April 2011 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

i/o opening error for PCI access
by Sengottuvelan S April 4, 2011

April 4, 2011

Hi All, I am trying to access /dev/mem in my user process. I could not access because not a privileged access. I tried to use iopl(3) call in linux 2.6, but i am getting unresolved symbol for this. Is any other way to get access in user process. I am not sure how to solve this. Can you someone throw some light on this. if(iopl(3)){ fprintf(stderr, "Cannot get I/O permissions (being root helps)"); return -1; } if ((fd = open("/dev/mem", O_RDWR | O_SYNC)) < 0) { fprintf(stderr, "Failed to open /dev/mem"); return -1; } -- Regards, S. Sengottuvelan. -- Regards, S. Sengottuvelan.

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GSOC 2011 proposal: Linux kernel library
by Lucian Adrian Grijincu April 3, 2011

April 3, 2011

Hi guys, I'd like to work for GSOC on a Linux Kernel project. The Linux Foundation says that for stuff that's not LSB/a11y/drivers/wireless/printing I should contact you guys. https://www.linuxfoundation.org/collaborate/workgroups/gsoc/google-summer-c… = Introduction = A few years ago, me and a teacher of mine worked on something we call Linux Kernel Library (LKL). LKL is a pseudo-architecture (more similar to user mode linux, than to x86, arm, sparc). The build result of LKL is a library that you can embed in other programs. You have a project and you need to access data from an ext2/3/4/reiser/btrfs/etc. disk image? You want your project to run in userspace in any OS (Linux/BSD/Windows/Mac/Haiku or another OS which provides some required functionalities). Then link to LKL and you can add that disk image as a LKL device, LKL-mount it, and call LKL-system calls to interact with data from that image. You want to build a FS driver for another OS? You can build a driver and link (statically) LKL into it. Proof-of-concept implementations of FS drivers for Windows and Haiku have been implemented. = What I'd like to do for GSOC = The version of LKL we have now is old. It was hacked together based on 2.6.27, and forward ported by me a couple of times, but along the way I managed to mess some things up and introduced some bugs. I'd like to start over and rewrite it from scratch hoping to push it into mainline. The version we have now has some limitations and works on 32 bit archs. I'll make it support 64bit arch too. The embedded Linux kernel sees a uni-processor virtual system. SMP support will have to be added. Mapping from real-devices (a disk image file, a disk partition, an ethernet card) to virtual LKL devices have to be added to be able to use LKL. While we have some drivers right now more will be needed to be able to make LKL more useful. There are other todos, but this email is getting too large. I'd like to know whether anyone here is interested in this project and would like to mentor it for GSOC. If there's some positive feedback on this I'll write an application describing all of these in detail. = About me = I'm a masters student at Politehnica University of Bucharest. Apart from non-kernel jobs, I worked for a year months as a contractor for a company in Romania doing (in-house) Linux kernel development related to network scalability. I have started working with upstream a bit too (last patch series sent if you're interested: http://thread.gmane.org/gmane.linux.kernel/1121889) -- . ..: Lucian

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Re: ARM : Kernel : Setting up of MMU in head.S
by Dave Hylands April 3, 2011

April 3, 2011

Hi Prakash, On Wed, Mar 30, 2011 at 11:01 PM, Prakash K.B. <prakashk75(a)gmail.com> wrote: > Merci mate. :-) > > On Thu, Mar 31, 2011 at 3:59 AM, Dave Hylands <dhylands(a)gmail.com> wrote: >> >> Hi Prakash, >> >> On Wed, Mar 30, 2011 at 2:35 PM, Dave Hylands <dhylands(a)gmail.com> wrote: ...snip... >> When the MMU table is turned on, the PC is still at 0x800xxxx, so even >> though the kernel has 0xc00xxxxx mapped to 0x800xxxxx it also has to >> have 0x800xxxxx mapped to 0x800xxxxx. > > [Prakash] I think you meant to say "So even though the kernel intends to map > 0xc00XXXX to 0x800XXX in the future, it has currently mapped 0x800xxx to > 0x800xxx. No. the create_page_table function creates a page table which has 0x800xxxxx and 0xc00xxxxx both mapped to 0x800xxxxx. The one store intrustion saves the identity mapping (for 1 Mb) and the loop sets up the 0xc00xxxxx to 0x800xxxxx mapping. The identity portion is used as we discussed, and a few instructions after turning on the MMU, the CPU then does a jump from the 0x800xxxxx space to the 0xc00xxxxx space. After that, the identity mapping is no longer needed. Shortly after this, head.S calls into the start_kernel function (from init/main.c) and the paging_init function reinitializes the MMU removing the identity mapping. > > Now that I know this identity mapping is done on purpose, I hope to make > good progress with the succeeding sequence. > > Do you confirm that only one entry is written into this L1 table because > both mmu_enable and enable_mmu_end are on the same section? Yeah - essentially, that one mapping entry covers 1Mb of code space, which is sufficient to cover all of head.S, which is always at the front of the kernel image. -- Dave Hylands Shuswap, BC, Canada http://www.davehylands.com

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GSoC project idea: HFS Plus journal
by Naohiro Aota April 2, 2011

April 2, 2011

Hi, I see some of you are talking about GSoC participation. I'm also thinking of it. I have MacBookPro booting both MacOSX and Linux. Now Linux can write the filesystem safely only when HFS Plus journal is off. My life would be more better if Linux have complete HFS Plus filesystem read/write support. So I'm thinking of implementing HFS Plus Journal support on Linux. I've searched and found a technote about HFS Plus format describe its Journal [1]. How do you think about it? Regards, Naohiro [1] http://developer.apple.com/library/mac/technotes/tn/tn1150.html#Journal

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Regarding enable paging code and swapper_pg_dir.
by mindentropy April 1, 2011

April 1, 2011

Hi All, In the code http://lxr.linux.no/#linux+v2.6.12/arch/i386/kernel/head.S#L186 I am not able to understand what's the reason for subtracting swapper_pg_dir with __PAGE_OFFSET(0xc0000000). i.e. movl $swapper_pg_dir-__PAGE_OFFSET Shouldn't it be movl $swapper_pg_dir, %eax? Thanks.

