On 10/20/17 18:52, Ard Biesheuvel wrote: > On 20 October 2017 at 17:51, Laszlo Ersek <[email protected]> wrote: >> On 10/20/17 18:39, Ard Biesheuvel wrote: >>> On 20 October 2017 at 17:37, Gao, Liming <[email protected]> wrote: >>>> Ard: >>>> This case is to share the same value between PeiCore and SecCore. I also >>>> think it will be better to define one fixed PCD in MdeModulePkg.dec for >>>> this value. Could you submit bugzillar to catch this issue first? >>>> >>> >>> Certainly! >> >> Would it be possible to define the PCD as UINT32, and task 64-bit SEC >> (and PEI_CORE) code to first construct the wider value manually (in a >> register or otherwise)? >> >> Just thinking out loud. >> > > Could you think the reasoning behind that out loud as well?
Haha, good stab :) Sure. In your patch you have: +#define INIT_CAR_VALUE 0x5AA55AA55AA55AA5 for 64-bit, and +#define INIT_CAR_VALUE 0x5AA55AA5 for 32-bit. Both 64-bit assembly code in SEC, and 64-bit C-code in the PEI_CORE, can easily compose the large value from the small value, starting from FixedPcdGet32(). The alternatives are: - asking the 32-bit assembly code to truncate the 64-bit constant -- it won't compile, - defining *two* FixedAtBuild PCDs, one for 32-bit, another for 64-bit SEC -- an idea probably not universally liked. ... When I originally started writing my previous email, I even thought about introducing the PCD as UINT16 :) But then I realized, if any platform lacks *some* 32-bit mode when it sets up the stack in assembly, for C-language entry, then the platform won't be supported by edk2. Thanks Laszlo _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
