Re: [Adeos-main] adeos_enter/exit_syscall

[Philippe Gerum <rpm@xenomai.org>]

On Thu, 2004-08-05 at 00:16, aaron durbin wrote:
> I have a question concerning the adeos_enter_syscall routine.  Is there
> normally event monitors for syscall entry (SYSCALL_PROLOGUE)? 

Not normally when no domain is loaded. The Linux domain by itself does
not intercept (its own) syscalls. But other domains might want this
(RTAI does).

>  If so and
> handle_event returns non-zero then one automatically restores the registers
> and returns w/o calling the system call.  Doesn't this destroy the call?
> 

It prevents its execution by the Linux kernel actually. Think of a more
prioritary (in the sense higher in the pipeline than Linux) that wants
to intercept some specific syscalls issued by regular Linux apps, and
provides a replacement for them. In such a case, you might not want the
original syscall to be handled by Linux too; so you make sure that it is
not propagated to Linux -- this translates in having handle_event return
non-zero (because adeos_propagate_event is not called for the said
syscall in the upper domain handler).

> -Aaron
> 
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-- 

Philippe.