Date: Thu, 1 Jan 2015 13:34:53 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Andre Albsmeier <andre@fbsd.ata.myota.org> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, freebsd-x11@freebsd.org Subject: Re: [PATCH] Fixing panic in vt_fb_blank() if fb_size is not a multiple of fb_stride Message-ID: <CAJ-Vmok%2B-AK47sC9HVSV-50K3LGzkscCdzebzcN=tWR4rsSaJA@mail.gmail.com> In-Reply-To: <20150101192219.GA46601@voyager> References: <20150101192219.GA46601@voyager>
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oh cool! Would you mind filing a PR? This is a pretty nifty find, good work! (https://bugs.freebsd.org/submit/) -adrian On 1 January 2015 at 11:22, Andre Albsmeier <andre@fbsd.ata.myota.org> wrote: > [Crossposting to -hackers and -x11 as this is vt and i915kms related] > > I can reliably crash an older notebook (Fujitsu E8310) with Intel > graphics (GM965) by loading i915kms after having booted but only > if vt(4) is used instead of old syscons. > > Reason for the crash is a page fault in vt_fb_blank() which is > in /sys/dev/vt/hw/fb/vt_fb.c: > > #7 0xc08c929e in bcopy () at /src/src-9/sys/i386/i386/support.s:198 > #8 0xc08d93e0 in memmove (dest=0xedfd3c00, src=0xeda30000, n=5632) at /src/src-9/sys/libkern/memmove.c:36 > #9 0xc053fac7 in vt_fb_mem_copy (sc=0xc6919500, offset_to=5913600, offset_from=0, size=5632) at /src/src-9/sys/dev/fb/fbd.c:205 > #10 0xc060370e in vt_fb_blank (vd=0xc09c3c40, color=<value optimized out>) at /src/src-9/sys/dev/vt/hw/fb/vt_fb.c:179 > #11 0xc0603b10 in vt_fb_init (vd=0xc09c3c40) at /src/src-9/sys/dev/vt/hw/fb/vt_fb.c:306 > #12 0xc06098db in vt_allocate (drv=0xc09c3b80, softc=0xc6919500) at /src/src-9/sys/dev/vt/vt_core.c:1970 > > in vt_fb_blank() we find: > > for (o = info->fb_stride; o < info->fb_size; o += info->fb_stride) { > info->copy(info, o, 0, info->fb_stride); > } > > fb_size gets calculated in intelfb_create() which is in > /sys/dev/drm2/i915/intel_fb.c as > > size = mode_cmd.pitches[0] * mode_cmd.height; > size = roundup2(size, PAGE_SIZE); > > with fb_stride being the result of > > mode_cmd.pitches[0] = roundup2( (mode_cmd.width * ((sizes->surface_bpp + 7) / 8), 64); > > So with my funky resolution of 1400 x 1050 @32bit we get > > fb_stride = 5632 > fb_size = 5914624 > > We see that fb_stride won't fit into fb_size in whole numbers > (5914624 / 5632 = 1050.18181818181818181818) so this is why > the loop runs beyond fb_size and gives a page fault. > > I am now using this modified loop in vt_fb_blank() which does > not try to run to the end of the fb by replacing > > info->fb_size > > by > > info->fb_height * info->fb_stride > > for (o = info->fb_stride; o < info->fb_height * info->fb_stride; o += info->fb_stride) { > info->copy(info, o, 0, info->fb_stride); > } > > All this is on 9.3-STABLE. I have no idea if this is the correct > solution but at least I can use vt instead of sc on this notebook. > > -Andre > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"
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