checkpatch.pl investigation for false-positives

Hi Lukas,

I looked at different error messages and came-up with a list of possible false positives reports by checkpatch script.

First, is about BAD_SIGN_OFF warning for Duplicate signature. Though it is obvious to have these warnings but I am wondering about situations where there is some other signature between two exactly same signatures.
For instance,

commit 3f9c6d38797e9903937b007a341dad0c251765d6
...

Signed-off-by Jonathan Cameron <[email protected]>

Acked-by Andrew F. Davis <[email protected]>

Cc <[email protected]>

Signed-off-by Jonathan Cameron <[email protected]>

commit 79ea1e12c0b8540100e89b32afb9f0e6503fad35

    ...
    Signed-off-by: Johannes Berg <[email protected]>
    Link: https://lore.kernel.org/r/20200604120420.b1dc540a7e26.I55

dcca56bb5bdc5d7ad66a36a0b42afd7034d8be@changeid

Signed-off-by Johannes Berg <[email protected]>

I'm not familiar how/when these situations can occur. But if these scenarios are commonly acceptable then the script should not report
a warning for duplicate signatures.

---

Second, is about WHILE_AFTER_BRACE errors.

Example commit: 6f8a57ccf8511724e6f48d732cb2940889789ab2

The error message suggests to move the empty while loop with close brace of an if block which is not recommended according to the code style.

The possible correction would be consider checking the type of block that is ending and report only when the do block is found.

---

Third, is about EXECUTE_PERMISSIONS errors where the script reports an error for a python (possible with others scripts as well) script with file mode set as '100755' but file name does not include '.py' extension and is not present under the 'scripts' directory tree.

So, a python script file named 'binfmt_script' with file mode '100755'
is erroneously reported by the script as:

ERROR:EXECUTE_PERMISSIONS: do not set execute permissions for source files #39: FILE: tools/testing/selftests/exec/binfmt_script

even when it is okay to make the script file executable.

Example commit b081320f0693cce0394f7c8bad9fba0b25982186

A possible solution to this would be to use the script's first line for determining whether the file is a executable file or not.

Quoted 22 lines · Ujjwal Kumar

Hi Lukas,

I looked at different error messages and came-up with a list of possible false positives reports by checkpatch script.

First, is about BAD_SIGN_OFF warning for Duplicate signature. Though it is obvious to have these warnings but I am wondering about situations where there is some other signature between two exactly same signatures.
For instance,

commit 3f9c6d38797e9903937b007a341dad0c251765d6
...

Signed-off-by Jonathan Cameron <[email protected]>

Acked-by Andrew F. Davis <[email protected]>

Cc <[email protected]>

Signed-off-by Jonathan Cameron <[email protected]>

commit 79ea1e12c0b8540100e89b32afb9f0e6503fad35

    ...
    Signed-off-by: Johannes Berg <[email protected]>
    Link: https://lore.kernel.org/r/20200604120420.b1dc540a7e26.I55

Quoted 7 lines

dcca56bb5bdc5d7ad66a36a0b42afd7034d8be@changeid

Signed-off-by Johannes Berg <[email protected]>

I'm not familiar how/when these situations can occur. But if these scenarios are commonly acceptable then the script should not report
a warning for duplicate signatures.

That is a typical situation when a maintainer sends their own patches to a mailing list and then picks them up again. Hmm, I need to think about if that should be addressed. You could of course detect the Link:
with lore.kernel.org and identify that all further sign offs are now part of the patch integration. Running checkpatch.pl on git commits is not the most common thing, so it might just be a minor issue.

Let us keep it in mind for now.

Quoted 4 lines

---

Second, is about WHILE_AFTER_BRACE errors.

Quoted 9 lines

Example commit: 6f8a57ccf8511724e6f48d732cb2940889789ab2

The error message suggests to move the empty while loop with close brace of an if block which is not recommended according to the code style.

The possible correction would be consider checking the type of block that is ending and report only when the do block is found.

Okay, that is going to be tricky... maybe clang-format and friends is the better tool to handle that eventually. I would not pick that to investigate further, just because it is quite tricky. checkpatch.pl is already just doing some rough estimation and not really parsing the syntax tree.

Quoted 13 lines

---

Third, is about EXECUTE_PERMISSIONS errors where the script reports an error for a python (possible with others scripts as well) script with file mode set as '100755' but file name does not include '.py' extension and is not present under the 'scripts' directory tree.

So, a python script file named 'binfmt_script' with file mode '100755'
is erroneously reported by the script as:

ERROR:EXECUTE_PERMISSIONS: do not set execute permissions for source files #39: FILE: tools/testing/selftests/exec/binfmt_script

Quoted 7 lines

even when it is okay to make the script file executable.

