practical pursposes Linear and virtual addresses are the same. As far as Virtual to
physical is concerned it works as you mentioned : (0xc0000000 + PA) = VA. The
kernel is placed in the physical memory starting from the first mega byte(0x00100000),
so the VA of the first kernel code is 0xc0100000.
Thanks, Rithin.
prasanna wakhare wrote:
hi,
this part of the kernel is tricky,i'm confused,abt
linux kernel,
as VA=>LA as flat memory mode
and LA is then mapped to PA by paging
but why to do one to one mapping,
might be coz,before paging is turned on every VA generated by processor are same as linear address,and to PA
say byte at PA x is actually at processor generated
address 0xc0000000+x,
but when segmenattion is turned off(base address 0)
and paging turned on,
to maintain the mapping of (0xc0000000 +y)=> 0+y here 1-1 map=> 0+y
processor va due to segmentaion PA
otherwise would be
0xc0000000+y
but for first few LA=>PA first few page table entries must 1 to 1 map with PA
I.E LA=>PA
or i'm totally confused
--- Bora Þahin <borasahin@netone.com.tr> wrote:
Hello Rithin,
Saturday, April 10, 2004, 2:59:07 PM, you wrote:
RKS> Hi, RKS> I have question regarding the physical memory allocation for the RKS> kernel code and data. During the initialization of the system, the RKS> kernel page tables are created and a one to one mapping of the linear RKS> addresses starting from (0xC0000000)to the physical addresses(starting RKS> at 0x00000000, correct me if I'm wrong)is created. My question is will RKS> these pages always be in memory ?
If i understand you correctly, yes... Say kernel is 2 MB. Then it begins 0xC010_0000 and ends 0xC030_0000. It maps to physical 0x0010_0000 - 0x0030_0000 addr range. This pages always in mem, never swapped...
-- Bora Sahin borasahin.port5.com
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