> ah, i think so - <braunr> then you don't need to do it again - <teythoon> right, I overlooked that - - -## IRC, freenode, #hurd, 2013-07-12 - - <teythoon> recursively traversing all translators from / turns out to be - more dangerous than I expected - <teythoon> ... if done by a translator bound somewhere below /... - <teythoon> my interpretation is that the mtab translator tries to talk to - itself and deadlocks - <teythoon> (and as a side effect the whole system kinda just stops...) - - -## IRC, freenode, #hurd, 2013-07-15 - - <youpi> teythoon: did you discuss with braunr about returning port vs path - in fsys_get_children? - <teythoon> youpi: we did - <teythoon> as I wrote I looked at the getcwd source you pointed me at - <teythoon> and I started to code up something similar - <teythoon> but as far as I can see there's no way to tell from a port - referencing a file the directory this file is located in - <youpi> ah, right, there was a [0] mail - <youpi> teythoon: because it doesn't have a "..", right - <teythoon> about Neals concerns, he's right about not covering passive - translators very well - <teythoon> but the solution he proposed was similar to what I tried to do - first - <youpi> I don't like half-covering passive translators at all, to be honest - :) - <youpi> either covering them completely, or not at all, would be fine - <teythoon> and then braunr convinced me that the "recursive" approach is - more elegant and hurdish, and I came to agree with him - <teythoon> youpi: one could scan the filesystem at translator startup and - populate the list - <youpi> by "Neal's solution", you mean an mtab registry? - <teythoon> yes - <braunr> so, let's see what linux does when renaming parent directories - <teythoon> mount points you mean? - <youpi> teythoon: browsing the whole filesystem just to find passive - translators is costly - <youpi> teythoon, braunr: and that won't prevent the user from unexpectedly - starting other translators at will - <braunr> scary - <teythoon> youpi: but that requires the privilege to open the device - <youpi> the fact that a passive translator is set is nothing more than a - user having the intent of starting a translator - <braunr> linux retains the original path in the mount table - <youpi> heh - <teythoon> youpi: any unprivileged user can trigger a translator startup - <youpi> sure, but root can do that too - <youpi> and expect the system to behave nicely - <teythoon> but if I'm root and want to fsck something, I won't start - translators accessing the device just before that - <teythoon> but if there's a passive translator targetting the device, - someone else might do that - <youpi> root does not always completely control what he's doing - <youpi> linux for instance does prevent from mounting a filesystem being - checked - <teythoon> but still, including passive translators in the list would at - least prevent anyone starting an translator by accident, isn't that worth - doing then? - <youpi> if there's a way to prevent root too, that's better than having a - half-support for something which we don't necessarily really want - <youpi> (i.e. an exclusive lock on the underlying device) - <teythoon> right, that would also do the trick - <teythoon> btw, some programs or scripts seem to hardcode /proc/mounts and - procfs and I cannot bind a translator to /proc/mounts since it is - read-only and the node does not exist - <kilobug> IMHO automatically starting translators is a generic feature, and - passive translator is just a specific instance of it; but we could very - well have, like an "autofs" that automatically start translators in tar - archives and iso images, allowing to cd into any tar/iso on the system; - implementing such things is part of the Hurd flexibility, the "core - system" shouldn't be too aware on how translators are started - <youpi> so in the end, storing where the active translator was started - first seems okayish according to what linux has been exposing for decades - <youpi> kilobug: indeed - <teythoon> it could serve a mounts with a passive translator by default, or - a link to /run/mtab, or an simple file so we could bind a translator to - that node - <youpi> I'd tend to think that /proc/mounts should be a passive translator - and /run/mtab / /etc/mtab a symlink to it - <youpi> not being to choose the translator is a concern however - <teythoon> ok, I'll look into that - <youpi> it could be an empty file, and people be able to set a translator - on it - <teythoon> if it had a passive translator, people still could bind their - own translator to it later on, right? - <teythoon> afaics the issue currently is mostly, that there is no mounts - node and it is not possible to create one - <youpi> right - <teythoon> cool - <youpi> so with the actual path, you can even check for caller's permission - to read the path - <youpi> i.e. not provide any more information than the user would be able - to get from browsing by hand - <teythoon> sure, that concern of Neil's is easy to address - <youpi> I'm not so much concerned by stale paths being shown in mtab - <youpi> the worst that can happen is a user not being able to umount the - path - <youpi> but he can settrans -g it - <youpi> (which he can't on linux ;) ) - <teythoon> yes, and the device information is still valid - <youpi> yes - <braunr> despite the parent dir being renamed, linux is still able to - umount the new path - <teythoon> and so is our current umount - <braunr> good - <teythoon> (if one uses the mount point as argument) - <braunr> what's the current plan concerning /proc/mounts ? - <teythoon> serving a node with a passive translator record - <braunr> ? - <teythoon> so that /hurd/mtab / is started on access - <braunr> i mean, still planning on using the recursive approach instead of - a registry ? - <teythoon> ah - <teythoon> I do not feel confident enough to decide this, but I agree with - you, it feels elegant - <teythoon> and it works :) - <teythoon> modulo the translator deadlocking if it talks to itself, any - thoughts on that? - <youpi> it is a non-threaded translator I guess? - <teythoon> currently yes - <youpi> making it threaded should fix the issue - <teythoon> I tried to make the mtab translator multithreaded but that - didn't help - <youpi> that's odd - <teythoon> maybe I did it wrong - <braunr> i don't find it surprising - <braunr> well, not that surprising :p - <braunr> on what lock does it block ? - <teythoon> as far as i can see the only difference of hello and hellot-mt - is that it uses a different dispatcher and has lot's of locking, right? - <teythoon> braunr: I'm