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Hardware interactions on Linux
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Does anyone here have any tips on using inb and outb for interacting with hardware on a Linux system? iopl(2) and inb(0x61) don't seem to work very nicely... Infact, inb(0x61) gives me a segfault.
PS: My reliance on this forum is starting to become embarrassing
PS: My reliance on this forum is starting to become embarrassing
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Join Date: Aug 2005
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>>Does anyone here have any tips on using inb and outb for interacting with hardware on a Linux system?
Yes -- you can not use them because the os won't let you access the ports directly.
>>Infact, inb(0x61) gives me a segfault.
Yup
Yes -- you can not use them because the os won't let you access the ports directly.
>>Infact, inb(0x61) gives me a segfault.
Yup
Last edited by Ancient Dragon; Mar 23rd, 2008 at 6:22 pm.
Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.
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Originally Posted by Ancient Dragon 
>>Does anyone here have any tips on using inb and outb for interacting with hardware on a Linux system?
Yes -- you can not use them because the os won't let you access the ports directly.
>>Infact, inb(0x61) gives me a segfault.
Yup
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Join Date: Aug 2005
Posts: 15,379
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Solved Threads: 1466
No version of MS-Windows since Win95 nor any version of *nix will allow you to use those inp and outp functions. So putting Vista back won't help you either.
Don't PM me with questions -- you might get a nasty PM in response. If you have a question then post it in one of the forums.
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Originally Posted by Ancient Dragon
No version of MS-Windows since Win95 nor any version of *nix will allow you to use those inp and outp functions. So putting Vista back won't help you either.
I realize that this thread is old, but it is still useful to correct an erroneous assertion about inb(), outb(), etc., especially given that Google drops people in here when looking for an answer to why these functions segfault, even when all the advice featured elsewhere is followed.
The truth is that these functions do in fact work, even under the most recent versions of the kernel (as of 8/11/09). However, they will not work from a user mode program unless the program is run as root (sudo...). It is also true that they will segfault if iopl(3) is not used. iopl(2) is not good enough. It is also true that the method of using ioperm() fails, apparently no matter how it is used. This may have worked in older kernels, but it now always gives a segfault. The only means of using these function seems to be calling iopl(3) first. (Ubuntu Interpid, 2.6.28-15-generic, x86_64 GNU/Linux)
The truth is that these functions do in fact work, even under the most recent versions of the kernel (as of 8/11/09). However, they will not work from a user mode program unless the program is run as root (sudo...). It is also true that they will segfault if iopl(3) is not used. iopl(2) is not good enough. It is also true that the method of using ioperm() fails, apparently no matter how it is used. This may have worked in older kernels, but it now always gives a segfault. The only means of using these function seems to be calling iopl(3) first. (Ubuntu Interpid, 2.6.28-15-generic, x86_64 GNU/Linux)
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