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Re: Userland filesystems and LD_PRELOAD
- To: glibc-linux at ricardo dot ecn dot wfu dot edu
- Subject: Re: Userland filesystems and LD_PRELOAD
- From: "tjk at tksoft dot com" <tjk at tksoft dot com>
- Date: Fri, 7 Apr 2000 12:03:25 -0700 (PDT)
- Reply-To: glibc-linux at ricardo dot ecn dot wfu dot edu
There was discussion of this issue a couple of months
back. The issue was well covered at the time.
The archives are probably the best place to look.
> I am interested in userland filesystems using system call hooking and
> no kernel support (not even Coda or NFS). However in the documentation of
> one such filesystem, avfs (http://www.inf.bme.hu/~mszeredi/avfs/) there
> The 'preload' method works by "overriding" the system calls in the
> libc library, and replacing them with versions that can emulate
> virtual files.
> Since GLIBC 6.1 this "overriding" is made impossible for many
> systemcalls, and so this method cannot be used anymore. This change
> and its effects have been discussed with the GLIBC developers, and the
> result has been that it will remain so in the future.
> So how and why is this overriding made impossible?
> I think there would be software who could use this method, if hooking
> filesystem calls (just like hooking malloc, DNS and user database) would
> be possible. And not all users have root access (so they cannot use
> kernel tricks).
> - Jani