Re: [PATCH 25/28] s390: pci: don't print uninitialized data for debugging

[Sebastian Ott]

On Tue, 18 Oct 2016, Martin Schwidefsky wrote:
> On Tue, 18 Oct 2016 00:16:13 +0200
> Arnd Bergmann  wrote:
> 
> > gcc correctly warns about an incorrect use of the 'pa' variable
> > in case we pass an empty scatterlist to __s390_dma_map_sg:
> > 
> > arch/s390/pci/pci_dma.c: In function '__s390_dma_map_sg':
> > arch/s390/pci/pci_dma.c:309:13: warning: 'pa' may be used uninitialized in 
> > this function [-Wmaybe-uninitialized]
> > 
> > This adds a bogus initialization to the function to sanitize
> > the debug output.  I would have preferred a solution without
> > the initialization, but I only got the report from the
> > kbuild bot after turning on the warning again, and didn't
> > manage to reproduce it myself.
> > 
> > Signed-off-by: Arnd Bergmann 
> > ---
> >  arch/s390/pci/pci_dma.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
> > index 7350c8b..6b2f72f 100644
> > --- a/arch/s390/pci/pci_dma.c
> > +++ b/arch/s390/pci/pci_dma.c
> > @@ -423,7 +423,7 @@ static int __s390_dma_map_sg(struct device *dev, struct 
> > scatterlist *sg,
> > dma_addr_t dma_addr_base, dma_addr;
> > int flags = ZPCI_PTE_VALID;
> > struct scatterlist *s;
> > -   unsigned long pa;
> > +   unsigned long pa = 0;
> > int ret;
> > 
> > size = PAGE_ALIGN(size);
> 
> The compiler is right. pa is set in the for-loop. If "dma_addr < 
> dma_addr_base + size"
> is never true and __dma_purge_tlb() returns with an error, pa *is* 
> uninitialized.
> The fix seems sensible to me.

Although that could only happen if map_sg is called with zero length sg
list entries I'm in favor getting rid of that warning.

Acked-by: Sebastian Ott 

Regards,
Sebastian

Re: [PATCH 25/28] s390: pci: don't print uninitialized data for debugging

[Sebastian Ott]

On Tue, 18 Oct 2016, Martin Schwidefsky wrote:
> On Tue, 18 Oct 2016 00:16:13 +0200
> Arnd Bergmann  wrote:
> 
> > gcc correctly warns about an incorrect use of the 'pa' variable
> > in case we pass an empty scatterlist to __s390_dma_map_sg:
> > 
> > arch/s390/pci/pci_dma.c: In function '__s390_dma_map_sg':
> > arch/s390/pci/pci_dma.c:309:13: warning: 'pa' may be used uninitialized in 
> > this function [-Wmaybe-uninitialized]
> > 
> > This adds a bogus initialization to the function to sanitize
> > the debug output.  I would have preferred a solution without
> > the initialization, but I only got the report from the
> > kbuild bot after turning on the warning again, and didn't
> > manage to reproduce it myself.
> > 
> > Signed-off-by: Arnd Bergmann 
> > ---
> >  arch/s390/pci/pci_dma.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
> > index 7350c8b..6b2f72f 100644
> > --- a/arch/s390/pci/pci_dma.c
> > +++ b/arch/s390/pci/pci_dma.c
> > @@ -423,7 +423,7 @@ static int __s390_dma_map_sg(struct device *dev, struct 
> > scatterlist *sg,
> > dma_addr_t dma_addr_base, dma_addr;
> > int flags = ZPCI_PTE_VALID;
> > struct scatterlist *s;
> > -   unsigned long pa;
> > +   unsigned long pa = 0;
> > int ret;
> > 
> > size = PAGE_ALIGN(size);
> 
> The compiler is right. pa is set in the for-loop. If "dma_addr < 
> dma_addr_base + size"
> is never true and __dma_purge_tlb() returns with an error, pa *is* 
> uninitialized.
> The fix seems sensible to me.

Although that could only happen if map_sg is called with zero length sg
list entries I'm in favor getting rid of that warning.

Acked-by: Sebastian Ott 

Regards,
Sebastian

Re: [PATCH 25/28] s390: pci: don't print uninitialized data for debugging

[Martin Schwidefsky]

On Tue, 18 Oct 2016 00:16:13 +0200
Arnd Bergmann  wrote:

> gcc correctly warns about an incorrect use of the 'pa' variable
> in case we pass an empty scatterlist to __s390_dma_map_sg:
> 
> arch/s390/pci/pci_dma.c: In function '__s390_dma_map_sg':
> arch/s390/pci/pci_dma.c:309:13: warning: 'pa' may be used uninitialized in 
> this function [-Wmaybe-uninitialized]
> 
> This adds a bogus initialization to the function to sanitize
> the debug output.  I would have preferred a solution without
> the initialization, but I only got the report from the
> kbuild bot after turning on the warning again, and didn't
> manage to reproduce it myself.
> 
> Signed-off-by: Arnd Bergmann 
> ---
>  arch/s390/pci/pci_dma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
> index 7350c8b..6b2f72f 100644
> --- a/arch/s390/pci/pci_dma.c
> +++ b/arch/s390/pci/pci_dma.c
> @@ -423,7 +423,7 @@ static int __s390_dma_map_sg(struct device *dev, struct 
> scatterlist *sg,
>   dma_addr_t dma_addr_base, dma_addr;
>   int flags = ZPCI_PTE_VALID;
>   struct scatterlist *s;
> - unsigned long pa;
> + unsigned long pa = 0;
>   int ret;
> 
>   size = PAGE_ALIGN(size);

