[PATCH] misc: pci_endpoint_test: Handle BAR sizes larger than INT_MAX

[PATCH] misc: pci_endpoint_test: Handle BAR sizes larger than INT_MAX

[Niklas Cassel]

Running 'pcitest -b 0' fails with "TEST FAILED" when the BAR0 size
is e.g. 8 GB.

The return value of the pci_resource_len() macro can be larger than that
of a signed integer type. Thus, when using 'pcitest' with an 8 GB BAR,
the bar_size of the integer type will overflow.

Change bar_size from integer to resource_size_t to prevent integer
overflow for large BAR sizes with 32-bit compilers.

Co-developed-by: Hans Zhang <18255117159@163.com>
Signed-off-by: Hans Zhang <18255117159@163.com>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
Hans submitted a patch for this that was reverted because apparently some
gcc-7 arm32 compiler doesn't like div_u64(). In order to avoid debugging
gcc-7 arm32 compiler issues, simply replace the division with addition,
which arguably makes the code simpler as well.

 drivers/misc/pci_endpoint_test.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
index d5ac71a49386..8e48a15100f1 100644
--- a/drivers/misc/pci_endpoint_test.c
+++ b/drivers/misc/pci_endpoint_test.c
@@ -272,9 +272,9 @@ static const u32 bar_test_pattern[] = {
 };
 
 static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
-					enum pci_barno barno, int offset,
-					void *write_buf, void *read_buf,
-					int size)
+					enum pci_barno barno,
+					resource_size_t offset, void *write_buf,
+					void *read_buf, int size)
 {
 	memset(write_buf, bar_test_pattern[barno], size);
 	memcpy_toio(test->bar[barno] + offset, write_buf, size);
@@ -287,10 +287,11 @@ static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
 static int pci_endpoint_test_bar(struct pci_endpoint_test *test,
 				  enum pci_barno barno)
 {
-	int j, bar_size, buf_size, iters;
+	resource_size_t bar_size, offset = 0;
 	void *write_buf __free(kfree) = NULL;
 	void *read_buf __free(kfree) = NULL;
 	struct pci_dev *pdev = test->pdev;
+	int buf_size;
 
 	if (!test->bar[barno])
 		return -ENOMEM;
@@ -314,11 +315,12 @@ static int pci_endpoint_test_bar(struct pci_endpoint_test *test,
 	if (!read_buf)
 		return -ENOMEM;
 
-	iters = bar_size / buf_size;
-	for (j = 0; j < iters; j++)
-		if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j,
-						 write_buf, read_buf, buf_size))
+	while (offset < bar_size) {
+		if (pci_endpoint_test_bar_memcmp(test, barno, offset, write_buf,
+						 read_buf, buf_size))
 			return -EIO;
+		offset += buf_size;
+	}
 
 	return 0;
 }
-- 
2.48.1

Re: [PATCH] misc: pci_endpoint_test: Handle BAR sizes larger than INT_MAX

[Frank Li]

