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Help needed: mmap and physical memory access
Posted by manaav
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Help needed: mmap and physical memory access March 24, 2009 09:46AM |
Hi All,
For some testing purpose I need to use mmap having file descriptor received out of /dev/mem. But, I have no idea about what offset I should use. It would certainly be very helpful if someone could suggest as what offset should I use. The required (desired) length is 1MB.
And, system I am using is FC9.
Regards,
Manav Swargiary
For some testing purpose I need to use mmap having file descriptor received out of /dev/mem. But, I have no idea about what offset I should use. It would certainly be very helpful if someone could suggest as what offset should I use. The required (desired) length is 1MB.
And, system I am using is FC9.
Regards,
Manav Swargiary
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Re: Help needed: mmap and physical memory access September 09, 2009 10:22PM |
How about 1. Use a memory area (say void *buf, either a stack buffer or on-heap one) of your process; 2. Find out its physical address (a tiny kernel driver module might be needed); 3. Use the physical address as the offset when mapping.
Read/write this physical address is safe absolutely because it belong to you.
It is that what we had done, please visit [effogpled.googlecode.com] for
1. The driver module AddrMap: SVN/devel/effo/codebase/kmod
2. Find out the physical address of a user space buffer of the process and do write/read/verify test: SVN/devel/effo/codebase/applets/test/addrmap
Notes: 1. Filter of /dev/mem accessing should be off in kernel configuration; 2. You may need to lock (mlock) the memory area in the RAM to prevent it from being swapped out.
Hope it helpful
-The Effo Staff
Read/write this physical address is safe absolutely because it belong to you.
It is that what we had done, please visit [effogpled.googlecode.com] for
1. The driver module AddrMap: SVN/devel/effo/codebase/kmod
2. Find out the physical address of a user space buffer of the process and do write/read/verify test: SVN/devel/effo/codebase/applets/test/addrmap
Notes: 1. Filter of /dev/mem accessing should be off in kernel configuration; 2. You may need to lock (mlock) the memory area in the RAM to prevent it from being swapped out.
Hope it helpful
-The Effo Staff
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Re: Help needed: mmap and physical memory access October 14, 2009 11:07PM |
Registered: 11 months ago Posts: 7 |
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Re: Help needed: mmap and physical memory access October 15, 2009 10:16PM |
Please visit
kmod folder and the AddrMap driver, [code.google.com]
user space usage, the mem_addrmap folder, [code.google.com]
and the concept verification and test code, the addrmap folder, [code.google.com].
If you download a Effo GPLed Framework sample, named gpled_framework.samples.tar.bz2, then you could run "make" to build and run the test.
Reference document, named EffoGPLedRef.pdf, concepts document EffoDesign_MemTest.pdf.
You could download samples and documents from [code.google.com].
-Pat
The Effo Staff
Effo Project, [effo.sourceforge.net]
kmod folder and the AddrMap driver, [code.google.com]
user space usage, the mem_addrmap folder, [code.google.com]
and the concept verification and test code, the addrmap folder, [code.google.com].
If you download a Effo GPLed Framework sample, named gpled_framework.samples.tar.bz2, then you could run "make" to build and run the test.
Reference document, named EffoGPLedRef.pdf, concepts document EffoDesign_MemTest.pdf.
You could download samples and documents from [code.google.com].
-Pat
The Effo Staff
Effo Project, [effo.sourceforge.net]
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Re: Help needed: mmap and physical memory access December 10, 2009 12:41AM |