On 09.09.2008 02:46, Kevin O'Connor wrote: > On Mon, Sep 08, 2008 at 05:38:59PM +0200, Carl-Daniel Hailfinger wrote: > >> On 08.09.2008 17:23, Stefan Reinauer wrote: >> >>> No. There is no RAM at that position. >>> >>> >> That means we either >> - have to tell gcc that the stack moved in the middle of a function or >> - redesign v3 stage1 completely. >> > > I don't think that is true. >
Well, if the stack location during CAR is in a place that will have no RAM after CAR, we must move the stack or use virtual memory addresses (fun!). > As before, I think _moving_ the stack is a bad idea. However, I don't > see any reason not to start using a new stack and discard the old. > Doing so is both simple and reliable. > > I've attached a code snippet below - it's only to illustrate the > general idea. > Yes, and it won't work because there can't be global variables in stage1 because there's no place to store them. We already had code to do that jump a few hundred revisions ago and we killed it because it was extremely difficult to follow. The stack switching is a processor dependent operation because it has to be coupled with disabling CAR. That means you have to follow calls a few levels deep just to see how the end of stage1 is executed. > That said, I think having disable_car() jump to the next stage is > probably faster and more flexible. > It is a world of pain and I'm still determined to find a way to avoid it, possibly by mapping some RAM into the CAR area through the use of virtual memory. Regards, Carl-Daniel -- http://www.hailfinger.org/ -- coreboot mailing list [email protected] http://www.coreboot.org/mailman/listinfo/coreboot
