Subject: Re: #ifdef in syscalls.master considered harmful
To: Matt Thomas <>
From: Steven M. Bellovin <>
List: tech-kern
Date: 08/31/2006 14:36:50
On Thu, 31 Aug 2006 09:11:35 -0700, Matt Thomas <>

> The fallout of my making PTRACE conditional has made me realize that
> #ifdefs in syscalls.master are never the right thing.  They just overly
> complicate the code.  The only downside to no #ifdefs in syscall.master
> is that *sysent.c always has a call to optional syscall.  This can
> be resolved by including a include files which will #define the syscall
> to sys_nosys.  Or the actual syscall could always return ENOSYS.
Agreed, strongly.  (I'm more and more inclined to the notion that almost
all #ifdefs are evil, especially in the kernel, but that's a rant for
another time.)

		--Steven M. Bellovin,