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diff --git a/open_issues/anatomy_of_a_hurd_system.mdwn b/open_issues/anatomy_of_a_hurd_system.mdwn deleted file mode 100644 index 496d2a06..00000000 --- a/open_issues/anatomy_of_a_hurd_system.mdwn +++ /dev/null @@ -1,1430 +0,0 @@ -[[!meta copyright="Copyright © 2011, 2012, 2013, 2014 Free Software Foundation, -Inc."]] - -[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable -id="license" text="Permission is granted to copy, distribute and/or modify this -document under the terms of the GNU Free Documentation License, Version 1.2 or -any later version published by the Free Software Foundation; with no Invariant -Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license -is included in the section entitled [[GNU Free Documentation -License|/fdl]]."]]"""]] - -[[!taglink open_issue_documentation]] - -A bunch of this should also be covered in other (introductionary) material, -like Bushnell's Hurd paper. All this should be unfied and streamlined. - -[[!toc]] - - -# IRC, freenode, #hurd, 2011-03-08 - - <foocraft> I've a question on what are the "units" in the hurd project, if - you were to divide them into units if they aren't, and what are the - dependency relations between those units(roughly, nothing too pedantic - for now) - <antrik> there is GNU Mach (the microkernel); there are the server - libraries in the Hurd package; there are the actual servers in the same; - and there is the POSIX implementation layer in glibc - <antrik> relations are a bit tricky - <antrik> Mach is the base layer which implements IPC and memory management - <foocraft> hmm I'll probably allocate time for dependency graph generation, - in the worst case - <antrik> on top of this, the Hurd servers, using the server libraries, - implement various aspects of the system functionality - <antrik> client programs use libc calls to use the servers - <antrik> (servers also use libc to communicate with other servers and/or - Mach though) - <foocraft> so every server depends solely on mach, and no other server? - <foocraft> s/mach/mach and/or libc/ - <antrik> I think these things should be pretty clear one you are somewhat - familiar with the Hurd architecture... nothing really tricky there - <antrik> no - <antrik> servers often depend on other servers for certain functionality - - -# Bootstrap - -## [[hurd_init]] - -## IRC, freenode, #hurd, 2011-03-12 - - <dEhiN> when mach first starts up, does it have some basic i/o or fs - functionality built into it to start up the initial hurd translators? - <antrik> I/O is presently completely in Mach - <antrik> filesystems are in userspace - <antrik> the root filesystem and exec server are loaded by grub - <dEhiN> o I see - <dEhiN> so in order to start hurd, you would have to start mach and - simultaneously start the root filesystem and exec server? - <antrik> not exactly - <antrik> GRUB loads all three, and then starts Mach. Mach in turn starts - the servers according to the multiboot information passed from GRUB - <dEhiN> ok, so does GRUB load them into ram? - <dEhiN> I'm trying to figure out in my mind how hurd is initially started - up from a low-level pov - <antrik> yes, as I said, GRUB loads them - <dEhiN> ok, thanks antrik...I'm new to the idea of microkernels, but a - veteran of monolithic kernels - <dEhiN> although I just learned that windows nt is a hybrid kernel which I - never knew! - <rm> note there's a /hurd/ext2fs.static - <rm> I belive that's what is used initially... right? - <antrik> yes - <antrik> loading the shared libraries in addition to the actual server - would be unweildy - <antrik> so the root FS server is linked statically instead - <dEhiN> what does the root FS server do? - <antrik> well, it serves the root FS ;-) - <antrik> it also does some bootstrapping work during startup, to bring the - rest of the system up - - -## IRC, freenode, #hurd, 2014-01-03 - - <teythoon> hmpf, the hurd bootstrapping process is complicated and fragile, - maybe to the point that it is to be considered broken - <teythoon> aiui the hurd uses the filesystem for service lookup - <teythoon> older mach documentation suggests that there once existed a name - server instead for this purpose - <teythoon> the hurd approach is elegant and plan9ish - <teythoon> the problem is in the early bootstrapping - <teythoon> what if the root filesystem is r/o and there is no /servers or - /servers/exec ? - <teythoon> e. g. rm /servers/exec && reboot -> the rootfs dies early in the - hurd server bootstrap :/ - <braunr> well yes - <braunr> it's normal to have such constraints - <teythoon> uh no - <braunr> at the same time, the boot protocol must be improved, if only to - support userspace disk drivers - <teythoon> totally unacceptable - <braunr> why not ? - <teythoon> b/c my box just died and lost it's exec node - <braunr> so ? - <braunr> loosing the exec node is unacceptable - <youpi> well, linux dies too if you don't have /dev populated at least a - bit - <braunr> not being able to boot without the "exec" service is pretty normal - <braunr> the hurd turns the vfs into a service directory - <teythoon> the exec service is there, only the lookup mechanism is broken - <braunr> replacing the name server you mentioned earlier - <teythoon> yes - <braunr> if you don't have services, you don't have them - <braunr> i don't see the problem - <braunr> the problem is the lookup mechanism getting broken - <teythoon> ... that easily - <braunr> imagine a boot protocol based on a ramfs filled from a cpio - <teythoon> i do actually ;) - <braunr> there would be no reason at all the lookup mechanism would break - <teythoon> yes - <teythoon> but the current situation is not acceptable - <braunr> i agree - <teythoon> ^^ - <braunr> ext2fs is too unreliable for that - <braunr> but using the VFS as a directory is more than acceptable - <braunr> it's probably the main hurd feature - <teythoon> yes - <braunr> i see it rather as a circular dependency problem - <braunr> and if you have good ideas, i'm all ear for propel ... :> - <braunr> antrik already talked about some of them for the bootstrap - protocol - <braunr> we should sum them up somewhere if not done already - <teythoon> i've been pondering how to install a tmpfs translator as root - translator - <teythoon> braunr: we could create a special translator for /servers - <braunr> maybe - <teythoon> very much like fakeroot, it just proxies messages to a real - translator - <teythoon> but if operations like settrans fail, we handle them - transparently, like an overlay - <braunr> i consider /servers to be very close to /dev - <teythoon> yes - <braunr> so something like devfs seems obvious yes - <braunr> i don't even think there needs to be an overlay - <teythoon> y not ? - <braunr> why does /servers need real nodes ? - <teythoon> for persistence - <braunr> what for ? - <teythoon> e.g. crash server selection - <braunr> hm ok - <teythoon> network configuration - <braunr> i personally wouldn't make that persistent - <braunr> it can be configured in files and installed at boot time - <teythoon> me neither, but that's how it's currently done - <braunr> are you planning to actually work on that soon ? - <teythoon> if we need no persistence, we can just use tmpfs - <braunr> it wouldn't be a mere tmpfs - <teythoon> it could - <braunr> it's a tmpfs that performs automatic discovery and registration of - system services - <teythoon> with some special wrapper that preserves e.g. /servers/exec - <teythoon> oh - <braunr> so rather, devtmpfs - <teythoon> it is o_O :p - <braunr> ? - <braunr> what is what ? - <teythoon> well, it could be a tmpfs and some utility creating the nodes - <braunr> whether the node management is merged in or separate doesn't - matter that much i guess - <braunr> i'd personally imagine it merged, and tmpfs available as a - library, so that stuff like sysfs or netstatfs can easily be written - - -## IRC, freenode, #hurd, 2014-02-12 - - <teythoon> braunr: i fixed all fsys-related receiver lookups in libdiskfs - and surely enough