This is a note to let you know that I've just added the patch titled
fbdev: Fix sys_imageblit() for arbitrary image widths
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
fbdev-fix-sys_imageblit-for-arbitrary-image-widths.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit e1cca0a03c04260fd928c958d3b55a9d8dbd61b4
Author: Thomas Zimmermann <tzimmermann@xxxxxxx>
Date: Sun Mar 13 20:29:51 2022 +0100
fbdev: Fix sys_imageblit() for arbitrary image widths
[ Upstream commit 61bfcb6a3b981e8f19e044ac8c3de6edbe6caf70 ]
Commit 6f29e04938bf ("fbdev: Improve performance of sys_imageblit()")
broke sys_imageblit() for image width that are not aligned to 8-bit
boundaries. Fix this by handling the trailing pixels on each line
separately. The performance improvements in the original commit do not
regress by this change.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Fixes: 6f29e04938bf ("fbdev: Improve performance of sys_imageblit()")
Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Tested-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20220313192952.12058-2-tzimmermann@xxxxxxx
Stable-dep-of: c2d22806aecb ("fbdev: fix potential OOB read in fast_imageblit()")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/video/fbdev/core/sysimgblt.c b/drivers/video/fbdev/core/sysimgblt.c
index 722c327a381bd..335e92b813fc4 100644
--- a/drivers/video/fbdev/core/sysimgblt.c
+++ b/drivers/video/fbdev/core/sysimgblt.c
@@ -188,7 +188,7 @@ static void fast_imageblit(const struct fb_image *image, struct fb_info *p,
{
u32 fgx = fgcolor, bgx = bgcolor, bpp = p->var.bits_per_pixel;
u32 ppw = 32/bpp, spitch = (image->width + 7)/8;
- u32 bit_mask, eorx;
+ u32 bit_mask, eorx, shift;
const char *s = image->data, *src;
u32 *dst;
const u32 *tab;
@@ -229,17 +229,23 @@ static void fast_imageblit(const struct fb_image *image, struct fb_info *p,
for (i = image->height; i--; ) {
dst = dst1;
+ shift = 8;
src = s;
+ /*
+ * Manually unroll the per-line copying loop for better
+ * performance. This works until we processed the last
+ * completely filled source byte (inclusive).
+ */
switch (ppw) {
case 4: /* 8 bpp */
- for (j = k; j; j -= 2, ++src) {
+ for (j = k; j >= 2; j -= 2, ++src) {
*dst++ = colortab[(*src >> 4) & bit_mask];
*dst++ = colortab[(*src >> 0) & bit_mask];
}
break;
case 2: /* 16 bpp */
- for (j = k; j; j -= 4, ++src) {
+ for (j = k; j >= 4; j -= 4, ++src) {
*dst++ = colortab[(*src >> 6) & bit_mask];
*dst++ = colortab[(*src >> 4) & bit_mask];
*dst++ = colortab[(*src >> 2) & bit_mask];
@@ -247,7 +253,7 @@ static void fast_imageblit(const struct fb_image *image, struct fb_info *p,
}
break;
case 1: /* 32 bpp */
- for (j = k; j; j -= 8, ++src) {
+ for (j = k; j >= 8; j -= 8, ++src) {
*dst++ = colortab[(*src >> 7) & bit_mask];
*dst++ = colortab[(*src >> 6) & bit_mask];
*dst++ = colortab[(*src >> 5) & bit_mask];
@@ -259,6 +265,21 @@ static void fast_imageblit(const struct fb_image *image, struct fb_info *p,
}
break;
}
+
+ /*
+ * For image widths that are not a multiple of 8, there
+ * are trailing pixels left on the current line. Print
+ * them as well.
+ */
+ for (; j--; ) {
+ shift -= ppw;
+ *dst++ = colortab[(*src >> shift) & bit_mask];
+ if (!shift) {
+ shift = 8;
+ ++src;
+ }
+ }
+
dst1 += p->fix.line_length;
s += spitch;
}
