Task Switching and the Stack

[Opcode]

http://www.amazon.com/exec/obidos/tg/detail/-/0201721872/102-2695169-7548952?v=glance
http://www.amazon.com/exec/obidos/tg/detail/-/0735610215/ref=pd_sim_b_3/102-2695169-7548952?%5Fencoding=UTF8&v=glance

and

http://www.windowsitlibrary.com/Content/356/04/1.html

[The Dude of Dudes]

Hi AeroAsm,

Re: Sharing Stack Parameters among different processes

When you pass Stack Params to a Windows API function, the OS copies a pointer to them in edx and then does a switch to Ring0, which has it's own stack. Each Process has a user and Kernel stack for security reasons.

As far as implementing a memory manager, paging would be a lot more work than you think. If this is only a hobby OS, and you're not worried about security I would just use Segmentation (paging disabled). This way, the address you specify with segment/offset translates directly into a physical one. ie. 0000:FFFF = FFFF physical. If paging is enabled, the processor translates segment/offset to a linear addrress and then uses a page directory (and maybe a page table depending on the page size you choose) to get the  actual physical address. YOU have to create and update these page tables/directories when memory is allocated, when page faults occur (program tries to access an address that does not have an entry in the page table), when memory is freed, when memory sits 'idle' and should be paged out to a swapfile. It would be very cool to write a Memory Manager that uses paging, though!

[thomasantony]

See the tuts at

http://www.cyberscriptorium.com/osjournal/cgi-bin/index.pl?action=listtopic&topic=2

Thomas :U