not sure, partly because that wrecked havoc on the - whole system - <teythoon> it just freezes - <teythoon> but it wasn't permanent. once i let it running and it recovered - <braunr> consider using a subhurd - <teythoon> ah right, I ment to set up one anyway, but my first attempts - were not successful, not sure why - <teythoon> anyway, is there a way to prevent this in the first place? - <teythoon> if one could compare ports that'd be helpful - <youpi> Mmm, did you try to simply compare the number? - <teythoon> with the bootstrap port I presume? - <youpi> Mmm, no, the send port and the receive port would be different - <youpi> no, with the receive port - <teythoon> ah - <braunr> comparing the numbers should work - <braunr> youpi: no they should be the same - <youpi> braunr: ah, then it should work yes - <braunr> that's why there are user ref counts - <youpi> ok - <braunr> only send-once rights have their own names - <teythoon> btw, I'll push my work to darnassus from now on, - e.g. http://darnassus.sceen.net/gitweb/?p=teythoon/hurd.git;a=shortlog;h=refs/heads/feature-mtab-translator-v3-wip - - -## [[open_issues/libnetfs_passive_translators]] - - -## IRC, freenode, #hurd, 2013-07-16 - - <teythoon> which port is the receive port of a translator? I mean, how is - it called in the source, there is no port in sight named receive anywhere - I looked. - <braunr> teythoon: what is the "receive port of a translator" ? - <teythoon> braunr: we talked yesterday about preventing the mtab deadlock - by comparing ports - <teythoon> I asked which one to use for the comparison, youpi said the - receive port - <braunr> i'm not sure what he meant - <braunr> it could be the receive port used for the RPC - <braunr> but i don't think it's exported past mig stub code - <teythoon> weird, I just reread it. I asked if i should use the bootstrap - port, and he said receive port, but it might have been addressed to you? - <teythoon> you were talking about send and receive ports being singletons - or not - <teythoon> umm - <braunr> no i answered him - <braunr> he was wondering if the receive port could actually be used for - comparison - <braunr> i said it can - <braunr> but still, i'm not sure what port - <braunr> if it's urgent, send him a mail - <teythoon> no, my pipeline is full of stuff I can do instead ;) - <braunr> :) - - -## IRC, freenode, #hurd, 2013-07-17 - - <teythoon> braunr: btw, comparing ports solved the deadlock in the mtab - translator rather easily - <braunr> :) - <braunr> which port then ? - <teythoon> currently I'm stuck though, I'm not sure how to address Neals - concern wrt to access permission checks - <teythoon> I believe it's called control port - <braunr> ok - <teythoon> the one one gets from doing the handshake with the parent - <braunr> i thought it was the bootstrap port - <braunr> but i don't know the details so i may be wrong - <braunr> anyway - <teythoon> yes - <braunr> what is the permission problem again ? - <teythoon> 871u73j4zp.wl%neal@walfield.org - <braunr> well, you could perform a lookup on the stored path - <braunr> as if opening the node - <teythoon> if I look at any server implementation of a procedure from - fs.defs (say libtrivfs/file-chmod.c [bad example though, that looks wrong - to me]), there is permission checking being done - <teythoon> any server implementation of a procedure from fsys.defs lacks - permission checks, so I guess it's being done somewhere else - <braunr> i must say i'm a bit lost in this discussion - <braunr> i don't know :/ - <braunr> can *you* sum up the permission problem please ? - <braunr> i mean here, now, in just a few words ? - <teythoon> ok, so I'm extending the fsys api with the get_children - procedure - <teythoon> that one should not return any children x/y if the user doing - the request has no read permissions on x - <braunr> really ? - <braunr> why so ? - <teythoon> the same way ls x would not reveal the existence of y - <braunr> i could also say unlike cat /proc/mounts - <braunr> i can see why we would want that - <braunr> i also can see why we could let this behaviour in place - <braunr> let's admit we do want it - <teythoon> true, but I thought this could easily be addressed - <braunr> what you could do is - <teythoon> now I'm not sure b/c I cannot even find the permission checking - code for any fsys_* function - <braunr> for each element in the list of child translators - <braunr> perform a lookup on the stored path on behalf of the user - <braunr> and add to the returned list if permission checks pass - <braunr> teythoon: note that i said lookup on the path, which is an fs - interface - <braunr> i assume there is no permission checking for the fsys interface - because it's done at the file (fs) level - <teythoon> i think so too, yes - <teythoon> sure, if I only knew who made the request in the first place - <teythoon> the file-* options have a convenient credential handle passed in - as first parameter - <teythoon> s/options/procedures/ - <teythoon> surely the fsys-* procedures also have a means of retrieving - that information, I just don't know how - <braunr> mig magic - <braunr> teythoon: see file_t in hurd_types.defs - <braunr> there is the macro FILE_INTRAN which is defined in subdirectories - (or not) - <teythoon> ah, retrieving the control port requires permissions, and the - fsys-* operations then operate on the control port? - <braunr> see libdiskfs/fsmutations.h for example - <braunr> uh yes but that's for < braunr> i assume there is no permission - checking for the fsys interface because it's done at the file (fs) level - <braunr> i'm answering < teythoon> sure, if I only knew who made the - request in the first place - <braunr> teythoon: do we understand each other or is there still something - fuzzy ? - <teythoon> braunr: thanks for the pointers, I'll read up on that a bit - later - <braunr> teythoon: ok - - -## IRC, freenode, #hurd, 2013-07-18 - - <teythoon> braunr: back to the permission checking problem for the - fsys_get_children interface - <teythoon> I can see how this could be easily implemented in the mtab - translator, it asks the translator for the list of children and then - checks if the user has permission to read the parent dir - <teythoon> but that is pointless, it has to be implemented in the - fsys_get_children server function - <braunr> yes - <braunr> why is it pointless ? - <teythoon> because one could circumvent the restriction by doing the - fsys_get_children call w/o the mtab translator - <braunr> uh no - <braunr> you got it wrong - <braunr> what i suggested is that fsys_get_children does it before - returning a list - <braunr> the problem is that the mtab translator has a different identity - from the users accessing it - <teythoon> yes, but I cannot see how to do this, b/c at this point I do not - have the user credentials - <braunr> get them - <teythoon> how? - <braunr> 16:14 < braunr> mig magic - <braunr> 16:15 < braunr> teythoon: see file_t in hurd_types.defs - <braunr> 16:16 < braunr> there is the macro FILE_INTRAN which is defined in - subdirectories (or not) - <braunr> 16:16 < braunr> see libdiskfs/fsmutations.h for example - <teythoon> i saw that - <braunr> is there a problem i don't see then ? - <braunr> i suppose you should define FSYS_INTRAN rather - <braunr> but the idea is the same - <teythoon> won't that change all the function signatures of the fsys-* - family? - <braunr> that's probably the only reason not to implement this feature - right now - <teythoon> then again, that change is probably easy and mechanic in nature, - might be an excuse to play around with coccinelle - <braunr> why not - <braunr> if you have the time - <teythoon> right, if this can be done, the mtab translator (if run as root) - could get credentials matching the users credentials to make that - request, right? - <braunr> i suppose - <braunr> i'm not sure it's easy to make servers do requests on behalf of - users on the hurd - <braunr> which makes me wonder if the mtab functionality shouldn't be - implemented in glibc eheheh .... - <braunr> but probably not - <teythoon> well, I'll try out the mig magic thing and see how painful it is - to fix everything ;) - <braunr> good luck - <braunr> honestly, i'm starting to think it's deviating too much from your - initial goal - <braunr> i'd be fine with a linux-like /proc/mounts - <braunr> with a TODO concerning permissions - <teythoon> ok, fine with me :) - <braunr> confirm it with the other mentors please - <braunr> we have to agree quickly on this - <teythoon> y? - - <teythoon> braunr: I actually believe that the permission issue can be - addressed cleanly and unobstrusively - <teythoon> braunr: would you still be opposed to the get_children approach - if that is solved? - <teythoon> the filesystem is a tree and the translators "creating" that - tree are a more coarse version of that tree - <teythoon> having a method to traverse that tree seems natural to me - <braunr> teythoon: it is natural - <braunr> i'm just worried it's a bit too complicated, unnecessary, and - out-of-scope for the problem at hand - <braunr> (which is /proc/mounts, not to forget it) - - -## IRC, freenode, #hurd, 2013-07-19 - - <teythoon> braunr: I think you could be a bit more optimistic and - supportive of the decentralized approach - <teythoon> I know the dark side has cookies and strong language and it's - mighty tempting - <teythoon> but both are bad for you :p - - -## IRC, freenode, #hurd, 2013-07-22 - - <youpi> teythoon: AIUI, you should be able to run the mtab translator as - no-user (i.e. no uid) - <teythoon> youpi: yes, that works fine - - <youpi> teythoon: so there is actually no need to define FSYS_INTRAN, doing - it by hand as you did is fine, right? - <youpi> (/me backlogs mails...) - <teythoon> youpi: yes, the main challenge was to figure out what mig does - and how the cpp is involved - <youpi> heh :) - <teythoon> my patch does exactly the same, but only for this one server - function - <teythoon> youpi: I'm confused by your mail, why are read permissions on - all path components necessary? - <braunr> teythoon: only execution normally - <youpi> teythoon: to avoid letting a user discover a translator running on - a hidden directory - <teythoon> braunr: exactly, and that is tested - <youpi> e.g. ~/home/foo is o+x, but o-r - <youpi> and I have a translator running on ~/home/foo/aZeRtYuyU - <youpi> I don't want that to show up on /proc/mounts - <braunr> youpi: i don't understand either: why isn't execution permission - enough ? - <teythoon> youpi: but that requires testing for read on the *last* - component of the *dirname* of your translator, and that is tested - <youpi> let me take another example :) - <youpi> e.g. ~/home/foo/aZeRtYuyU is o+x, but o-r - <youpi> and I have a translator running on ~/home/foo/aZeRtYuyU/foo - <youpi> ergl sorry, I meant this actually: - <teythoon> yes, that won't show up then in the mtab for users that are not - you and not root - <youpi> e.g. ~/home/foo is o+x, but o-r - <youpi> and I have a translator running on ~/home/foo/aZeRtYuyU/foo - <teythoon> ah - <teythoon> hmm, good point - <braunr> ? - * braunr still confused - <teythoon> well, qwfpgjlu is the secret - <teythoon> and that is revealed by the fsys_get_children procedure - <braunr> then i didn't understand the description of the call right - <braunr> > + /* check_access performs the same permission check as is - normally - <braunr> > + done, i.e. it checks that all but the last path components - are - <braunr> > + executable by the requesting user and that the last - component is - <braunr> > + readable. */ - <teythoon> braunr: youpi argues that this is not enough in this case - <braunr> from that, it looks ok to me - <youpi> the function and the documentation agree, yes - <youpi> but that's not what we want - <braunr> and that's where i fail to understand - <youpi> again, see my example - <braunr> i am - <braunr> 10:43 < youpi> e.g. ~/home/foo is o+x, but o-r - <braunr> ok - <youpi> so the user is not supposed to find out the secret - <braunr> then your example isn't enough to describe what's wron - <braunr> g - <youpi> checking read permission only on ~/home/foo/aZeRtYuyU will not - garantee that - <braunr> ah - <braunr> i thought foo was the last component - <youpi> no, that's why I changed my example - <braunr> hum - <braunr> 10:43 < youpi> e.g. ~/home/foo is o+x, but o-r - <braunr> 10:43 < youpi> and I have a translator running on - ~/home/foo/aZeRtYuyU/foo - <braunr> i meant, the last foo - <teythoon> still, this is easily fixed - <youpi> sure - <youpi> just has to be :) - <teythoon> youpi, braunr: so do you think that this approach will work? - <youpi> I believe so - <braunr> i still don't see the problem, so don't ask me :) - <braunr> i've been sick all week end and hardly slept, which might explain - <braunr> in the example, "all but the last path components" is - "~/home/foo/aZeRtYuyU" - <braunr> right ? - <youpi> braunr: well, I haven't looked at the details - <youpi> but be it the last, or but-last doesn't change the issue - <youpi> if my ~/hidden is o-r,o+x - <youpi> and I have a translator on ~/hidden/a/b/c/d/e - <youpi> checking only +x on hidden is not ok - <braunr> but