[PATCH] dmaengine: qcom: fix gpi undefined behavior

[PATCH] dmaengine: qcom: fix gpi undefined behavior

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

gcc points out an incorrect error handling loop:

drivers/dma/qcom/gpi.c: In function 'gpi_ch_init':
drivers/dma/qcom/gpi.c:1254:15: error: iteration 2 invokes undefined behavior [-Werror=aggressive-loop-optimizations]
 1254 |  struct gpii *gpii = gchan->gpii;
      |               ^~~~
drivers/dma/qcom/gpi.c:1951:2: note: within this loop
 1951 |  for (i = i - 1; i >= 0; i++) {
      |  ^~~

Change the loop to correctly walk backwards through the
initialized fields rather than off into the woods.

Fixes: 5d0c3533a19f ("dmaengine: qcom: Add GPI dma driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/dma/qcom/gpi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
index 8d39d3e24686..9c211104ddbf 100644
--- a/drivers/dma/qcom/gpi.c
+++ b/drivers/dma/qcom/gpi.c
@@ -1948,7 +1948,7 @@ static int gpi_ch_init(struct gchan *gchan)
 	return ret;
 
 error_start_chan:
-	for (i = i - 1; i >= 0; i++) {
+	for (i = i - 1; i >= 0; i--) {
 		gpi_stop_chan(&gpii->gchan[i]);
 		gpi_send_cmd(gpii, gchan, GPI_CH_CMD_RESET);
 	}
-- 
2.29.2

Re: [PATCH] dmaengine: qcom: fix gpi undefined behavior

[Vinod Koul]

On 03-01-21, 14:57, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> gcc points out an incorrect error handling loop:
> 
> drivers/dma/qcom/gpi.c: In function 'gpi_ch_init':
> drivers/dma/qcom/gpi.c:1254:15: error: iteration 2 invokes undefined behavior [-Werror=aggressive-loop-optimizations]
>  1254 |  struct gpii *gpii = gchan->gpii;
>       |               ^~~~
> drivers/dma/qcom/gpi.c:1951:2: note: within this loop
>  1951 |  for (i = i - 1; i >= 0; i++) {
>       |  ^~~
> 
> Change the loop to correctly walk backwards through the
> initialized fields rather than off into the woods.

Applied, thanks

-- 
~Vinod

Re: [PATCH] dmaengine: qcom: fix gpi undefined behavior

[patchwork-bot+linux-arm-msm]

Hello:

This patch was applied to qcom/linux.git (refs/heads/for-next):

On Sun,  3 Jan 2021 14:57:29 +0100 you wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> gcc points out an incorrect error handling loop:
> 
> drivers/dma/qcom/gpi.c: In function 'gpi_ch_init':
> drivers/dma/qcom/gpi.c:1254:15: error: iteration 2 invokes undefined behavior [-Werror=aggressive-loop-optimizations]
>  1254 |  struct gpii *gpii = gchan->gpii;
>       |               ^~~~
> drivers/dma/qcom/gpi.c:1951:2: note: within this loop
>  1951 |  for (i = i - 1; i >= 0; i++) {
>       |  ^~~
> 
> [...]

Here is the summary with links:
  - dmaengine: qcom: fix gpi undefined behavior
    https://git.kernel.org/qcom/c/0bd1bf86ab79

You are awesome, thank you!
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