The HyperNews Linux KHG Discussion Pages
Linux Kernel Hackers' Guide
Due to the fact that nearly every post to this site recently has been either by rude cracker-wannabes asking how to break into other people's systems or a request for basic technical support, posting to the KHG has been disabled, probably permanently. For now, you can read old posts, but you cannot send replies. In any case, there are now far better resources available.
Go get the real thing!
Alessandro Rubini wrote Linux Device Drivers, which is what the KHG could have been (maybe) but isn't. If you have a question and can't find the answer here, go get a copy of Linux Device Drivers and read it--chances are that when you are done, you will not need to ask a question here.
Run, don't walk to get a copy of this book.
Go read The Linux Kernel if you want an introduction to the Linux kernel that is better than the KHG. It is a great complement to Linux Device Drivers. Read it.
Table of Contents
-
Tour of the Linux Kernel
- This is a somewhat incomplete tour of the Linux Kernel, based on Linux 1.0.9 and the 1.1.x development series. Most of it is still relevant.
-
Device Drivers
- The most common Linux kernel programming task is writing a new device driver. The great majority of the code in the kernel is new device drivers; between 1.2.13 and 2.0 the size of the source code more than doubled, and most of that was from adding device drivers.
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Filesystems
- Adding a filesystem to Linux doesn't have to involve magic...
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Linux Memory Management
- A few outdated documents, and one completely new one by David Miller on the Linux cache flush architecture.
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How System Calls Work on Linux/i86
- Although this was written while Linux 0.99.2 was current, it still applies. A few filenames may need updating. find is your friend--just respond with the changes and they will be added.
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Other Sources of Information
- The KHG is just one collection of information about the Linux kernel. There are others!
Membership and Subscription
At the bottom of the page, you will notice two hyperlinks (among several others): Subscribe and Members. Using the KHG to its fullest involves these two hyperlinks, even though you are not required to be a member to read these pages and post responses.
Membership
HyperNews membership is site-wide. That is, you only need to sign up and become a member once for the entire KHG. It doesn't take much to be a member. Each member is identified by a unique name, which can either be a nickname or an email address. We suggest using your email address; that way it will be unique and easy to remember. On the other hand, you may want to choose a nickname if you expect to be changing your email address at any time.
We also want your real name, email address, and home page (if you have one). You can give us your phone and address if you want. You will be asked to choose a password. You can change any of these items at any time by clicking on the Membership hyperlink again.
Subscription
Subscribing to a page puts you on a mailing list to be sent notification of any new responses to the page to which you are subscribed. You subscribe separately to each page in which you are interested by clicking the Subscription link on the page to which you want to subscribe. You are also subscribed, by default, to pages that you write.
When you subscribe to a page, you subscribe to that page and all of its responses.
Contributing
Please respond to these pages if you have something to add. Think of posting a response rather like posting to an email list, except that an editor might occasionally come along to clean things up and/or put them in the main documents' bodies. So if you would post it to an email list in a similar discussion, it is probably appropriate to post here.
In order to make reading these pages a pleasure for everyone, any incomprehensible, unrelated, outdated, abusive, or other completely unnecessary post may be removed by an administrator. So if you have a message that would be inappropriate on a mailing list, it's probably also inappropriate here.
The administrators have the final say on what's appropriate. We don't expect this to become an issue...
About the new KHG
The Linux Kernel Hackers' Guide has changed quite a bit since its original conception four years ago. I struggled along with the help of many other hackers to produce a document that lived primarily on paper, and was intended to document the kernel in much the same way that a program's user guide is intended to document the program for users.
It was less successful than most user guides, for a number of reasons:
- I was working on it part time, and was otherwise busy.
- The Linux kernel is a moving target.
- I am not personally capable of documenting the entire Linux kernel.
- I became far too concerned with making the typesetting pretty, getting bogged down in details and making the document typographically noisy at the same time.
I floundered around, trying to be helpful, and made at least one right decision: most of the people who needed to read the old KHG needed to write device drivers, and the most fully-developed part of the KHG was the device driver section.