won't the call also check a b c d ? - <youpi> yes, but that's not what matters - <youpi> what matters is that hidden is o-r - <braunr> hm - <youpi> so the mtab translator is not supposed to reveal that there is an - "a" in there - <braunr> ok i'm starting to understand - <braunr> so r must be checked on all components too - <youpi> yes - <braunr> right - <youpi> to simulate the user doing ls, cd, ls, cd, etc. - <braunr> well, not cd - <braunr> ah - <youpi> for being able to do ls, you have to be able to do cd - <braunr> as an ordered list of commands - <braunr> ok - <teythoon> agreed. can you think of any more issues? - <braunr> so both x and r must be checked - <youpi> so in the end this RPC is really a shortcut for a find + fsysopts - script - <youpi> teythoon: I don't see any - <braunr> teythoon: i couldn't take a clear look at the patch but - <braunr> do you perform a lookup on all nodes ? - <teythoon> yes, all nodes on the path from the root to the one specified by - the mount point entry in the active translator list - <braunr> let me rephrase - <braunr> do you at some point do a lookup, similar to a find, on all nodes - of a translator ? - <teythoon> no - <braunr> good - <teythoon> yes - <braunr> iirc, neal raised that concern once - <teythoon> and I'll also fix settrans --recursive not to iterate over *all* - nodes either - <braunr> great - <braunr> :) - <teythoon> fsys_set_options with do_children=1 currently does that (I've - only looked at the diskfs version) - - -## IRC, freenode, #hurd, 2013-07-27 - - <teythoon> youpi: ah, I just found msg_get_init_port, that should make the - translator detection feasible - - -## IRC, freenode, #hurd, 2013-07-31 - - <teythoon> braunr: can I discover the sender of an rpc message? - <braunr> teythoon: no - <braunr> teythoon: what do you mean by "sender" ? - <teythoon> braunr: well, I'm trying to do permission checks in the - S_proc_mark_essential server function - <braunr> ok so, the sending user - <braunr> that should be doable - <teythoon> I've got a struct proc *p courtesy of a mig intran mutation and - a port lookup - <teythoon> but that is not necessarily the sender, right? - <braunr> proc is really the server i know the least :/ - <braunr> there is permission checking for signals - <braunr> it does work - <braunr> you should look there - <teythoon> yes, there are permission checks there - <teythoon> but the only argument the rpc has is a mach_port_t refering to - an object in the proc server - <braunr> yes - <teythoon> anyone can obtain such a handle for any process, no? - <braunr> can you tell where it is exactly please ? - <braunr> i don't think so, no - <teythoon> what? - <braunr> 14:42 < teythoon> but the only argument the rpc has is a - mach_port_t refering to an object in the proc server - <teythoon> ah - <braunr> the code you're referring to - <braunr> a common way to give privileges to public objects is to provide - different types of rights - <braunr> a public (usually read-only) right - <braunr> and a privileged one, like host_priv which you may have seen - <braunr> acting on (modifying) a remote object normally requires the latter - <teythoon> http://paste.debian.net/20795/ - <braunr> i thought you were referring to existing code - <teythoon> well, there is existing code doing permission checks the same - way I'm doing it there - <braunr> where is it please ? - <braunr> mgt.c ? - <teythoon> proc/mgt.c (S_proc_setowner) for example - <teythoon> yes - <braunr> that's different - <teythoon> but anyone can obtain such a reference by doing proc_pid2proc - <braunr> the sender is explicitely giving the new uid - <braunr> yes but not anyone is already an owner of the target process - <braunr> (although it may look like anyone has the right to clear the owner - oO) - <teythoon> see, that's what made me worry, it is not checked who's the - sender of the message - <teythoon> unless i'm missing something here - <teythoon> ah - <teythoon> I am - <teythoon> pid2proc returns EPERM if one is not the owner of the process in - question - <teythoon> all is well - <braunr> ok - <braunr> it still requires the caller process though - <teythoon> what? - <braunr> see check_owner - <braunr> the only occurrence i find in the hurd is in libps/procstat.c - <braunr> MGET(PSTAT_PROCESS, PSTAT_PID, proc_pid2proc (server, ps->pid, - &ps->process)); - <braunr> server being the proc server AIUI - <teythoon> yes, most likely - <braunr> but pid2proc describes this first argument to be the caller - process - <teythoon> ah but it is - <braunr> ? - <teythoon> mig magic :p - <teythoon> MIGSFLAGS="-DPROCESS_INTRAN=pstruct_t reqport_find (process_t)" - \ - <teythoon> MIGSFLAGS="-DPROCESS_INTRAN=pstruct_t reqport_find (process_t)" - \ - <braunr> ah nice - <braunr> hum no - <braunr> this just looks up the proc object from a port name, which is - obvious - <braunr> what i mean is - <braunr> 14:53 < braunr> MGET(PSTAT_PROCESS, PSTAT_PID, proc_pid2proc - (server, ps->pid, &ps->process)); - <braunr> this is done in libps - <braunr> which can be used by any process - <braunr> server is the proc server for this process (it defines the process - namespace) - <teythoon> yes, but isn't the port to the proc server different for each - process? - <braunr> no, the port is the same (the name changes only) - <braunr> ports are global non-first class objects - <teythoon> and the proc server can thus tell with the lookup which process - it is talking to? - <braunr> that's the thing - <braunr> from pid2proc : - <braunr> S_proc_pid2proc (struct proc *callerp - <braunr> [...] - <braunr> if (! check_owner (callerp, p)) - <braunr> check_owner (struct proc *proc1, struct proc *proc2) - <braunr> "Returns true if PROC1 has `owner' privileges over PROC2 (and can - thus get its task port &c)." - <braunr> callerp looks like it should be the caller process - <braunr> but in libps, it seems to be the proc server - <braunr> this looks strange to me - <teythoon> yep, to me too, hence my confusion - <braunr> could be a bug that allows anyone to perform pid2proc - <teythoon> braunr: well, proc_pid2proc (getproc (), 1, ...) fails with - EPERM as expected for me - <braunr> ofc it does with getproc() - <braunr> but what forces a process to pass itself as the first argument ? - <teythoon> braunr: nothing, but what else would it pass there? - <braunr> 14:53 < braunr> MGET(PSTAT_PROCESS, PSTAT_PID, proc_pid2proc - (server, ps->pid, &ps->process)); - <braunr> everyone knows the proc server - <braunr> ok now, that's weird - <braunr> teythoon: does getproc() return the proc server ? - <teythoon> I think so, yes - <teythoon> damn those distributed systems, all of their sources are so - distributed too - <braunr> i suspect there is another layer of dark glue in the way - <teythoon> I cannot even find getproc :/ - <braunr> hurdports.c:GETSET (process_t, proc, PROC) - <braunr> that's the dark glue :p - <teythoon> ah, so it must be true that the ports to the proc server are - indeed process specific, right? - <braunr> ? - <teythoon> well, it is not one port to the proc server that everyone knows - <braunr> it is - <braunr> what makes you think it's not ? - <teythoon> proc_pid2proc (getproc (), 1, ...) fails with EPERM for anyone - not being root, but succeeds for root - <braunr> hm right - <teythoon> if getproc () were to return the same port, the proc server - couldn't distinguish these - <braunr> indeed - <braunr> in which case getproc() actually returns the caller's process - object at its proc server - <teythoon> yes, that is better worded - <braunr> teythoon: i'm not sure it's true actually :/ - <teythoon> braunr: well, exploit or it didn't happen - <braunr> teythoon: getproc() apparently returns a bootstrap port - <braunr> we must find the code that sets this port - <braunr> i have a hard time doing that :/ - <pinotree> isn't part of the stuff which is passed to a new process by - exec? - <teythoon> braunr: I know that feeling - <braunr> pinotree: probably - <braunr> still hard to find .. - <pinotree> search in glibc - <teythoon> braunr: exec/exec.c:1654 asks the proc server for the proc - object to use for the new process - <teythoon> so how much of hurd do I have to rebuild once i changed struct - procinfo in hurd_types.h? - <teythoon> oh noez, glibc uses it too :/ - - -## IRC, freenode, #hurd, 2013-08-01 - - <teythoon> I need some pointers on building the libc, specifically how to - point libcs build system to my modified hurd headers - <teythoon> nlightnfotis: hi - <teythoon> nlightnfotis: you rebuild the libc right? do you have any hurd - specific pointers for doing so? - <nlightnfotis> teythoon, I have not yet rebuild the libc (I was planning - to, but I followed other courses of action) Thomas had pointed me to some - resources on the Hurd website. I can look them up for you - <nlightnfotis> teythoon, here are the instructions - http://darnassus.sceen.net/~hurd-web/open_issues/glibc/debian/ - <nlightnfotis> and the eglibc snapshot is here - http://snapshot.debian.org/package/eglibc/ - <teythoon> nlightnfotis: yeah, I found those. the thing is I changed a - struct in the hurd_types.h header, so now I want to rebuild the libc with - that header - <teythoon> and I cannot figure out how to point libcs build system to my - hurd headers - <teythoon> :/ - <nlightnfotis> can you patch eglibc and build that one instead? - <pochu> teythoon: put your header in the appropriate /usr/include/ dir - <teythoon> pochu: is there no other way? - <pinotree> iirc nope - <pochu> teythoon: you may be able to pass some flag to configure, but I - don't know if that will work in this specific case - <teythoon> ouch >,< that explains why I haven't found one - <pochu> check ./configure --help, it's usually FOO_CFLAGS (so something - like HURD_CFLAGS maybe) - <pochu> but then you may need _LIBS as well depending on how you changed - the header... so in the end it's just easier to put the header in - /usr/include/ - <braunr> teythoon: did you find the info for your libc build ? - <teythoon> braunr: well, i firmlinked my hurd_types.h into /usr/include/... - <braunr> ew - <braunr> i recommend building debian packages - <teythoon> but the build was not successful, looks unrelated to my changes - though - <teythoon> I tried that last week and the process took more than eight - hours and did not finish - <braunr> use darnassus - <braunr> it takes about 6 hours on it - <teythoon> I shall try again and skip the unused variants - <braunr> i also suggest you use ./debian/rules build - <braunr> and then interrupt the build process one you see it's building - object files - <braunr> go to the hurd-libc-i386 build dir, and use make lib others - <braunr> make lib builds libc, others is for companion libraries lik - libpthread - <braunr> actually building libc takes less than an hour - <braunr> so once you validate your build this way, you know building the - whole debian package will succedd - <braunr> succeed* - <teythoon> so how do I get the build system to pick up my hurd_types.h? - <braunr> sorry if this is obvious to you, you might be more familiar with - debian than i am :) - <braunr> patch the hurd package - <braunr> append your own version string like +teythoon.hurd.1 - <braunr> install it - <braunr> then build libc - <braunr> i'll reboot darnassus so you have a fresh and fast build env - <braunr> almost a month of uptime without any major issue :) - <teythoon> err, but I cannot install my hurd package on darnassus, can I? I - don't think that'd be wise even if it were possible - <braunr> teythoon: rebooted, enjoy - <braunr> why not ? - <braunr> i often do it for my own developments - <braunr> teythoon: screen is normally available - <braunr> teythoon: be aware that fakeroot-tcp is known to hang when pfinet - is out of ports (that's a bug) - <braunr> it takes more time to reach that bug since a patch that got in - less than a year ago, but it still happens - <braunr> the hurd packages are quick to build, and they should only provide - the new header, right ? - <braunr> you can include the functionality too in the packages if you're - confident enough - <teythoon> but my latest work on the killing of essential processes issues - involves patching hurd_types.h and that in a way that breaks the ABI, - hence the need to rebuild the libc (afaiui) - <braunr> teythoon: yes, this isn't uncommon - <teythoon> braunr: this is much more intrusive than anything I've done so - far, so I'm not so confident in my changes for now - <braunr> teythoon: show me the patch please - <teythoon> braunr: it's not split up yet, so kind of messy: - http://paste.debian.net/21403/ - <braunr> teythoon: did you make sure to add RPCs at the end of defs files ? - <teythoon> yes, I got burned by this one on my very first attempt, you - pointed out that mistake - <braunr> :) - <braunr> ok - <braunr> you're changing struct procinfo - <braunr> this really breaks the abi - <teythoon> yes - <braunr> i.e. you can't do that - <teythoon> I cannot put it at the end b/c of that variable length array - <braunr> you probably should add another interface - <teythoon> that'd be easier, sure, but this will slow down procfs even - more, no? - <braunr> that's secondary - <braunr> it won't