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

[Niklas Cassel <cassel@kernel.org>]

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