use objcopy to patch or poke an elf file?

[John Breitenbach]

Hi,
  I've got a program which contains a const static variable which is 
intended to contain a checksum.

After linking, I process that file with a program and then I would like 
to overwrite the contents of that
variable with the actual checksum.  I was hoping that objcopy would give 
me a method to poke that in but
I don't see it.  I could place that variable in its own section, then 
all I would have to do is something similar
to the --add-section sect=filename.  But what I really need is 
"--replace-section-contents sect=filename"

Two methods I can think of are:
   1) declare the variable in its own file and own section.  Construct a 
file containing the correct checksum
      then compile it and relink the executable.

  2) process the file, searching for and replacing the initialized with 
the computed checksum.

Is there a better idea out there?
John