On Thu, Jan 23, 2025 at 10:59:07AM +0100, Niklas Cassel wrote:
> Running 'pcitest -b 0' fails with "TEST FAILED" when the BAR0 size
> is e.g. 8 GB.
>
> The return value of the pci_resource_len() macro can be larger than that
> of a signed integer type. Thus, when using 'pcitest' with an 8 GB BAR,
> the bar_size of the integer type will overflow.
>
> Change bar_size from integer to resource_size_t to prevent integer
> overflow for large BAR sizes with 32-bit compilers.
>
> Co-developed-by: Hans Zhang <18255117159@163.com>
> Signed-off-by: Hans Zhang <18255117159@163.com>
> Signed-off-by: Niklas Cassel <cassel@kernel.org>
> ---
> Hans submitted a patch for this that was reverted because apparently some
> gcc-7 arm32 compiler doesn't like div_u64(). In order to avoid debugging
> gcc-7 arm32 compiler issues, simply replace the division with addition,
> which arguably makes the code simpler as well.
>
>  drivers/misc/pci_endpoint_test.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
> index d5ac71a49386..8e48a15100f1 100644
> --- a/drivers/misc/pci_endpoint_test.c
> +++ b/drivers/misc/pci_endpoint_test.c
> @@ -272,9 +272,9 @@ static const u32 bar_test_pattern[] = {
>  };
>
>  static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
> -					enum pci_barno barno, int offset,
> -					void *write_buf, void *read_buf,
> -					int size)
> +					enum pci_barno barno,
> +					resource_size_t offset, void *write_buf,
> +					void *read_buf, int size)
>  {
>  	memset(write_buf, bar_test_pattern[barno], size);
>  	memcpy_toio(test->bar[barno] + offset, write_buf, size);
> @@ -287,10 +287,11 @@ static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
>  static int pci_endpoint_test_bar(struct pci_endpoint_test *test,
>  				  enum pci_barno barno)
>  {
> -	int j, bar_size, buf_size, iters;
> +	resource_size_t bar_size, offset = 0;
>  	void *write_buf __free(kfree) = NULL;
>  	void *read_buf __free(kfree) = NULL;
>  	struct pci_dev *pdev = test->pdev;
> +	int buf_size;
>
>  	if (!test->bar[barno])
>  		return -ENOMEM;
> @@ -314,11 +315,12 @@ static int pci_endpoint_test_bar(struct pci_endpoint_test *test,
>  	if (!read_buf)
>  		return -ENOMEM;
>
> -	iters = bar_size / buf_size;
> -	for (j = 0; j < iters; j++)
> -		if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j,
> -						 write_buf, read_buf, buf_size))
> +	while (offset < bar_size) {
> +		if (pci_endpoint_test_bar_memcmp(test, barno, offset, write_buf,
> +						 read_buf, buf_size))
>  			return -EIO;
> +		offset += buf_size;
> +	}

Actually, you change code logic although functionality is the same. I feel
like you should mention at commit message or use origial code by just
change variable type.

#ifdef CONFIG_PHYS_ADDR_T_64BIT
typedef u64 phys_addr_t;
#else
typedef u32 phys_addr_t;
#endif

typedef phys_addr_t resource_size_t;

resource_size_t may 32bit at some configuration. But I don't know what
happen when 8G bar pci device attached to such system.

Frank

>
>  	return 0;
>  }
> --
> 2.48.1
>

Re: [PATCH] misc: pci_endpoint_test: Handle BAR sizes larger than INT_MAX

[Niklas Cassel]

On Thu, Jan 23, 2025 at 10:54:19AM -0500, Frank Li wrote:
> On Thu, Jan 23, 2025 at 10:59:07AM +0100, Niklas Cassel wrote:
> > Running 'pcitest -b 0' fails with "TEST FAILED" when the BAR0 size
> > is e.g. 8 GB.
> >
> > The return value of the pci_resource_len() macro can be larger than that
> > of a signed integer type. Thus, when using 'pcitest' with an 8 GB BAR,
> > the bar_size of the integer type will overflow.
> >
> > Change bar_size from integer to resource_size_t to prevent integer
> > overflow for large BAR sizes with 32-bit compilers.
> >
> > Co-developed-by: Hans Zhang <18255117159@163.com>
> > Signed-off-by: Hans Zhang <18255117159@163.com>
> > Signed-off-by: Niklas Cassel <cassel@kernel.org>
> > ---
> > Hans submitted a patch for this that was reverted because apparently some
> > gcc-7 arm32 compiler doesn't like div_u64(). In order to avoid debugging
> > gcc-7 arm32 compiler issues, simply replace the division with addition,
> > which arguably makes the code simpler as well.
> >
> >  drivers/misc/pci_endpoint_test.c | 18 ++++++++++--------
> >  1 file changed, 10 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
> > index d5ac71a49386..8e48a15100f1 100644
> > --- a/drivers/misc/pci_endpoint_test.c
> > +++ b/drivers/misc/pci_endpoint_test.c
> > @@ -272,9 +272,9 @@ static const u32 bar_test_pattern[] = {
> >  };
> >
> >  static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
> > -					enum pci_barno barno, int offset,
> > -					void *write_buf, void *read_buf,
> > -					int size)
> > +					enum pci_barno barno,
> > +					resource_size_t offset, void *write_buf,
> > +					void *read_buf, int size)
> >  {
> >  	memset(write_buf, bar_test_pattern[barno], size);
> >  	memcpy_toio(test->bar[barno] + offset, write_buf, size);
> > @@ -287,10 +287,11 @@ static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
> >  static int pci_endpoint_test_bar(struct pci_endpoint_test *test,
> >  				  enum pci_barno barno)
> >  {
> > -	int j, bar_size, buf_size, iters;
> > +	resource_size_t bar_size, offset = 0;
> >  	void *write_buf __free(kfree) = NULL;
> >  	void *read_buf __free(kfree) = NULL;
> >  	struct pci_dev *pdev = test->pdev;
> > +	int buf_size;
> >
> >  	if (!test->bar[barno])
> >  		return -ENOMEM;
> > @@ -314,11 +315,12 @@ static int pci_endpoint_test_bar(struct pci_endpoint_test *test,
> >  	if (!read_buf)
> >  		return -ENOMEM;
> >
> > -	iters = bar_size / buf_size;
> > -	for (j = 0; j < iters; j++)
> > -		if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j,
> > -						 write_buf, read_buf, buf_size))
> > +	while (offset < bar_size) {
> > +		if (pci_endpoint_test_bar_memcmp(test, barno, offset, write_buf,
> > +						 read_buf, buf_size))
> >  			return -EIO;
> > +		offset += buf_size;
> > +	}
> 
> Actually, you change code logic although functionality is the same. I feel
> like you should mention at commit message or use origial code by just
> change variable type.
> 
> #ifdef CONFIG_PHYS_ADDR_T_64BIT
> typedef u64 phys_addr_t;
> #else
> typedef u32 phys_addr_t;
> #endif