be easier, breaking the abi may break updates - <braunr> in which case it's impossible - <braunr> another way would be to ues a new procinfo struct - <braunr> like struct procinfo2 - <braunr> but then you need a transition step so that all users switch to - that new version - <braunr> which is the best way to deal with these issues imo, but this time - not the easiest :) - <teythoon> ok, so I'll introduce another rpc and make sure that one is - extensible - <braunr> hum no - <braunr> this usually involves using a version anyway - <teythoon> no? but it is likely that we need to save more addresses of this - kind in the future - <braunr> in which case it will be hanlded as an independant problem with a - true solution such as the one i mentioned - <teythoon> it could return an array of vm_address_ts with a length - indicating how many items were returned - <braunr> it's ugly - <braunr> the code is already confusing enough - <braunr> keep names around for clarity - <teythoon> ok, point taken - <braunr> really, don't mind additional RPCs when first adding new features - <braunr> once the interface is stable, a new and improved version becomes a - new development of its own - <braunr> you're invited to work on that after gsoc :) - <braunr> but during gsoc, it just seems like an unnecessary burden - <teythoon> ok cool, I really like that way of extending Hurd, it's really - easy - <teythoon> and feels so natural - <braunr> i share your concern about performances, and had a similar problem - when adding page cache information to gnumach - <braunr> in the end, i'll have to rework that again - <braunr> because i tried to extend it beyond what i needed - <teythoon> true, I see how that could happen easily - <braunr> the real problem is mig - <braunr> mig limits subsystems to 100 calls - <braunr> it's clearly not enough - <braunr> in x15, i intend to use 16 bits for subsystems and 16 bits for - RPCs, which should be plenty - <teythoon> that limit seems rather artificial, it's not a power of two - <braunr> yes it is - <teythoon> so let's fix it - <braunr> mach had many artificial static limits - <braunr> eh :D - <braunr> not easy - <braunr> replies are encoded by taking the request ID and adding 100 - <teythoon> uh - <braunr> "uh" indeed - <teythoon> so we need an intermediate version of mig that accepts both - id+100 and dunno id+2^x as replies for id - <teythoon> or -id - 1 - <braunr> that would completely break the abi - <teythoon> braunr: how so? the change would be in the *_server functions - and be compatible with the old id scheme - <braunr> how do you make sure id+2^x doesn't conflict with another id ? - <teythoon> oh, the id is added to the subsystem id? - <teythoon> to obtain a global message id? - <braunr> yes - <teythoon> ah, I see - <teythoon> ah, but the hurd subsystems are 1000 ids apart - <teythoon> so id+100 or id +500 would work - <braunr> we need to make sure it's true - <braunr> always true - <teythoon> so how many bits do we have for the message id in mach? - <teythoon> (mig?) - <braunr> mach shouldn't care, it's entirely a mig thing - <braunr> well yes and no - <braunr> mach defines the message header, which includes the message id - <braunr> see mach/message.h - <braunr> mach_msg_id_t msgh_id; - <braunr> typedef integer_t mach_msg_id_t; - <teythoon> well, if that is like a 32 bit integer, then allow -id-1 as - reply and forbid ids > 2^x / 2 - <braunr> yes - <braunr> seems reasonable - <teythoon> that'd give us an smooth upgrade path, no? - <braunr> i think so - - -## IRC, freenode, #hurd, 2013-08-28 - - <youpi> teythoon: Mmm, your patch series does not make e.g. ext2fs provide - a diskfs_get_source, does it? - - -## IRC, freenode, #hurd, 2013-08-29 - - <teythoon> youpi: that is correct - <youpi> teythoon: Mmm, I must be missing something then: as such the patch - series introduces an RPC, but only EOPNOTSUPP is ever returned in all - cases for now? - <youpi> ah - <youpi> /* Guess based on the last argument. */ - <youpi> since ext2fs & such report their options with store last, it seems - ok indeed - <youpi> it still seems a bit lame not to return that information in - get_source - <teythoon> yes - <teythoon> well, if it had been just for me, I would not have created that - rpc, but only guessing was frowned uppon iirc - <teythoon> then again, maybe this should be used and then the mtab - translator could skip any translators that do not provide this - information to filter out non-"filesystem" translators - <youpi> guessing is usually trap-prone, yes - <youpi> if it is to be used by mtab, then maybe it should be documented as - being used by mtab - <youpi> otherwise symlink would set a source, for instance - <youpi> while we don't really want it here - <teythoon> why would the symlink translator answer to such requests? it is - not a filesystem-like translator - <youpi> no, but the name & documentation of the RPC doesn't tell it's only - for filesystem-like translators - <youpi> well, the documentation does say "filesystem" - <youpi> but it does not clearly specify that one shouldn't implement - get_source if one is not a filesystme - <youpi> "If the concept of a source is applicable" works for a symlink - <youpi> that could be the same for eth-filter, etc. - <teythoon> right - <youpi> Mmm, that said it's fsys.defs - <youpi> not io.defs - <youpi> teythoon: it is the fact that we get EOPNOTSUPP (i.e. fsys - interface supported, just not that call), and not MIG_BAD_ID (i.e. fsys - interface not supported), that filters out symlink & such, right? - <teythoon> that's what I was thinking, but that's based on my - interpretation of EOPNOPSUPP of course ;) - <youpi> teythoon: I believe that for whatever is a bit questionable, even - if you put yourself on the side that people will probably agree on, the - discussion will still take place so we make sure it's the right side :) - <youpi> (re: start/end_code) - <teythoon> I'm not sure I follow - <teythoon> youpi: /proc/pid/stat seems to be used a lot: - http://codesearch.debian.net/search?q=%22%2Fproc%2F.