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

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