September 2012 - kernelnewbies@kernelnewbies.org

compile kernel 3.0.34 errors
by wenrongbupt Sept. 14, 2012

Sept. 14, 2012

Hi guys, I am using Fedora 13(kernel version is 2.6.33.3-85.fc13.i686.PAE) and try to build kernel 3.0.34. I am follow these steps: make mrproper make bzImage make modules make modules_install make install Every step is succeed except make install It has following errors: ERROR: modinfo: could not find module twofish ERROR: modinfo: could not find module i2c I don't know how to solve this problem.Please help me!Thank you very much. Regards Vincent

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hardware support
by Littlefield, Tyler Sept. 14, 2012

Sept. 14, 2012

hello all: I had a question. I get an address mmio error when I try to boot my debian box, along with this: INIT_I2C_LONG_IF I'm curious of something. I have an 8-core AMD zambesi, is there support for this yet? I also have channel interleaving turned on (we can't really get it off), is this also something Linux would have issues with? -- Take care, Ty http://tds-solutions.net The aspen project: a barebones light-weight mud engine: http://code.google.com/p/aspenmud He that will not reason is a bigot; he that cannot reason is a fool; he that dares not reason is a slave

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Mult core cpus - SMP
by Kshemendra KP Sept. 13, 2012

Sept. 13, 2012

Hi, Does multi core CPU act like SMP system. Regards Kshemendra

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Re: kernel stack memory
by Kshemendra KP Sept. 13, 2012

Sept. 13, 2012

Not sure for all the tasks slab is created initailly with contiguous memory. Slab cache is shrinked when the system is low on memory. If the memory is contiguous wriring few bytes after the kernel stack may corrupt a task_struct of other task and it may for eg. corrupt the linked list element resuling in a crash. If it is not contiguous, then it may corrupt some other data. If the data is crucial like link or based on the value some decision is taken then it will crash. If some statistics field is overwritten it may not impact the system stability. On Thu, Sep 13, 2012 at 12:42 PM, shubham sharma <shubham20006(a)gmail.com>wrote: > Hi, > > On Thu, Sep 13, 2012 at 12:29 PM, Kshemendra KP > <kshemendra(a)suphalaam.com> wrote: > > > > In user space when you write beyond your address space (if your write > > crosses > > the page boundary alloacted to you), then process is terminated. In the > > kernel > > you are still writinng inside the kernel address space. Your write is not > > beyond > > kernel address space. > > > > Secondly you are corrupting some other data structure. The kernel stack > is > > part > > of task_struct of the running process, a kmalloc or slab allocator might > > have > > provided this memory (task_-struct). When you write beyond this if the > > write modiefies some crucial data structure that may result in hang or a > > crash. > > I did a quick calculation on this. The number of slab objects > allocated for task_struct in my system are 280 and each size of each > object is 3264 > > ---8<--- > root@shubh-VirtualBox:~# cat /proc/slabinfo | grep task_struct > task_struct 262 280 3264 10 8 : tunables 0 0 > 0 : slabdata 28 28 0 > ---8<--- > > So if my understanding is correct, in case if i define an array of > more than 280*3264 bytes then it will corrupt the task_struct of at > least one significantly important process or at least the task_struct > of the process for my terminal will get corrupted? > > > > > > > > > > > On Thu, Sep 13, 2012 at 12:15 PM, shubham sharma <shubham20006(a)gmail.com > > > > wrote: > >> > >> Hi, > >> > >> As far as i know, the size of stack allocated in the kernel space is > >> 8Kb for each process. But in case i use more than 8Kb of memory from > >> the stack then what will happen? I think that in that case the system > >> would crash because i am accessing an illegal memory area. I wrote > >> kernel module in which i defined an integer array whose size was 8000. > >> But still it did not crash my system. Why? > >> > >> The module i wrote was as follows: > >> > >> #include <linux/kernel.h> > >> #include <linux/module.h> > >> > >> int __init init_my_module(void) > >> { > >> int arr[8000]; > >> printk("%s:%d\tmodule initilized\n", __func__, __LINE__); > >> arr[1] = 1; > >> arr[4000] = 1; > >> arr[7999] = 1; > >> printk("%s:%d\tarr[1]:%d, arr[4000]:%d, arr[7999]:%d\n", > __func__, > >> __LINE__, arr[1], arr[4000], arr[7999]); > >> return 0; > >> } > >> > >> void __exit cleanup_my_module(void) > >> { > >> printk("exiting\n"); > >> return; > >> } > >> > >> module_init(init_my_module); > >> module_exit(cleanup_my_module); > >> > >> MODULE_LICENSE("GPL"); > >> > >> _______________________________________________ > >> Kernelnewbies mailing list > >> Kernelnewbies(a)kernelnewbies.org > >> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > > > >

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Re: thread notifier on x86?
by Yang Chengwei Sept. 13, 2012

Sept. 13, 2012

On Wed, Sep 12, 2012 at 05:21:04PM +0800, snail wrote: > What is this? a patch? > You mean the last mail or thread notify or the .asc attachment? My last email just asked a question, not a patch. And .asc attachment is a GPG signature. -- Thanks, Chengwei > > ------------------ Original ------------------ > From: "Yang Chengwei"; > Date: 2012 9 12 ( ) 4:37 > To: "kernelnewbies"; > Subject: thread notifier on x86? > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >

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thread notifier on x86?
by Yang Chengwei Sept. 12, 2012

Sept. 12, 2012

Hi List, I found that the thread_notifier_register() defined in arch/arm/include/asm/thread_notify.h but can't found it for x86 platform. Does there an equivalent on x86 platform? -- Thanks, Chengwei

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Clarification needed on register_netdevice_notifier behavior.
by Paraneetharan Chandrasekaran Sept. 10, 2012

Sept. 10, 2012

Hi all, I encountered a behavior of register_netdevice_notifier. Upon the registration a notifier, it calls the notifier looping through each net_device and invokes the notifier. If, at some instance, the notifier fails with error, it rollsback each of net_device it had been notified earlier. Pls take a look at the function. I am not sure whether the rolling back part is done for a reason. Does this not possibly cause undesirable behaviors in the notifier's client for the reason that it had been misinformed that all the net_devices' are unregistered? -- Regards, Paraneetharan C

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Linux Kernel Development
by Kaushal Shriyan Sept. 9, 2012

Sept. 9, 2012

Hi, I am interested to contribute to linux kernel development process. I have been working on Linux for the last ten years and have been a great fan of Linux OS since beginning. Any good references to start learning C and understand the linux kernel source code. Regards, Kaushal

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Places where the kernel modifies itself (.text) during runtime
by Andrew Case Sept. 6, 2012

Sept. 6, 2012

Hello, I am trying to determine all the ways/methods in which the kernel will modify its own .text section after the machine has booted. I am working with the latest Fedora kernel (3.5.2-3.fc17.x86_64). So far I have identified: 1) smp_locks 2) .alt_instructions - although from writing a script to parse the alt_instr structures, it seems these may not affect .text, any clarification on this would be greatly appreciated. 3) dynamic ftracing (related to mcount) 4) I also see where the paravirt instructions (PVOP_CALL4) seems to compile as absolute call instructions, but then become relative calls at runtime. I figured this one out this by diffing the disassembly of xen_cpuid_base in both memory and from the vmlinux after noticing they were not the same: # diff xen_cpuid_base-memory xen_cpuid_base-disk 20,21c20 < 0000003C E8A2E5A3FF call dword 0xffffffffffa3e5e3 < 00000041 6690 xchg ax,ax --- > 0000003C FF142580DCC181 call qword [0xffffffff81c1dc80] and the 0xffffffff81c1dc80 instruction relates to the cpuid function which ends up in paravirt code. Any clarifications or links to docs on this changing of the calls in the paravirt subsystem would be helpful. I also would like to find out if the kernel changes itself in any other way besides those that I have listed. Thanks, Andrew

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module loading issue module_layout
by Kshemendra KP Sept. 5, 2012

Sept. 5, 2012

Hi As the kernel source not available for running kernel code of an Andodiod tablet, I could not able to match module_layout address of my loadable module with the android tablet running kernel even the kernel versions are same. Is there a way to generate build environment in such a situation as the manufacture source is bit deviated from source he has posted on the net. Regards

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