the bootstrap hangs with no indication whats wrong - <braunr> teythoon: use mach_print :/ - <teythoon> braunr: the hurd bootstrap is both fragile and hard to tweak in - interesting ways :/ - <braunr> teythoon: i agree with that - <braunr> teythoon: maybe this will help : - http://wiki.hurdfr.org/upload/graphviz/dot9b65733655309d059dca236f940ef37a.png - <braunr> although i guess you probably already know that - <teythoon> heh, unicode for the win >,< - <braunr> :/ - - -# Source Code Documentation - -Provide a cross-linked sources documentation, including generated files, like -RPC stubs. - - * <http://www.gnu.org/software/global/> - - -# [[Hurd_101]] - - -# [[hurd/IO_path]] - -Need more stuff like that. - - -# IRC, freenode, #hurd, 2011-10-18 - - <frhodes> what happens @ boot. and which translators are started in what - order? - <antrik> short version: grub loads mach, ext2, and ld.so/exec; mach starts - ext2; ext2 starts exec; ext2 execs a few other servers; ext2 execs - init. from there on, it's just standard UNIX stuff - - -# IRC, OFTC, #debian-hurd, 2011-11-02 - - <sekon_> is __dir_lookup a RPC ?? - <sekon_> where can i find the source of __dir_lookup ?? - <sekon_> grepping most gives out rvalue assignments - <sekon_> -assignments - <sekon_> but in hurs/fs.h it is used as a function ?? - <pinotree> it should be the mig-generated function for that rpc - <sekon_> how do i know how its implemented ?? - <sekon_> is there any way to delve deeprer into mig-generated functions - <tschwinge> sekon_: The MIG-generated stuff will either be found in the - package's build directory (if it's building it for themselves), or in the - glibc build directory (libhurduser, libmachuser; which are all the - available user RPC stubs). - <tschwinge> sekon_: The implementation can be found in the various Hurd - servers/libraries. - <tschwinge> sekon_: For example, [hurd]/libdiskfs/dir-lookup.c. - <tschwinge> sekon_: What MIG does is provide a function call interface for - these ``functions'', and the Mach microkernel then dispatches the - invocation to the corresponding server, for example a /hurd/ext2fs file - system (via libdiskfs). - <tschwinge> sekon_: This may help a bit: - http://www.gnu.org/software/hurd/hurd/hurd_hacking_guide.html - - -# IRC, freenode, #hurd, 2012-01-08 - - <abique> can you tell me how is done in hurd: "ls | grep x" ? - <abique> in bash - <youpi> ls's standard output is a port to the pflocal server, and grep x's - standard input is a port to the pflocal server - <youpi> the connexion between both ports inside the pflocal server being - done by bash when it calls pipe() - <abique> youpi, so STDOUT_FILENO, STDIN_FILENO, STDERR_FILENO still exists - ? - <youpi> sure, hurd is compatible with posix - <abique> so bash 1) creates T1 (ls) and T2 (grep), then create a pipe at - the pflocal server, then connects both ends to T1 and T2, then start(T1), - start(T2) ? - <youpi> not exactly - <youpi> it's like on usual unix, bash creates the pipe before creating the - tasks - <youpi> then forks to create both of them, handling them each side of the - pipe - <abique> ok I see - <youpi> s/handling/handing/ - <abique> but when you do pipe() on linux, it creates a kernel object, this - time it's 2 port on the pflocal ? - <youpi> yes - <abique> how are spawned tasks ? - <abique> with fork() ? - <youpi> yes - <youpi> which is just task_create() and duplicating the ports into the new - task - <abique> ok - <abique> so it's easy to rewrite fork() with a good control of duplicated - fd - <abique> about threading, mutexes, conditions, etc.. are kernel objects or - just userland objects ? - <youpi> just ports - <youpi> (only threads are kernel objects) - <abique> so, about efficiency, are pipes and mutexes efficient ? - <youpi> depends what you call "efficient" - <youpi> it's less efficient than on linux, for sure - <youpi> but enough for a workable system - <abique> maybe hurd is the right place for a userland thread library like - pth or any fiber library - <abique> ? - <youpi> hurd already uses a userland thread library - <youpi> libcthreads - <abique> is it M:N ? - <youpi> libthreads, actually - <youpi> yes - -Actually, the Hurd has never used an M:N model. Both libthreads (cthreads) and libpthread use an 1:1 model. - - <abique> nice - <abique> is the task scheduler in the kernel ? - <youpi> the kernel thread scheduler, yes, of course - <youpi> there has to be one - <abique> are the posix open()/readdir()/etc... the direct vfs or wraps an - hurd layer libvfs ? - <youpi> they wrap RPCs to the filesystem servers - <antrik> the Bushnell paper is probably the closest we have to a high-level - documentation of these concepts... - <antrik> the Hurd does not have a central VFS component at all. name - lookups are performed directly on the individual FS servers - <antrik> that's probably the most fundamental design feature of the Hurd - <antrik> (all filesystem operations actually, not only lookups) - - -## IRC, freenode, #hurd, 2012-01-09 - - <braunr> youpi: are you sure cthreads are M:N ? i'm almost sure they're 1:1 - <braunr> and no modern OS is a right place for any thread userspace - library, as they wouldn't have support to run threads on different - processors (unless processors can be handled by userspace servers, but - still, it requires intimate cooperation between the threading library and - the kernel/userspace server in any case - <youpi> braunr: in libthreads, they are M:N - <youpi> you can run threads on different processors by using several kernel - threads, there's no problem in there, a lot of projects do this - <braunr> a pure userspace library can't use kernel threads - <braunr> at least pth was explacitely used on systems like bsd at a time - when they didn't have kernel threads exactly for that reason - <braunr> explicitely* - <braunr> and i'm actually quite surprised to learn that we have an M:N - threading model :/ - <youpi> why do you say "can't" ? - <braunr> but i wanted to reply to abique and he's not around - <youpi> of course you need kernel threads - <youpi> but all you need is to bind them - <braunr> well, what i call a userspace threading library is a library that - completely implement threads without the support of the kernel - <braunr> or only limited support, like signals - <youpi> errr, you can't implement anything with absolutely no support of - the kernel - <braunr> pth used only SIGALRM iirc - <youpi> asking for more kernel threads to use more processors doesn't seem - much - <braunr> it's not - <braunr> but i'm refering to what abique said - <braunr> 01:32 < abique> maybe hurd is the right place for a userland - thread library like pth or any fiber library - <youpi> well, it's indeed more, because the glibc lets external libraries - provide their mutex - <youpi> while on linux, glibc doesn't - <braunr> i believe he meant removing thread support from the kernel :p - <youpi> ah - <braunr> and replying "nice" to an M:N threading model is also suspicious, - since experience seems to show 1:1 models are better - <youpi> "better" ???? - <braunr> yes - <youpi> well - <youpi> I don't have any time to argue about that - <youpi> because that'd be extremely long - <braunr> simpler, so far less bugs, and also less headache concerning posix - conformance - <youpi> but there's no absolute "better" here - <youpi> but less performant - <youpi> less flexible - <braunr> that's why i mention experience :) - <youpi> I mean experience too - <braunr> why less performant ? - <youpi> because you pay kernel transition - <youpi> because you don't know anything about the application threads - <youpi> etc. - <braunr> really ? - <youpi> yes - <braunr> i fail to see where the overhead is - <youpi> I'm not saying m:n is generally better than 1:1 either - <youpi> thread switch, thread creation, etc. - <braunr> creation is slower, i agree, but i'm not sure it's used frequently - enough to really matter - <youpi> it is sometimes used frequently enough - <youpi> and in those cases it would be a headache to avoid it - <braunr> ok - <braunr> i thought thread pools were used in those cases - <youpi> synchronized with kernel mutexes ? - <youpi> that's still slow - <braunr> it reduces to the thread switch overhead - <braunr> which, i agree is slightly slower - <braunr> ok, i's a bit less performant :) - <braunr> well don't futexes exist just for that too ? - <youpi> yes and no - <youpi> in that case they don't help - <youpi> because they do sleep - <youpi> they help only when the threads are living - <braunr> ok - <youpi> now as I said I don't have to talk much more, I have to leave :) - - -# IRC, freenode, #hurd, 2012-12-06 - - <braunr> spiderweb: have you read - http://www.gnu.org/software/hurd/hurd-paper.html ? - <spiderweb> I'll have a look. - <braunr> and also the beginning of - http://ftp.sceen.net/mach/mach_a_new_kernel_foundation_for_unix_development.pdf - <braunr> these two should provide a good look at the big picture the hurd - attemtps to achieve - <Tekk_> I can't help but wonder though, what advantages were really - achieved with early mach? - <Tekk_> weren't they just running a monolithic unix server like osx does? - <braunr> most mach-based systems were - <braunr> but thanks to that, they could provide advanced features over - other well established unix systems - <braunr> while also being compatible - <Tekk_> so basically it was just an ease of development thing - <braunr> well that's what mach aimed at being - <braunr> same for the hurd - <braunr> making things easy - <Tekk_> but as a side effect hurd actually delivers on the advantages of - microkernels aside from that, but the older systems wouldn't, correct? - <braunr> that's how there could be network file systems in very short time - and very scarce resources (i.e. developers working on it), while on other - systems it required a lot more to accomplish that - <braunr> no, it's not a side effect of the microkernel - <braunr> the hurd retains and extends the concept of flexibility introduced - by mach - <Tekk_> the improved stability, etc. isn't a side effect of being able to - restart generally thought of as system-critical processes? - <braunr> no - <braunr> you can't restart system critical processes on the hurd either - <braunr> that's one feature of minix, and they worked hard on it - <Tekk_> ah, okay. so that's currently just the domain of minix - <Tekk_> okay - <Tekk_> spiderweb: well, there's 1 advantage of minix for you :P - <braunr> the main idea of mach is to make it easy to extend unix - <braunr> without having hundreds of system calls - -[[/system_call]]. - - <braunr> the hurd keeps that and extends it by making many operations - unprivileged - <braunr> you don't need special code for kernel modules any more - <braunr> it's easy - <braunr> you don't need special code to handle suid bits and other ugly - similar hacks, - <braunr> it's easy - <braunr> you don't need fuse - <braunr> easy - <braunr> etc.. - - -# Service Directory - -## IRC, freenode, #hurd, 2012-12-06 - - <spiderweb> what is the #1 feature that distinguished hurd from other - operating systems. the concept of translators. (will read more when I get - more time). - <braunr> yes, translators - <braunr> using the VFS as a service directory - <braunr> and the VFS permissions to control access to those services - - -## IRC, freenode, #hurd, 2013-05-23 - - <gnu_srs> Hi, is there any efficient way to control which backed - translators are called via RPC with a user space program? - <gnu_srs> Take for example io_stat: S_io_stat is defined in boot/boot.c, - pfinet/io-ops.c and pflocal/io.c - <gnu_srs> And the we have libdiskfs/io-stat.c:diskfs_S_io_stat, - libnetfs/io-stat.c:netfs_S_io_stat, libtreefs/s-io.c:treefs_S_io_stat, - libtrivfs/io-stat.c:trivfs_S_io_stat - <gnu_srs> How are they related? - <braunr> gnu_srs: it depends on the server (translator) managing the files - (nodes) you're accessing - <braunr> so use fsysopts to know the server, and see what this server uses - <gnu_srs> fsysopts /hurd/pfinet and fsysopts /hurd/pflocal gives the same - answer: ext2fs --writable --no-inherit-dir-group --store-type=typed - device:hd0s1 - <braunr> of course - <braunr> the binaries are regular files - <braunr> see /servers/socket/1 and /servers/socket/2 instead - <braunr> which are the nodes representing the *service* - <braunr> again, the hurd uses the file system as a service directory - <braunr> this usage of the file system is at the core of the hurd design - <braunr> files are not mere files, they're service names - <braunr> it happens that, for most files, the service behind them is the - same as for regular files - <braunr> gnu_srs: this *must* be obvious for you to do any tricky work on - the hurd - - <gnu_srs> Anyway, if I create a test program calling io_stat I assume - S_io_stat in pflocal is called. - <gnu_srs> How to make the program call S_io_stat in pfinet instead? - <braunr> create a socket managed by pfinet - <braunr> i.e. an inet or inet6 socket - <braunr> you can't assume io_stat is serviced by pflocal - <braunr> only stats on unix sockets of pipes will be - <braunr> or* - <gnu_srs> thanks, what about the *_S_io_stat functions? - <braunr> what about them ? - <gnu_srs> How they fit into the picture, e.g. diskfs_io_stat? - <gnu_srs> *diskfs_S_io_stat - <braunr> gnu_srs: if you open a file managed by a server using libdiskfs, - e.g. ext2fs, that one will be called - <gnu_srs> Using the same user space call: io_stat, right? - <braunr> it's all userspace - <braunr> say rather, client-side - <braunr> the client calls the posix stat() function, which is implemented - by glibc, which converts it into a call to io_stat, and sends it to the - server managing the open file - <braunr> the io_stat can change depending on the server - <braunr> the remote io_stat implementation, i mean - <braunr> identify the server, and you will identify the actual - implementation - - -## IRC, freenode, #hurd, 2013-06-30 - - <hacklu> hi, what is the replacer of netname_check_in? - - <hacklu> I want to ask another question. in my opinion, the rpc is the - mach's way, and the translator is the hurd's way. so somebody want to - lookup a service, it should not need to ask the mach kernel know about - this query. the hurd will take the control. - <hacklu> am I right? - <braunr> no - <braunr> that's nonsense - <braunr> service lookups has never been in mach - <braunr> first mach based systems used a service directory, whereas the - hurd uses the file system for that - <braunr> you still need mach to communicate with either of those - <hacklu> how to understand the term of service directory here? - <braunr> a server everyone knows - <braunr> which gives references to other servers - <braunr> usually, depending on the name - <braunr> e.g. name_lookup("net") -> port right to network server - <hacklu> is that people use netname_check_in to register service in the - past? now used libtrivfs? - <braunr> i don't know about netname_check_in - <braunr> old mach (not gnumach) documentation might mention this service - directory - <braunr> libtrivfs doesn't have much to do with that - <braunr> on the hurd, the equivalent is the file system - <hacklu> maybe that is outdate, I just found that exist old doc, and old - code which can't be build. - <braunr> every process knows / - <braunr> the file system is the service directory - <braunr> nodes refer to services - <hacklu> so the file system is the nameserver, any new service should - register in it before other can use - <braunr> and the file system is distributed, so looking up a service may - require several queries - <braunr> setting a translator is exactly that, registering a program to - service requests on a node - <braunr> the file system isn't one server though - <braunr> programs all know about /, but then, lookups are recursive - <braunr> e.g. if you have / and /home, and are looking for - /home/hacklu/.profile, you ask / which tells you about /home, and /home - will give you a right to /home/hacklu/.profile - <hacklu> even in the past, the mach don't provide