Hi, On Fri, Dec 9, 2011 at 10:15 AM, Rafal Jaworowski <r...@semihalf.com> wrote: > > On 2011-12-08, at 17:53, Nathan Whitehorn wrote: > >> On 12/08/11 03:01, Piotr Nowak wrote: >>> We're working on PowerPC target using GCC 4.2.1 >>> and FreeBSD 6.1. It seems like we have similar >>> problem. In our case GCC sometimes very unfortunately >>> optimize code with -fno-omit-frame-pointer. >>> >>> Example shown below covers file sys/powerc/booke/pmap.c >>> and function pmap_kenter. If we disassemble kernel binary >>> we have: >>> >>> c019998c: 4b ec 6a ed bl c0060478<_mtx_unlock_spin_flags> >>> c0199990: 81 61 00 00 lwz r11,0(r1) >>> c0199994: 80 0b 00 04 lwz r0,4(r11) >>> c0199998: 7d 61 5b 78 mr r1,r11 >>> c019999c: 82 ab ff d4 lwz r21,-44(r11) >>> c01999a0: 7c 08 03 a6 mtlr r0 >>> c01999a4: 82 cb ff d8 lwz r22,-40(r11) >>> c01999a8: 82 eb ff dc lwz r23,-36(r11) >>> c01999ac: 83 0b ff e0 lwz r24,-32(r11) >>> c01999b0: 83 2b ff e4 lwz r25,-28(r11) >>> c01999b4: 83 4b ff e8 lwz r26,-24(r11) >>> c01999b8: 83 6b ff ec lwz r27,-20(r11) >>> >>> As you can see stack pointer on R1 is being updated >>> before stashed data were pulled off stack. (mr r1,r11) >>> As a result of this we have chance to get crash when >>> any interrupt hit shortly after stack pointer update. >>> The interrupt prologue will override not yet pulled off >>> pmap_kenter function data. >>> >>> The problem occures only with -fno-omit-frame-pointer >>> and not every branch returns are beeing corrupted. >>> >>> Do you think this issue may be somehow related to yours? >>> Are there any patches/solutions to fix it? >> >> Should we turn off -fno-omit-frame-frame-pointer on PPC then? It's enabled >> in default kernel builds. > > I think that's a good idea. Even though we have managed to trigger this only > in rare cases, the problem is real and the code generated is broken i.e. > leads to corruption and panics. > How can you make any conclusion without having seen a single line of code actually triggering the problem ? That sounds very irresponsible...
- Arnaud _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