There is a clear need for further development of the KHG, and it's clear that my making it a monolithic document stood in the way of progress. The KHG is now a series of more or less independent web pages, with places for readers to leave comments and corrections that can be incorporated in the document at the maintainer's leisure--and are available to readers before they are incorporated.
The KHG is now completely web-based. There will be no official paper version. You need kernel source code nearby to read the KHG anyway, and I want to shift the emphasis from officially documenting the Linux kernel to being a learning resource about the Linux kernel--one that may well be useful to other people who want to document one part or another of the Linux kernel more fully, as well as to people who just want to hack the kernel.
Enjoy!
Copyright (C) 1996,1997 Michael K. Johnson, [email protected]
Messages
- 349. Loading shared objects - How? by Wesley Terpstra
- 342. How can I see the current kernel configuration? by Melwin
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- 1. My mouse no work in X windows by alfonso santana
- 340. The crash(1M) command in Linux? by Dmitry
- 338. Where can I gen detailed info on VM86 by Sebastien Plante
- 335. How to print floating point numbers from the kernel? by [email protected]
- 333. PS/2 Mouse Operating in Remote Mode by Andrei Racz
- 331. basic module by [email protected]
- 329. How to check if the user is local? by [email protected]
- 328. Ldt & Privileges by Ganesh
- 326. skb queues by Rahul Singh
- 323. Page locking (for DMA) and process termination? by Espen Skoglund
- 322. SMP code by [email protected]
- 319. Porting GC: Difficulties with pthreads by Talin
- 314. Linux for "Besta - 88"? by Dmitry
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- 1. MVME147 Linux by Edward Tulupnikov
- 313. /proc/locks by Marco Morandini
- 310. syscall by [email protected]
- 308. How to run a bigger kernel ? by Kyung D. Ryu
- 300. Linux Terminal Device Driver by Nils Appeldoorn
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- 1. Terminal DD by Doug McNash
- 297. DMA to user allocated buffer ? by Chris Read
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- 1. allocator-example in A.Rubini's book by Thomas Sefzick
- 293. Patching problems by Maryam
-
- 1. Untitled by [email protected]
- 290. Ethernet Collision by jerome bonnet
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- 1. Ethernet collisions by Juha Laine
- 289. Segmentation in Linux by Andrew Sampson
- 288. How can the kernel copy directly data from one process to another process? by Jürgen Zeller
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- 1. Use the /Proc file system by [email protected]
- 286. Remapping Memory Buffer using vmalloc/vma_nopage by Brian W. Taylor
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- 1. Fixed.... strncpy to blame by Brian W. Taylor
- 283. Does memory area assigned by "vmalloc()" get swapped to disk? by Saurabh Desai
-
- 1. Lock the pages in memory by [email protected]
- -> How about assigning a fixed size array...does it get swapped too? by saurabh desai
- 282. Creative Lab's DVD Encore by Brandon
- 274. TCP sliding window by Olivier
- 273. Packets and default route versus direct route by Steve Resnick
- 269. IPv6 description - QoS Implementation - 2 IP Queues by wehrle
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- 2. See the kernel IPv4 implementation documentation by Juha Laine
- 268. writing to user file directly from kernel space, How can it be done? by Johan
- 267. how can i increase the number of processes running? by ElmerFudd
- 261. How do I change the amount of time a process is allowed before it is pre-empted? by [email protected]
- 260. Network device stops after a while by Andrew Ordin
-
- 1. Untitled by Andrew
- 259. Does MMAP work with Redhat 4.2? by Guy
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- 1. Yes, it works just fine. by Michael K. Johnson
-
- 3. What about mprotect? by Sengan Baring-Gould
- 2. It Works! Thanks! by Guy
- 256. multitasking by Dennis J Perkins
-
- 1. Answer by David Welch
- -> multitasking by Dennis J Perkins
- -> answer by David Welch
- 247. linux on sparc by darrin hodges
- 241. How to call a function in user space from inside the kernel ? by Ronald Tonn
-