*%2Fstat%22 - <teythoon> that does not mean that start/endcode is used, but still it - seems like a good thing to mimic Linux closely - <youpi> stat is used a lot for cpu usage for instance, yes - <youpi> start/endcode, I really wonder who is using it - <youpi> using it for kernel thread detection looks weird to me :) - <youpi> (questionable): I mean that even if you take the time to put - yourself on the side that people will probably agree on, the discussion - will happen - <youpi> it has to happen so people know they agree on it - <youpi> I've seen that a lot in various projects (not only CS-related) - <teythoon> ok, I think I got it - <teythoon> it's to document the reasons for (not) doing something? - <youpi> something like this, yes - <youpi> even if you look right, people will try to poke holes - <youpi> just to make sure :) - <teythoon> btw, I think it's rather unusual that our storeio experiments - would produce such different results - <teythoon> you're right about the block device, no idea why I got a - character file there - <teythoon> I used settrans -ca /tmp/hello.unzipped /hurd/storeio -T - gunzip:file /tmp/hello - <teythoon> also I tried stacking the translator on /tmp/hello directly, - from what I've gathered that should be possible, but I failed - <teythoon> ftr I use the exec server with all my patches, so the unzipping - code has been removed from it - <youpi> ah, I probably still have it - <youpi> it shouldn't matter here, though - <teythoon> I agree - <youpi> how would you stack it? - <youpi> I've never had a look at that - <youpi> I'm not sure attaching the translator to the node is done before or - after the translator has a change to open its target - <teythoon> right - <teythoon> but it could be done, if storeio used the reference to the - underlying node, no? - <youpi> yes - <youpi> btw, you had said at some point that you had issues with running - remap. Was the issue what you fixed with your patches? - * youpi realizes that he should have shown the remap.c source code during - his presentation - <teythoon> well, I tried to remap /servers/exec (iirc) and that failed - <teythoon> then again, I recently played with remap and all seemed fine - <teythoon> but I'm sure it has nothing to do with my patches - <youpi> ok - <teythoon> those I came up with investigating fakeroot-hurd - <teythoon> and I saw that this also aplies to remap.sh - <teythoon> *while - <youpi> yep, they're basically the same - <teythoon> btw, I somehow feel settrans is being abused for chroot and - friends, there is no translator setting involved - <youpi> chroot, the command? or the settrans option? - <youpi> I don't understand what you are pointing at - <teythoon> the settrans option being used by fakeroot, remap and (most - likely) our chroot - <youpi> our chroot is just a file_reparent call - <youpi> fakeroot and remap do start a translator - <teythoon> yes, but it is not being bound to a node, which is (how I - understand it) what settrans does - <teythoon> the point being that if settrans is being invoked with --chroot, - it does something completely different (see the big if (chroot) {...} - blocks) - <teythoon> to a point that it might be better of in a separate command - <youpi> Mmm, indeed, a lot of the options don't make sense for chroot - - -## IRC, freenode, #hurd, 2013-09-06 - - <braunr> teythoon: do you personally prefer /proc being able to implement - /proc/self on its own, or using the magic server to tell clients to - resolve those specific cases themselves ? - <pinotree> imho solving the "who's the sender of an rpc" could solve both - the SCM_CREDS implementation and the self case in procfs - -[[open_issues/SENDMSG_SCM_CREDS]], -[[hurd/translator/procfs/jkoenig/discussion]], *`/proc/self`*. - - <braunr> pinotree: yes - <braunr> but that would require servers impersonating users to some extent - <braunr> and this seems against the hurd philosophy - <pinotree> and there was also the fact that you could create a - fake/different port when sending an rpc - <braunr> to fake what ? - <pinotree> the sender identiy - <pinotree> *identity - <braunr> what ? - <braunr> you mean intermediate servers can do that - <teythoon> braunr: I don't know if I understand all the implications of - your question, but the magic server is the only hurd server that actually - implements fsys_forward (afaics), so why not use that? - <braunr> teythoon: my question was rather about the principle - <braunr> do people find it acceptable to entrust a server with their - authority or not - <braunr> on the hurd, it's clearly wrong - <braunr> but then it means you need special cases everywhere, usually - handled by glibc - <braunr> and that's something i find wrong too - <braunr> it restricts extensibility - <braunr> the user can always change its libc at runtime, but in practice, - it's harder to perform than simply doing it in the server - <teythoon> braunr: then I think I didn't get the question at all - <braunr> teythoon: it's kind of the same issue that you had with the mtab - translator - <braunr> about showing or not some entries the user normally doesn't have - access to - <braunr> this problem occurs when there is more than one server on the - execution path and the servers beyond the first one need credentials to - reply something meaningful - <braunr> the /proc/self case is a perfect one - <braunr> (conceptually, it's client -> procfs -> symlink) - <braunr> 1/ procfs tells the client it needs to handle this specially, - which is what the hurd does with magic - <braunr> 2/ procfs assumes the identity of the client and the symlink - translator can act as expected because of that - <braunr> teythoon: what way do you find better ? - <teythoon> braunr: by "procfs assumes the identity" you mean procfs - impersonating the user? - <braunr> yes - <teythoon> braunr: tbh I still do not see how this can be implemented at - all b/c the /proc/self symlink is not about identity (which can be - derived from the peropen struct initially created by fsys_getroot) but - the pid of the callee (which afaics is nowhere to be found) - <teythoon> s/callee/caller/ - <teythoon> the one doing the rpc - <braunr> impersonating the user isn't only about identity - <braunr> actually, it's impersonating the client - <teythoon> yes, client is the term >,< - <braunr> so basically, asking proc about the properties of the process - being impersonated - <teythoon> proc o_O - <braunr> it's not hard, it's just a big turn in the way the system would - function - <braunr> teythoon: ? - <teythoon> you lost me somewhere - <braunr> the client is the process - <braunr> not the user - <teythoon> in order to implement /proc/self properly, one has to get the - process id of the process doing the /proc/self lookup, right? - <braunr> yes - <braunr> actually, we would even slice it more and have the client be a - thread - <teythoon> so how do you get to that piece of information at all? - <braunr> the server inherits a special port designating the client, which - allows it to query proc about its properties, and assume it's identity in - servers such as auth - <braunr> its* - <teythoon> ah, but that