Hello Frank,

I personally think that is a horrible idea :)

We do not want to introduce ifdefs in the middle of the code, unless
in exceptional circumstances, like architecture specific optimized code.


Kind regards,
Niklas

Re: [PATCH] misc: pci_endpoint_test: Handle BAR sizes larger than INT_MAX

[Frank Li]

On Thu, Jan 23, 2025 at 07:35:06PM +0100, Niklas Cassel wrote:
> On Thu, Jan 23, 2025 at 10:54:19AM -0500, Frank Li wrote:
> > On Thu, Jan 23, 2025 at 10:59:07AM +0100, Niklas Cassel wrote:
> > > Running 'pcitest -b 0' fails with "TEST FAILED" when the BAR0 size
> > > is e.g. 8 GB.
> > >
> > > The return value of the pci_resource_len() macro can be larger than that
> > > of a signed integer type. Thus, when using 'pcitest' with an 8 GB BAR,
> > > the bar_size of the integer type will overflow.
> > >
> > > Change bar_size from integer to resource_size_t to prevent integer
> > > overflow for large BAR sizes with 32-bit compilers.
> > >
> > > Co-developed-by: Hans Zhang <18255117159@163.com>
> > > Signed-off-by: Hans Zhang <18255117159@163.com>
> > > Signed-off-by: Niklas Cassel <cassel@kernel.org>
> > > ---
> > > Hans submitted a patch for this that was reverted because apparently some
> > > gcc-7 arm32 compiler doesn't like div_u64(). In order to avoid debugging
> > > gcc-7 arm32 compiler issues, simply replace the division with addition,
> > > which arguably makes the code simpler as well.
> > >
> > >  drivers/misc/pci_endpoint_test.c | 18 ++++++++++--------
> > >  1 file changed, 10 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
> > > index d5ac71a49386..8e48a15100f1 100644
> > > --- a/drivers/misc/pci_endpoint_test.c
> > > +++ b/drivers/misc/pci_endpoint_test.c
> > > @@ -272,9 +272,9 @@ static const u32 bar_test_pattern[] = {
> > >  };
> > >
> > >  static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
> > > -					enum pci_barno barno, int offset,
> > > -					void *write_buf, void *read_buf,
> > > -					int size)
> > > +					enum pci_barno barno,
> > > +					resource_size_t offset, void *write_buf,
> > > +					void *read_buf, int size)
> > >  {
> > >  	memset(write_buf, bar_test_pattern[barno], size);
> > >  	memcpy_toio(test->bar[barno] + offset, write_buf, size);
> > > @@ -287,10 +287,11 @@ static int pci_endpoint_test_bar_memcmp(struct pci_endpoint_test *test,
> > >  static int pci_endpoint_test_bar(struct pci_endpoint_test *test,
> > >  				  enum pci_barno barno)
> > >  {
> > > -	int j, bar_size, buf_size, iters;
> > > +	resource_size_t bar_size, offset = 0;
> > >  	void *write_buf __free(kfree) = NULL;
> > >  	void *read_buf __free(kfree) = NULL;
> > >  	struct pci_dev *pdev = test->pdev;
> > > +	int buf_size;
> > >
> > >  	if (!test->bar[barno])
> > >  		return -ENOMEM;
> > > @@ -314,11 +315,12 @@ static int pci_endpoint_test_bar(struct pci_endpoint_test *test,
> > >  	if (!read_buf)
> > >  		return -ENOMEM;
> > >
> > > -	iters = bar_size / buf_size;
> > > -	for (j = 0; j < iters; j++)
> > > -		if (pci_endpoint_test_bar_memcmp(test, barno, buf_size * j,
> > > -						 write_buf, read_buf, buf_size))
> > > +	while (offset < bar_size) {
> > > +		if (pci_endpoint_test_bar_memcmp(test, barno, offset, write_buf,
> > > +						 read_buf, buf_size))
> > >  			return -EIO;
> > > +		offset += buf_size;
> > > +	}
> >
> > Actually, you change code logic although functionality is the same. I feel
> > like you should mention at commit message or use origial code by just
> > change variable type.
> >
> > #ifdef CONFIG_PHYS_ADDR_T_64BIT
> > typedef u64 phys_addr_t;
> > #else
> > typedef u32 phys_addr_t;
> > #endif
>
> Hello Frank,
>
> I personally think that is a horrible idea :)
>
> We do not want to introduce ifdefs in the middle of the code, unless
> in exceptional circumstances, like architecture specific optimized code.

