On Mon, 2003-09-29 at 10:31, Finney, Steve wrote: > What would be the downside to enabling 64 bit operations in user space on a 32 bit kernel (setting the PX bit in the status register?). The particular issue is that I want to access 64 bit-memory mapped registers, and I really need to do it as an atomic operation. I tried borrowing sibyte/64bit.h from the kernel, but I get an illegal instruction on the double ops. > The most glaring problem is you violate the rule that the 64-bit GPRs are sign-extended when running a 32-bit binary. There are all kinds of assumptions in the hardware and software that depend on the GPRs being sign-extended, and to violate this will risk some serious instability of the software. > Also, assuming this isn't a horrible idea, is there any obvious single place where "default" values in the CP0 status register get set? > > Thanks, > sf -- Michael Uhler, Chief Technology Officer MIPS Technologies, Inc. Email: uhler@mips.com Pager:uhler_p@mips.com 1225 Charleston Road Voice: (650)567-5025 FAX: (650)567-5225 Mountain View, CA 94043 Mobile: (650)868-6870 Admin: (650)567-5085
