* [PATCH] drm/pl111: Use 64-bit arithmetic instead of 32-bit
@ 2018-07-03 23:51 Gustavo A. R. Silva
2018-07-04 14:11 ` Gustavo A. R. Silva
0 siblings, 1 reply; 2+ messages in thread
From: Gustavo A. R. Silva @ 2018-07-03 23:51 UTC (permalink / raw)
To: Eric Anholt, David Airlie; +Cc: dri-devel, linux-kernel, Gustavo A. R. Silva
Add suffix UL to constant 1000 in order to give the compiler complete
information about the proper arithmetic to use.
Notice that such constant is used in a context that expects an
expression of type u64 (64 bits, unsigned) and the following
expression is currently being evaluated using 32-bit arithmetic:
mode->clock * 1000
Addresses-Coverity-ID: 1466139 ("Unintentional integer overflow")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
drivers/gpu/drm/pl111/pl111_display.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/pl111/pl111_display.c b/drivers/gpu/drm/pl111/pl111_display.c
index a432eb7..61d51b4 100644
--- a/drivers/gpu/drm/pl111/pl111_display.c
+++ b/drivers/gpu/drm/pl111/pl111_display.c
@@ -63,7 +63,7 @@ pl111_mode_valid(struct drm_crtc *crtc,
* We use the pixelclock to also account for interlaced modes, the
* resulting bandwidth is in bytes per second.
*/
- bw = mode->clock * 1000; /* In Hz */
+ bw = mode->clock * 1000UL; /* In Hz */
bw = bw * mode->hdisplay * mode->vdisplay * cpp;
bw = div_u64(bw, mode->htotal * mode->vtotal);
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] drm/pl111: Use 64-bit arithmetic instead of 32-bit
2018-07-03 23:51 [PATCH] drm/pl111: Use 64-bit arithmetic instead of 32-bit Gustavo A. R. Silva
@ 2018-07-04 14:11 ` Gustavo A. R. Silva
0 siblings, 0 replies; 2+ messages in thread
From: Gustavo A. R. Silva @ 2018-07-04 14:11 UTC (permalink / raw)
To: Eric Anholt, David Airlie; +Cc: dri-devel, linux-kernel
Hi,
Please, ignore this. I should have used ULL instead of UL.
I'll send v2 shortly.
Thanks
--
Gustavo
On 07/03/2018 06:51 PM, Gustavo A. R. Silva wrote:
> Add suffix UL to constant 1000 in order to give the compiler complete
> information about the proper arithmetic to use.
>
> Notice that such constant is used in a context that expects an
> expression of type u64 (64 bits, unsigned) and the following
> expression is currently being evaluated using 32-bit arithmetic:
>
> mode->clock * 1000
>
> Addresses-Coverity-ID: 1466139 ("Unintentional integer overflow")
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
> drivers/gpu/drm/pl111/pl111_display.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/pl111/pl111_display.c b/drivers/gpu/drm/pl111/pl111_display.c
> index a432eb7..61d51b4 100644
> --- a/drivers/gpu/drm/pl111/pl111_display.c
> +++ b/drivers/gpu/drm/pl111/pl111_display.c
> @@ -63,7 +63,7 @@ pl111_mode_valid(struct drm_crtc *crtc,
> * We use the pixelclock to also account for interlaced modes, the
> * resulting bandwidth is in bytes per second.
> */
> - bw = mode->clock * 1000; /* In Hz */
> + bw = mode->clock * 1000UL; /* In Hz */
> bw = bw * mode->hdisplay * mode->vdisplay * cpp;
> bw = div_u64(bw, mode->htotal * mode->vtotal);
>
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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