how to switch from kernel mode to user mode

manas_sem · 01-23-2007, 01:00 AM

How to switch from kernel mode to user mode in linux (For i386)....what are the linux source files which have this switching code ?

varun_shrivastava · 01-23-2007, 01:29 AM

code can be found at
/usr/src/linux-2.6.19.2/include/asm-i386/unistd.h

manas_sem · 01-23-2007, 04:59 AM

Quote:

Originally Posted by varun_shrivastava

code can be found at
/usr/src/linux-2.6.19.2/include/asm-i386/unistd.h

the code in "include/asm-i386/unistd.h " is for system calls ,i.e.,
to go to kernel mode. i want to know the code for switching to user mode from kernel mode....

jlliagre · 01-23-2007, 09:14 AM

The code to switch from kernel to user mode is simply an assembly code RTI (return from interrupt) or equivalent, just like the code to initiate a system call is triggering some kind of interrupt with TRAP, or equivalent, depending on the architecture.