linux-kernel - srcversion hash does not cover all the module's source/dependency files

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Date: Wed, 14 Feb 2024 10:42:55 +0100
From: Radek Krejci <radek.krejci@...cle.com>
To: masahiroy@...nel.org, linux-kbuild@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Subject: srcversion hash does not cover all the module's source/dependency
 files

Hi,
I've found a bug in modpost - when it gets the list of source files to 
generate srcversion hash, it skips all the source/dependency files 
except for the first one.

There is patch [1] in v5.8rc1 replacing get_next_line() by get_line() in 
parse_source_file() function. Besides other things, the difference 
between those 2 functions is that get_next_line() trims the leading 
spaces of the line being returned. The issue is, that the source (deps_ 
located at the same directory) file names in the list, being processed 
in parse_source_file(), are indented. So, when the code gets to 
"Terminate line at first space, to get rid of final ' \'", it 
effectively hides the source file name from further processing, since 
the first space is at the beginning of the line.

I checked this behavior with modpost from v5.4 and v5.14 (and confirmed 
with the current master in git). In my case, my kernel module had just 2 
source files - mymodule.c and mymodule.h (both located at the same 
directory). With modpost from v5.4, the code change in any of the files 
was reflected in srcversion hash. But with modpost from v5.14 (and 
master) there is no hash change when the code change appears in the 
header file, which is listed at the end of the deps_ list. I believe 
this is quite simple to reproduce with any module, but if needed, I can 
prepare some example code to reproduce the issue.

I noticed this [2] email thread in the list. It mentions a similar 
issue. However, since it happened a half year before the change [1] was 
introduced and because I was unable to find any further details, 
including the promised patch, I believe that these 2 things are unrelated.

The enclosed patch worked for me, but there might be some other 
consequences that I've missed, so feel free to modify it on your own or 
let me know.

Is there anything else I can do to help fixing this issue?

Regards,
Radek Krejci

[1] - 
https://lore.kernel.org/linux-kbuild/20200601055731.3006266-26-masahiroy@kernel.org/
[2] - 
https://lore.kernel.org/linux-kbuild/CAN19L9G-mFN-MTmw0FS3ZX4d1MjeoL2U+s-Fk7Qw9UYWn5Q1YA@mail.gmail.com/ 

View attachment "0001-modpost-trim-leading-spaces-when-processing-source-f.patch" of type "text/x-patch" (1123 bytes)