4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Thomas Zimmermann tzimmermann@suse.de
[ 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@suse.de Fixes: 6f29e04938bf ("fbdev: Improve performance of sys_imageblit()") Reviewed-by: Javier Martinez Canillas javierm@redhat.com Acked-by: Daniel Vetter daniel.vetter@ffwll.ch Tested-by: Geert Uytterhoeven geert@linux-m68k.org Cc: Thomas Zimmermann tzimmermann@suse.de Cc: Javier Martinez Canillas javierm@redhat.com Cc: Sam Ravnborg sam@ravnborg.org Link: https://patchwork.freedesktop.org/patch/msgid/20220313192952.12058-2-tzimmer... Stable-dep-of: c2d22806aecb ("fbdev: fix potential OOB read in fast_imageblit()") Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/video/fbdev/core/sysimgblt.c | 29 ++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-)
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; }