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diff --git a/service_solahart_jakarta_selatan__082122541663/anatomy_of_a_hurd_system.mdwn b/service_solahart_jakarta_selatan__082122541663/anatomy_of_a_hurd_system.mdwn new file mode 100644 index 00000000..496d2a06 --- /dev/null +++ b/service_solahart_jakarta_selatan__082122541663/anatomy_of_a_hurd_system.mdwn @@ -0,0 +1,1430 @@ +[[!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 |