Here's the latest version of the patches: http://people.freebsd.org/~avg/zfsboot.patches.4.diff

John, the first of the patches implements the approach that we previously discussed. All arguments are passed starting at a fixed offset that should provide enough space for extending argument list. The first of the extended arguments should
be a size of the arguments (including the size field). Then it's easy to write something like: struct xargs { uint32_t size; ... }; ... struct xargs xargs; xargs.size = sizeof(xargs); ... __exec(..., xargs);

Marius, Gavin, patch 1f94d9a is my attempt of adapting your sparc64 ZFS code to my larger
changes in patch ae5a9c6. I have the patches separate to facilitate the review. They should be committed together. I have only compile-tested the sparc64/ofw part,
so it could have some grave bugs or omissions. Could you please review and/or test this patch? I will greatly appreciate any discussion, suggestions, help.

I again invite everyone else to take part in the review and testing.