name register service, - there must be an other server to provide this service? - <braunr> yes - <braunr> what's nonsense in your sentence is comparing RPCs and translators - <braunr> translators are merely servers attached to the file system, using - RPCs to communicate with the rest of the system - <hacklu> I know yet, the two just one thing. - <braunr> no - <braunr> two things :p - <braunr> completely different and unrelated except for one using the other - <hacklu> ah, just one used aonther one. - <hacklu> is exist anyway to anounce service except settrans with file node? - <braunr> more or less - <braunr> tasks can have special ports - <braunr> that's how one task knows about / for example - <braunr> at task creation, a right to / is inserted in the new task - <hacklu> I think this is also a file node way. - <braunr> no - <braunr> if i'm right, auth is referenced the same way - <braunr> and there is no node for auth - <hacklu> how the user get the port of auth with node? - <braunr> it's given when a task is created - <hacklu> pre-set in the creation of one task? - <braunr> i'm unconfortable with "pre-set" - <braunr> inserted at creation time - <braunr> auth is started very early - <braunr> then tasks are given a reference to it - - -# IRC, freenode, #hurd, 2012-12-10 - - <spiderweb> I want to work on hurd, but I think I'm going to start with - minix, I own the minix book 3rd ed. it seems like a good intro to - operating systems in general. like I don't even know what a semaphore is - yet. - <braunr> well, enjoy learning :) - <spiderweb> once I finish that book, what reading do you guys recommend? - <spiderweb> other than the wiki - <braunr> i wouldn't recommend starting with a book that focuses on one - operating system anyway - <braunr> you tend to think in terms of what is done in that specific - implementation and compare everything else to that - <braunr> tannenbaum is not only the main author or minix, but also the one - of the book http://en.wikipedia.org/wiki/Modern_Operating_Systems - <braunr> - http://en.wikipedia.org/wiki/List_of_important_publications_in_computer_science#Operating_systems - should be a pretty good list :) - - -# IRC, freenode, #hurd, 2013-03-12 - - <mjjc> i have a question regarding ipc in hurd. if a task is created, does - it contain any default port rights in its space? i am trying to deduce - how one calls dir_lookup() on the root translator in glibc's open(). - <kilobug> mjjc: yes, there are some default port rights, but I don't - remember the details :/ - <mjjc> kilobug: do you know where i should search for details? - <kilobug> mjjc: hum either in the Hurd's hacking guide - https://www.gnu.org/software/hurd/hacking-guide/ or directly in the - source code of exec server/libc I would say, or just ask again the - question here later on to see if someone else has more information - <mjjc> ok, thanks - <pinotree> there's also rpctrace to, as the name says, trace all the rpc's - executed - <braunr> some ports are introduced in new tasks, yes - <braunr> see - http://www.gnu.org/software/hurd/hacking-guide/hhg.html#The-main-function - <braunr> and - <braunr> - http://www.gnu.org/software/hurd/gnumach-doc/Task-Special-Ports.html#Task-Special-Ports - <mjjc> yes, the second link was just what i was looking for, thanks - <braunr> the second is very general - <braunr> also, the first applies to translators only - <braunr> if you're looking for how to do it for a non-translator - application, the answer is probably somewhere in glibc - <braunr> _hurd_startup i'd guess - - -# IRC, freenode, #hurd, 2013-06-15 - - <damo22> ive been reading a little about exokernels or unikernels, and i - was wondering if it might be relevant to the GNU/hurd design. I'm not - too familiar with hurd terminology so forgive me. what if every - privileged service was compiled as its own mini "kernel" that handled (a) - any hardware related to that service (b) any device nodes exposed by that - service etc... - <braunr> yes but not really that way - <damo22> under the current hurd model of the operating system, how would - you talk to hardware that required specific timings like sound hardware? - <braunr> through mapped memory - <damo22> is there such a thing as an interrupt request in hurd? - <braunr> obviously - <damo22> ok - <damo22> is there any documentation i can read that involves a driver that - uses irqs for hurd? - <braunr> you can read the netdde code - <braunr> dde being another project, there may be documentation about it - <braunr> somewhere else - <braunr> i don't know where - <damo22> thanks - <damo22> i read a little about dde, apparently it reuses existing code from - linux or bsd by reimplementing parts of the old kernel like an api or - something - <braunr> yes - <damo22> it must translate these system calls into ipc or something - <damo22> then mach handles it? - <braunr> exactly - -[[/system_call]]. - - <braunr> that's why i say it's not the exokernel way of doing things - <damo22> ok - <damo22> so does every low level hardware access go through mach?' - <braunr> yes - <braunr> well no - <braunr> interrupts do - <braunr> ports (on x86) - <braunr> everything else should be doable through mapped memory - <damo22> seems surprising that the code for it is so small - <braunr> 1/ why surprising ? and 2/ "so small" ? - <damo22> its like the core of the OS, and yet its tiny compared to say the - linux kernel - <braunr> it's a microkenrel - <braunr> well, rather an hybrid - <braunr> the size of the equivalent code in linux is about the same - <damo22> ok - <damo22> with the model that privileged instructions get moved to - userspace, how does one draw the line between what is OS and what is user - code - <braunr> privileged instructions remain in the kernel - <braunr> that's one of the few responsibilities of the kernel - <damo22> i see, so it is an illusion that the user has privilege in a sense - <braunr> hum no - <braunr> or, define "illusion" - <damo22> well the user can suddenly do things never imaginable in linux - <damo22> that would have required sudo - <braunr> yes - <braunr> well, they're not unimaginable on linux - <braunr> it's just not how it's meant to work - <damo22> :) - <braunr> and why things like fuse are so slow - <braunr> i still don't get "i see, so it is an illusion that the user has - privilege in a sense" - <damo22> because the user doesnt actually have the elevated privilege its - the server thing (translator)? - <braunr> it does - <braunr> not at the hardware level, but at the system level - <braunr> not being able to do it directly doesn't mean you can't do it - <damo22> right - <braunr> it means you need indirections - <braunr> that's what the kernel provides - <damo22> so the user cant do stuff like outb 0x13, 0x1 - <braunr> he can - <braunr> he also can on linux - <damo22> oh - <braunr> that's an x86 specifity though - <damo22> but the user would need hardware privilege to do that - <braunr> no - <damo22> or some kind of privilege - <braunr> there is a permission bitmap in the TSS that allows userspace to - directly access some ports - <braunr> but that's really x86 specific, again - <damo22> i was using it as an example - <damo22> i mean you wouldnt want userspace to directly access everything - <braunr> yes - <braunr> the only problem with that is dma reall - <braunr> y - <braunr> because dma usually access physical memory directly - <damo22> are you saying its good to let userspace access everything minus - dma? - <braunr> otherwise you can just centralize permissions in one place (the - kernel or an I/O server for example) - <braunr> no - <braunr> you don't let userspace access everything - <damo22> ah - <damo22> yes - <braunr> userspace asks for permission to access one specific part (a - memory range through mapping) - <braunr> and can't access the rest (except through dma) - <damo22> except through dma?? doesnt that pose a large security threat? - <braunr> no - <braunr> you don't give away dma access to anyone - <braunr> only drivers - <damo22> ahh - <braunr> and drivers are normally privileged applications anyway - <damo22> so a driver runs in userspace? - <braunr> so the only effect is that bugs can affect other address spaces - indirectly - <braunr> netdde does - <damo22> interesting - <braunr> and they all should but that's not the case for historical reasons - <damo22> i want to port ALSA to hurd userspace :D - <braunr> that's not so simple unfortunately - <braunr> one of the reasons it's hard is that pci access needs arbitration - <braunr> and we don't have that yet - <damo22> i imagine that would be difficult - <braunr> yes - <braunr> also we're not sure we want alsa - <braunr> alsa drivers, maybe, but probably not the interface itself - <damo22> its tangled spaghetti - <damo22> but the guy who wrote JACK for audio hates OSS, and believes it is - rubbish due to the fact it tries to read and write to a pcm device node - like a filesystem with no care for timing - <braunr> i don't know audio well enough to tell you anything about that - <braunr> was that about oss3 or oss4 ? - <braunr> also, the hurd isn't a real time system - <braunr> so we don't really care about timings - <braunr> but with "good enough" latencies, it shouldn't be a problem - <damo22> but if the audio doesnt reach the sound card in time, you will get - a crackle or a pop or a pause in the signal - <braunr> yep - <braunr> it happens on linux too when the system gets some load - <damo22> some users find this unnacceptable - <braunr> some users want real time systems - <braunr> using soft real time is usually plenty enough to "solve" this kind - of problems - <damo22> will hurd ever be a real time system? - <braunr> no idea - <youpi> if somebody works on it why not - <youpi> it's the same as linux - <braunr> it should certainly be simpler than on linux though - <damo22> hmm - <braunr> microkernels are well suited for real time because of the well - defined interfaces they provide and the small amount of code running in - kernel - <damo22> that sounds promising - <braunr> you usually need to add priority inheritance and take care of just - a few corner cases and that's all - <braunr> but as youpi said, it still requires work - <braunr> and nobody's working on it - <braunr> you may want to check l4 fiasco.oc though - - -# System Personality - -## IRC, freenode, #hurd, 2013-07-29 - - <teythoon> over the past few days I gained a new understanding of the Hurd - <braunr> teythoon: really ? :) - <tschwinge> teythoon: That it's a complex and distributed system? ;-) - <tschwinge> And at the same time a really simple one? - <tschwinge> ;-D - <teythoon> it's just a bunch of mach programs and some do communicate and - behave in a way a posix system would, but that is more a convention than - anything else - <teythoon> tschwinge: yes, kind of simple and complex :) - <braunr> the right terminology is "system personality" - <braunr> 11:03 < teythoon> over the past few days I gained a new - understanding of the Hurd - <braunr> teythoon: still no answer on that :) - <teythoon> braunr: ah, I spent lot's of time with the core servers and - early bootstrapping and now I gained the feeling that I've seen the Hurd - for what it really is for the first time - - -# RPC Interfaces - -## IRC, freenode, #hurd, 2013-09-03 - - <rekado> I'm a little confused by the hurd and incubator git repos. - <rekado> DDE is only found in the dde branch in incubator, but not in the - hurd repo. - <rekado> Does this mean that DDE is not ready for master yet? - <braunr> yes - <rekado> If DDE is not yet used in the hurd (except in the dde branch in - the incubator repo), does pfinet use some custom glue code to use the - Linux drivers? - <braunr> this has nothing to do with pfinet - <braunr> pfinet is the networking stack, netdde are the networking drivers - <braunr> the interface between them doesn't change, whether drivers are in - kernel or not - <rekado> I see - - -# IRC, freenode, #hurd, 2013-09-20 - - <giuscri> HI there, I have no previous knowledge about OS's. I'm trying to - undestand the structure of the Hurd and the comparison between, say, - Linux way of managing stuff ... - <giuscri> for instance, I read: "Unlike other popular kernel software, the - Hurd has an object-oriented structure that allows it to evolve without - compromising its design." - <giuscri> that means that while for adding feature to the Linux-kernel you - have to add some stuff `inside` a procedure, whilst in the Hurd kernel - you can just, in principle at least, add an object and making the kernel - using it?... - <giuscri> Am I making stuff too simple? - <giuscri> Thanks - <braunr> not exactly - <braunr> unix historically has a "file-oriented" structure - <braunr> the hurd allows servers to implement whatever type they want, - through the ability to create custom interfaces - <braunr> custom interfaces means custom calls, custom semantics, custom - methods on objects - <braunr> you're not restricted to the set of file interfaces (open, seek, - read, write, select, close, etc..) that unix normally provides - <giuscri> braunr: uhm ...some example? - <braunr> see processes for example - <braunr> see - http://darnassus.sceen.net/gitweb/savannah_mirror/hurd.git/tree/HEAD:/hurd - <braunr> this is the collection of interfaces the hurd provides - <braunr> most of them map to unix calls, because gnu aims at posix - compatibility too - <braunr> some are internal, like processes - <braunr> or authentication - <braunr> but most importantly, you're not restricted to that, you can add - your own interfaces - <braunr> on a unix, you'd need new system calls - <braunr> or worse, extending through the catch-all ioctl call - <giuscri> braunr: mhn ...sorry, not getting that. - <braunr> what part ? - <kilobug> ioctl has become such a mess :s - <giuscri> braunr: when you say that Unix is `file-oriented` you're - referring to the fact that sending/receiving data to/from the kernel is - designed like sending/receiving data to/from a file ...? - <braunr> not merely sending/receiving - <braunr> note how formatted your way of thinking is - <braunr> you directly think in terms of sending/receiving (i.e. read and - write) - <giuscri> braunr: (yes) - <braunr> that's why unix is file oriented, access to objects is done that - way - <braunr> on the hurd, the file interface is one interface - <braunr> there is nothing preventing you from implementing services with a - different interface - <braunr> as a real world example, people interested in low latency - profesionnal audio usually dislike send/recv - <braunr> see - http://lac.linuxaudio.org/2003/zkm/slides/paul_davis-jack/unix.html for - example - <kilobug> braunr: how big and messy ioctl has become is a good proof that - the Unix way, while powerful, does have its limits - <braunr> giuscri: keep in mind the main goal of the hurd is extensibility - without special privileges - <giuscri> braunr: privileges? - <braunr> root - <giuscri> braunr: what's wrong with privileges? - <braunr> they allow malicious/buggy stuff to happne - <braunr> and have dramatic effects - <giuscri> braunr: you're obviously *not* referring to the fact that once - one have the root privileges could change some critical-data - <giuscri> ? - <braunr> i'm referring to why privilege separation exists in the first - place - <braunr> if you have unprivileged users, that's because you don't want them - to mess things up - <braunr> on unix, extending the system requires privileges, giving those - who do it the ability to destroy everything - <giuscri> braunr: yes, I think the same - <braunr> the hurd is designed to allow unprivileged users to extend their - part of the system, and to some extent share that with other users - <braunr> although work still remains to completely achieve that - <giuscri> braunr: mhn ...that's the `server`-layer between the - single-application and kernel ? - <braunr> the multi-server based approach not only allows that, but - mitigates damage even when privileged servers misbehave - <braunr> one aspect of it yes - <braunr> but as i