- 1. How to call a user routine from kernel mode by David Welch
- 240. Can I map kernel (device driver) memory into user space ? by Ronald Tonn
- 237. driver x_open,x_release work, x_ioctl,x_write don't by Carl Schwartz
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- 1. Depmod Unresolved symbols? by Carl Schwartz
- 235. How to sleep for x jiffies? by Trent Piepho
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- 1. Use add_timer/del_timer (in kernel/sched.c) by Amos Shapira
- 234. Adding code to the Linux Kernel by Patrick
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- 1. /dev/random by Simon Green
- 231. MSG_WAITALL flag by Leonard Mosescu
- 230. possible bug in ipc/msg.c by Michael Adda
- 225. scheduler Question by Arne Spetzler
-
- 1. Untitled by Ovsov
- -> thanks by arne spetzler
- 221. File Descriptor Passing? by The Llamatron
- 220. Linux SMP Scheduling by Angela
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- 2. Finding definitions in the source by Felix Rauch
- 1. Re: Linux SMP Scheduling by Franky
- 217. Difference between ELF and kernel file by Thomas Prokosch
- 216. How kernel communicates with outside when it's started? by Xuan Cao
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- 1. Printing to the kernel log by Thomas Prokosch
- 213. The way from a kernel hackers' idea to an "official" kernel? by Roger Schreiter
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- 1. [email protected] by Michael K. Johnson
- 212. Curious about sleep_on_interruptible() in ancient kernels. by Colin Howell
- 208. Server crashes using 2.0.32 and SMP by Steve Resnick
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- 1. Debugging server crash by Balaji Srinivasan
- -> More Information by Steve Resnick
- -> it should not have happenned... by Balaji Srinivasan
- 207. Signals ID definitions by Franky
- 206. the segment D000 is not visible by [email protected]
- 205. ICMP - Supressing Messages in 2.1.82 Kernel by Brent Johnson
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- 1. Change /etc/syslog.conf by Balaji Srinivasan
- 203. Modem bits by Franky
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- 1. Untitled by Kostya
- 200. I need some way to measure the time a process spend in READY QUEUE by Leandro Gelasi
- 197. How to make sockets work whilst my process is in kernel mode? by Mikhail Kourinny
- 193. Realtime Problem by Uwe Gaethke
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- 1. SCHED_FIFO scheduling by Balaji Srinivasan
- 190. inodes by Ovsov
- 186. Difference between SOCK_RAW SOCK_PACKET by Chris Leung
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- 1. SOCK_PACKET by Eddie Leung
- 185. Need additional termcap entries for TERM=linux by Karl Bullock
- 184. Question on Umount or sys_umount by teddy
- 183. Passing file descriptors to the kernel by Pradeep Gore
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- 1. A way to "transform" a file descriptor into a struct file* in a user process by Lorenzo Cavallaro
- 181. Dead Man Timer by Jody Winston
- 179. raw sockets by lightman
- 178. a kernel-hacking newbie by Bradley Lawrence
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- 2. A place to start.
- 1. Modems in general by Ian Carr-de Avelon
- 176. How to write CD-ROM Driver ? Any Source Code ? by Madhura Upadhya
- 174. Measuring the scheduler overhead by Jasleen Kaur
- 173. Where can I find the tcpdump or snoop in linux? by wangc@taurus
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- 1. man which by [email protected]
- 172. Timers don't work?? by Joshua Liew
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- 1. Timers Work... by Balaji Srinivasan
- 171. problem of Linux's bridge code by wangc@taurus
- 170. Documention on writing kernel modules by Erik Nygren
- 168. How to display a clock on my console? by keco
- 167. Difference between SCO and Linux drivers. by M COTE
- 165. Changing the scheduler from round robin to shortest job first for kernel 2.0 and up by [email protected]
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- 2. Improving the Scheduer by Lee Ingram
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- 1. Improving the Scheduler : use QNX-like by Leandro Gelasi
- 1. Re: Changing the sched. from round robin to shortest job first for kernel 2.0 and up. by Pirasenna V.T.
