- l4-hackers - example.com Site

486/Pentium version problems
by Edmund GRIMLEY EVANS 12 Mar '99

12 Mar '99

Following the instructions at os.inf.tu-dresden.de/fiasco/use.html I built Fiasco and the Hello World server worked. Excellent! Then I tried building L4-Linux and it didn't work ... Then I noticed that grub-ext2fs-floppy apparently already contains everything you need to run L4-Linux except for L4 itself. So I just copied the fiasco "main" that I had built onto the floppy image as supplied, hacked menu.lst a bit at random, and tried that. That didn't work either, but the thing that caught my attention was a message something like this: RMGR: L4/Pentium ... I was running this on a 486. So my questions are: Do the same executables (main, rmgr, sigma0, glinux.gz) run on both 486 and Pentium, or do different versions have to be built? If the latter, are the versions in grub-ext2fs-floppy supposed to work only on Pentium? If so, how can I build a version for 486 when compiling on a 686 machine? (And also, could the code be made to run on both? It would make life easier ...) Edmund

1 0

ADV: New Daul Mount Copy Holder
by remove＠1vm.com 24 Feb '99

24 Feb '99

Amazing new copy holder can be mounted directly on your computer monitor or it can be used freestanding. Unique design is specifically engineered to increase your efficiency while reducing eye strain, stress, and fatigue. Quality Rubbermaid features include adjustable viewing positions, non-glare surface, spring load paper clamp and detachable line guide. Folds flat for easy out-of-the-way storage. This isn't a cheap clip on, but a full platform copy holder. Special internet savings click here http://www.1vm.com/~rcc and save over $20 from comparable models. Sender: Robert Craig Corp. Phone: 1-800-890-7510 Email: robertcraigcorp(a)prodigy.net Details: http://www.1vm.com/~rcc Remove: REMOVE(a)1vm.com To be removed from future service notifications reply to: REMOVE(a)1vm.com

1 0

Big break!
by Ronald 24 Feb '99

24 Feb '99

Start your own 1-900 business! People are making $$$ week, after week in the 1-900 business. We'll teach you all of our "incredible secrets that will take your new exciting business to a whole new level! It's The Simplest and Most Exciting Business You Could Ever Start! *You'll use our "state" of the art equipment! *You'll use our "Live 1 on 1 Psychics" & "Chat Line" girls! *You'll use our incredible Date Line program(s)! No chargbacks! Quick payouts! No expertise needed! Complete programs start at only $99 (no additional charges) The only thing you'll have to do is advertise! This is an excellent turn key business. We also have excellent turn key programs if you want to own your own "top" of the line adult web site. ACT NOW!!! For a free color brochure: reply to: mailto:megagreen@usa.net?subject=brochure with the following information please: NAME:____________________________ ADDRESS:____________________________ CITY/STATE/ZIP:____________________________ PHONE:____________________________ (optional) remove at: mailto:xpoc@eudoramail.com?subject=remove

1 0

Re: L4 Mapping question
by Michael Hohmuth 23 Feb '99

23 Feb '99

"Adam 'WeirdArms' Wiggins" <awiggins(a)cse.unsw.edu.au> writes: > What TID does the kernel use for its ipc to Sigma0 to request > memory mapping for kernel usage. L4/x86 uses task 1, local thread 0, for communication with Sigma0. The Fiasco kernel doesn't do any IPC operations on behalf of itself -- so no thread id here. Michael -- hohmuth(a)innocent.com, hohmuth(a)sax.de http://www.sax.de/~hohmuth/

1 0

Re: L4 Mapping question
by Michael Hohmuth 23 Feb '99

23 Feb '99

Robert Kaiser <rob(a)sysgo.de> writes: > I was aware that the bookkeeping would have to be in the kernel, otherwise > flush couldn't work as described in the manual. Only, how does it work ? > > Theoretically, each task could map each of it's pages to up to 2047 other > tasks. So, the kernel would need to maintain ~2K entries per mapped page > and task. This can't be! The only explanation I can think of right now > is that the kernel allocates room for entries dynamically, assuming that > the actual number of required entries will always be far less than > the theoretical limit. But that would mean you can break the system > simply by doing a big enough number of mappings. Each mapping of a physical page from virtual address VA1 in a task T1 to VA2 in T2 is kept track of using a kernel data structure called ``mapping entry.'' This data structure is allocated dynamically, but from a fixed-size pool (where the size can be specified at compile time or boot time). It's true that you can break the system by establishing an excessive number of mappings. There are several ways to deal with that, but I don't think any of them has been implemented in the freely-available research kernels; one way is detailed in Jochen Liedtke et al.'s paper ``Preventing Denial-of-Service Attacks on a µ-Kernel for WebOSes'' which is available from <URL:http://os.inf.tu-dresden.de/papers_ps/jochen/Denhot.ps>. > On Mon, 22 Feb 1999, Volkmar Uhlig wrote: > > In the current L4-implementation of Jochen Liedtke, one mapping entry is 16 > > Bytes.The Alpha implementation (done by me) needs 32 Bytes per entry (64 > > bit address space - and a lot of trix). The Fiasco kernel does not use > > lists. They need about 4 Bytes per entry + an some overhead per frame (I > > left bevore it was finished) > > I am getting the distinct feeling that I am missing something > very simple :-(. So, at the risk of looking like a complete fool: > How do you keep track of up to 2K tasks in a 16 Byte entry ? The 16-bytes structure is what I described as a ``mapping entry'' above. Mapping entries belonging to one physical page are linked to each other in a binary-tree structure using pointers. Michael -- hohmuth(a)innocent.com, hohmuth(a)sax.de http://www.sax.de/~hohmuth/