kind of functionality isn't there at the moment, is - it? - <braunr> it's not, by design - <teythoon> right, hence my confusion - <braunr> instead, servers use the magic translator to send a "retry with - special handling" message to clients - <teythoon> right, so the procfs could bounce that back to the libc handler - that of course knows its pid - <braunr> yes - <teythoon> right, so now at last I got the whole question :) - <braunr> :) - <teythoon> ugh, I just found the FS_RETRY_MAGICAL handler in the libc :-/ - <braunr> ? - <braunr> why "ugh" ? - <teythoon> well, I'm inclined to think this is the bad kind of magic ;) - <braunr> do i need to look at the code to understand ? - <teythoon> ok, so I think option 1/ is easily implemented, option 2/ has - consequences that I cannot fully comprehend - <braunr> same for me - <teythoon> no, but you yourself said that you do not like that kind of - logic being implemented in the libc - <braunr> well - <braunr> easily - <braunr> i'm not so sure - <braunr> it's easy to code, but i assume checking for magic replies has its - cost - <teythoon> why not? the code is doing a big switch over the retryname - supplied by the server - <teythoon> we could stuff getpid() logic in there - <braunr> 14:50 < braunr> it's easy to code, but i assume checking for magic - replies has its cost - <teythoon> what kind of cost? computational cost? - <braunr> yes - <braunr> the big switch you mentioned - <braunr> run every time a client gets a reply - <braunr> (unless i'm mistaken) - <teythoon> a only for RETRY_MAGICAL replies - <braunr> but you need to test for it - <teythoon> switch (retryname[0]) - <teythoon> { - <teythoon> case '/': - <teythoon> ... - <teythoon> that should compile to a jump table, so the cost of adding - another case should be minimal, no? - <braunr> yes - <braunr> but - <braunr> it's even less than that - <braunr> the real cost is checking for RETRY_MAGICAL - <braunr> 14:55 < teythoon> a only for RETRY_MAGICAL replies - <braunr> so it's basically a if - <braunr> one if, right ? - <teythoon> no, it's switch'ing over doretry - <teythoon> you should pull up the code and see for yourself. it's in - hurd/lookup-retry.c - <braunr> ok - <braunr> well no, that's not what i'm looking for - <teythoon> it's not o_O - <braunr> i'm looking for what triggers the call to lookup_retry - <braunr> teythoon: hm ok, it's for lookups only, that's decent - <braunr> teythoon: 1/ has the least security implications - <teythoon> yes - <braunr> it could slightly be improved with e.g. a well defined interface - so a user could preload a library to extend it - <teythoon> extend the whole magic lookup thing? - <braunr> yes - <teythoon> but that is no immediate concern, you are trying to fix - /proc/self, right? - <braunr> no, i'm thinking about the big picture for x15/propel, keeping the - current design or doing something else - <teythoon> oh, okay - <braunr> solving /proc/self looks actually very easy - <teythoon> well, I'd say this depends a lot on your trust model then - <teythoon> do you consider servers trusted? - <teythoon> (btw, will there be mutual authentication of clients/servers in - propel?) - <braunr> there were very interesting discussions about that during the - l4hurd project - <braunr> iirc, shapiro insisted that using a server without trusting it - (and there were specific terminology about trusting/relying/etc..) is - nonsense - <braunr> teythoon: i haven't thought too much about that yet, for now it's - supposed to be similar to what the hurd does - <teythoon> hm, then again trust is not an on/off thing imho - <braunr> ? - <teythoon> trusting someone to impersonate yourself is a very high level of - trust - <teythoon> s/is/requires/ - <teythoon> the mobile code paper suggests that mutual authentication might - be a good thing, and I tend to agree - <braunr> i'll have to read that again - <braunr> teythoon: for now (well, when i have time to work on it again - .. :)) - <braunr> i'm focusing on the low level stuff, in a way that won't disturb - such high level features - <braunr> teythoon: have you found something related to a thread-specific - port in the proc server ? - <braunr> hurd/process.defs:297: /* You are not expected to understand - this. */ - <braunr> \o/ - <teythoon> braunr: no, why would I (the thread related question) - <teythoon> braunr: yes, that comment also cought my eye :/ - <braunr> teythoon: because you read a lot of the proc code lately - <braunr> so maybe your view of it is better detailed than mine - - -## IRC, freenode, #hurd, 2013-09-13 - - * youpi crosses fingers - <youpi> yay, still boots - <youpi> teythoon: I'm getting a few spurious entries in /proc/mounts - <youpi> none /servers/socket/26 /hurd/pfinet interface=/dev/eth0, etc. - <youpi> /dev/ttyp0 /dev/ttyp0 /hurd/term name,/dev/ptyp0,type,pty-master 0 - 0 - <youpi> /dev/sd1 /dev/cons ext2fs - writable,no-atime,no-inherit-dir-group,store-type=typed 0 0 - <youpi> fortunately mount drops most of them - <youpi> but not /dev/cons - <youpi> spurious entries in df are getting more and more common on linux - too anyway... - <youpi> ah, after a console restart, I don't have it any more - <youpi> I'm getting df: `/dev/cons': Operation not supported instead - - -## IRC, freenode, #hurd, 2013-09-16 - - <youpi> teythoon: e2fsck does not seem to be seeing that a given filesystem - is mounted - <youpi> /dev/sd0s1 on /boot type ext2 (rw,no-inherit-dir-group) - <youpi> and still # e2fsck -C 0 /dev/sd0s1 - <youpi> e2fsck 1.42.8 (20-Jun-2013) - <youpi> /dev/sd0s1 was not cleanly unmounted, check forced. - <youpi> (yes, both /etc/mtab and /run/mtab point to /proc/mounts) - <tschwinge> Yes, that is a "known" problem. - <youpi> tschwinge: no, it's supposed to be fixed by the mtab translator :) - <pinotree> youpi: glibc's paths.h points to /var/run/mtab (for us) - <tschwinge> youpi: Oh. But this is by means of mtab presence, and not by - proper locking? (Which is at least something, of course!) - <youpi> /var/run points to /run - <youpi> tschwinge: yes - <youpi> anyway, got to run - - -## IRC, freenode, #hurd, 2013-09-20 - - <braunr> teythoon: how come i see three mtab translators running ? - <braunr> 6 now oO - <braunr> looks like df -h spawns a few every time - <teythoon> yes, weird... - <braunr> accessing /proc/mounts does actually - <braunr> teythoon: more bug fixing for you :) - - -## IRC, freenode, #hurd, 2013-09-23 - - <teythoon> so it might be a problem with either libnetfs (which afaics has - never supported passive translator records before) or procfs, but tbh I - haven't investigated this yet |