Date: Wed, 22 Apr 2009 21:58:31 -0500 From: Nathan Whitehorn <nwhitehorn@freebsd.org> To: Andreas Tobler <andreast-list@fgznet.ch> Cc: freebsd-ppc@freebsd.org Subject: Re: Fatal kernel trap during boot 8.0-CURRENT Message-ID: <49EFD957.2010605@freebsd.org> In-Reply-To: <49E76291.4000002@fgznet.ch> References: <D350790D-5AC3-4AD5-821E-6431ADAA0A2A@fahrners.de> <49E76291.4000002@fgznet.ch>
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Andreas Tobler wrote: > Jochen Fahrner wrote: >> Hi, >> after a fews days of power off I wanted to boot the 8.0 kernel I >> installed last week on my iMac G3. >> I got a kernel trap after starting sc0 driver: >> >> ======================= >> sc0: Unknown <16 virtual consoles, flags=0x300> >> Timecounter "decrementer" frequency 24960000 Hz quality 0 >> Timecounters tick every 10.000 msec >> >> fatal kernel trap: >> exception = 0x7 (program) >> srr0 = 0x509168 >> srr1 = 0x83032 >> lr = 0x4f9788 >> curthread = 0x633a30 >> pid = 0, comm=swapper >> thread pid 0 tid 100000 >> Stopped at 0x509168 >> illegal instruction 7c0049ce >> ========================== >> >> I could repeat this several times. >> Then I booted my old 7.1 kernel without problems. >> After that I also could boot 8.0 again. > > Fyi, I experience the same on my imac G3. And I use the same procedure > to get back to -CURRENT. This is related to Altivec support. 7c0049ce is stvx v0,r0,r9, which is the first executed Altivec instruction in save_vec(), and the faulting address is close to where to save_vec() ends up in my kernel. save_vec() can only be called if the process is marked with PCB_VEC. I have no idea how that ends up happening, and I can't duplicate the problem on my G3. One option would be to insert a panic() or a kdb_backtrace() into enable_vec(), which might at least tell us where it is getting called from... The only thing I can think of is that the 750 is taking a performance monitor exception and falling through to the EXC_VEC handler, which will try to turn on Altivec. The way Altivec support works is that only Altivec-aware processors should ever fault to EXC_VEC, in which case we should be fine setting PCB_VEC on the process. Very confusing... -Nathanhome | help
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