[PATCH][next] init: Kconfig: Disable -Wstringop-overflow for GCC-11

[PATCH][next] init: Kconfig: Disable -Wstringop-overflow for GCC-11

[Gustavo A. R. Silva]

-Wstringop-overflow is buggy in GCC-11. Therefore, we should disable
this option specifically for that compiler version. To achieve this,
we introduce a new configuration option: GCC11_NO_STRINGOP_OVERFLOW.

The compiler option related to string operation overflow is now managed
under configuration CC_STRINGOP_OVERFLOW. This option is enabled by
default for all other versions of GCC that support it.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 Makefile     |  4 +++-
 init/Kconfig | 12 ++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 2cfd71ae3a86..8adc611fb611 100644
--- a/Makefile
+++ b/Makefile
@@ -982,7 +982,9 @@ NOSTDINC_FLAGS += -nostdinc
 # perform bounds checking.
 KBUILD_CFLAGS += $(call cc-option, -fstrict-flex-arrays=3)
 
-KBUILD_CFLAGS += $(call cc-option, -Wstringop-overflow)
+#Currently, disable -Wstringop-overflow for GCC 11, globally.
+KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-option, -Wno-stringop-overflow)
+KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
 
 # disable invalid "can't wrap" optimizations for signed / pointers
 KBUILD_CFLAGS	+= -fno-strict-overflow
diff --git a/init/Kconfig b/init/Kconfig
index 9ffb103fc927..aaaa99a5d2a9 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -876,6 +876,18 @@ config CC_NO_ARRAY_BOUNDS
 	bool
 	default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC11_NO_ARRAY_BOUNDS
 
+# Currently, disable -Wstringop-overflow for GCC 11, globally.
+config GCC11_NO_STRINGOP_OVERFLOW
+	def_bool y
+
+config CC_NO_STRINGOP_OVERFLOW
+	bool
+	default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC_VERSION < 120000 && GCC11_NO_STRINGOP_OVERFLOW
+
+config CC_STRINGOP_OVERFLOW
+	bool
+	default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW
+
 #
 # For architectures that know their GCC __int128 support is sound
 #
-- 
2.34.1

Re: [PATCH][next] init: Kconfig: Disable -Wstringop-overflow for GCC-11

[Kees Cook]

On Thu, Nov 30, 2023 at 02:52:10PM -0600, Gustavo A. R. Silva wrote:
> -Wstringop-overflow is buggy in GCC-11. Therefore, we should disable

Can you add some links for this? For example, maybe this?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97490

Or discussions from -next builds?

> this option specifically for that compiler version. To achieve this,
> we introduce a new configuration option: GCC11_NO_STRINGOP_OVERFLOW.
> 
> The compiler option related to string operation overflow is now managed
> under configuration CC_STRINGOP_OVERFLOW. This option is enabled by
> default for all other versions of GCC that support it.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

But yeah, let's get this landed to keep new warnings from appearing...

Reviewed-by: Kees Cook <keescook@chromium.org>


> ---
>  Makefile     |  4 +++-
>  init/Kconfig | 12 ++++++++++++
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 2cfd71ae3a86..8adc611fb611 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -982,7 +982,9 @@ NOSTDINC_FLAGS += -nostdinc
>  # perform bounds checking.
>  KBUILD_CFLAGS += $(call cc-option, -fstrict-flex-arrays=3)
>  
> -KBUILD_CFLAGS += $(call cc-option, -Wstringop-overflow)
> +#Currently, disable -Wstringop-overflow for GCC 11, globally.
> +KBUILD_CFLAGS-$(CONFIG_CC_NO_STRINGOP_OVERFLOW) += $(call cc-option, -Wno-stringop-overflow)
> +KBUILD_CFLAGS-$(CONFIG_CC_STRINGOP_OVERFLOW) += $(call cc-option, -Wstringop-overflow)
>  
>  # disable invalid "can't wrap" optimizations for signed / pointers
>  KBUILD_CFLAGS	+= -fno-strict-overflow
> diff --git a/init/Kconfig b/init/Kconfig
> index 9ffb103fc927..aaaa99a5d2a9 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -876,6 +876,18 @@ config CC_NO_ARRAY_BOUNDS
>  	bool
>  	default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC11_NO_ARRAY_BOUNDS
>  
> +# Currently, disable -Wstringop-overflow for GCC 11, globally.
> +config GCC11_NO_STRINGOP_OVERFLOW
> +	def_bool y
> +
> +config CC_NO_STRINGOP_OVERFLOW
> +	bool
> +	default y if CC_IS_GCC && GCC_VERSION >= 110000 && GCC_VERSION < 120000 && GCC11_NO_STRINGOP_OVERFLOW
> +
> +config CC_STRINGOP_OVERFLOW
> +	bool
> +	default y if CC_IS_GCC && !CC_NO_STRINGOP_OVERFLOW
> +
>  #
>  # For architectures that know their GCC __int128 support is sound
>  #
> -- 
> 2.34.1
> 

-- 
Kees Cook

Re: [PATCH][next] init: Kconfig: Disable -Wstringop-overflow for GCC-11

[Gustavo A. R. Silva]

On 11/30/23 15:07, Kees Cook wrote:
> On Thu, Nov 30, 2023 at 02:52:10PM -0600, Gustavo A. R. Silva wrote:
>> -Wstringop-overflow is buggy in GCC-11. Therefore, we should disable
> 
> Can you add some links for this? For example, maybe this?
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97490
> 
> Or discussions from -next builds?

Done. :)

> 
>> this option specifically for that compiler version. To achieve this,
>> we introduce a new configuration option: GCC11_NO_STRINGOP_OVERFLOW.
>>
>> The compiler option related to string operation overflow is now managed
>> under configuration CC_STRINGOP_OVERFLOW. This option is enabled by
>> default for all other versions of GCC that support it.
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> But yeah, let's get this landed to keep new warnings from appearing...
> 

I just applied this to my -next tree.

> Reviewed-by: Kees Cook <keescook@chromium.org>

Thanks!
--
Gustavo