> In short, does anyone know full sequence of steps that take place when > an interrupt is raised either in kernel or in user mode? Which > functions get called, and, where are they stored in the source code? > Hi Lukas, that's what I found in the 2.4 Kernel Sources, Linux Kernel Internals, Understanding the Linux Kernel about interrupt handling on ia32: All interrupt handlers perform the same 4 basic actions: 1. Save the IRQ value and the registers contents in the Kernel Mode stack: Code is stored in 'arch/i386/kernel/i8259.c': 27 /* 28 * Common place to define all x86 IRQ vectors 29 * 30 * This builds up the IRQ handler stubs using some ugly macros in irq.h 31 * 32 * These macros create the low-level assembly IRQ routines that save 33 * register context and call do_IRQ(). do_IRQ() then does all the 34 * operations that are needed to keep the AT (or SMP IOAPIC) 35 * interrupt-controller happy. 36 */ Saving registers is the first task of the interrupt handler. The interrupt handler for IRQn is named IRQn_interrupt, its address is included in the interrupt gate stored in the proper IDT entry. The same BUILD_IRQ macro is duplicated 16 times, once for each IRQ number, so you'll get 16 different interrupt handler entry points. Each BUILD_IRQ expands to the following assembly language fragment: IRQn_interrupt: pushl $n-256 jmp common_interrupt This saves on the stack the IRQ number associated with the interrupt minus 256 (Subtracting 256 from an IRQ number yields a negative number. Positive numbers are reserved to identify system calls); the same code for all interrupt handlers can then be executed while referring to this number. The common code can be found in the BUILD_COMMON_IRQ macro, which expands to the following assembly language fragment: common_interrupt: SAVE_ALL call do_IRQ jmp ret_from_intr ________________________________________________________________________ ____ 2. Send an acknowledgment to the PIC that is servicing the IRQ line, thus allowing it to issue further interrupts. Code is stored in ' arch/i386/kernel/irq.c': That's not clear to me ________________________________________________________________________ 3. Execute the interrupt service routines (ISRs) associated with all the devices that share the IRQ. Code is stored in ' arch/i386/kernel/irq.c': 558 /* 559 * do_IRQ handles all normal device IRQ's (the special 560 * SMP cross-CPU interrupts have their own specific 561 * handlers). 562 */ ________________________________________________________________________ __ 4. Terminate by jumping to the ret_from_intr( ) address. Code is stored in ' arch/i386/kernel/entry.S': ... 248 ENTRY(ret_from_intr) 249 GET_CURRENT(%ebx) 250 ret_from_exception: 251 movl EFLAGS(%esp),%eax # mix EFLAGS and CS 252 movb CS(%esp),%al 253 testl $(VM_MASK | 3),%eax ... Hope this helps, Regards, Thomas -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
