Hi,
Commit fe1378a - "ARM: use r9 for gd" - broke the ABI for users of the U-Boot API on ARM. Users I am aware of are GRUB and the FreeBSD loader. Since I only spotted this on Saturday, this code is well and truly in the wild, so any users of the API will need to preserve both r8 and r9 on syscalls for the foreseeable future (which is not the end of the world).
Sometime last year I proposed a change to make the API syscall entry and exit points responsible for maintaining full procedure-call standard compliance, although the patch I provided was on the hackier side of good (and probably wrong).
I would now like to ask in a more open-ended way - is there any chance that we could solve this in a generic way, such that consumers of the API need not be aware of U-Boot internal ABI changes?
If the assumtions that the global data pointer is: a) a pointer b) writable are not both safe, then this could be achieved by arch-specific asm entry/exit points.
/ Leif