1 0

Re: L4 Mapping question
by Michael Hohmuth 23 Feb '99

23 Feb '99

vuhlig(a)us.ibm.com writes: > The idea is, that the kernel can revoke pages from sigma 0, what is not > implemented yet. [...] I don't think it is a part of the Sigma0 specification that Sigma0 should be able to handle the case where the kernel revokes mappings of pages mapped into Sigma0. Instead, Sigma0 is pretty safe to assume that it magically owns---and has access to---all physically- addressable memory (maybe with the exception of the kernel-private code and data sections; the experts are still out on this one). Michael -- hohmuth(a)innocent.com, hohmuth(a)inf.tu-dresden.de http://home.pages.de/~hohmuth/

2 1

Re: L4 Mapping question
by Michael Hohmuth 23 Feb '99

23 Feb '99

I wrote: > The resource manager Rmgr (which is normally used to startup L4/x86 > and Fiasco) handles the nitty-gritty details of telling the kernel > where it should find its Sigma0 server. In order to avoid any confusion: In a typical booting scenario on the x86, the Rmgr bootstrappig code runs even before the L4 or Fiasco kernel has been started. It is invoked directly by the boot loader and handles all initializations to be done before the kernel starts up: It finds the raw ELF binaries for the kernel and Sigma0 which the boot-loader has dropped in memory, interpretes them (i.e., moves them to their load addresses), configures the kernel (e.g., tells it the location of Sigma0 and Rmgr task entry points), and starts it. For more information, please read the Rmgr manpage at <URL:http://os.inf.tu-dresden.de/L4/l4libman/rmgr.html>. Michael -- hohmuth(a)innocent.com, hohmuth(a)sax.de http://www.sax.de/~hohmuth/

1 0

L4 Mapping question
by Robert Kaiser 23 Feb '99

23 Feb '99

Hi all, I have a question regarding mapping in L4: I read in the L4 reference manual that Sigma0 maps each page only once. It does allow multiple mappings of a page to the same address space (i.e. task), but it does not allow multiple mappings to different tasks. Is this a specific feature of Sigma0 or is this true of all pagers ? I'm asking because I wonder how the fpage_unmap operation works: If a task is allowed to map a page to an unlimited number of different tasks (i.e. 2047 as there are up to 2048 tasks), then the bookkeeping involved in implementing fpage_unmap would require that a pager would theoretically need to keep track of up to 2047 tasks per page in order to allow fpage_unmap to revoke all mappings of a particular page. That looks like a tremendous overhead, so there must either be some limit to the number of mappings or there is something else I'm missing. Could someone please enlighten me about this ? Thanks in advance Rob ---------------------------------------------------------------- Robert Kaiser email: rkaiser(a)sysgo.de SYSGO RTS GmbH Carl-Zeiss-Str. 41 phone: (49) 6131 9138-80 D-55129 Mainz / Germany fax: (49) 6131 9138-10

3 3

Re: L4 Mapping question
by Michael Hohmuth 23 Feb '99

23 Feb '99

"Adam 'WeirdArms' Wiggins" <awiggins(a)cse.unsw.edu.au> writes: > A related question here. Is there any particular reason/need for > sigma zero to be a once off pager? Why not have an inteligent resource > manager for sigma zero? In L4/x86 and Fiasco, this is easily possible. Sigma0 runs on user level and can be substituted at boot time with any program you like. The resource manager Rmgr (which is normally used to startup L4/x86 and Fiasco) handles the nitty-gritty details of telling the kernel where it should find its Sigma0 server. Michael -- hohmuth(a)innocent.com, hohmuth(a)sax.de http://www.sax.de/~hohmuth/

1 0

INCREASE YOUR PROFITS INSTANTLY!
by Shawn 22 Feb '99

22 Feb '99

***INCREASE YOUR PROFITS*** ACCEPT CREDIT CARDS FOR YOUR BUSINESS AND INCREASE YOUR PROFITS 30%-50%! *INTERNET *STOREFRONT *HOMEBASED OR *MAIL ORDER BUSINESS WE SPECIALIZE IN HELPING THE SMALL BUSINESS OWNER! IF YOU CALL IN THE NEXT FIVE DAYS, YOU WILL RECEIVE: NO APPLICATION FEE NO PROGRAMMING FEE CALL 1-888-264-9272 OUR BUSINESS HOURS ARE 9:00 A.M. TO 6:00 P.M. MST Remove at: mailto:mcau@hotbot.com?subject=remove

1 0