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Broadcom Ethernet card not working with new kernels - intermittently being registered as two different devices
by julie Sullivan April 1, 2011

April 1, 2011

Hi list, Celejar (see message copied below) has been having problems with his Broadcom BCM4401-B0 Ethernet card not working on very recent kernels - it seems to be sporadically registered either as the correct device or as a completely different Broadcom device on a different subsystem and IRQ. He has emailed various mailing lists and, more recently, linux-kernel, netdev, devel.linuxdriverproject and the b44 driver maintainer but so far without any response. I would need to do a _lot_ of swotting up on device registration semantics to even know where to start looking, so can anyone here help? Any ideas? NOTE: _please do_ cc him as I don't think he is subscribed to kernelnewbies. Cheers Julie ------------------------------------------------------------------------- [I have previously posted this issue to the Debian user, lkml and netdev MLs, but no one has replied with any suggestions. It has been suggested that I try these addresses.] Hi, With recent kernels (git pulls of vanillas sources from kernel.org, mainline and 2.6.38.1), my Broadcom BCM4401-B0 Ethernet card, normally driven by the b44 driver, has stopped working. Poking around, I discovered that the card is (sometimes) no longer correctly identified; it now (sometimes) shows up (with 'lspci -v' as root) as this bizarre device: 06:01.0 Network and computing encryption device: Broadcom Corporation Device 0010 (rev 02) (prog-if 10) Subsystem: Allied Telesis, Inc Device 0010 Flags: fast devsel, IRQ 10 Memory at d0000000 (32-bit, non-prefetchable) [disabled] [size=8K] Capabilities: [40] Power Management version 2 This is what it looks like when it's correctly detected: 06:01.0 Ethernet controller: Broadcom Corporation BCM4401-B0 100Base-TX (rev 02) Subsystem: Acer Incorporated [ALI] Device 0090 Flags: bus master, fast devsel, latency 64, IRQ 21 Memory at d0000000 (32-bit, non-prefetchable) [size=8K] Capabilities: [40] Power Management version 2 Kernel driver in use: b44 I'm currently seeing the problem with 2.6.38.1. What on earth is this all about? IIANM, the same kernel will sometimes detect the card correctly, and sometimes incorrectly; this will make doing a bisection somewhat tricky. Any suggestions, or further tests I should try, or information I should provide? Celejar -- foffl.sourceforge.net - Feeds OFFLine, an offline RSS/Atom aggregator mailmin.sourceforge.net - remote access via secure (OpenPGP) email ssuds.sourceforge.net - A Simple Sudoku Solver and Generator _______________________________________________ devel mailing list devel(a)linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/devel

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Problem with event handler in Timer interrupt
by Asha R April 1, 2011

April 1, 2011

Hi All, I am working on Linux 2.6.27 version. I am facing problem in timer interrupt. I get the timer interrupt but in the handler, *evt->event_handler* generates prefetch abort. The same code works with Linux 2.6.37 version. Please let me know if anyone has faced this problem before. Regards, Asha

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how to get kernel functions calling stack/invokation ordert
by sri April 1, 2011

April 1, 2011

Hi, Is there a way to find, in the kernel src tree, which routine/function is calling another function OR kernel function invocation stack order? This would be helpful for me to know the various steps/functionalities involved during executing something in kernel space. -Sri-

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Debug Kernel Crash
by swathi suresh April 1, 2011

April 1, 2011

Hello All, I wanted to know what is the best way to generate the kernel crash dump on kernel panic, after doing some searching, i came to know we can use kexec to load a new kernel on the kernel, i followed the instruction from the following links http://www.dedoimedo.com/computers/kdump.html http://www.developertutorials.com/tutorials/linux/reboot-linux-faster-07220… I do found that the kernel load properly with the, kexec -l option followed by kexec -e option, but when i set the kernel to be loaded on kernel panic using the option kexec -p, i see that after kernel crash, the system just hangs, it wont even try to load the new kernel. following are the commands am using. Can some one point, if there is any thing wrong with this. chkconfig kdump on /etc/init.d/kdump start kexec -l --append="`cat /proc/cmdline`" --initrd=/boot/initrd.img-2.6.35.10-kdump /boot/vmlinuz-2.6.35.10-kdump kexec -e works fine and loads the kernel successfully, i will be able to see *starting new kernel* in the shell * * * chkconfig kdump on /etc/init.d/kdump start * kexec -p --append="`cat /proc/cmdline`" --initrd=/boot/initrd.img-2.6.35.10* -kdump ** /boot/vmlinuz-2.6.35.10 -kdump * * * i simulate the panic by using echo 1 > /proc/sys/kernel/sysrq echo c > /proc/sysrq-trigger which just crash the kernel and system hangs, and it does not show any message *starting new kernel.* * * Thanks,

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Requirement of Linux port
by Jacky Lam April 1, 2011

April 1, 2011

Hi All, Is there any document on web summarized the hardware (especially, CPU) that a Linux depends on. For example, if a CPU doesn't support misaligned access (no exception will be generated when misalignment access), can Linux run on that? Thanks. BR, Jacky

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