I'm trying to create executables with custom program segments.
Specifically, I'm trying to make it possible to have an application
running under CMU Common Lisp that comes in a single file. There are
good and sufficient reasons IMHO for doing this. :-)

What I do is to process the CMU Lisp memory image into files that have
ELF headers. Then I use a modified linker script to have ld create an
executable from the C-code based loader .o files that also includes
these ELF files and puts them in their own program segments. Then
when the executable is run, the OS automatically restores them into
the right places in memory.

I've gotten everything up to linking the executable to work, but I've
run across a problem. The problem is that when the system loads the
file, it sets the break after the end of my last custom segment,
instead of after the end of the .data segment. The load_elf_binary
function in /usr/src/linux-XXXX/fs/binfmt_elf.c does this.

This causes several problems, the most immediate of which is that
normal C code that accesses global variables gets a segmentation
violation.

I was able to get this scheme to work happily under FreeBSD. I ran
into a similar problem as described above with FreeBSD, but was able
to work around it by putting my segments earlier in the program header
table than the .data segment, thereby fooling FreeBSD into thinking
its .data segment is the last one even though mine came later in
memory. Unfortunately Linux is too smart for this.

I'd be interested in hearing if anyone out there knows what I'm
talking about and has any comments on what I'm trying to do. I'd
especially appreciate suggestions on how to do it!

Thanks in advance,

--
Fred Gilham gilham@csl.sri.com | I wish I could get the product I
sell or service I provide to become a human right. Then people would
be forced to pay for it and use it. The only drawback is that, like
schoolteachers, I probably would wind up actually doing something else.