Difference between kernel logical address and kernel virtual address

Difference between kernel logical address and kernel virtual address

[Abhinav Misra]

Hi,

In LDD3 book at Ch-15 they mentioned all types of address used in the
kernel.
But wrt the book, not able to understand the difference between kernel
logical and virtual address.

Can somebody elaborate the same with some eg.

BR,Abhinav
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Difference between kernel logical address and kernel virtual address

[Anirban Roy]

Hi,

There are 2 type of virtual address.
One which needs Page table to do the convertion from VIR to PHY.
other which is offset to PHYSICAL_PAGE_OFFSET. [ this is actually also
called as logical address ]. One can directly calculate the Physical
address if Logical address is given.

virtual addess where u need a Page Table to do a conversion.

Virtual address - one way fo calculation . [ address got from vmalloc ]

         CR3 + PGD(Virtual Address ) + PMD ( virtual address )+ PTE (
Virtual address )= Physical address

Logical address below is called LOW MEM [ usually get from kmalloc ]

    Virtual address - PHYSICAL_PAGE_OFFSET = physical address.

regards
Anirban Roy



On Sat, Aug 18, 2018 at 8:18 AM, Abhinav Misra
<abhitheextremeeng@gmail.com> wrote:
> Hi,
>
> In LDD3 book at Ch-15 they mentioned all types of address used in the
> kernel.
> But wrt the book, not able to understand the difference between kernel
> logical and virtual address.
>
> Can somebody elaborate the same with some eg.
>
> BR,Abhinav
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
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>