Hi, Roushan Ali wrote: > Thank you for your quick reply. You're welcome. Please answer at the bottom of the original message, and please do not include irrelevants parts of the mail in your answer. > who does the processor switch ? Is it done by hardware or by kernel ? The priviledge switch is done by the processor, on some event, generally an interruption in a priviledge level which is lower than the priviledge needed to run the interrupt handler. > Again, if the interrupt is generated by "int" instruction by a > user process, then how it is > handled ? Same process. The processor sees in the IDT that the interrupt handler corresponding to that interrupt needs to be executed in a priviledge level greater than the current one, and thus performs a priviledge level change, and execute the interrupt handler in the desired priviledge level. You should refer to Intel Developer Manual Volume 3 for details about this. If you speak french, you can also refer to the articles concerning the SOS operating system, available at http://sos.enix.org. Sincerly, Thomas -- Thomas Petazzoni thomas.petazzoni@xxxxxxxx -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
