linux-kernel - Re: [PATCHv3 0/4] sys

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Date:	Mon, 19 Nov 2007 14:52:24 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Ulrich Drepper <drepper@...hat.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mingo@...e.hu, tglx@...utronix.de, torvalds@...ux-foundation.org
Subject: Re: [PATCHv3 0/4] sys_indirect system call

On Sat, 17 Nov 2007 00:31:36 -0500
Ulrich Drepper <drepper@...hat.com> wrote:


> 
>   union indirect_params i;
>   i.file_flags.flags = O_CLOEXEC;

This setup forbids future addons to file_flags

In three years, when we want to add a new indirect feature to socket() 
call, do we need a new indirect2() syscall ?

So I suggest using :

   union indirect_params i = {
      .file_flags.flags = O_CLOEXEC,
   };
fd = syscall (__NR_indirect, &r, &i, sizeof (i));

Or better, you could avoid using 'union indirect_params' in user code, and 
only use the substructs for each function.
/* define this in some include file of course */
  struct file_flags {
	int flags;
  };
/* use it */
struct file_flags ff = { .flags = O_CLOEXEC};
fd = syscall (__NR_indirect, &r, &ff, sizeof(ff));

This to avoid to copy to kernel un-necessary data, and permitting futures changes.

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