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* [PATCH] net/mlx5: fpga: avoid uninitialized return codes
@ 2017-09-14 11:06 Arnd Bergmann
  2017-09-14 12:54 ` Leon Romanovsky
  0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2017-09-14 11:06 UTC (permalink / raw)
  To: Ilan Tayari, Saeed Mahameed, Matan Barak, Leon Romanovsky
  Cc: Arnd Bergmann, Boris Pismenny, netdev, linux-rdma, linux-kernel

calling mlx5_fpga_mem_{read,write}_i2c() with a zero length on
older compiler version such as gcc-4.6 results in a warning that
the return code is not initialized:

drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c:147:6: error: ‘err’ may be used uninitialized in this function [-Werror=uninitialized]
drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c:126:6: error: ‘err’ may be used uninitialized in this function [-Werror=uninitialized]

On newer compilers, the 'err' variable is optimized away in this
code path and assumed to be zero when the loop completes, so we
don't get this warning.

I'm changing the function here to instead return -EINVAL for the
case, under the assumption that it was never meant to be called
with a zero length argument.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82203
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
index 3c11d6e2160a..914fb9d77a1a 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
@@ -64,7 +64,7 @@ static int mlx5_fpga_mem_read_i2c(struct mlx5_fpga_device *fdev, size_t size,
 	size_t max_size = MLX5_FPGA_ACCESS_REG_SIZE_MAX;
 	size_t bytes_done = 0;
 	u8 actual_size;
-	int err;
+	int err = -EINVAL;
 
 	if (!fdev->mdev)
 		return -ENOTCONN;
@@ -93,7 +93,7 @@ static int mlx5_fpga_mem_write_i2c(struct mlx5_fpga_device *fdev, size_t size,
 	size_t max_size = MLX5_FPGA_ACCESS_REG_SIZE_MAX;
 	size_t bytes_done = 0;
 	u8 actual_size;
-	int err;
+	int err = -EINVAL;
 
 	if (!fdev->mdev)
 		return -ENOTCONN;
-- 
2.9.0

^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] net/mlx5: fpga: avoid uninitialized return codes
  2017-09-14 11:06 [PATCH] net/mlx5: fpga: avoid uninitialized return codes Arnd Bergmann
@ 2017-09-14 12:54 ` Leon Romanovsky
  2017-09-14 18:39   ` Saeed Mahameed
  0 siblings, 1 reply; 3+ messages in thread
From: Leon Romanovsky @ 2017-09-14 12:54 UTC (permalink / raw)
  To: Arnd Bergmann
  Cc: Ilan Tayari, Saeed Mahameed, Matan Barak, Boris Pismenny, netdev,
	linux-rdma, linux-kernel

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On Thu, Sep 14, 2017 at 01:06:18PM +0200, Arnd Bergmann wrote:
> calling mlx5_fpga_mem_{read,write}_i2c() with a zero length on
> older compiler version such as gcc-4.6 results in a warning that
> the return code is not initialized:
>
> drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c:147:6: error: ‘err’ may be used uninitialized in this function [-Werror=uninitialized]
> drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c:126:6: error: ‘err’ may be used uninitialized in this function [-Werror=uninitialized]
>
> On newer compilers, the 'err' variable is optimized away in this
> code path and assumed to be zero when the loop completes, so we
> don't get this warning.
>
> I'm changing the function here to instead return -EINVAL for the
> case, under the assumption that it was never meant to be called
> with a zero length argument.

I agree with you that size can't be zero and this patch will fix the
warning, but if it is possible, I will prefer to have this check is
written explicitly and not implicitly.

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
index 3c11d6e2160a..0e85bebe1dad 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
@@ -69,6 +69,9 @@ static int mlx5_fpga_mem_read_i2c(struct mlx5_fpga_device *fdev, size_t size,
 	if (!fdev->mdev)
 		return -ENOTCONN;

+	if (!size)
+		return -EINVAL;
+
 	while (bytes_done < size) {
 		actual_size = min(max_size, (size - bytes_done));

