May 2014 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Customization of Linux kernel to port on a embedded system
by Saurabh Jain May 31, 2014

May 31, 2014

Hello every one ! I am new to embedded systems. I want to learn how to customize Linux kernel source code to make it portable on a ARM based board (like raspberry pi) . As i said m new in this field , so any guide / link from where i should start to learn about it?

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How to customize Linux Kernel for a ARM board ( embedded system)
by Saurabh Jain May 31, 2014

May 31, 2014

Hello every one ! I have posted a question already , but i think i did not formatted my problem exactly . So i am posting it again . I am new to Embedded system field . We all know that now a days Linux kernel is being used in most of the Embedded system . I want a book or link , so that i can understand and can learn how and where we can make changes in the Linux kernel to make it compatible for a Embedded board (like any ARM board ). I did not know anything about it , i want a fresh knowledge and start . So please help me from where i should start , i need your experience about some good book , and please tell me a good book which i should prefer . Thank You!

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Completely open sourced ARM board
by Saurabh Jain May 30, 2014

May 30, 2014

Hello every one ! I am learning how to customize Linux kernel to make it portable on embedded systems. To test my customized kernel , i want a completely open sourced ARM board . I listened about Raspberry pi but it's firmware "start.elf" is not open source. So can anybody tell me the name of the ARM board which is completely open sourced ? And can there exists any such board whose ROM/AVRAM contents can also be replaced ? Thank you !

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how to benchmark a malloc implementation
by Aaditya Gavandalkar May 30, 2014

May 30, 2014

Hello, I am working on a version of ptmalloc3 and trying to make changes to it, in order to make it more suitable for my application. But i want to evaluate its performance against default implementation. So please suggest some ways using which benchmarking can be performed. thank you. Kind regards, Aaditya Gavandalkar

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about consistent_init function
by Chan Kim May 30, 2014

May 30, 2014

Hello, In http://lxr.free-electrons.com/source/arch/arm/mm/dma-mapping.c?v=3.3#L162, in line 208, Could anybody kindly explain why it increases the variable 'base' by PMD_SIZE? Is the consistent memory chunck initialized by PMD_SIZE? It seems to me the consistent_init allocates only the skeleton of the page table (with final pte entries empty) for the consistent memory region. Then when is the actual pte entries filled? In ARM how does this work? I'm trying to allocate memory for dma (uncached region) for our sparc processor using dma_alloc_writecombine which is from arm. Is this a correct approach? (dma_alloc_coherent seems to be for smaller size), I need almost 2MB buffer. Any help or suggestion will be appreciated. Thanks, Chan

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Need help related to Eudyptula Task 08
by Rahul Garg May 30, 2014

May 30, 2014

Hi All, I am stuck at Task 08. Problem is I have to send files and changes using send-email utility. As per my understanding, whenever we need to add a new file to git, we use git add command, it creates a patch for it and then we will send it. But when I did it, I got response saying that you should not send new file as a patch, So I want to know how can I send this new file then ? And if I directly attach this file, how will I link my further 2 mails to this original mail ? Regards Rahul

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Extract the payload of the packet from SKB buffer at Layer-2
by Ramana Reddy May 29, 2014

May 29, 2014

Hi All, Is there any mechanism to get the payload area after extracting the transport header from skb at layer-2. I think we can do this with the combination of skb_full and skb_reset_mac_header, skb_reset_network_header, and skb_reset_transport_header functions. My main interest is extract the payload from the skb and reset the all the headers so that the skb remains unchanged. Help in this regards is highly appreciated. Thanks, Ramana.

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how to detect kernel memory overflow ?
by RS May 29, 2014

May 29, 2014

Hello How to detect the kernel memory overflow errors? There are many tools to detect the user mode program memory problems, like the memcheck(Valgrind), is there any tools for the kernel ? The Kmemcheck detects some uses of uninitialized memory, can not detect the overflow errors. Thanks, HeChuan

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mmap() only version of ptmalloc3 and how to benchmark it
by Aaditya Gavandalkar May 28, 2014

May 28, 2014

Hello, I am a undergraduate student currently and I am working on a version of ptmalloc3 that uses only mmap() system call to satisfy all types of allocation requests and use of brk() is completely removed/avoided as college project. The memory allocated using mmap() is also backed by a disk file (which helps to reduce swap-in + swap-out time of process but adds a extra overhead). Considering the case where only a single resource intensive and critical application is using this version of ptmalloc for allocation purposes. Rest of the programs are using default implementation. Then in this case this will be saving swap-in + swap-out time but will add disk file read+write overheads and also sync overhead. So considering all these points, is it of any advantage to save on swapping time while having all those extra overheads. Also could you please point out how I can benchmark it and test how my version is working against the original one. Thank you. Kind regards, Aaditya Gavandalkar

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"killed" message!
by Nada Saif May 28, 2014

May 28, 2014

Hi, I created a system call that deals with files - when I try to test the system call . I got a "killed " message. What this means? Thanks, Nada

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