You miss understand what my means. I copy it from type.h to indicate
resource_size_t is not 64bit at all platforms.

Frank
>
>
> Kind regards,
> Niklas

Re: [PATCH] misc: pci_endpoint_test: Handle BAR sizes larger than INT_MAX

[Niklas Cassel]

On Thu, Jan 23, 2025 at 02:09:24PM -0500, Frank Li wrote:
> On Thu, Jan 23, 2025 at 07:35:06PM +0100, Niklas Cassel wrote:
> > >
> > > Actually, you change code logic although functionality is the same. I feel
> > > like you should mention at commit message or use origial code by just
> > > change variable type.
> > >
> > > #ifdef CONFIG_PHYS_ADDR_T_64BIT
> > > typedef u64 phys_addr_t;
> > > #else
> > > typedef u32 phys_addr_t;
> > > #endif
> >
> > Hello Frank,
> >
> > I personally think that is a horrible idea :)
> >
> > We do not want to introduce ifdefs in the middle of the code, unless
> > in exceptional circumstances, like architecture specific optimized code.
> 
> You miss understand what my means. I copy it from type.h to indicate
> resource_size_t is not 64bit at all platforms.

I know that resource_size_t is typedefed to phys_addr_t, which can be 32-bit
or 64-bit. (I compile tested this patch on 32-bit both with and without PAE.)

resource_size_t is the type returned by pci_resource_len().
That is why the patch in subject changes the type to use resource_size_t.
IMO, it does not make sense to use any other type (e.g. u64), since the
value returned by pci_resource_len() will still be limited to what can be
represented by resource_size_t.

A BARs larger than 4GB, on systems with 32-bit resource_size_t, will get
disabled by PCI core:
https://github.com/torvalds/linux/blob/v6.13/drivers/pci/probe.c#L265-L270

So all good.



As for your question why I don't keep the division, please read the comment
section in this patch (where the changelog usually is), or read the thread:
https://lore.kernel.org/linux-pci/20250109094556.1724663-1-18255117159@163.com/T/#t

I guess I could have added:
"
In order to handle 64-bit resource_type_t on 32-bit platforms, we would
have needed to use a function like div_u64() or similar. Instead, change
the code to use addition instead of division. This avoids the need for
div_u64() or similar, while also simplifying the code.
"

Let me send a V2 with that senctence added to address your review comment.


Kind regards,
Niklas