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From: Ed Maste <emaste@freebsd.org>
Date: Thu, 1 Jan 2015 19:58:49 -0500
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Subject: Re: [PATCH] Fixing panic in vt_fb_blank() if fb_size is not a
 multiple of fb_stride
To: Andre Albsmeier <andre@fbsd.ata.myota.org>
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On 1 January 2015 at 14:22, 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:
>
...
>
> 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);
>         }

Thank you for the report and investigation. This is fixed in HEAD by
r268771 and r268796, which rework vt_fb_blank. There are a number of
other vt(4) changes that are not in stable/9; I will see if most/all
of it may be feasibly merged back, or otherwise commit a change for
this problem.