Ron? I believe that fix is really needed and the may have been the culprit of some real-world unexplained strangeness.
Regards, Carl-Daniel On 08.10.2008 03:05, Carl-Daniel Hailfinger wrote: > On 08.10.2008 02:29, Peter Stuge wrote: > >> Carl-Daniel Hailfinger wrote: >> >> >>> Fix v3 GeodeLX stack and global variable pointer corruption. >>> We had a jump instead of a call to stage1_main in geodelx/stage0.S. That >>> means all accesses to bist and init_detected were off by 8 bytes and >>> collided with accesses to the global variable pointer. >>> >>> >> Can you explain what, if any, effect this bug had or could have had >> in practice? >> >> > > Sure. > 1.) If gcc had decided to reload bist from stack after initializing the > global variable pointer, bist would have been nonzero, an indicator for > processor failure. > 2.) If gcc had decided to use the stack location of bist as a scratch > register (and it probably is free to do so as long as the contents are > restored before returning), it would have clobbered the global variable > pointer, leading to NULL pointer dereferences. > 3.) Any accesses to init_detected would have resulted in accessing 4 > bytes above the top of stack (0x87ffc-0x87fff), something the rest of > the code deliberately avoids. > > Regards, > Carl-Daniel > > -- http://www.hailfinger.org/ -- coreboot mailing list: [email protected] http://www.coreboot.org/mailman/listinfo/coreboot
