How to fix CHECK warning: testing a 'safe expression'

How to fix CHECK warning: testing a 'safe expression'

[Murali Karicheri]

netdev maintainers,

I got a comment to address CHECK warning and wondering how to address 
'warning: testing a 'safe expression' which appears when using
IS_ERR_OR_NULL(foo)

where foo is defined as

struct foo_type *foo;

The foo get assigned only NULL or ERR_PTR(error code). So I believe the 
usage is correct. But then how do I make the CHECK happy of its usage?

I have tried doing a grep on the current usage of IS_ERR_OR_NULL() and 
found 276 of them causes this warning in the v3.18 version of the kernel 
that I am using

$ grep -r "warning: testing a 'safe expression" * | wc -l
276

1) Can someone explain what this warning means?

2) Is it acceptable to post patches to netdev list with this warning?

3) if not, how this is expected to be fixed? Any example usage to fix 
this warning will be helpful.

Thanks in advance for
-- 
Murali Karicheri
Linux Kernel, Texas Instruments

How to fix CHECK warning: testing a 'safe expression' ?

[Murali Karicheri]

I am trying to address CHECK warnings in my driver and wondering how to 
resolve 'warning: testing a 'safe expression' which appears when using
IS_ERR_OR_NULL(foo)

where foo is defined as

struct foo_type *foo;

The foo get assigned only NULL or ERR_PTR(error code). So I believe the
usage is correct. But then how do I make the CHECK happy of its usage?

I have tried a grep to check on the current usage of IS_ERR_OR_NULL() 
and found 276 of them causes this warning in the v3.18 version of the 
kernel that I am using

$ grep -r "warning: testing a 'safe expression" * | wc -l
276

Can someone help me undestand what this means and how to fix the same?

I run folling for CHECK

make C=2 CF="-D__CHECK_ENDIAN__" CHECK=sparse

Thanks in advance for your suggestions.
-- 
Murali Karicheri
Linux Kernel, Texas Instruments
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Re: How to fix CHECK warning: testing a 'safe expression' ?

[Bjorn Helgaas]

[+cc Christopher, linux-kernel (this doesn't sound like a PCI-specific
question)]

On Wed, Dec 17, 2014 at 9:18 AM, Murali Karicheri <m-karicheri2@ti.com> wrote:
> I am trying to address CHECK warnings in my driver and wondering how to
> resolve 'warning: testing a 'safe expression' which appears when using
> IS_ERR_OR_NULL(foo)
>
> where foo is defined as
>
> struct foo_type *foo;
>
> The foo get assigned only NULL or ERR_PTR(error code). So I believe the
> usage is correct. But then how do I make the CHECK happy of its usage?
>
> I have tried a grep to check on the current usage of IS_ERR_OR_NULL() and
> found 276 of them causes this warning in the v3.18 version of the kernel
> that I am using
>
> $ grep -r "warning: testing a 'safe expression" * | wc -l
> 276
>
> Can someone help me undestand what this means and how to fix the same?
>
> I run folling for CHECK
>
> make C=2 CF="-D__CHECK_ENDIAN__" CHECK=sparse

If you can share your actual code or point to it in the tree, you
might get more specific help.

Bjorn

Re: How to fix CHECK warning: testing a 'safe expression' ?

[Murali Karicheri]

On 12/17/2014 01:49 PM, Bjorn Helgaas wrote:
> [+cc Christopher, linux-kernel (this doesn't sound like a PCI-specific
> question)]
>
> On Wed, Dec 17, 2014 at 9:18 AM, Murali Karicheri<m-karicheri2@ti.com>  wrote:
>> I am trying to address CHECK warnings in my driver and wondering how to
>> resolve 'warning: testing a 'safe expression' which appears when using
>> IS_ERR_OR_NULL(foo)
>>
>> where foo is defined as
>>
>> struct foo_type *foo;
>>
>> The foo get assigned only NULL or ERR_PTR(error code). So I believe the
>> usage is correct. But then how do I make the CHECK happy of its usage?
>>
>> I have tried a grep to check on the current usage of IS_ERR_OR_NULL() and
>> found 276 of them causes this warning in the v3.18 version of the kernel
>> that I am using
>>
>> $ grep -r "warning: testing a 'safe expression" * | wc -l
>> 276
>>
>> Can someone help me undestand what this means and how to fix the same?
>>
>> I run folling for CHECK
>>
>> make C=2 CF="-D__CHECK_ENDIAN__" CHECK=sparse
>
> If you can share your actual code or point to it in the tree, you
> might get more specific help.
>
> Bjorn

For example I get

   CHECK   drivers/pci/host/pci-keystone.c
include/linux/err.h:40:16: warning: testing a 'safe expression'

Actually it is for IS_ERR_OR_NULL() call in the file which is the only
one call in the file.