was just saying, even root servers can't mess things too - much - <braunr> for example, our old (sometimes buggy) networking stack can be - restarted when it behaves wrong - <braunr> the only side effect being some applications (ssh and exim come to - mind) which need to be restarted too because they don't expect the - network stack to be restarted - <giuscri> braunr: ...instead? - <braunr> ? - <kilobug> giuscri: on Linux, if the network stack crash/freezes, you don't - have any other option than rebooting the system - usually with a nice - "kernel pani" - <kilobug> giuscri: and you may even get filesystem corruption "for free" in - the bundle - <braunr> and hoping it didn't corrupt something important like file system - caches before being flushed - <giuscri> kilobug, braunr : mhn, ook - - -# IRC, freenode, #hurd, 2013-10-13 - - <ahungry> ahh, ^c isn't working to cancel a ping - is there alternative? - <braunr> ahungry: ctrl-c does work, you just missed something somewhere and - are running a shell directly on a console, without a terminal to handle - signals - - -# IRC, freenode, #hurd, 2013-11-04 - - <braunr> nalaginrut: you can't use the hurd for real embedded stuff without - a lot of work on it - <braunr> but the hurd design applies very well to embedded environments - <braunr> the fact that we're able to dynamically link practically all hurd - servers against the c library can visibly reduce the system code size - <braunr> it also reduces the TCB - <nalaginrut> what about the memory occupation? - <braunr> code size is about memory occupation - <teythoon> also, the system is composable like lego, don't need tcp - don't - include pfinet then - <braunr> the memory overheald of a capability based system like the hurd - are, well, capabilities - <braunr> teythoon: that's not an argument compared to modular kernels like - linux - <teythoon> yes it is - <braunr> why ? - <braunr> if you don't need tcp in linux, you just don't load it - <braunr> same thing - <teythoon> ok, right - <braunr> on the other hand, a traditional unix kernel can never be linked - against the c library - <braunr> much less dynamically - <teythoon> right - <nalaginrut> I think the point is that it's easy to cut, since it has - better modularity than monolithic, and could be done in userland relative - easier - <braunr> modularity isn't better - <braunr> that's a big misconception - <teythoon> also, restarting components is easier on a distributed system - <braunr> on the hurd, this is a side effect - <braunr> and it doesn't apply well - <nalaginrut> braunr: oops, misconception - <braunr> many core servers such as proc, auth, exec, the root fs server - can't be restarted at all - <teythoon> not yet - <braunr> and servers like pfinet can be restarted, but at the cost of posix - servers not expecting that - <braunr> looping on errors such as EBADF because the target socket doesn't - exist any more - <teythoon> I've been working on a restartable exec server during some of my - gsoc weekends - <braunr> ah right - <braunr> linux has kexec - <braunr> and can be patched at run time - <nalaginrut> sounds like Hurd needs something similar to generalizable - continuation - <braunr> so again, it's not a real advantage - <braunr> no - <nalaginrut> sorry serilizable - <braunr> that would persistence - <braunr> personally, i don't want it at all - <teythoon> yes it is a real advantage, b/c the means of communication - (ports) is common to every IPC method on Hurd, and ports are first class - objects - <teythoon> so preserving the state is much easier on Hurd - <braunr> if a monolithic kernel can do it too, it's not a real advantage - <teythoon> yes, but it is more work - <braunr> that is one true advantage of the hurd - <braunr> but don't reuse it each time - <nalaginrut> oh, that's nice for the ports - <teythoon> why not? - <braunr> what we're talking about here is resilience - <braunr> the fact that it's easier to implement doesn't mean the hurd is - better because it has resilience - <braunr> it simply means the hurd is better because it's easier to - implement things on it - <braunr> same for development in general - <braunr> debugging - <braunr> virtualization - <braunr> etc.. - <nalaginrut> yes, but why we stick to compare it to monolithic - <braunr> but it's still *one* property - <teythoon> well, minix advertises this feature a lot, even if minix can - only restart very simple things like printer servers - <braunr> minix sucks - <braunr> let them advertise what they can - <teythoon> ^^ - <nalaginrut> it has cool features, that's enough, no need to find a feature - that monolithic can never done - <braunr> no it's not enough - <braunr> minix isn't a general purpose system - <braunr> let's just not compare it to general purpose systems - - -# IRC, freenode, #hurd, 2013-11-08 - - <teythoon> and, provided you have suitable language bindings, you can - replace almost any hurd server with your own implementation in any - language - <crocket> teythoon: language bindings? - <crocket> Do you mean language bindings against C libraries? - <teythoon> either that or for the low level mach primitives - <crocket> For your information, IPC is independent of languages. - <teythoon> sure, that's the beauty - <crocket> Why is hurd best for replacing parts written in C with other - languages? - <teythoon> because Hurd consists of many servers, each server managing one - kind of resource - <teythoon> so you have /hurd/proc managing posix processes - <teythoon> you could reimplement /hurd/proc in say python or go, and - replace just that component of the Hurd system - <teythoon> you cannot do this with any other (general purpose) operating - system that I know of - <teythoon> you could incrementally replace the Hurd with your own - Hurd-compatible set of servers written in X - <teythoon> use a language that you can verify, i.e. prove that a certain - specification is fulfilled, and you end up with an awesome stable and - secure operating system - <crocket> Any microkernel OS fits the description. - <crocket> teythoon, Does hurd have formal protocols for IPC communications? - <teythoon> sure, name some other general purpose and somewhat - posix-compatible microkernel based operating system please - <teythoon> what do you mean by formal protocols ? - <crocket> IPC communications need to be defined in documents. - <teythoon> the "wire" format is specified of course, the semantic not so - much - <crocket> network protocols exist. - <crocket> HTTP is a transport protocol. - <crocket> Without formal protocols, IPC communications suffer from - debugging difficulties. - <crocket> Formal protocols make it possible to develop and test each module - independently. - <teythoon> as I said, the wire format is specified, the semantics only in - written form in the source - <teythoon> this is an example of the ipc specification for the proc server - http://git.savannah.gnu.org/cgit/hurd/hurd.git/tree/hurd/process.defs - <crocket> teythoon, how file server interacts with file clients should be - defined as a formal protocol, too. - <teythoon> do you consider the ipc description a kind of formal protocol ? - <crocket> - http://git.savannah.gnu.org/cgit/hurd/hurd.git/tree/hurd/process.defs can - be considered as a formal protocol. - <crocket> However, the file server protocol should be defined on top of IPC - protocol. - <teythoon> the file server protocol is in fs.defs - <teythoon> every protocol spoken is defined in that ipc description - language - <teythoon> it is used to derive code from - <braunr> crocket: not any system can be used to implement system services - in any language - <braunr> in theory, they do, but in theory only - <braunr> the main reason they don't is because most aren't posix compliant - from the ground up - <braunr> posix compliance is achieved through virtualization - <braunr> which isolates services too much for them to get useful, - notwithstanding the impacts on performance, memory, etc.. - <crocket> braunr, Do you mean it's difficult to achieve POSIX