The ret fromintr Function
The ret_from_intr( ) function is essentially equivalent to ret_from_exception( ) :
ret from intr:
movl $0xffffe000,%ebx andl %esp,%ebx jmp ret from exception
Before invoking ret_from_exception( ) , ret_from_intr( ) loads in the ebx register the address of the current's process descriptor (see Section 3.2.2). This is necessary because the ret_from_sys_call( ) function, which can be invoked by ret_from_exception( ), expects to find that address in ebx. On the other hand, when ret_from_exception( ) starts, the ebx register has already been loaded with current's address by the exception handler (see Section 4.5.1 earlier in this chapter).
Continue reading here: The ret fromsyscall Function
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