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scripts/misc-check: check missing #include <linux/export.h> when W=1

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The problem was described in commit 5b20755b77 ("init: move THIS_MODULE
from <linux/export.h> to <linux/init.h>").

To summarize it again here: <linux/export.h> is included by most C files,
even though only some of them actually export symbols. This is because
some headers, such as include/linux/{module.h,linkage}, needlessly
include <linux/export.h>.

I have added a more detailed explanation in the comments of
scripts/misc-check.

This problem will be fixed in two steps:

 1. Add #include <linux/export.h> directly to C files that use
    EXPORT_SYMBOL()
 2. Remove #include <linux/export.h> from header files that do not use
    EXPORT_SYMBOL()

This commit addresses step 1; scripts/misc-check will warn about *.[ch]
files that use EXPORT_SYMBOL() but do not include <linux/export.h>.
This check is only triggered when the kernel is built with W=1.

We need to fix 4000+ files. I hope others will help with this effort.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Masahiro Yamada 2025-06-01 22:31:29 +09:00
parent 3a44052b72
commit a934a57a42
1 changed files with 43 additions and 0 deletions
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43
scripts/misc-check
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@ -9,4 +9,47 @@ check_tracked_ignored_files () {
sed 's/$/: warning: ignored by one of the .gitignore files/' >&2
}
# Check for missing #include <linux/export.h>
#
# The rule for including <linux/export.h> is very simple:
# Include <linux/export.h> only when you use EXPORT_SYMBOL(). That's it.
#
# However, some headers include <linux/export.h> even though they are completely
# unrelated to EXPORT_SYMBOL().
#
# One example is include/linux/module.h. Please note <linux/module.h> and
# <linux/export.h> are orthogonal. <linux/module.h> should be included by files
# that can be compiled as modules. In other words, <linux/module.h> should be
# included by EXPORT_SYMBOL consumers. In contrast, <linux/export.h> should be
# included from EXPORT_SYMBOL providers, which may or may not be modular.
# Hence, include/linux/module.h should *not* include <linux/export.h>.
#
# Another example is include/linux/linkage.h, which is completely unrelated to
# EXPORT_SYMBOL(). Worse, it is included by most C files, which means, most C
# files end up including <linux/export.h>, even though only some of them
# actually export symbols. Hence, include/linux/linkage.h should *not* include
# <linux/export.h>.
#
# Before fixing such headers, we must ensure that C files using EXPORT_SYMBOL()
# include <linux/export.h> directly, since many C files currently rely on
# <linux/export.h> being included indirectly (likely, via <linux/linkage> etc.).
#
# Therefore, this check.
#
# The problem is simple - the warned files use EXPORT_SYMBOL(), but do not
# include <linux/export.h>. Please add #include <linux/export.h> to them.
#
# If the included headers are sorted alphabetically, please insert
# <linux/export.h> in the appropriate position to maintain the sort order.
# For this reason, this script only checks missing <linux/export.h>, but
# does not automatically fix it.
check_missing_include_linux_export_h () {
git -C "${srctree:-.}" grep --files-with-matches -E 'EXPORT_SYMBOL((_NS)?(_GPL)?|_GPL_FOR_MODULES)\(.*\)' \
-- '*.[ch]' :^tools/ :^include/linux/export.h |
xargs -r git -C "${srctree:-.}" grep --files-without-match '#include[[:space:]]*<linux/export\.h>' |
xargs -r printf "%s: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing\n" >&2
}
check_tracked_ignored_files
check_missing_include_linux_export_h