[PATCH] tty/serial: digicolor: Fix bad usage of IS_ERR_VALUE

[Andrzej Hajda]

On 02/11/2016 04:32 PM, Guenter Roeck wrote:
> On Thu, Feb 11, 2016 at 07:45:11AM +0100, Andrzej Hajda wrote:
>> On 02/11/2016 04:38 AM, Guenter Roeck wrote:
>>> On 02/10/2016 07:21 AM, Arnd Bergmann wrote:
>>>> On Tuesday 09 February 2016 18:37:46 Guenter Roeck wrote:
>>>>> On 02/09/2016 07:26 AM, Arnd Bergmann wrote:
>>>>>> On Tuesday 09 February 2016 07:08:59 Guenter Roeck wrote:
>>>>>>> IS_ERR_VALUE() assumes that its parameter is an unsigned long.
>>>>>>> It can not be used to check if an unsigned int reflects an error.
>>>>>>> Doing so can result in the following build warning.
>>>>>>>
>>>>>>> drivers/tty/serial/digicolor-usart.c: In function ‘digicolor_uart_probe’:
>>>>>>> include/linux/err.h:21:38: warning:
>>>>>>>           comparison is always false due to limited range of data type
>>>>>>> drivers/tty/serial/digicolor-usart.c:485:6: note:
>>>>>>>           in expansion of macro ‘IS_ERR_VALUE’
>>>>>>>
>>>>>>> If that warning is seen, an error return from platform_get_irq() is missed.
>>>>>>>
>>>>>>>
>>>>>> The patch looks correct to me, but what compiler version and which kernel
>>>>>> tree is it that triggered the warning?
>>>>>>
>>>>>> Andrzej Hajda just modified the definition of IS_ERR_VALUE(), and the
>>>>>> changes are still under discussion, but I don't see that warning with
>>>>>> any of the versions.
>>>>>>
>>>>> I see it with gcc 5.1 and 5.2 (and W=1). I did not see / notice Andrzej's patch.
>>>>>
>>>>> I agree that fixing the problem in IS_ERR_VALUE() is preferrable.
>>>>>
>>>>>
>>>> Ah, W=1 explains it. We are still debating about the proper solution. Al Viro
>>>> pointed out that most users of IS_ERR_VALUE() shouldn't be using it at all,
>>>> so your patch is probably best here after all.
>>>>
>>> Yes, after looking into it some more I agree. Coccinelle should be able to handle
>>> most of the conversions automatically. I actually tried to write a script, just
>>> for the fun of it, but it misses some of the problem cases in patch mode.
>>> Maybe I get it working tonight.
>>>
>>> Guenter
>>>
>> Maybe it can be helpful. The script which classifies all IS_ERR_VALUE
>> usages as
>> correct, signed, incorrect and unknown (cocci was not able to detect type).
>> Adding patch mode should be quite simple.
>>
>> // Options: --all-includes --include
>> include/uapi/linux/netfilter_ipv6/ip6_tables.h --include
>> include/uapi/linux/netfilter_ipv4/ip_tables.h --include
>> include/uapi/linux/netfilter_arp/arp_tables.h --include
>> include/uapi/linux/netfilter/x_tables.h --include include/linux/mm_types.h
>>
>> virtual context
>> virtual report
>>
>> @r@
>> typedef bool, u8, u16, u32, u64, s8, s16, s32, s64, __u64, dma_addr_t,
>> Elf32_Addr, Elf64_Addr;
>> {unsigned long, size_t} ev;
>> {short, int, long, s16, s32, ssize_t} ew;
>> {char, unsigned char, unsigned short, unsigned int, long long, unsigned
>> long long, bool, u8, u16, u32, u64, s64, __u64, dma_addr_t, Elf32_Addr,
>> Elf64_Addr} ei;
>> expression eu;
>> position p;
>> @@
>>
>> IS_ERR_VALUE(\(ev \| ew \| ei \| eu \))@p
>>
>> @script:python depends on report@
>> p << r.p = [];
>> ev << r.ev = "";
>> ew << r.ew = "";
>> ei << r.ei = "";
>> eu << r.eu = "";
> This doesn't work for me; it bails out at the assignments. If I remove
> the assignments, it does not report anything.
>
> Any idea what might be wrong ?

Old version of spatch. Default values are supported since 1.0.3.

Regards
Andrzej