linux/scripts/remove-stale-files
Masahiro Yamada 4e9903b086 fortify: refactor test_fortify Makefile to fix some build problems
There are some issues in the test_fortify Makefile code.

Problem 1: cc-disable-warning invokes compiler dozens of times

To see how many times the cc-disable-warning is evaluated, change
this code:

  $(call cc-disable-warning,fortify-source)

to:

  $(call cc-disable-warning,$(shell touch /tmp/fortify-$$$$)fortify-source)

Then, build the kernel with CONFIG_FORTIFY_SOURCE=y. You will see a
large number of '/tmp/fortify-<PID>' files created:

  $ ls -1 /tmp/fortify-* | wc
       80      80    1600

This means the compiler was invoked 80 times just for checking the
-Wno-fortify-source flag support.

$(call cc-disable-warning,fortify-source) should be added to a simple
variable instead of a recursive variable.

Problem 2: do not recompile string.o when the test code is updated

The test cases are independent of the kernel. However, when the test
code is updated, $(obj)/string.o is rebuilt and vmlinux is relinked
due to this dependency:

  $(obj)/string.o: $(obj)/$(TEST_FORTIFY_LOG)

always-y is suitable for building the log files.

Problem 3: redundant code

  clean-files += $(addsuffix .o, $(TEST_FORTIFY_LOGS))

... is unneeded because the top Makefile globally cleans *.o files.

This commit fixes these issues and makes the code readable.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20240727150302.1823750-2-masahiroy@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
2024-08-15 09:26:02 -07:00

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#!/bin/sh
set -e
# When you move, remove or rename generated files, you probably also update
# .gitignore and cleaning rules in the Makefile. This is the right thing
# to do. However, people usually do 'git pull', 'git bisect', etc. without
# running 'make clean'. Then, the stale generated files are left over, often
# causing build issues.
#
# Also, 'git status' shows such stale build artifacts as untracked files.
# What is worse, some people send a wrong patch to get them back to .gitignore
# without checking the commit history.
#
# So, when you (re)move generated files, please move the cleaning rules from
# the Makefile to this script. This is run before Kbuild starts building
# anything, so people will not be annoyed by such garbage files.
#
# This script is not intended to grow endlessly. Rather, it is a temporary scrap
# yard. Stale files stay in this file for a while (for some release cycles?),
# then will be really dead and removed from the code base entirely.
rm -f *.spec
rm -f lib/test_fortify.log