The compiler is right. pa is set in the for-loop. If "dma_addr < dma_addr_base 
+ size"
is never true and __dma_purge_tlb() returns with an error, pa *is* 
uninitialized.
The fix seems sensible to me.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

Re: [PATCH 25/28] s390: pci: don't print uninitialized data for debugging

[Martin Schwidefsky]

On Tue, 18 Oct 2016 00:16:13 +0200
Arnd Bergmann  wrote:

> gcc correctly warns about an incorrect use of the 'pa' variable
> in case we pass an empty scatterlist to __s390_dma_map_sg:
> 
> arch/s390/pci/pci_dma.c: In function '__s390_dma_map_sg':
> arch/s390/pci/pci_dma.c:309:13: warning: 'pa' may be used uninitialized in 
> this function [-Wmaybe-uninitialized]
> 
> This adds a bogus initialization to the function to sanitize
> the debug output.  I would have preferred a solution without
> the initialization, but I only got the report from the
> kbuild bot after turning on the warning again, and didn't
> manage to reproduce it myself.
> 
> Signed-off-by: Arnd Bergmann 
> ---
>  arch/s390/pci/pci_dma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
> index 7350c8b..6b2f72f 100644
> --- a/arch/s390/pci/pci_dma.c
> +++ b/arch/s390/pci/pci_dma.c
> @@ -423,7 +423,7 @@ static int __s390_dma_map_sg(struct device *dev, struct 
> scatterlist *sg,
>   dma_addr_t dma_addr_base, dma_addr;
>   int flags = ZPCI_PTE_VALID;
>   struct scatterlist *s;
> - unsigned long pa;
> + unsigned long pa = 0;
>   int ret;
> 
>   size = PAGE_ALIGN(size);

The compiler is right. pa is set in the for-loop. If "dma_addr < dma_addr_base 
+ size"
is never true and __dma_purge_tlb() returns with an error, pa *is* 
uninitialized.
The fix seems sensible to me.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

[PATCH 25/28] s390: pci: don't print uninitialized data for debugging

[Arnd Bergmann]

gcc correctly warns about an incorrect use of the 'pa' variable
in case we pass an empty scatterlist to __s390_dma_map_sg:

arch/s390/pci/pci_dma.c: In function '__s390_dma_map_sg':
arch/s390/pci/pci_dma.c:309:13: warning: 'pa' may be used uninitialized in this 
function [-Wmaybe-uninitialized]

This adds a bogus initialization to the function to sanitize
the debug output.  I would have preferred a solution without
the initialization, but I only got the report from the
kbuild bot after turning on the warning again, and didn't
manage to reproduce it myself.

Signed-off-by: Arnd Bergmann 
---
 arch/s390/pci/pci_dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
index 7350c8b..6b2f72f 100644
--- a/arch/s390/pci/pci_dma.c
+++ b/arch/s390/pci/pci_dma.c
@@ -423,7 +423,7 @@ static int __s390_dma_map_sg(struct device *dev, struct 
scatterlist *sg,
dma_addr_t dma_addr_base, dma_addr;
int flags = ZPCI_PTE_VALID;
struct scatterlist *s;
-   unsigned long pa;
+   unsigned long pa = 0;
int ret;
 
size = PAGE_ALIGN(size);
-- 
2.9.0

[PATCH 25/28] s390: pci: don't print uninitialized data for debugging

[Arnd Bergmann]

gcc correctly warns about an incorrect use of the 'pa' variable
in case we pass an empty scatterlist to __s390_dma_map_sg:

arch/s390/pci/pci_dma.c: In function '__s390_dma_map_sg':
arch/s390/pci/pci_dma.c:309:13: warning: 'pa' may be used uninitialized in this 
function [-Wmaybe-uninitialized]

This adds a bogus initialization to the function to sanitize
the debug output.  I would have preferred a solution without
the initialization, but I only got the report from the
kbuild bot after turning on the warning again, and didn't
manage to reproduce it myself.

Signed-off-by: Arnd Bergmann 
---
 arch/s390/pci/pci_dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/pci/pci_dma.c b/arch/s390/pci/pci_dma.c
index 7350c8b..6b2f72f 100644
--- a/arch/s390/pci/pci_dma.c
+++ b/arch/s390/pci/pci_dma.c
@@ -423,7 +423,7 @@ static int __s390_dma_map_sg(struct device *dev, struct 
scatterlist *sg,
dma_addr_t dma_addr_base, dma_addr;
int flags = ZPCI_PTE_VALID;
struct scatterlist *s;
-   unsigned long pa;
+   unsigned long pa = 0;
int ret;
 
size = PAGE_ALIGN(size);
-- 
2.9.0