Thanks

>
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82203
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
> index 3c11d6e2160a..914fb9d77a1a 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
> @@ -64,7 +64,7 @@ static int mlx5_fpga_mem_read_i2c(struct mlx5_fpga_device *fdev, size_t size,
>  	size_t max_size = MLX5_FPGA_ACCESS_REG_SIZE_MAX;
>  	size_t bytes_done = 0;
>  	u8 actual_size;
> -	int err;
> +	int err = -EINVAL;
>
>  	if (!fdev->mdev)
>  		return -ENOTCONN;
> @@ -93,7 +93,7 @@ static int mlx5_fpga_mem_write_i2c(struct mlx5_fpga_device *fdev, size_t size,
>  	size_t max_size = MLX5_FPGA_ACCESS_REG_SIZE_MAX;
>  	size_t bytes_done = 0;
>  	u8 actual_size;
> -	int err;
> +	int err = -EINVAL;
>
>  	if (!fdev->mdev)
>  		return -ENOTCONN;
> --
> 2.9.0
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

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^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] net/mlx5: fpga: avoid uninitialized return codes
  2017-09-14 12:54 ` Leon Romanovsky
@ 2017-09-14 18:39   ` Saeed Mahameed
  0 siblings, 0 replies; 3+ messages in thread
From: Saeed Mahameed @ 2017-09-14 18:39 UTC (permalink / raw)
  To: Leon Romanovsky
  Cc: Arnd Bergmann, Ilan Tayari, Saeed Mahameed, Matan Barak,
	Boris Pismenny, Linux Netdev List, linux-rdma, linux-kernel

On Thu, Sep 14, 2017 at 5:54 AM, Leon Romanovsky <leonro@mellanox.com> wrote:
> On Thu, Sep 14, 2017 at 01:06:18PM +0200, Arnd Bergmann wrote:
>> calling mlx5_fpga_mem_{read,write}_i2c() with a zero length on
>> older compiler version such as gcc-4.6 results in a warning that
>> the return code is not initialized:
>>
>> drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c:147:6: error: ‘err’ may be used uninitialized in this function [-Werror=uninitialized]
>> drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c:126:6: error: ‘err’ may be used uninitialized in this function [-Werror=uninitialized]
>>
>> On newer compilers, the 'err' variable is optimized away in this
>> code path and assumed to be zero when the loop completes, so we
>> don't get this warning.
>>
>> I'm changing the function here to instead return -EINVAL for the
>> case, under the assumption that it was never meant to be called
>> with a zero length argument.

Thanks Arnd, Looks good.

>
> I agree with you that size can't be zero and this patch will fix the
> warning, but if it is possible, I will prefer to have this check is
> written explicitly and not implicitly.
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
> index 3c11d6e2160a..0e85bebe1dad 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
> @@ -69,6 +69,9 @@ static int mlx5_fpga_mem_read_i2c(struct mlx5_fpga_device *fdev, size_t size,
>         if (!fdev->mdev)
>                 return -ENOTCONN;
>
> +       if (!size)
> +               return -EINVAL;
> +

Or simply trust the caller :), and avoid redundant code.

>         while (bytes_done < size) {
>                 actual_size = min(max_size, (size - bytes_done));
>
> Thanks
>
>>
>> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82203
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> ---
>>  drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
>> index 3c11d6e2160a..914fb9d77a1a 100644
>> --- a/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
>> +++ b/drivers/net/ethernet/mellanox/mlx5/core/fpga/sdk.c
>> @@ -64,7 +64,7 @@ static int mlx5_fpga_mem_read_i2c(struct mlx5_fpga_device *fdev, size_t size,
>>       size_t max_size = MLX5_FPGA_ACCESS_REG_SIZE_MAX;
>>       size_t bytes_done = 0;
>>       u8 actual_size;
>> -     int err;
>> +     int err = -EINVAL;
>>
>>       if (!fdev->mdev)
>>               return -ENOTCONN;
>> @@ -93,7 +93,7 @@ static int mlx5_fpga_mem_write_i2c(struct mlx5_fpga_device *fdev, size_t size,
>>       size_t max_size = MLX5_FPGA_ACCESS_REG_SIZE_MAX;
>>       size_t bytes_done = 0;
>>       u8 actual_size;
>> -     int err;
>> +     int err = -EINVAL;
>>
>>       if (!fdev->mdev)
>>               return -ENOTCONN;
>> --
>> 2.9.0
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2017-09-14 18:39 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2017-09-14 11:06 [PATCH] net/mlx5: fpga: avoid uninitialized return codes Arnd Bergmann
2017-09-14 12:54 ` Leon Romanovsky
2017-09-14 18:39   ` Saeed Mahameed

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