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SubjectRe: Java in Linux kernel: some issues
Date
: 
: Why not simply load /usr/sbin/unknown-exec and have this user level
: program determine what to do with the file, checking magic numbers and
: running the appropriate interpreter. I would even allow you to run file
: on whatever you are trying to exec and handle that to postcript or
: whatever if that's what you want ;)
:
: If /usr/sbin/unknown-exec doesn't exist you have normal pre-java-patch
: behavior, but if it is there it receives the arguments to exec as its
: arguments. I imagine it doing something along these lines:
:
: open argv[0]
: check magic numbers
: if (is-java) exec(java,args...)
: else if (is-foo-p-code) exec(foo,args...)
: .
: .
: .
: else return "cannot execute binary file"
:
Maybe I am missing someting, but:

0) I will suggest /sbin/unknown-exec (which can be symbolic link
to /usr/sbin).

1) argv[0] can have no relation
to the executable (i.e. open (argv[0],...) can fail). So for example
you will not able to have a java-interpreted login shell :-).

2) After you exec() /usr/sbin/unknown-exec, you are not allowed
to return "cannot execute binary file" (ENOEXEC, I think), since
there is no longer a text which has called exec(). So you have
no valid return address.

-Yenya

--
Jan "Yenya" Kasprzak | mailto:kas@muni.cz | http://www.fi.muni.cz/~kas/
[[[[ Student of Informatics, Faculty of Informatics, Masaryk University ]]]]
[[[[ Czech Linux Homepage: http://www.fi.muni.cz/~kas/linux/ ]]]]
``Hoping the problem magically goes away by ignoring it is the "microsoft
approach to programming" and should never be allowed.'' --Linus Torvalds



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