The expression 1 << 31 results in undefined behaviour because the type of
integer constant 1 is (signed) int and the result of shifting 1 by 31 bits
is not representable in the (signed) int type.
Change the type of 1 to unsigned int by adding the U suffix.
Signed-off-by: Xenia Ragiadakou <[email protected]>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index cd48590ada30..44fbd499edea 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -96,7 +96,7 @@
#define CR2_E2H (1 << 0)
#define ARM_SMMU_GBPA 0x44
-#define GBPA_UPDATE (1 << 31)
+#define GBPA_UPDATE (1U << 31)
#define GBPA_ABORT (1 << 20)
#define ARM_SMMU_IRQ_CTRL 0x50
--
2.34.1
On Thu, Jun 30, 2022 at 09:39:59AM +0300, Xenia Ragiadakou wrote:
> The expression 1 << 31 results in undefined behaviour because the type of
> integer constant 1 is (signed) int and the result of shifting 1 by 31 bits
> is not representable in the (signed) int type.
>
> Change the type of 1 to unsigned int by adding the U suffix.
>
> Signed-off-by: Xenia Ragiadakou <[email protected]>
> ---
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index cd48590ada30..44fbd499edea 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -96,7 +96,7 @@
> #define CR2_E2H (1 << 0)
>
> #define ARM_SMMU_GBPA 0x44
> -#define GBPA_UPDATE (1 << 31)
> +#define GBPA_UPDATE (1U << 31)
There are loads of these kicking around in the kernel sources and we compile
with -fno-strict-overflow.
If you really want to change these, then let's use the BIT() macro instead,
but I think it's really just churn.
Will
On 7/1/22 17:34, Will Deacon wrote:
> On Thu, Jun 30, 2022 at 09:39:59AM +0300, Xenia Ragiadakou wrote:
>> The expression 1 << 31 results in undefined behaviour because the type of
>> integer constant 1 is (signed) int and the result of shifting 1 by 31 bits
>> is not representable in the (signed) int type.
>>
>> Change the type of 1 to unsigned int by adding the U suffix.
>>
>> Signed-off-by: Xenia Ragiadakou <[email protected]>
>> ---
>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
>> index cd48590ada30..44fbd499edea 100644
>> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
>> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
>> @@ -96,7 +96,7 @@
>> #define CR2_E2H (1 << 0)
>>
>> #define ARM_SMMU_GBPA 0x44
>> -#define GBPA_UPDATE (1 << 31)
>> +#define GBPA_UPDATE (1U << 31)
> There are loads of these kicking around in the kernel sources and we compile
> with -fno-strict-overflow.
>
> If you really want to change these, then let's use the BIT() macro instead,
> but I think it's really just churn.
>
> Will
Hi Will,
I thought that since in commit 587e6c10a7ce89a5924fdbeff2ec524fbd6a124b
there was a similar fix to Q_OVERFLOW_FLAG (see below)
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -183,7 +183,7 @@
#define Q_IDX(llq, p) ((p) & ((1 <<
(llq)->max_n_shift) - 1))
#define Q_WRP(llq, p) ((p) & (1 << (llq)->max_n_shift))
-#define Q_OVERFLOW_FLAG (1 << 31)
+#define Q_OVERFLOW_FLAG (1U << 31)
#define Q_OVF(p) ((p) & Q_OVERFLOW_FLAG)
#define Q_ENT(q, p) ((q)->base + \
Q_IDX(&((q)->llq), p) * \
then it would make sense to fix GBPA_UPDATE in the same way.
Xenia