Example commit b081320f0693cce0394f7c8bad9fba0b25982186

A possible solution to this would be to use the script's first line for determining whether the file is a executable file or not.

That seems reasonable. Maybe the rule needs an update anyway because executable scripts can also be in tools/...

I suggest to have a look at the discussion of this patch where we already discussed out the role of execute permissions in the kernel repository:

https://lore.kernel.org/linux-kernel-mentees/20200827060523.6fi34tcrg5xndzuu@mrinalpandey/#t

Mrinal never followed up on the two potential tasks in
https://lore.kernel.org/linux-kernel-mentees/alpine.DEB.2.21.2008310714560.8556@felia/

Ujjwal, maybe you can look at the build scripts and check if there are any places where the build really relies on the file being executable (which we currently do guarantee)?

If there are some questions to the task, feel free to ask.

Lukas

Quoted 89 lines · Lukas Bulwahn

Quoted 22 lines · Ujjwal Kumar

Hi Lukas,

I looked at different error messages and came-up with a list of possible false positives reports by checkpatch script.

First, is about BAD_SIGN_OFF warning for Duplicate signature. Though it is obvious to have these warnings but I am wondering about situations where there is some other signature between two exactly same signatures.
For instance,

commit 3f9c6d38797e9903937b007a341dad0c251765d6
...

Signed-off-by Jonathan Cameron <[email protected]>

Acked-by Andrew F. Davis <[email protected]>

Cc <[email protected]>

Signed-off-by Jonathan Cameron <[email protected]>

commit 79ea1e12c0b8540100e89b32afb9f0e6503fad35

    ...
    Signed-off-by: Johannes Berg <[email protected]>
    Link: https://lore.kernel.org/r/20200604120420.b1dc540a7e26.I55

Quoted 7 lines

dcca56bb5bdc5d7ad66a36a0b42afd7034d8be@changeid

Signed-off-by Johannes Berg <[email protected]>

I'm not familiar how/when these situations can occur. But if these scenarios are commonly acceptable then the script should not report
a warning for duplicate signatures.

That is a typical situation when a maintainer sends their own patches to a mailing list and then picks them up again. Hmm, I need to think about if that should be addressed. You could of course detect the Link:
with lore.kernel.org and identify that all further sign offs are now part of the patch integration. Running checkpatch.pl on git commits is not the most common thing, so it might just be a minor issue.

Let us keep it in mind for now.

Quoted 4 lines

---

Second, is about WHILE_AFTER_BRACE errors.

Quoted 9 lines

Example commit: 6f8a57ccf8511724e6f48d732cb2940889789ab2

The error message suggests to move the empty while loop with close brace of an if block which is not recommended according to the code style.

The possible correction would be consider checking the type of block that is ending and report only when the do block is found.

Okay, that is going to be tricky... maybe clang-format and friends is the better tool to handle that eventually. I would not pick that to investigate further, just because it is quite tricky. checkpatch.pl is already just doing some rough estimation and not really parsing the syntax tree.

Quoted 13 lines

---

Third, is about EXECUTE_PERMISSIONS errors where the script reports an error for a python (possible with others scripts as well) script with file mode set as '100755' but file name does not include '.py' extension and is not present under the 'scripts' directory tree.

So, a python script file named 'binfmt_script' with file mode '100755'
is erroneously reported by the script as:

ERROR:EXECUTE_PERMISSIONS: do not set execute permissions for source files #39: FILE: tools/testing/selftests/exec/binfmt_script

Quoted 7 lines

even when it is okay to make the script file executable.

Example commit b081320f0693cce0394f7c8bad9fba0b25982186

A possible solution to this would be to use the script's first line for determining whether the file is a executable file or not.

That seems reasonable. Maybe the rule needs an update anyway because executable scripts can also be in tools/...

I suggest to have a look at the discussion of this patch where we already discussed out the role of execute permissions in the kernel repository:

Quoted 9 lines

https://lore.kernel.org/linux-kernel-mentees/20200827060523.6fi34tcrg5xndzuu@mrinalpandey/#t

Mrinal never followed up on the two potential tasks in
https://lore.kernel.org/linux-kernel-mentees/alpine.DEB.2.21.2008310714560.8556@felia/

Ujjwal, maybe you can look at the build scripts and check if there are any places where the build really relies on the file being executable (which we currently do guarantee)?

I unset executable bit on all the files, and tried building the kernel. The configuration step itself fails and hence it appears that build process and Makefiles do rely on the executable bits for scripts.

The init/Kconfig file is the reason behind failing builds. I prefixed the script calls with relevant interpreters and now I can successfully configure and build the kernel. Though I have not tried building all the modules (only the ones relevant to my system configuration). I'll be able to give a final opinion after making all the modules (my system is too slow with a dual core cpu :( ).