Re: Preliminary ELF prebinding patches available.

Brad Knowles wrote:
> At 10:31 PM -0700 2003/05/25, Marcel Moolenaar wrote:
> >  Hence, prebind information is decoupled from the executable. One
> >  of the more obvious complexities is the fact that the naming scheme
> >  is such that multiple binaries can have the same prebind cache file.
> >  The collision is currently not handled, other than making sure that
> >  the prebind information for binary A1 is not used by binary A2. But
> >  other complexities exist. What if by some unlucky draw of faith you
> >  have two totally independent executables that both resolve to the
> >  same prebind file *and* happen to have the same build ID? You have
> >  an undetectable collision.
> 
>         How painful would it be to do a checksum (ideally, MD5 hash) of
> the binary in question?  Or at least recording path to the binary
> within the prebind cache file?  Or maybe file metadata like the
> ownership, permissions, and date/time stamp?

A hash is a bad idea.  To check it, you would have to read
all the pages, and lose your speed win from the pre-binding.
8-).

Much better to use the inode number, device ID, and timestamp
(the first two to verify a matching file, the last to reset
the cache, should the file change).

Personally, I prefer putting the information in an ELF section
in the file itself; you're going to have a hell of a time with
removing stale cache entries, without any tight coupling of
what is, essentially, metadata.

-- Terry