compliance - with haskell? - <braunr> crocket: i mean most l4 based systems aren't posix - <braunr> genode isn't posix - <braunr> helenos is by design not posix - <braunr> the hurd is the only multi server system providing such a good - level of posix conformance - <braunr> and with tls on the way, we'll support even more non-posix - applications that are nonetheless very common on unices because of - historical interfaces still present, such as mcontext - <braunr> and modern ones - <braunr> e.g. ruby is now working, go should be there after tls - * teythoon drools over the perspective of having go on the Hurd... - <crocket> braunr, Is posix relevant now? - <braunr> it's hugely relevant - <braunr> conforming to posix and some native unix interfaces is the only - way to reuse a lot of existing production applications - <braunr> and for the matter at hand (system services not written in c), it - means almost readily getting runtimes for other languages than c - <braunr> something other microkernel based system will not have - <braunr> imagine this - <braunr> one day, one of us could create a company for a hurd-like system, - presenting this idea as the killer feature - <braunr> by supporting posix, customers could port their software with very - little effort - <braunr> *very little effort* is what makes software attractive - <crocket> - http://stackoverflow.com/questions/1806585/why-is-linux-called-a-monolithic-kernel/1806597#1806597 - says "The disadvantage to a microkernel is that asynchronous IPC - messaging can become very difficult to debug, especially if fibrils are - implemented." - <crocket> " GNU Hurd suffers from these debugging problems (reference)." - <braunr> stackoverflow is usually a nice place - <braunr> but concerning microkernel stuff, you'll read a lot of crap - anywhere - <braunr> whether it's sync or async, tracking references is a hard task - <braunr> it's a bit more difficult in distributed systems, but not that - much if the proper debugging features are provided - <braunr> we actually don't suffer from that too much - <braunr> many of us have been able to debug reference leaks in the past, - without too much trouble - <braunr> we lack some tools that would give us a better view of the system - state - <crocket> braunr, But is it more difficult with microkernel? - <braunr> crocket: it's more difficult with distributed systems - <crocket> How much more difficult? - <braunr> i don't know - <crocket> distributed systems - <braunr> not much - <crocket> braunr, How do you define distributed systems? - <braunr> crocket: not monolithic - <crocket> braunr, Hurd is distributed, then. - <braunr> multiserver if you prefer - <braunr> yes it is - <crocket> braunr, So it is more difficult with hurd. - <crocket> How much more difficult? How do you debug? - <braunr> just keep in mind that a monolithic system can run on a - microkenrel - <braunr> we use tools that show us references - <crocket> braunr, like? - <braunr> like portinfo - <crocket> braunr, Does hurd use unix-socket to implement IPC? - <braunr> no - <braunr> unix-socket use mach ipc - <crocket> I'm confused - <braunr> ipc is provided by the microkernel, gnumach (a variant of mach) - <braunr> unix sockets are provided by one of the hurd servers (pflocal) - <braunr> servers and clients communicate through mach ipc - <crocket> braunr, Do you think it's feasible to build servers in haskell? - <braunr> why not ? - <crocket> ok - <teythoon> I've been thinking about that - <teythoon> in go, with cgo, you can call go functions from c code - <teythoon> so it should be possible to create bindings for say libtrivfs - <crocket> I'd like to write an OS in clojure or haskell. - <braunr> crocket: what for ? - <crocket> braunr, I want to see a better system programming language than - C. - <braunr> i don't see how clojure or haskell would be "better system - programming languages" than c - <braunr> and even assuming that, what for ? - <crocket> braunr, It's better for programmers. - <crocket> haskell - <crocket> haskell is expressive. - <braunr> personally i disagree - <braunr> it's better for some things - <braunr> not for system programming - <gnufreex> For system programming, Google Go is trying to replace C. But I - doubt it will. - <braunr> we may not be referring to the same thing here when we say "system - programming" - <crocket> braunr, What do you think is a better one? - <braunr> crocket: i don't think there is a better one currently - <crocket> braunr, Even Rust and D? - <braunr> i don't know them well enough - <braunr> certainly not D if it's what i think it is - <crocket> C is too slow. - <crocket> C is too slow to develop. - <braunr> depends - <braunr> again, i disagree - <braunr> rust looks good but i don't know it well to comment - <crocket> C is a tank, and clojure is an airplane. - <crocket> A tank is reliable but slow. - <crocket> Clojure is fast but lacks some accuracy. - <braunr> c is as reliable as the developer is skilled with it - <braunr> it's clearly not a tank - <braunr> there are many traps - <gnufreex> crocket: are you suggesting to rewrite Hurd in Clojure? - <crocket> no - <crocket> Why rewrite hud? - <crocket> hurd - <crocket> I'd rather start from scratch. - <braunr> which is what a rewrite is - <gnufreex> I am not expert on Clojure, but I don't think it is made for - system programming. - <gnufreex> If you want alternate language, I thing Go is only serious - candidate other than C - <crocket> Or Rust - <crocket> However, some people wrote OSes in haskell. - <braunr> again, why ? - <braunr> if it's only for the sake of using another language, i think it's - bad reason - <crocket> Because haskell provides a high level of abstraction that helps - programmers. - <crocket> It is more secure with monads. - <gnufreex> If you want your OS to become successful Free Software project, - you have to use popular language. Haskell is not. - <gnufreex> Most Haskell programmers are not into kernels - <gnufreex> They do high level stuff. - <gnufreex> So little contributors. - <braunr> crocket: so you aim at security ? - <gnufreex> I mean, candidats for contribution - <crocket> braunr, security and higher abstraction. - <braunr> i don't understand higher abstraction - <crocket> braunr, FP can be useful to systems. - <braunr> FP ? - <neal> functional programming - <braunr> right - <braunr> but you can abstract a lot with c too, with more efforts - <crocket> braunr, like that's easy. - <braunr> it's not that hard - <braunr> i'm just questioning the goals and the solution of using a - particular language - <braunr> the reason c is still the preferred language for system - programming is because it provides control over how the hardware does - stuff - <braunr> which is very important for performance - <braunr> the hurd never took off because of bad performance - <braunr> performance doesn't mean doing things faster, it means being able - to do things or not, or doing things a new way - <braunr> so ok, great, you have your amazing file system written in - haskell, and you find out it doesn't scale at all beyond some threshold - of processors or memory - <crocket> braunr, L4 is fast. - <braunr> l4 is merely an architecture abstraction - <braunr> and it's not written in haskell :p - <braunr> don't assume anything running on top of something fast will be - fast - <crocket> Hurd is slow and written in C. - <braunr> yes - <braunr> not because of c though - <crocket> Becuase it's microkernel? - <braunr> because c wasn't used well enough to make the most of the hardware - in many places - <braunr> far too many places - <crocket> A microkernel can be as fast as a monolithic kernel according to - L4. - <braunr> no - <braunr> it can't - <braunr> it can for very specific cases - <braunr> almost none of which are real world - <braunr> but that's not the problem - <braunr> again, i'm questioning your choice of another language in relation - to your goals, that's all - <braunr> c can do things you really can't do easily in other languages - <braunr> be