Thanks for answering so promptly. Some more information...
We are using the mpc8xx-2.2.13 Kernel (Dan's) with the FPU and Memory Management patches. We are using glibc 2.1 (compiled ourselves) for our application (linking statically) and libc 1.99 for everything else. Our system is stand-alone, running from flash, although at times we have the ethernet connected for mounting our development box's drive. We have multiple boards running. Some boards do seem more likely than others to panic. This is a very intermittent problem. I have a special application program that will run automatically at bootup and shut the processor power down for a minute, powerup, and then have the reboot sequence starts over again. I've seen it run 21 hours like this before a panic occurs. I have another system (2 boards that communicate every 4 minutes using AX.25) that ran all weekend but I did not reboot the board--just kept the application running--with no panic problem. This seems to be a boot related problem, although we have observed that usually the panic occurs on running a program from bash; although, one time I saw it panic in the init process (exec from main.c). The panic usually if not always occurs on the FIRST run of a program. If it works once, it will not panic on this particular bootup ever. Wolfgang's suggestion makes a lot of sense to me: "Usually this means that you are running on an old mask revision of the CPU, which still has the (in)famous "Cache Corruption When Writing to Special Registers" bug." I read in the MPC823 user's manual that accessing some off-core SFR's can cause the software emulation exception with PR=0 if there is a bus error (why should there be a bus error?? this isn't answered), which would cause the particular message of "Kernel Mode Software FPU Emulation". We will try turning off the cache as a test. Lucinda Schafer Adaptive Micro-Ware, Inc. Staff Software Engineer -----Original Message----- From: Dan Malek [mailto:[EMAIL PROTECTED] Sent: Monday, June 12, 2000 2:44 PM To: Lucinda Schafer Cc: linuxppc-embedded at lists.linuxppc.org; cort at cs.nmt.edu; paulus at cs.anu.edu.au Subject: Re: Software Emulation Kernel Panic Lucinda Schafer wrote: > On our MPC823-based custom boards, we are experiencing the "Kernel Mode > Software FPU Emulation" panic This has little to do with floating point. Nearly all instructions the processor can't decode are vectored to this function. It assumes the primary reason you are here is to emulate floating point instructions. If the function can't decode the instruction as a floating point operation, it is really something the processor can't execute, so the panic message spews forth. > Could you shed some light on some situations where this may happen? This can be either a software or hardware bug. If it is a software bug, just unravel the stack backtrace and debug it. It could be a trashed stack frame, resulting in a bad function return address, or some indirect function call that was not properly computed. It could also happen because of a hardware bug while fetching instructions from memory. Verify the NIP instruction that it tried to decode is what is really supposed to be at that location in memory. This is a typical failure when the UPM is not programmed correctly. Since this is a custom board, have you verified all memory cycles? Disable the cache and try again, you will probably get a different result. -- Dan ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
