hi, segmantation cannot disable,as specified in intel manuals,although we can make it off by giving base address 0x00000000, and this is what linux kernel does ,but not write from boot ,and thus as specified in mail about kernel physical memory allocation at boot, it has to specified some base address in descriptors so to generate LA greater than 0xc0000000 for that base address in descriptors are 0xc0000000 then after paging is on segmenatation is off i want to inquire this is true or not thanks Prasanna V. Wakhare --- Rithin K Shetty <rkshetty@unity.ncsu.edu> wrote: > There is no segmentation in Linux though there > is a provision for > it. So for all > 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 > >> > >> > >>-- > >>Kernelnewbies: Help each other learn about the > Linux > >>kernel. > >>Archive: > >>http://mail.nl.linux.org/kernelnewbies/ > >>FAQ: http://kernelnewbies.org/faq/ > >> > >> > >> > > > > > >__________________________________ > >Do you Yahoo!? > >Yahoo! Tax Center - File online by April 15th > >http://taxes.yahoo.com/filing.html > > > >-- > >Kernelnewbies: Help each other learn about the > Linux kernel. > >Archive: > http://mail.nl.linux.org/kernelnewbies/ > >FAQ: http://kernelnewbies.org/faq/ > > > > > > > > > -- > Rithin K Shetty > Graduate Student (Computer Science) > North Carolina State University > Raleigh, NC > Ph: (919)834-6782 > Homepage: http://www4.ncsu.edu/~rkshetty > > > > -- > Kernelnewbies: Help each other learn about the Linux > kernel. > Archive: > http://mail.nl.linux.org/kernelnewbies/ > FAQ: http://kernelnewbies.org/faq/ > __________________________________ Do you Yahoo!? Yahoo! Tax Center - File online by April 15th http://taxes.yahoo.com/filing.html -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
