Re: system call handling

From: Petko Manolov (petkan@dce.bg)
Date: Wed Nov 01 2000 - 07:21:48 EST


mdaljeet@in.ibm.com wrote:
>
> Hi,
>
> By looking into the structure of GDT as used by linux kernel(file
> include/asm/desc.c, kernel ver 2.4), it appears as if linux kernel does not
> use the "call gate descriptors" for system call handling. Is this correct?

You're looking at wrong place. Look at linux/arch/i386/kernel/traps.c
 
> If it is correct then how does the system calls are handled by the kernel
> (basically how does the control gets transferred to kernel)? Does the CS of
> linux kernel handles the system calls? what are the advantages of using
> this scheme?

System calls in Linux are performed as an interrupt gate (0x80). It is
not
necessary to use call gate. On i386 arch both are almost identical.

        Petkan
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