How can I set CPL=0 for WBINVD in NASM (Linux)

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yousafsajjad
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How can I set CPL=0 for WBINVD in NASM (Linux)

Post by yousafsajjad »

Hi,
I just started working on nasm 2 weeks ago and I am stuck at something (of course). Can anyone please tell me how can I set CPL=0 so that I can use WBINVD
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Brendan
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Re: How can I set CPL=0 for WBINVD in NASM (Linux)

Post by Brendan »

Hi,
yousafsajjad wrote:I just started working on nasm 2 weeks ago and I am stuck at something (of course). Can anyone please tell me how can I set CPL=0 so that I can use WBINVD
You can't, unless you're writing kernel code or a device driver (which runs as part of the kernel as a kernel module).

This basically means that normal processes can't screw everything up when the programmer makes the mistake of thinking that they want to use something like WBINVD... ;-)

Note: the CLFLUSH instruction may be what you actually want...


Cheers,

Brendan
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yousafsajjad
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Re: How can I set CPL=0 for WBINVD in NASM (Linux)

Post by yousafsajjad »

Yeah it seems like it would work but in this description it says something like "Invalidates the cache line that contains the linear address specified with the source operand from all levels of the processor cache hierarchy". I am not much sure what that suppose to mean
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Combuster
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Re: How can I set CPL=0 for WBINVD in NASM (Linux)

Post by Combuster »

The linear address is the address passed into the paging system. It's the same as the virtual address unless you use segmentation (which most people don't).
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