- 164. meanings of file->private_data by [email protected]
- 162. /dev/signalprocess by flatmax
- 161. how to track VM page access sequence? by shawn
- 160. Whats the difference between dev_tint(dev) and mark_bh(NET_BH)? by Jaspreet Singh
- 159. PCI by [email protected]
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- 1. RE: PCI by Armin A. Arbinger
- 158. Can I make syscall from inside a kernel module? by Shawn Chang
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- 3. Re: Can I make syscall from inside a kernel module? by Massoud Asgharifard
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- 1. Make a syscall despite of wrong fs!! by Mikhail Kourinny
- 2. code snip to make a sys_* call from a module by Pradeep Gore
- 1. Dont use system calls within kernel...(esp sys_mlock) by Balaji Srinivasan
- 157. Untitled by Steve Durst
- 154. RAW Sockets (Art)
- 153. use phy mem by WYB
- 151. HyperNews for RH Linux ? by Eigil Krogh Sorensen
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- 1. Not really needed by Cameron
- 150. about raw ethernet frame: how to do it ? by [email protected]
- 149. process table by Blaz Novak
- 148. Stream drivers by Nick Egorov
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- 3. Streams drivers
- 1. Stream in Solaris by [email protected]
- 143. Xircom External Ethernet driver anywhere? by mike head
- 140. interruptible_sleep_on() too slow! by Bill Blackwell
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- 1. wrong functions by Michael K. Johnson
- 139. creating a kernel relocatable module by Simon Kittle
- 138. Up to date serial console patches by Simon Green
- 136. Kernel-Level Support for Checkpointing on Linux? by Argenis R. Fernandez
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- 1. Working on it. by Jan Rychter
- 135. Problem creating a new system call by sauru
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- 3. How did the file /arch/i386/kernel/entry.S do its job by Wang Ju
- 2. system call returns "Bad Address". Why? by sauru
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- 1. Re:return values by C.H.Gopinath
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- 2. Re:return values by Sameer Shah
- 1. possible reason for segmentation fault
- 1. Creating a new sytem call: solution by C.H.Gopinath
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- 2. problem with system call slot 167 by Todd Medlock
- 1. Kernel Debuggers for Linux by sauru
- 133. Resetting interface counters by Keith Dart
- 130. writing/accessing modules by Jones MB
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- 1. Use a device driver and read()/write()/ioctl() by Michael K. Johnson
- -> getting to the kernel's memory by Jones MB
- -> use buffers! by Rubens
- 124. Help with CPU scheduler! by Lerris
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- 1. Response to "Help with CPU scheduler!" by Jeremy Impson
- -> Response to "Help with CPU scheduler!" (Redux) by Jeremy Impson
- 117. calling interupts from linux by John J. Binder
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- 1. You can't by Michael K. Johnson
- -> Calling BIOS interrupts from Linux kernel by Ian Collier
- -> Possible, but takes work by Michael K. Johnson
- -> VBE video driver by Ian Collier
- -> VM86 mode at which abstraction level? by Michael K. Johnson
- 116. DVD-ROM and Linux? (sorry if it's off topic...) by Joel Hardy
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- 3. DVD-ROM and linux by [email protected]
- 2. Response to DVD and Mpeg in Linux by Mike Corrieri
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- 1. DVD Encryption by Mark Treiber
- -> Untitled by Tim
- -> DVD?
