[PATCH 1/2] kbuild: remove redundant CONFIG_KASAN check from scripts/Makefile.kasan

[PATCH 1/2] kbuild: remove redundant CONFIG_KASAN check from scripts/Makefile.kasan

[Masahiro Yamada]

Since commit e0fe0bbe57b8 ("kbuild: include scripts/Makefile.* only
when relevant CONFIG is enabled"), this file is included only when
CONFIG_KASAN=y.

This ifdef is redundant.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 scripts/Makefile.kasan | 2 --
 1 file changed, 2 deletions(-)

diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index f4beee1b0013..1532f1a41a8f 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -1,8 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
-ifdef CONFIG_KASAN
 CFLAGS_KASAN_NOSANITIZE := -fno-builtin
 KASAN_SHADOW_OFFSET ?= $(CONFIG_KASAN_SHADOW_OFFSET)
-endif
 
 ifdef CONFIG_KASAN_GENERIC
 
-- 
2.25.1

[PATCH 2/2] kbuild: move CFLAGS_{KASAN,UBSAN,KCSAN} exports to relevant Makefiles

[Masahiro Yamada]

Move CFLAGS_KASAN*, CFLAGS_UBSAN, CFLAGS_KCSAN to Makefile.kasan,
Makefile.ubsan, Makefile.kcsan, respectively.

This commit also avoids the same -fsanitize=* flags being added to
CFLAGS_UBSAN multiple times.

Prior to this commit, the ubsan flags were appended by the '+='
operator, without any initialization. Some build targets such as
'make bindeb-pkg' recurses to the top Makefile, and ended up with
adding the same flags to CFLAGS_UBSAN twice.

Clear CFLAGS_UBSAN with ':=' to make it a simply expanded variable.
This is better than a recursively expanded variable, which evaluates
$(call cc-option, ...) multiple times before Kbuild starts descending
to subdirectories.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

 Makefile               | 1 -
 scripts/Makefile.kasan | 2 ++
 scripts/Makefile.kcsan | 2 +-
 scripts/Makefile.ubsan | 3 +++
 4 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index ec2330ce0fc5..4b5a305e30d2 100644
--- a/Makefile
+++ b/Makefile
@@ -517,7 +517,6 @@ export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
 export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
-export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN CFLAGS_KCSAN
 export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
 export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
 export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
index 1532f1a41a8f..1e000cc2e7b4 100644
--- a/scripts/Makefile.kasan
+++ b/scripts/Makefile.kasan
@@ -47,3 +47,5 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
 		$(instrumentation_flags)
 
 endif # CONFIG_KASAN_SW_TAGS
+
+export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE
diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan
index c50f27b3ac56..cec50d74e0d0 100644
--- a/scripts/Makefile.kcsan
+++ b/scripts/Makefile.kcsan
@@ -9,7 +9,7 @@ endif
 
 # Keep most options here optional, to allow enabling more compilers if absence
 # of some options does not break KCSAN nor causes false positive reports.
-CFLAGS_KCSAN := -fsanitize=thread \
+export CFLAGS_KCSAN := -fsanitize=thread \
 	$(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0) -fno-optimize-sibling-calls) \
 	$(call cc-option,$(call cc-param,tsan-instrument-read-before-write=1)) \
 	$(call cc-param,tsan-distinguish-volatile=1)
diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
index 27348029b2b8..c661484ee01f 100644
--- a/scripts/Makefile.ubsan
+++ b/scripts/Makefile.ubsan
@@ -1,4 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
+
+export CFLAGS_UBSAN :=
+
 ifdef CONFIG_UBSAN_ALIGNMENT
       CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
 endif
-- 
2.25.1

Re: [PATCH 2/2] kbuild: move CFLAGS_{KASAN,UBSAN,KCSAN} exports to relevant Makefiles

[Marco Elver]

On Thu, 10 Sep 2020 at 15:45, Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> Move CFLAGS_KASAN*, CFLAGS_UBSAN, CFLAGS_KCSAN to Makefile.kasan,
> Makefile.ubsan, Makefile.kcsan, respectively.
>
> This commit also avoids the same -fsanitize=* flags being added to
> CFLAGS_UBSAN multiple times.
>
> Prior to this commit, the ubsan flags were appended by the '+='
> operator, without any initialization. Some build targets such as
> 'make bindeb-pkg' recurses to the top Makefile, and ended up with
> adding the same flags to CFLAGS_UBSAN twice.
>
> Clear CFLAGS_UBSAN with ':=' to make it a simply expanded variable.
> This is better than a recursively expanded variable, which evaluates
> $(call cc-option, ...) multiple times before Kbuild starts descending
> to subdirectories.
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
>  Makefile               | 1 -
>  scripts/Makefile.kasan | 2 ++
>  scripts/Makefile.kcsan | 2 +-
>  scripts/Makefile.ubsan | 3 +++
>  4 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index ec2330ce0fc5..4b5a305e30d2 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -517,7 +517,6 @@ export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
>
>  export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS KBUILD_LDFLAGS
>  export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
> -export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE CFLAGS_UBSAN CFLAGS_KCSAN
>  export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
>  export KBUILD_AFLAGS_MODULE KBUILD_CFLAGS_MODULE KBUILD_LDFLAGS_MODULE
>  export KBUILD_AFLAGS_KERNEL KBUILD_CFLAGS_KERNEL
> diff --git a/scripts/Makefile.kasan b/scripts/Makefile.kasan
> index 1532f1a41a8f..1e000cc2e7b4 100644
> --- a/scripts/Makefile.kasan
> +++ b/scripts/Makefile.kasan
> @@ -47,3 +47,5 @@ CFLAGS_KASAN := -fsanitize=kernel-hwaddress \
>                 $(instrumentation_flags)
>
>  endif # CONFIG_KASAN_SW_TAGS
> +
> +export CFLAGS_KASAN CFLAGS_KASAN_NOSANITIZE
> diff --git a/scripts/Makefile.kcsan b/scripts/Makefile.kcsan
> index c50f27b3ac56..cec50d74e0d0 100644
> --- a/scripts/Makefile.kcsan
> +++ b/scripts/Makefile.kcsan
> @@ -9,7 +9,7 @@ endif
>
>  # Keep most options here optional, to allow enabling more compilers if absence
>  # of some options does not break KCSAN nor causes false positive reports.
> -CFLAGS_KCSAN := -fsanitize=thread \
> +export CFLAGS_KCSAN := -fsanitize=thread \
>         $(call cc-option,$(call cc-param,tsan-instrument-func-entry-exit=0) -fno-optimize-sibling-calls) \
>         $(call cc-option,$(call cc-param,tsan-instrument-read-before-write=1)) \
>         $(call cc-param,tsan-distinguish-volatile=1)

This doesn't apply to -next, which has some KCSAN changes for the next
merge window. Although it seems git-merge figures out the resolution
for the conflict automatically.

Other than that,

Acked-by: Marco Elver <elver@google.com>

Thank you!

> diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
> index 27348029b2b8..c661484ee01f 100644
> --- a/scripts/Makefile.ubsan
> +++ b/scripts/Makefile.ubsan
> @@ -1,4 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0
> +
> +export CFLAGS_UBSAN :=
> +
>  ifdef CONFIG_UBSAN_ALIGNMENT
>        CFLAGS_UBSAN += $(call cc-option, -fsanitize=alignment)
>  endif
> --
> 2.25.1
>