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e08d6de4e5
The kbuild cache was introduced to remember the result of shell
commands, some of which are expensive to compute, such as
$(call cc-option,...).
However, this turned out not so clever as I had first expected.
Actually, it is problematic. For example, "$(CC) -print-file-name"
is cached. If the compiler is updated, the stale search path causes
build error, which is difficult to figure out. Another problem
scenario is cache files could be touched while install targets are
running under the root permission. We can patch them if desired,
but the build infrastructure is getting uglier and uglier.
Now, we are going to move compiler flag tests to the configuration
phase. If this is completed, the result of compiler tests will be
naturally cached in the .config file. We will not have performance
issues of incremental building since this testing only happens at
Kconfig time.
To start this work with a cleaner code base, remove the kbuild
cache first.
Revert the following commits:
Commit 9a234a2e3843 ("kbuild: create directory for make cache only when necessary")
Commit e17c400ae194 ("kbuild: shrink .cache.mk when it exceeds 1000 lines")
Commit 4e56207130ed ("kbuild: Cache a few more calls to the compiler")
Commit 3298b690b21c ("kbuild: Add a cache for generated variables")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.