From: Brendan Higgins <brendanhiggins@google.com>
To: Masahiro Yamada <masahiroy@kernel.org>
Cc: linux-kbuild <linux-kbuild@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Anders Roxell <anders.roxell@linaro.org>,
Sami Tolvanen <samitolvanen@google.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
"David S. Miller" <davem@davemloft.net>,
Haren Myneni <haren@us.ibm.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Ingo Molnar <mingo@redhat.com>, Jiri Kosina <jikos@kernel.org>,
Joe Lawrence <joe.lawrence@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Michal Marek <michal.lkml@markovi.net>,
Miroslav Benes <mbenes@suse.cz>,
Paul Mackerras <paulus@samba.org>, Petr Mladek <pmladek@suse.com>,
Rich Felker <dalias@libc.org>,
Russell King <linux@armlinux.org.uk>,
Tal Gilboa <talgi@mellanox.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
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<linux-kselftest@vger.kernel.org>,
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live-patching@vger.kernel.org
Subject: Re: [PATCH v2 1/2] kbuild: introduce ccflags-remove-y and asflags-remove-y
Date: Tue, 7 Jul 2020 12:58:01 -0700 [thread overview]
Message-ID: <CAFd5g46eCjZA-e4akYc1K8u29tp94gpmrAOxZ_joZ=9kJtZeuA@mail.gmail.com> (raw)
In-Reply-To: <20200707092117.963394-1-masahiroy@kernel.org>
On Tue, Jul 7, 2020 at 2:22 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> CFLAGS_REMOVE_<file>.o filters out flags when compiling a particular
> object, but there is no convenient way to do that for every object in
> a directory.
>
> Add ccflags-remove-y and asflags-remove-y to make it easily.
>
> Use ccflags-remove-y to clean up some Makefiles.
>
> The add/remove order works as follows:
>
> [1] KBUILD_CFLAGS specifies compiler flags used globally
>
> [2] ccflags-y adds compiler flags for all objects in the
> current Makefile
>
> [3] ccflags-remove-y removes compiler flags for all objects in the
> current Makefile (New feature)
>
> [4] CFLAGS_<file> adds compiler flags per file.
>
> [5] CFLAGS_REMOVE_<file> removes compiler flags per file.
>
> Having [3] before [4] allows us to remove flags from most (but not all)
> objects in the current Makefile.
>
> For example, kernel/trace/Makefile removes $(CC_FLAGS_FTRACE)
> from all objects in the directory, then adds it back to
> trace_selftest_dynamic.o and CFLAGS_trace_kprobe_selftest.o
>
> Please note ccflags-remove-y has no effect to the sub-directories.
> In contrast, the previous notation got rid of compiler flags also from
> all the sub-directories.
>
> arch/arm/boot/compressed/
> arch/powerpc/xmon/
> arch/sh/
> kernel/trace/
>
> ... have no sub-directories.
>
> lib/
>
> ... has several sub-directories.
>
> To keep the behavior, I added ccflags-remove-y to all Makefiles
> in subdirectories of lib/, except:
>
> lib/vdso/Makefile - Kbuild does not descend into this Makefile
> lib/raid/test/Makefile - This is not used for the kernel build
>
> I think commit 2464a609ded0 ("ftrace: do not trace library functions")
> excluded too much. In later commit, I will try to remove ccflags-remove-y
> from sub-directory Makefiles.
>
> Suggested-by: Sami Tolvanen <samitolvanen@google.com>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Acked-by: Brendan Higgins <brendanhiggins@google.com> (KUnit)
next prev parent reply other threads:[~2020-07-07 19:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-07 9:21 [PATCH v2 1/2] kbuild: introduce ccflags-remove-y and asflags-remove-y Masahiro Yamada
2020-07-07 9:21 ` [PATCH v2 2/2] kbuild: trace functions in subdirectories of lib/ Masahiro Yamada
2020-07-07 16:02 ` Steven Rostedt
2020-07-22 2:08 ` Masahiro Yamada
2020-07-22 20:49 ` Steven Rostedt
2020-07-08 6:52 ` Petr Mladek
2020-07-08 9:23 ` Petr Mladek
2020-07-22 2:10 ` Masahiro Yamada
2020-07-07 19:58 ` Brendan Higgins [this message]
2020-07-07 21:25 ` [PATCH v2 1/2] kbuild: introduce ccflags-remove-y and asflags-remove-y Anders Roxell
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