On Sunday 03 Apr 2011 2:22:19 am James Light wrote: > On Sat, Apr 02, 2011 at 11:18:19PM +0530, mindentropy wrote: > > On Saturday 02 Apr 2011 9:55:35 pm James Light wrote: > > > To put the physical address into cr3 later. > > > $swapper_pg_dir is not the PHYSICAL address of the PGD. > > > > Correct me if I am wrong but a mov $foo,%eax would move the address of > > foo variable to eax right? Or is there a macro somewhere where they are > > adding PAGE_OFFSET to the address so that the $swapper_pg_dir - > > __PAGE_OFFSET justifies? > > Right, but it uses the logical address of foo which n the case of > swapper_pg_dir must be converted to a > physical address. When paging is not enabled, linear addresses are > interpreted as physical addressess. So it has to get this logical address > only one step farther into a linear address. > > So, this "swapper_pg_dir" is a symbol in a section of code. That section of > code has an associated segment and this symbol lives at a particular > location in that section and thus in that segment, and that particular > location, relative to the beginning of the section is it's offset. Combine > those two and > you have the logical address of swapper_pg_dir. > Ok I think I got where the addresses are assigned. Its in the linker script vmlinux.lds. I got the precise answer here http://tldp.org/HOWTO/Linux-i386- Boot-Code-HOWTO/kernel_head.html I had completely forgotten about linker scripts. I was getting confused as the ENTRY(swapper_pg_dir) has ORG 0x10000 as the offset. Was struggling to find where the .text address was. _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
