[Linux-kernel-mentees] [PATCH] checkpatch: fix false positive for REPEATED_WORD warning

[Aditya]

On 21/10/20 8:48 pm, Joe Perches wrote:
> On Wed, 2020-10-21 at 20:31 +0530, Aditya Srivastava wrote:
>> Presence of hexadecimal address or symbol results in false warning
>> message by checkpatch.pl.
>>
>> For example, running checkpatch on commit b8ad540dd4e4 ("mptcp: fix
>> memory leak in mptcp_subflow_create_socket()") results in warning:
>>
>> WARNING:REPEATED_WORD: Possible repeated word: 'ff'
>>     00 00 00 00 00 00 00 00 00 2f 30 0a 81 88 ff ff  ........./0.....
> 
> Right.
> 
>> To avoid all such reports, add an additional regex check for a repeating
>> pattern of 4 or more 2-lettered words separated by space in a line.
> 
>> A quick evaluation on v5.6..v5.8 showed that this fix reduces
>> REPEATED_WORD warnings from 2797 to 1043.
> 
> Are many of the other 1043 false positives?
> Any pattern to them?
> 

Apart from the changes suggested by Dwaipayan in
https://lore.kernel.org/linux-kernel-mentees/20201017162732.152351-1-dwaipayanray1@gmail.com/

The 'ls -l' output seems to be another common false positive for
REPEATED_WORD (Frequency 106 over v5.6..v5.8). For eg.

WARNING:REPEATED_WORD: Possible repeated word: 'root'
#18:
  drwxr-xr-x. 2 root root    0 Apr 17 10:53 .

WARNING:REPEATED_WORD: Possible repeated word: 'nobody'
#28:
drwxr-xr-x 5 nobody nobody    0 Jan 25 18:08 .

WARNING:REPEATED_WORD: Possible repeated word: 'irogers'
#17:
  -rw-r----- 1 irogers irogers 553 Apr 17 14:31
../../../util/unwind-libdw.h

These can be avoided by using:
@@ -3050,8 +3050,10 @@ sub process {
 			}
 		}

-		if ($rawline =~ /^\+/ || $in_commit_log) {
+		if (($rawline =~ /^\+/ || $in_commit_log) &&
+		$rawline !~ /\b[a-z-]+.* \d{1,3} [a-zA-Z]+ \w+ +\d+ \w{3} \d{1,2}
\d{1,2}:\d{1,2}/) {

Sincerely
Aditya

>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
>> @@ -3050,8 +3050,10 @@ sub process {
>>  			}
>>  		}
>>  
>> -# check for repeated words separated by a single space
>> -		if ($rawline =~ /^\+/ || $in_commit_log) {
>> +# check for repeated words separated by a single space and
>> +# avoid repeating hex occurrences like 'ff ff fe 09 ...'
>> +		if (($rawline =~ /^\+/ || $in_commit_log) &&
>> +		$rawline !~ /(\b[0-9a-f]{2}( )+){4,}/) {
> 
> This might be better as \b$Hex to avoid FF FF
> and FFFFFFFF FFFFFFFF
> 
> I might add that check to the line below where
> the repeated words are checked against long
> ---
>  scripts/checkpatch.pl | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index fab38b493cef..929866999f81 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -3062,6 +3062,7 @@ sub process {
>  
>  				next if ($first ne $second);
>  				next if ($first eq 'long');
> +				next if ($first =~ /^$Hex$/;
>  
>  				if (WARN("REPEATED_WORD",
>  					 "Possible repeated word: '$first'\n" . $herecurr) &&
> 
>