[Linux-kernel-mentees] [PATCH] checkpatch: Improve SPDX license identifier check for script files

Mrinal Pandey mrinalmni at gmail.com
Sun Aug 9 07:22:40 UTC 2020


On 20/08/04 09:37PM, Lukas Bulwahn wrote:
> 
> 
> On Tue, 4 Aug 2020, Mrinal Pandey wrote:
> 
> > On 20/08/03 12:59PM, Lukas Bulwahn wrote:
> > > 
> > > 
> > > On Mon, 3 Aug 2020, Mrinal Pandey wrote:
> > > 
> > > > The diff content includes the SPDX licensing information but excludes the
> > > > shebang when a change is made to a script file in commit 37f8173dd849
> > > > ("locking/atomics: Flip fallbacks and  instrumentation") and commit
> > > > 075c8aa79d54 ("selftests: forwarding: tc_actions.sh: add matchall mirror
> > > > test"). In these cases checkpatch issues a false positive warning:
> > > > "Misplaced SPDX-License-Identifier tag - use line 1 instead".
> > > > 
> > > > Currently, if checkpatch finds a shebang in line 1, it expects the
> > > > license identifier in line 2. However, this doesn't work when a shebang
> > > > isn't found on the line 1.
> > > 
> > > It does not work when the diff does not contain line 1, but only line 2,
> > > because then the shebang check for line 1 cannot work.
> > > 
> > > > 
> > > > I noticed this false positive, while running checkpatch on the set of
> > > > commits from v5.7 to v5.8-rc1 of the kernel, on the said commits.
> > > > This false positive exists in checkpatch since commit a8da38a9cf0e
> > > > ("checkpatch: add test for SPDX-License-Identifier on wrong line #")
> > > > when the corresponding rule was first added.
> > > > 
> > > > The alternatives considered to improve this check were looking the file
> > > > to be a script by either examining the file extension or file permissions.
> > > >
> > > 
> > > Make this sentence shorter. Try.
> > >  
> > > > The evaluation on former option resulted in 120 files which had a shebang
> > > > in the first line but no file extension. This didn't look like a promising
> > > > result and hence I dropped the idea of using this approach.
> > > > 
> > > > The evaluation on the latter approach shows that there are 53 files in the
> > > > kernel which have an executable bit set but don't have a shebang in the
> > > > first line.
> > > > 
> > > > At the first sight on these 53 files, it seems that they either have a
> > > > wrong file permission set or could be reasonably extended with a shebang
> > > > and SPDX license information. Thus, further cleanup in the repository
> > > > would make the latter approach to work even more precisely.
> > > > 
> > > > Hence, I chose to check the file permissions to determine if the file is a
> > > > script and notify checkpatch to expect SPDX on second line for such files.
> > > >
> > > 
> > > There is no notification here. Think about better wording.
> > >  
> > > > Signed-off-by: Mrinal Pandey <mrinalmni at gmail.com>
> > > > ---
> > > >  scripts/checkpatch.pl | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > > 
> > > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > > > index 4c820607540b..bae1dd824518 100755
> > > > --- a/scripts/checkpatch.pl
> > > > +++ b/scripts/checkpatch.pl
> > > > @@ -3166,6 +3166,9 @@ sub process {
> > > >  		}
> > > >  
> > > >  # check for using SPDX license tag at beginning of files
> > > > +		if ($line =~ /^index\ .*\.\..*\ .*[7531]\d{0,2}$/) {
> > > > +			$checklicenseline = 2;
> > > > +		}
> > > 
> > > That check looks good now.
> > > 
> > > >  		if ($realline == $checklicenseline) {
> > > >  			if ($rawline =~ /^[ \+]\s*\#\!\s*\//) {
> > > >  				$checklicenseline = 2;
> > > 
> > > This is probably broken now. It should check for shebang in line 1 and 
> > > then set checklicenseline to line 2, right?
> > 
> > Sir,
> > 
> > Should we remove this check? Earlier when I checked for file extension
> > we had 120 cases where this check was also needed but now we have a
> > better heuristic which is going to work for all cases where license
> > should be on line 2 irrespective of the fact that we know the first line
> > or not.
> >
> 
> Are you sure about that? Where is the evaluation that proves your point?
> 
> E.g., are all files that contain a shebang really with an executable flag?
> 
> Which commands did you run to check this?
>  
> > If I am missing out on something and we should not be removing this check,
> > then I suggest placing the new heuristics below this block so that it doesn't
> > interfere with the existing logic.
> > 
> > Please let me know which path should I go about and then I shall resend
> > the patch with the modified commit message.
> > 
> 
> Think about the strengths and weaknesses of the potential solutions, then 
> show with some commands (as I did for example, for finding the first 
> lines previously) that you can show that it practically makes a 
> difference and you can numbers on those differences.
> 
> When you did that, send a new patch.
> 
> Lukas
> 
Sir,

I ran the evaluation as:

mrinalpandey at mrinalpandey:~/linux/linux$ cat get_permissions.sh
#!/bin/bash

for file in $(git ls-files)
do
        permissions="$(stat -c "%a %n" $file)"
        echo "$permissions"
done

mrinalpandey at mrinalpandey:~/linux/linux$ sh get_permissions.sh | grep ^[7531] > temp

mrinalpandey at mrinalpandey:~/linux/linux$ cut -d ' ' -f 2 temp > executables

mrinalpandey at mrinalpandey:~/linux/linux$ cat first_line.sh
#!/bin/bash
file="executables"
while IFS= read -r line
do
        firstline=`head -n 1 $line`
        printf '%s:%s\n' "$firstline" "$line"
done <"$file"

mrinalpandey at mrinalpandey:~/linux/linux$ cat executables | wc -l
611

mrinalpandey at mrinalpandey:~/linux/linux$ sh first_line.sh | grep ^#! | wc -l
head: error reading 'scripts/dtc/include-prefixes/arc': Is a directory
head: error reading 'scripts/dtc/include-prefixes/arm': Is a directory
head: error reading 'scripts/dtc/include-prefixes/arm64': Is a directory
head: error reading 'scripts/dtc/include-prefixes/c6x': Is a directory
head: error reading 'scripts/dtc/include-prefixes/dt-bindings': Is a directory
head: error reading 'scripts/dtc/include-prefixes/h8300': Is a directory
head: error reading 'scripts/dtc/include-prefixes/microblaze': Is a directory
head: error reading 'scripts/dtc/include-prefixes/mips': Is a directory
head: error reading 'scripts/dtc/include-prefixes/nios2': Is a directory
head: error reading 'scripts/dtc/include-prefixes/openrisc': Is a directory
head: error reading 'scripts/dtc/include-prefixes/powerpc': Is a directory
head: error reading 'scripts/dtc/include-prefixes/sh': Is a directory
head: error reading 'scripts/dtc/include-prefixes/xtensa': Is a directory
540

We can see that there are 71 files where the executable bit is set but
the first line is not a shebang. These include 13 directories which
throw the error above. Remaining 58 files(earlier the number was 53)
could be cleaned so that this heuristic works better as we saw. So, by
checking only for the executable bit we can say that license should be
on second line, we probably don't need to check for the shebang on line
1.
Please let me know if the evaluation makes sense.

Thank you.

> > Thank you. > > 
> > > > -- 
> > > > 2.25.1
> > > > 
> > > > 
> > 
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