[continued from previous message]
+ printk("** ** bit_putcs_aligned: vc->vc_font.data:
0x%lx\n", vc->vc_font.data );
+ printk("** ** bit_putcs_aligned: srcorig:
0x%lx\n", srcorig );
+
+ ch = prech & charmask;
+ printk("** ** bit_putcs_aligned: before: ch: 0x%x\n", ch);
+
+ if (ch >= charcnt)
+ ch = 32;
+ srcnew = vc->vc_font.data + ch * cellsize;
+ printk("** ** bit_putcs_aligned: after: ch: 0x%x\n", ch);
+ printk("** ** bit_putcs_aligned: charcnt: 0x%x\n", charcnt);
+ printk("** ** bit_putcs_aligned: cellsize: 0x%x\n", cellsize);
+ printk("** ** bit_putcs_aligned: ch * cellsize:
0x%x\n", (ch * cellsize));
+ printk("** ** bit_putcs_aligned: srcnew:
0x%lx\n", srcnew);
+ printk("** ** bit_putcs_aligned: srcorig - srcnew:
0x%lx\n", (srcorig - srcnew));
+
+ // src = srcorig; printk("** ** bit_putcs_aligned: srcorig\n");
+ src = srcnew; printk("** ** bit_putcs_aligned: srcnew\n");
+ printk("** ** bit_putcs_aligned: <<----------\n");
if (attr) {
update_attr(buf, src, attr, vc);
-------------------------- patch to generate log --------------------------
.
On Fri, Dec 26, 2025 at 3:18 PM William Burrow wrote:
>
> Hi, all.
> To summarize the message thread, commit 0998a6cb232 was found to be
> the issue. It is unclear why this commit causes an issue. It was
> added shortly after kernel v5.10.246 was released, so it was not
> necessary to bisect between 5.10.244 and 5.10.247, saving time.
> .
> In testing, it was found that the variable charcnt is set to zero,
> causing the if-statement to trigger. This should not happen. There
> may be a bug somewhere else that triggers this.
> .
> Patching the line after the added if-statement in that commit from ch
> = 0 to ch = 32 (space character) does not seem to fix the issue, it
> just changes it from a screen of symbols to a (mostly) blank screen.
> This is unexpected, since the address for the variable src should be
> the same calculated with the change of ch = 32 with this patch or the
> code before this patch.
> .
> Thanks for your time to review this bug.
> .
> ------------------------- suspected commit ----------------------
> diff --git a/drivers/video/fbdev/core/bitblit.c
> b/drivers/video/fbdev/core/bitblit.c
> index bb821b68f88c..4e774010d09f 100644
> --- a/drivers/video/fbdev/core/bitblit.c
> +++ b/drivers/video/fbdev/core/bitblit.c
> @@ -79,12 +79,16 @@ static inline void bit_putcs_aligned(struct
> vc_data *vc, struct fb_info *info,
> struct fb_image *image, u8 *buf, u8 *dst)
> {
> u16 charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
> + unsigned int charcnt = vc->vc_font.charcount;
> u32 idx = vc->vc_font.width >> 3;
> u8 *src;
>
> while (cnt--) {
> - src = vc->vc_font.data + (scr_readw(s++)&
> - charmask)*cellsize;
> + u16 ch = scr_readw(s++) & charmask;
> +
> + if (ch >= charcnt)
> + ch = 0;
> + src = vc->vc_font.data + (unsigned int)ch * cellsize;
>
> if (attr) {
> update_attr(buf, src, attr, vc);
> @@ -112,14 +116,18 @@ static inline void bit_putcs_unaligned(struct vc_data
*vc,
> u8 *dst)
> {
> u16 charmask = vc->vc_hi_font_mask ? 0x1ff : 0xff;
> + unsigned int charcnt = vc->vc_font.charcount;
> u32 shift_low = 0, mod = vc->vc_font.width % 8;
> u32 shift_high = 8;
> u32 idx = vc->vc_font.width >> 3;
> u8 *src;
>
> while (cnt--) {
> - src = vc->vc_font.data + (scr_readw(s++)&
> - charmask)*cellsize;
> + u16 ch = scr_readw(s++) & charmask;
> +
> + if (ch >= charcnt)
> + ch = 0;
> + src = vc->vc_font.data + (unsigned int)ch * cellsize;
>
> if (attr) {
> update_attr(buf, src, attr, vc);
> ------------------------- suspected commit ----------------------
>
> On Fri, Dec 26, 2025 at 12:48 PM Salvatore Bonaccorso
wrote:
> >
> > Control: tags -1 - moreinfo
> > Control: forwarded -1 https://lists.debian.org/debian-kernel
2025/12/msg00293.html https://lists.debian.org/debian-kernel/202
/12/msg00211.html
> >
> > Hi,
> >
> > On Sun, Dec 21, 2025 at 04:19:14PM +0000, Thorsten Glaser wrote:
> > > Hi Salvatore,
> > >
> > > >If you can do the bisect mentioned that would help identifying the
> > > >problem.
> > >
> > > I’m not in a position to do that currently, I don’t have a
> > > fast machine anyway and packed light, too. But at least X11
> > > works, so I’m fine currently.
> > >
> > > This is a Thinkpad X61 with Intel integrated graphics, FWIW.
> >
> > FTR, there is some progress in
> > https://lists.debian.org/debian-kernel/2025/12/msg00293.html (which
> > retrospectively we should have made a Debian BTS bug from the start
> > for easier tracking).
> >
> > Helge, can you please include the Debian bug #1123750 in next replies?
> >
> > Regards,
> > Salvatore
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