aware of that - <crocket> braunr, "Monolithic kernel are faster than microkernel . while - The first microkernel Mach is 50% slower than Monolithic kernel while - later version like L4 only 2% or 4% slower than the Monolithic kernel ." - <braunr> 14:05 < braunr> but concerning microkernel stuff, you'll read a - lot of crap anywhere - <braunr> simple counterexample : - <braunr> the measurements you're giving consider a bare l4 kernel with - nothing on top of it - <braunr> doing thread-to-thread ipc - <braunr> this model of communication is hardly used in any real world - application - <braunr> one of the huge features people look for with microkernels are - capabilities - <braunr> and that alone will bump your 4% up - <braunr> since capabilities will be used for practically every ipc - <crocket> ok - - -# Hurd From Scratch - -## IRC, freenode, #hurd, 2013-11-30 - - <hurdmaster> because I think there is no way to understand the whole pile, - you need to go step by step - <hurdmaster> for example, I'm starting with mach only, then adding one - server, then another and on each step I have working system - <hurdmaster> that's how I want to understand it - <teythoon> you are interested in the early bootstrapping of the hurd system - ? - <hurdmaster> now I'm starting debian gnu/mach, it hungs, show me black - screen and I have no idea how to fix it - <teythoon> if you are unable to fix this, why do you think you can build a - hurd system from scratch ? - <hurdmaster> not gnu/mach, gnu/hurd I mean - <teythoon> or, you could describe your problem in more detail and one of - the nice people around here might help you ;) - <hurdmaster> as I said, it will be easier to understand and fix bugs, if I - will go step by step, and I will be able to see where bugs appears - <hurdmaster> so you should help me with that - <teythoon> and I tend to disagree - <teythoon> but you could always read my blog. you'll learn lots of things - about bootstrapping a hurd system - <teythoon> but it's complicated - <hurdmaster> http://www.linuxfromscratch.org/ - <teythoon> also, you'll need at least four hurd servers before you'll - actually see much - <teythoon> five - <teythoon> yeah, i know lfs - <hurdmaster> if somebody is interested in creating such a project, let me - know - <teythoon> you seem to be interested - <hurdmaster> yes, but I need the a real hurd master to help me - <teythoon> become one. fix your system and get to know it - <hurdmaster> I need knowledge, somebody built the system but didn't write - documentation about it, I have to extract it from your heads - <teythoon> hurdmaster: extract something from here - http://teythoon.cryptobitch.de - <teythoon> I need my head ;) - <hurdmaster> thanks - <hurdmaster> okay, what's the smallest thing I can run? - <teythoon> life of a Hurd system starts with the root filesystem, and the - exec server is loaded but not started - <teythoon> you could get rid of the exec server and replace the root - filesystem with your own program - <teythoon> statically linked, uses no unix stuff, only mach stuff - <hurdmaster> can I get 'hello world' on pure mach? - <teythoon> you could - <teythoon> hurdmaster: actually, here it is: - http://darnassus.sceen.net/gitweb/rbraun/mach_print.git/ - <teythoon> compile it statically, put it somewhere in /boot - <teythoon> make sure you're running a debug kernel - <teythoon> load it from grub instead of /hurd/ext2fs.static - <teythoon> look at the grub config for how this is done - <teythoon> let me know if it worked ;) - - -# IRC, freenode, #hurd, 2014-03-04 - - <bwright> Can I run a single instance of hurd on multiple computers - <bwright> With them acting as different servers? - <braunr> no - <bwright> Like the fs server on one pc etc. - <bwright> Which os could I do this with? - <bwright> I assumed Mach RPC would support that. - <braunr> it can - <braunr> but we don't use it that way - <braunr> plan9 is probably better suited to what you want - <braunr> inferno too - <braunr> maybe dragonflybsd - <bwright> Yep. - <bwright> irAwesome. - <bwright> Plan9 is exactly it. - <braunr> enjoy - - -# IRC, freenode, #hurd, 2014-03-11 - - <ltx> Does anyone have a distributed OS over GNU/hurd project running? - <ltx> (GNU/hurd has many of the utilities to make this easy, but it still - requires some more utilities for transparent computation) - <braunr> not at the moment, no - <braunr> and i consider our ipc inappropriate if you want system able to - run over heterogeneous hardware - <braunr> or rather, our RPCs - <ltx> I haven't spent the time, this is speculative (in the worse "let's do - everything magically!" way.) - <ltx> Just wondering if this exists outside of plan9 (which is limited in - some ways.) - <braunr> dragonflybsd had plans for a SSI - <braunr> there are ancient research systems that actually did the job - <braunr> such as amoeba - <braunr> here at the hurd, we just don't have the manpower, and the people - spending time on the project have other interests - <ltx> Yeah, that seems like a large problem. - <ltx> GNU/hurd is self hosting (in the "I like working on it" way), yes? - <ltx> I've done some work on it, but don't really know how nice it is. - <braunr> yes it is - <ltx> Working from a microkernel to add pseudo-SSI features to a bunch of - servers seems like a much more trivial task than, say, modifying TLK. - <braunr> posix conformance and stability are good enough that more than 70% - of debian packages build and most of them work fine - <braunr> tlk the linux kernel ? - <ltx> Yes. - <braunr> first time i see this acronym :) - <braunr> and yes i agree, a microkernel is much much more suited for that - <braunr> but then, i consider a microkernel better suited for practically - everything ... :) - <ltx> :) - <ltx> I'm wondering how to mix SSI with network-awareness. - <braunr> mach used to have a network server - <braunr> which would merely act as a proxy for capabilities - <braunr> network drivers were in kernel though - <ltx> That's the simple way of sharing the sources. - <ltx> I'm wondering how we can make a software stack that's network aware; - completely transparent SSI can lead to inefficiencies in userspace, as it - may do things the kernels won't expect. Having to deal with the network - through a network server is a headache. - <braunr> what kind of problems do you have in mind ? - <ltx> Still working on defining the problem. I think that's half the - problem. - <ltx> (For any problem.) - <ltx> Beyond that, it's just some coding ;) - <braunr> ok - <braunr> sounds interesting :) - <braunr> i'd love to see a modern SSI in action - <braunr> but that's really a secondary goal for me so glad to see someone - making this his primary goal - <braunr> doctoral thesis ? - <ltx> ... Undergrad who's been hacking away since grade school. - <braunr> heh :) - <ltx> 18 y/o sophomore at a respected technical college, dealing with - boredom :) - <braunr> well throroughly thinking about "defining the problem" is an - excellent reflex - <teythoon> :) stick around, the hurd is fun - <braunr> it does help fight boredom a lot indeed ...... ) - <braunr> :) - <cluck> maybe it'd be possible to port the relevant features from plan9 now - that there is a gpl'ed version - <teythoon> either way, we'd need network-transparent mach messaging - <teythoon> which mach messaging could do, but gnumach does not implement - this currently - <cluck> teythoon: afaiui if there was a proper 9fs2000 hurd server the rest - could be hidden behind the curtains - <teythoon> ah, well, that sounds like a 9p network filesystem translator - <cluck> teythoon: also iirc plan9 uses libmach for some things so i suppose - a port wouldn't be completely impossible - <teythoon> given that in plan9 everything is a file, that might be enough - to use plan9 services - <cluck> teythoon: yes, it'd be the easiest route (at least initially) i - believe - <teythoon> careful, lots of stuff is named mach-something - <cluck> bloody ernest mach and his damned famous-ness-ish - <cluck> =) - <teythoon> :D |