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[PATCH] fbdev: Fix incorrect unaligned access in little-endian machines
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The drawing function cfbfillrect does not work correctly when access is not
unsigned-long aligned.  It manifests as extra lines of pixels that are not
complete drawn.  Reversing the shift operator solves the problem, so I would
presume that this bug would manifest only on little endian machines.  The
function cfbcopyarea may also have this bug.

Aligned access should present no problems.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Antonino A. Daplas authored and Linus Torvalds committed Dec 13, 2005
1 parent 7275b4b commit be0d9b6
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Showing 4 changed files with 36 additions and 36 deletions.
8 changes: 4 additions & 4 deletions drivers/video/cfbcopyarea.c
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Original file line number Diff line number Diff line change
Expand Up @@ -64,8 +64,8 @@ bitcpy(unsigned long __iomem *dst, int dst_idx, const unsigned long __iomem *src
int const shift = dst_idx-src_idx;
int left, right;

first = ~0UL >> dst_idx;
last = ~(~0UL >> ((dst_idx+n) % bits));
first = FB_SHIFT_HIGH(~0UL, dst_idx);
last = ~(FB_SHIFT_HIGH(~0UL, (dst_idx+n) % bits));

if (!shift) {
// Same alignment for source and dest
Expand Down Expand Up @@ -216,8 +216,8 @@ bitcpy_rev(unsigned long __iomem *dst, int dst_idx, const unsigned long __iomem

shift = dst_idx-src_idx;

first = ~0UL << (bits - 1 - dst_idx);
last = ~(~0UL << (bits - 1 - ((dst_idx-n) % bits)));
first = FB_SHIFT_LOW(~0UL, bits - 1 - dst_idx);
last = ~(FB_SHIFT_LOW(~0UL, bits - 1 - ((dst_idx-n) % bits)));

if (!shift) {
// Same alignment for source and dest
Expand Down
16 changes: 8 additions & 8 deletions drivers/video/cfbfillrect.c
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Original file line number Diff line number Diff line change
Expand Up @@ -110,8 +110,8 @@ bitfill_aligned(unsigned long __iomem *dst, int dst_idx, unsigned long pat, unsi
if (!n)
return;

first = ~0UL >> dst_idx;
last = ~(~0UL >> ((dst_idx+n) % bits));
first = FB_SHIFT_HIGH(~0UL, dst_idx);
last = ~(FB_SHIFT_HIGH(~0UL, (dst_idx+n) % bits));

if (dst_idx+n <= bits) {
// Single word
Expand Down Expand Up @@ -167,8 +167,8 @@ bitfill_unaligned(unsigned long __iomem *dst, int dst_idx, unsigned long pat,
if (!n)
return;

first = ~0UL >> dst_idx;
last = ~(~0UL >> ((dst_idx+n) % bits));
first = FB_SHIFT_HIGH(~0UL, dst_idx);
last = ~(FB_SHIFT_HIGH(~0UL, (dst_idx+n) % bits));

if (dst_idx+n <= bits) {
// Single word
Expand Down Expand Up @@ -221,8 +221,8 @@ bitfill_aligned_rev(unsigned long __iomem *dst, int dst_idx, unsigned long pat,
if (!n)
return;

first = ~0UL >> dst_idx;
last = ~(~0UL >> ((dst_idx+n) % bits));
first = FB_SHIFT_HIGH(~0UL, dst_idx);
last = ~(FB_SHIFT_HIGH(~0UL, (dst_idx+n) % bits));

if (dst_idx+n <= bits) {
// Single word
Expand Down Expand Up @@ -290,8 +290,8 @@ bitfill_unaligned_rev(unsigned long __iomem *dst, int dst_idx, unsigned long pat
if (!n)
return;

first = ~0UL >> dst_idx;
last = ~(~0UL >> ((dst_idx+n) % bits));
first = FB_SHIFT_HIGH(~0UL, dst_idx);
last = ~(FB_SHIFT_HIGH(~0UL, (dst_idx+n) % bits));

if (dst_idx+n <= bits) {
// Single word
Expand Down
36 changes: 12 additions & 24 deletions drivers/video/cfbimgblt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -76,18 +76,6 @@ static u32 cfb_tab32[] = {
#define FB_WRITEL fb_writel
#define FB_READL fb_readl