- 115. Kernel Makefile Configuration: how? by Simon Green
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- 2. How to add a driver to the kernel ? by jacek Radajewski
- 1. See include/linux/autoconf.h by Balaji Srinivasan
- 113. Multiprocessor Linux by Davis Terrell
-
- 1. Building an SMP kernel by Michael K. Johnson
- -> SMP and module versions by [email protected]
- 111. Improving event timers? by [email protected]
- 109. measuring time to load a virtual mem page from disk by kandr
- 94. using cli/sti() and save_flags/restore_flags() by george
- 93. Protected Mode by ac
-
- 2. 'Developers manual' from Intel(download)... by Mats Odman
- 1. Advanced 80386 Programming Techniques by Michael K. Johnson
- 92. DMA buffer sizes by [email protected]
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- 2. DMA limits by Albert Cahalan <acahalan at cs.uml.edu>
- 1. Not page size, page order by Michael K. Johnson
- 91. Problem Getting the Kernel small enough by [email protected]
-
- 2. Check it's the right file, zImage not vmlinux by Cameron
- 1. Usually easy, but.... by Ian Carr-de Avelon
- 89. How to create /proc/sys variables? by Orlando Cantieni
- 88. Linux for NeXT black? by Dale Amon
- 87. vremap() in kernel modules? by Liam Wickins
- 86. giveing compatiblity to win95 for ext2 partitions (for programmers forced to deal with both) by pharos
-
- 2. Well, What's the status of the Windows / Dos driver for Ext2? by Brock Lynn
- 1. Working on it! by ibaird
-
- 1. revision by ibarid
- -> Untitled by Olaf
- 84. setsockopt() error when triying to use ipfwadm for masquerading by [email protected]
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- 1. Re: masquerading by Charles Barrasso
- 83. reset the irq 0 timer after APM suspend by Dong Chen
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- 1. Re: fixed, patch for kernel 2.0.30 by Dong Chen
- 77. Source Code in C for make Linux partitions. by Limbert Sanabria
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- 1. Untitled by lolley
- 76. How can I "cheat" and change the IP address (src,dest) in the sent socket? by Rami
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- 5. Transparent Proxy by Zygo Blaxell
- 4. Untitled by [email protected]
- 3. Untitled by [email protected]
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- 2. Changing your IP address is easy, but... by Zygo Blaxell
- 1. You have to know a bit of C (if u wanna learn) ;) by Lorenzo Cavallaro
- 2. Untitled
- 1. Do it in the kernel by Michael K. Johnson
- 74. Where is the source file for accept() by [email protected]
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- 1. Here, in /usr/src/linux/net/socket.c by [email protected]
- 72. How can I use RAW SOCKETS in UNIX? by Rami
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- 1. Re: Raw sockets by [email protected]
- 69. the KHG in spanish? by Jorge Alvarado Revatta
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- 2. Si tenga preguntas, quisa yo pueda ayudarte. by KernelJock
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- 3. Tengo una pregunta by [email protected]
- 2. Español by LL2
- 1. No esta aqui! Pero... by Michael K. Johnson
- 67. How to get a Memory snapshot ? by Manuel Porras Brand
-
- 1. Why not to get a memory snapshot? by Jukka Santala
- -> Why you would want to get a memory snapshot by Dave M.
- 66. resources hard limits by [email protected]
-
- 1. Setting resource limits by Jukka Santala
- 65. How to invalidate a chache page by Gerhard Uttenthaler
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- 1. Read the rest of the KHG! by Michael K. Johnson
- 64. Where are the tunable parameters of the kernel? by [email protected]
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- 1. Kernel tunable parameters by Jukka Santala
- 62. How can my device driver access data structures in user space? by Stephan Theil
-
- 1. Forced Cast data type by Wang Ju
- 61. Problem in doing RAW SOCKET Programming by anjali sharma
-
- 1. Problem with ICMP echo-request/reply by Raghavendra Bhat
- 59. Tunable Kernel Parameters? by [email protected]
-
- 2. Increasing number of files in system by Simon Cooper
-
- 1. Increasing number of open files parameter by Simon Cooper
- 1. sysctl in Linux by Jukka Santala
-
- 1. Setting and getting kernel vars by [email protected]
- 58. ELF matters by Carlos Munoz