-- 
Murali Karicheri
Linux Kernel, Texas Instruments

Re: How to fix CHECK warning: testing a 'safe expression' ?

[Murali Karicheri]

On 12/17/2014 05:35 PM, Murali Karicheri wrote:
> On 12/17/2014 01:49 PM, Bjorn Helgaas wrote:
>> [+cc Christopher, linux-kernel (this doesn't sound like a PCI-specific
>> question)]
>>
>> On Wed, Dec 17, 2014 at 9:18 AM, Murali Karicheri<m-karicheri2@ti.com>
>> wrote:
>>> I am trying to address CHECK warnings in my driver and wondering how to
>>> resolve 'warning: testing a 'safe expression' which appears when using
>>> IS_ERR_OR_NULL(foo)
>>>
>>> where foo is defined as
>>>
>>> struct foo_type *foo;
>>>
>>> The foo get assigned only NULL or ERR_PTR(error code). So I believe the
>>> usage is correct. But then how do I make the CHECK happy of its usage?
>>>
>>> I have tried a grep to check on the current usage of IS_ERR_OR_NULL()
>>> and
>>> found 276 of them causes this warning in the v3.18 version of the kernel
>>> that I am using
>>>
>>> $ grep -r "warning: testing a 'safe expression" * | wc -l
>>> 276
>>>
>>> Can someone help me undestand what this means and how to fix the same?
>>>
>>> I run folling for CHECK
>>>
>>> make C=2 CF="-D__CHECK_ENDIAN__" CHECK=sparse
>>
>> If you can share your actual code or point to it in the tree, you
>> might get more specific help.
>>
>> Bjorn
>
> For example I get
>
> CHECK drivers/pci/host/pci-keystone.c
> include/linux/err.h:40:16: warning: testing a 'safe expression'
>
> Actually it is for IS_ERR_OR_NULL() call in the file which is the only
> one call in the file.
>
Here is the code snippet for your convenience

	struct device *dev = &pdev->dev;
	struct keystone_pcie *ks_pcie;
	struct pcie_port *pp;
	struct resource *res;
	void __iomem *reg_p;
	struct phy *phy;
	int ret = 0;

	ks_pcie = devm_kzalloc(&pdev->dev, sizeof(*ks_pcie),
				GFP_KERNEL);
	if (!ks_pcie) {
		dev_err(dev, "no memory for keystone pcie\n");
		return -ENOMEM;
	}
	pp = &ks_pcie->pp;

	/* initialize SerDes Phy if present */
	phy = devm_phy_get(dev, "pcie-phy");
===>    if (!IS_ERR_OR_NULL(phy)) {
		ret = phy_init(phy);
		if (ret < 0)
			return ret;
	}



-- 
Murali Karicheri
Linux Kernel, Texas Instruments

Re: How to fix CHECK warning: testing a 'safe expression' ?

[Christopher Li]

On Thu, Dec 18, 2014 at 6:37 AM, Murali Karicheri <m-karicheri2@ti.com> wrote:
>         if (!ks_pcie) {
>                 dev_err(dev, "no memory for keystone pcie\n");
>                 return -ENOMEM;
>         }
>         pp = &ks_pcie->pp;
>
>         /* initialize SerDes Phy if present */
>         phy = devm_phy_get(dev, "pcie-phy");
> ===>    if (!IS_ERR_OR_NULL(phy)) {
>                 ret = phy_init(phy);
>                 if (ret < 0)
>                         return ret;
>

Hi,

Do you have a smaller stand alone test case which I can reproduce with sparse?