#if defined (__BIG_ENDIAN)
#define LEFT_POS(bpp) (32 - bpp)
#define SHIFT_HIGH(val, bits) ((val) >> (bits))
#define SHIFT_LOW(val, bits) ((val) << (bits))
#define BIT_NR(b) (7 - (b))
#else
#define LEFT_POS(bpp) (0)
#define SHIFT_HIGH(val, bits) ((val) << (bits))
#define SHIFT_LOW(val, bits) ((val) >> (bits))
#define BIT_NR(b) (b)
#endif

static inline void color_imageblit(const struct fb_image *image,
struct fb_info *p, u8 __iomem *dst1,
u32 start_index,
Expand All @@ -109,7 +97,7 @@ static inline void color_imageblit(const struct fb_image *image,
val = 0;

if (start_index) {
u32 start_mask = ~(SHIFT_HIGH(~(u32)0, start_index));
u32 start_mask = ~(FB_SHIFT_HIGH(~(u32)0, start_index));
val = FB_READL(dst) & start_mask;
shift = start_index;
}
Expand All @@ -119,20 +107,20 @@ static inline void color_imageblit(const struct fb_image *image,
color = palette[*src];
else
color = *src;
color <<= LEFT_POS(bpp);
val |= SHIFT_HIGH(color, shift);
color <<= FB_LEFT_POS(bpp);
val |= FB_SHIFT_HIGH(color, shift);
if (shift >= null_bits) {
FB_WRITEL(val, dst++);

val = (shift == null_bits) ? 0 :
SHIFT_LOW(color, 32 - shift);
FB_SHIFT_LOW(color, 32 - shift);
}
shift += bpp;
shift &= (32 - 1);
src++;
}
if (shift) {
u32 end_mask = SHIFT_HIGH(~(u32)0, shift);
u32 end_mask = FB_SHIFT_HIGH(~(u32)0, shift);

FB_WRITEL((FB_READL(dst) & end_mask) | val, dst);
}
Expand Down Expand Up @@ -162,8 +150,8 @@ static inline void slow_imageblit(const struct fb_image *image, struct fb_info *
u32 i, j, l;

dst2 = (u32 __iomem *) dst1;
fgcolor <<= LEFT_POS(bpp);
bgcolor <<= LEFT_POS(bpp);
fgcolor <<= FB_LEFT_POS(bpp);
bgcolor <<= FB_LEFT_POS(bpp);

for (i = image->height; i--; ) {
shift = val = 0;
Expand All @@ -174,21 +162,21 @@ static inline void slow_imageblit(const struct fb_image *image, struct fb_info *

/* write leading bits */
if (start_index) {
u32 start_mask = ~(SHIFT_HIGH(~(u32)0, start_index));
u32 start_mask = ~(FB_SHIFT_HIGH(~(u32)0,start_index));
val = FB_READL(dst) & start_mask;
shift = start_index;
}

while (j--) {
l--;
color = (*s & 1 << (BIT_NR(l))) ? fgcolor : bgcolor;
val |= SHIFT_HIGH(color, shift);
color = (*s & 1 << (FB_BIT_NR(l))) ? fgcolor : bgcolor;
val |= FB_SHIFT_HIGH(color, shift);

/* Did the bitshift spill bits to the next long? */
if (shift >= null_bits) {
FB_WRITEL(val, dst++);
val = (shift == null_bits) ? 0 :
SHIFT_LOW(color,32 - shift);
FB_SHIFT_LOW(color,32 - shift);
}
shift += bpp;
shift &= (32 - 1);
Expand All @@ -197,7 +185,7 @@ static inline void slow_imageblit(const struct fb_image *image, struct fb_info *

/* write trailing bits */
if (shift) {
u32 end_mask = SHIFT_HIGH(~(u32)0, shift);
u32 end_mask = FB_SHIFT_HIGH(~(u32)0, shift);

FB_WRITEL((FB_READL(dst) & end_mask) | val, dst);
}
Expand Down
12 changes: 12 additions & 0 deletions include/linux/fb.h
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Original file line number Diff line number Diff line change
Expand Up @@ -833,6 +833,18 @@ struct fb_info {
#define fb_writeq(b,addr) (*(volatile u64 *) (addr) = (b))
#define fb_memset memset

#endif

#if defined (__BIG_ENDIAN)
#define FB_LEFT_POS(bpp) (32 - bpp)
#define FB_SHIFT_HIGH(val, bits) ((val) >> (bits))
#define FB_SHIFT_LOW(val, bits) ((val) << (bits))
#define FB_BIT_NR(b) (7 - (b))
#else
#define FB_LEFT_POS(bpp) (0)
#define FB_SHIFT_HIGH(val, bits) ((val) << (bits))
#define FB_SHIFT_LOW(val, bits) ((val) >> (bits))
#define FB_BIT_NR(b) (b)
#endif

/*
Expand Down

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