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- 1. Information about ELF Internals by Pat Ekman
- 57. Droping Packets by Charles Barrasso
-
- 1. [Selectively] Droping Packets by Jose R. cordones
- 56. The /proc/profile by Charles Barrasso
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- 1. readprofile systool by Jukka Santala
- 55. Can you block or ignore ICMP packets? by [email protected]
-
- 4. ICMP send rate limit / ignoring by Jukka Santala
-
- 1. Omission in earlier rate-limit... by Jukka Santala
- -> Patch worked... by Jukka Santala
- 3. Using ipfwadm by Charles Barrasso
-
- 1. ipfwadm configuration utility by Sonny Parlin
- 1. Icmp.c and kernal ping replies by Don Thomas
- 52. encaps documentation by Kuang-chun Cheng
- 51. Mounting Caldrea OpenDOS formatted fs's by Trey Childs
- 49. finding the address that caused a SIGSEGV. by Ben Shelef
- 47. sti() called too late. by Erik Thiele
-
- 1. sti() called too late. by Gadi Oxman
- 38. Module Development Info? by Mark S. Mathews
-
- 1. Needed here too by ajay
- 2. Help needed here too! by ajay
- 35. Need quicker timer than 100 ms in kernel-module by Erik Thiele
-
- 1. 10 ms timer patch by Reinhold J. Gerharz
-
- 2. please send me 10 ms timer patch by Tolga Ayav
- 1. Please send me the patch by Jin Hwang
-
- 1. UTIME: Microsecond Resolution Timers by BalajiSrinivasan
- 34. Need help with finding the linked list of unacked sk_buffs in TCP by Vijay Gupta
- 31. Partition Type by Suman Ball
- 30. New document on exception handling by Michael K. Johnson
- 29. How to make paralelism in to the kernel? by Delian Dlechev
- 27. readv/writev & other sock funcs by Dave Wreski
- 25. I'd like to see the scheduler chapter by Tim Bird
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- 1. Untitled by Vijay Gupta
- 3. Go ahead! by Michael K. Johnson
- 21. Unable to access KHG, port 8080 giving problem. by Srihari Nelakuditi
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- 1. Get a proxy by Michael K. Johnson
- 20. proc fs docs? by David Woodruff
-
- 1. Examples code as documentation by Jeremy Impson
- 18. What is SOCK_RAW and how do I use it? by arkane
-
- 1. What raw sockets are for. by Cameron MacKinnon
- 15. Linux kernel debugging by [email protected]
-
- 2. GDB for Linux by David Grothe
-
- 2. Another kernel debugging tool by David Hinds
-
- 2. Kernel debugging with breakpoints by Keith Owens
- -> Need help for debugging by C.H.Gopinath
- 1. gdb debugging of kernel now available by David Grothe
- 1. Device debugging by alombard©iiic.ethz.ch
- 9. Realtime mods anyone? by bill duncan
-
- 7. Summary of Linux Real-Time Status by Markus Kuhn
- 6. Hard real-time now available by Michael K. Johnson
-
- 2. Shortcomings of RT-Linux by Balaji Srinivasan
- 1. Firm Realtime available by Balaji Srinivasan
- 5. found some hacks ?!? by Mayk Langer
-
- 2. I want to know how to hack Red Hat Linux Release 5.0 by Kevin
- 4. POSIX.4 scheduler by Peter Monta
-
- 1. cli()/sti() latency, hard numbers by Ingo Molnar
- 2. Realtime is already done(!) by Kai Harrekilde-Petersen
- 1. 100 ms real time should be easy by jeff millar
-
- 1. Real-Time Applications with Linux POSIX.4 Scheduling by P. Woolley
- 7. Why can't we incorporate new changes in linux kernel in KHG ? by Praveen Kumar Dwivedi
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- 1. You can! by Michael K. Johnson
- 3. Kernel source code by Gabor J.Toth
-
- 1. The sounds of silence... by Gabor J.Toth
-
- 1. Breaking the silence :) by Kyle Ferrio
-
- 1. Scribbling in the margins by Michael K. Johnson
- 2. It requires thought... by Michael K. Johnson
- 2. Kernel source is already browsable online by Axel Boldt
- 2. Need easy way to download whole KHG
-
- 5. KHG being mirrored nightly for download! by Michael K. Johnson
- 2. postscript version of these documents? by Michael Stiller
-
- 1. Sure! by Michael K. Johnson
- -> Not so Sure! by jeff millar
- -> Enough already! by Michael K. Johnson
- 1. Mirror packages are available, but that's not really enough by Michael K. Johnson
-
- 4. Mirror whole KHG package, off line reading and Post to this site by Kim In-Sung
-
- 2. Untitled by Jim Van Zandt
- 1. That works. (using it now). Two tips: by Richard Braakman
-
- 2. Appears to be a bug in getwww, though... by Michael K. Johnson
- -> Sucking up to the wrong site... ;) by Jukka Santala
- 1. Help make the new KHG a success by Michael K. Johnson