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

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Message-ID: <549312BB.40400@ti.com>
Date:	Thu, 18 Dec 2014 12:45:31 -0500
From:	Murali Karicheri <m-karicheri2@...com>
To:	Christopher Li <sparse@...isli.org>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: How to fix CHECK warning: testing a 'safe expression' ?

On 12/17/2014 09:39 PM, Christopher Li wrote:
> On Thu, Dec 18, 2014 at 6:37 AM, Murali Karicheri<m-karicheri2@...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
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