Hi Bala, I wrote few articles for newbies on my blog. One of them is on system calls. It may be useful for newbies.
http://havefunwhileulearn.blogspot.com/2010/03/systems-calls.html http://havefunwhileulearn.blogspot.com/ thanks, have fun !!! On Tue, May 11, 2010 at 7:07 AM, Balachandar <[email protected]> wrote: > Hello, > We transit from ring3 to ring0 using 'int' or the new 'syscall/sysenter' > instruction. Does that mean that the page tables and other stuffs that needs > to be modified for the kernel is automatically done by the 'int' instruction > or the interrupt handler for the 'int 0x80' will do the required stuff and > jump to the respective system call. > > > Also when returning from a system call, we again need to go to user space. > For this we need to know the instruction address in the user space to > continue the user application. Where is that address stored. Does the 'ret' > instruction automatically changes the ring from ring3 to ring0 or where/how > this ring changing mechanism takes place? > > Then, i read that changing from ring3 to ring0 is not as costly as changing > from ring0 to ring3. Why is this so?? > > > Thanks, > > Bala >
