On Sun, Sep 09, 2012 at 03:30:08PM -0400, Rich Felker wrote: > Hi all, > The kernel syscall entry/exit code seems to always save and restore > r25. Is this stable/documented behavior I can rely on? If there's a > reason it _needs_ to be preserved, knowing that would help convince me > it's safe to assume it will always be done. The intended usage is to > be able to make syscalls (where the syscall # is not a constant that > could be loaded with lwi) without a stack frame, as in "move $2,$25 ; > syscall". Since there is no place where the syscall interface is documented other than in the code itself, I've written a new wiki article http://www.linux-mips.org/wiki/Syscall as start. It's still lacking on the more obscure points but it at least should have have answered your question, had it already existed when you asked. Ralf
