Hi ,
For x86 architechture
(RAM) SEGMENTATION( Mandatory )
Physical ------------------------------> Linear
Address Address
PAGING(Optional -Enabled For Linux)
Linear ------------------------------------>
Virtual
Address
Address
Now ,there are two cases :
<1> If only Segmentation is enabled , and there
is no Paging .
Terminology -> Logical Address == Linear Address
<2> If Segmentation & Paging ,both exist .
Terminology -> Logical Address == Virtual Address
The Translation of the Addresses is done by
the Memory Management Unit in the Processor .
This is done automatically . But, the Page tables (
for
Paging ) and LDT/GDT ( for Segmentation ) need to
be appropriately initialized .
Hope this clears your doubts .Please correct
me if I'am wrong .
Regards!
--- Kirk True <ktrue@movaris.com> wrote: > Hi all,
>
> I'm really confused about the differences between
> the logical, linear, and
> virtual addresses on x86 systems after reading
> "Linux Core Kernel
> Commentary" and "Understanding the Linux Kernel".
>
> "Linux Core Kernel Commentary" states that the
> logical address space is also
> known as the virtual address space (logical ==
> virtual). It then says that
> on x86 that the logical and linear address space is
> the same (logical ==
> linear). Thus virtual, linear, and logical addresses
> are all the same,
> right? What's the point of having three names for
> the same thing?
>
> "Understanding the Linux Kernel" states in chapter 1
> that a virtual address
> is the same as a logical address (logical ==
> virtual), but in chapter 2 it
> states that a linear address is also known as a
> virtual address (linear ==
> virtual).
>
> I'm also confused about who actually translates from
> the logical address to
> the linear address to the virtual address to the
> physical address. Does the
> CPU (and associated hardware) do this magically
> behind the scenes? Does the
> OS take care of the conversions? Does the OS set up
> the mapping that the CPU
> uses or vice-versa? Where in the kernel does this
> transformation take place?
>
> Lots of questions and ambiguous and seemingly
> inconsistent answers. Please
> help!
>
> Thanks,
> Kirk
>
> --
> Kernelnewbies: Help each other learn about the Linux
> kernel.
> Archive:
> http://mail.nl.linux.org/kernelnewbies/
> FAQ: http://kernelnewbies.org/faq/
>
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