On Fri, 10 Mar 2017 19:24:18 +0300
Gleb Fotengauer-Malinovskiy <glebfm@xxxxxxxxxxxx> wrote:
> The latest change of asm goto support check added passing of
> KBUILD_CFLAGS to compiler. When these flags reference gcc plugins,
> there is a race condition between the build of these plugins and their
> use in this asm goto support check.
>
> This change moves the check before all these references are added
> to KBUILD_CFLAGS. This is correct because subsequent KBUILD_CFLAGS
> modifications are not relevant to this check.
What exactly breaks when the race happens?
-- Steve
>
> Reported-by: Anton V. Boyarshinov <boyarsh@xxxxxxxxxxxx>
> Fixes: 35f860f9ba6a ("jump label: pass kbuild_cflags when checking for asm goto support")
> Cc: stable@xxxxxxxxxxxxxxx # v4.10
> Signed-off-by: Gleb Fotengauer-Malinovskiy <glebfm@xxxxxxxxxxxx>
> Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxxxxx>
> ---
> Makefile | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 165cf97..7e3aade 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -653,6 +653,12 @@ KBUILD_CFLAGS += $(call cc-ifversion, -lt, 0409, \
> # Tell gcc to never replace conditional load with a non-conditional one
> KBUILD_CFLAGS += $(call cc-option,--param=allow-store-data-races=0)
>
> +# check for 'asm goto'
> +ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-goto.sh $(CC) $(KBUILD_CFLAGS)), y)
> + KBUILD_CFLAGS += -DCC_HAVE_ASM_GOTO
> + KBUILD_AFLAGS += -DCC_HAVE_ASM_GOTO
> +endif
> +
> include scripts/Makefile.gcc-plugins
>
> ifdef CONFIG_READABLE_ASM
> @@ -798,12 +804,6 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
> # use the deterministic mode of AR if available
> KBUILD_ARFLAGS := $(call ar-option,D)
>
> -# check for 'asm goto'
> -ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-goto.sh $(CC) $(KBUILD_CFLAGS)), y)
> - KBUILD_CFLAGS += -DCC_HAVE_ASM_GOTO
> - KBUILD_AFLAGS += -DCC_HAVE_ASM_GOTO
> -endif
> -
> include scripts/Makefile.kasan
> include scripts/Makefile.extrawarn
> include scripts/Makefile.ubsan
>
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