Subject: Re: New idea on ELF prebinding
To: Bang Jun-Young <>
From: Luke Mewburn <>
List: tech-userlevel
Date: 11/22/2002 18:38:01
On Fri, Nov 22, 2002 at 04:27:30PM +0900, Bang Jun-Young wrote:
  | >   | - Every binary, including executable and shared object, has .csum
  | >   |   section inserted by ld(1) at compile time. It is 32-bit long and
  | >   |   used for storing checksum (CRC32) of the binary.
  | > 
  | > i'd prefer md5 or sha1 as a hash.
  | The basic idea is to use the checksum as a filename to lookup. For
  | example, if the checksum is FB369ADB, then ld.elf_so(1) tries to
  | find a file of the same name in /usr/libdata/reloc. So you don't
  | have to worry about moving binaries.

i'd prefer the preload stuff is tied to the csum, dev_t and ino_t of
the file, so that the cache is invalidated if the file moves...

  | I thought about MD5 as well, but it is too long to be used as a file
  | name. Probably a better method would be needed...

as jason mentioned, there's a performance issue with md5 as well.

  | >   |   If needed, elfreld(1) daemon regularly check if they are
  | >   |   still valid, and removes invalid files. Or you can remove
  | >   |   all of them, and ld.elf_so(1) will perform the same job
  | >   |   again for each binary it loads.
  | >
  | > do we even need an elfreld daemon?  does it matter if the cache grows.
  | So that someone won't complain about ever-growing cache directory. ;-)

oh, /var/db/reloc/ is a *directory* ...  i missed that in my first
reading of the idea.