On Thu, Sep 11, 2008 at 08:42:44AM -0700, ron minnich wrote: [...] > Given these rules, here is how disable_car can work on core 2 and > others that don't back CAR with RAM. > 1. compute a new stack area. The minimum size is the size of the > stack. Note that stack contains sysinfo (at its base). > It is acceptable to copy only the "active" stack; it is acceptable > to copy all of CAR. It is acceptable > to copy more data than the "active" stack and less data than all of > CAR. This flexibility makes > writing disable_car easier. > 2. copy the data to the new stack area in ram > 3. disable CAR > 4. adjust the return address on stack if needed (unlikely, since we're > executing from ROM, but who knows what the future may bring) > and then return.
Thanks Ron. This write up was very useful to me. Your proposal involves moving the stack with additional documentation to help prevent misuses. The idea of moving a stack makes my head hurt though - for example, it isn't immediately clear to me if gcc might take a pointer to a stack variable in some situations. I'm wondering what you felt was lacking in your previous idea of passing a new stack location/execution address into disable_car()? Also, in an earlier email I suggested the possibility of switching the stack before calling disable_car: http://www.coreboot.org/pipermail/coreboot/2008-September/038611.html do you know why that would not work? Thanks, -Kevin -- coreboot mailing list: [email protected] http://www.coreboot.org/mailman/listinfo/coreboot