Thanks

Chris

Re: How to fix CHECK warning: testing a 'safe expression' ?

[Murali Karicheri]

On 12/17/2014 09:39 PM, Christopher Li wrote:
> On Thu, Dec 18, 2014 at 6:37 AM, Murali Karicheri<m-karicheri2@ti.com>  wrote:
>>          if (!ks_pcie) {
>>                  dev_err(dev, "no memory for keystone pcie\n");
>>                  return -ENOMEM;
>>          }
>>          pp =&ks_pcie->pp;
>>
>>          /* initialize SerDes Phy if present */
>>          phy = devm_phy_get(dev, "pcie-phy");
>> ===>     if (!IS_ERR_OR_NULL(phy)) {
>>                  ret = phy_init(phy);
>>                  if (ret<  0)
>>                          return ret;
>>
>
> Hi,
>
> Do you have a smaller stand alone test case which I can reproduce with sparse?
>
> Thanks
>
> Chris
Thanks Chris for responding.

You could add this piece of code for testing

struct foo {
	int x;
	int y;
};

static struct foo *func1(struct device *dev)
{
	struct foo *fp;

	fp = devm_kzalloc(dev, sizeof(*fp), GFP_KERNEL);
	if (fp == NULL)
		return ERR_PTR(-ENOMEM);
	return fp;
}

And in one of your module in kernel add

	struct foo *fp;

	if (IS_ERR_OR_NULL(fp))
		return -ENOMEM;

and do

make C=2 CF="-D__CHECK_ENDIAN__" CHECK=sparse

You will see the CHECK warning against your module as

include/linux/err.h:40:16: warning: testing a 'safe expression'

Hope this helps.

-- 
Murali Karicheri
Linux Kernel, Texas Instruments

Re: How to fix CHECK warning: testing a 'safe expression'

[Murali Karicheri]

+ Josh

On 12/16/2014 01:23 PM, Murali Karicheri wrote:
> netdev maintainers,
>
> I got a comment to address CHECK warning and wondering how to address
> 'warning: testing a 'safe expression' which appears when using
> IS_ERR_OR_NULL(foo)
>
> where foo is defined as
>
> struct foo_type *foo;
>
> The foo get assigned only NULL or ERR_PTR(error code). So I believe the
> usage is correct. But then how do I make the CHECK happy of its usage?
>
> I have tried doing a grep on the current usage of IS_ERR_OR_NULL() and
> found 276 of them causes this warning in the v3.18 version of the kernel
> that I am using
>
> $ grep -r "warning: testing a 'safe expression" * | wc -l
> 276
>
> 1) Can someone explain what this warning means?
>
> 2) Is it acceptable to post patches to netdev list with this warning?
>
> 3) if not, how this is expected to be fixed? Any example usage to fix
> this warning will be helpful.
>
> Thanks in advance for


-- 
Murali Karicheri
Linux Kernel, Texas Instruments

Re: How to fix CHECK warning: testing a 'safe expression'

[Josh Triplett]

+linux-sparse

On Fri, Jan 02, 2015 at 09:51:25AM -0500, Murali Karicheri wrote:
> On 12/16/2014 01:23 PM, Murali Karicheri wrote:
> >netdev maintainers,
> >
> >I got a comment to address CHECK warning and wondering how to address
> >'warning: testing a 'safe expression' which appears when using
> >IS_ERR_OR_NULL(foo)
> >
> >where foo is defined as
> >
> >struct foo_type *foo;
> >
> >The foo get assigned only NULL or ERR_PTR(error code). So I believe the
> >usage is correct. But then how do I make the CHECK happy of its usage?
> >
> >I have tried doing a grep on the current usage of IS_ERR_OR_NULL() and
> >found 276 of them causes this warning in the v3.18 version of the kernel
> >that I am using
> >
> >$ grep -r "warning: testing a 'safe expression" * | wc -l
> >276
> >
> >1) Can someone explain what this warning means?
> >
> >2) Is it acceptable to post patches to netdev list with this warning?
> >
> >3) if not, how this is expected to be fixed? Any example usage to fix
> >this warning will be helpful.
> >
> >Thanks in advance for
> 
> 
> -- 
> Murali Karicheri
> Linux Kernel, Texas Instruments