Re: [PATCH v1] objtool: HAVE_XXHASH test uses HOSTCFLAGS.

[Hong, Yifan]

On Mon, Mar 2, 2026 at 5:03 PM HONG Yifan <elsk@xxxxxxxxxx> wrote:
>
> Previously, HAVE_XXHASH is tested by invoking HOSTCC without HOSTCFLAGS.
>
> Consider the following scenario:
>
> - The host machine has libxxhash installed
> - We build the kernel with HOSTCFLAGS containing a --sysroot that does
>   not have xxhash.h (for hermetic builds)
>
> In this case, HAVE_XXHASH is set to y, but when it builds objtool with
> HOSTCFLAGS, because the --sysroot does not contain xxhash.h, the
> following error is raised:
>
> <...>/common/tools/objtool/include/objtool/checksum_types.h:12:10: fatal error: 'xxhash.h' file not found
>    12 | #include <xxhash.h>
>       |          ^~~~~~~~~~
>
> To resolve the error, we test HAVE_XXHASH by invoking HOSTCC with
> HOSTCFLAGS.
>
> Signed-off-by: HONG Yifan <elsk@xxxxxxxxxx>
> ---
>  tools/objtool/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
> index 6964175abdfd..b8b8529f8ea9 100644
> --- a/tools/objtool/Makefile
> +++ b/tools/objtool/Makefile
> @@ -13,7 +13,7 @@ endif
>
>  ifeq ($(ARCH_HAS_KLP),y)
>         HAVE_XXHASH = $(shell printf "$(pound)include <xxhash.h>\nXXH3_state_t *state;int main() {}" | \
> -                     $(HOSTCC) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)
> +                     $(HOSTCC) $(HOSTCFLAGS) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)
>         ifeq ($(HAVE_XXHASH),y)
>                 BUILD_KLP        := y
>                 LIBXXHASH_CFLAGS := $(shell $(HOSTPKG_CONFIG) libxxhash --cflags 2>/dev/null) \
> --
> 2.53.0.473.g4a7958ca14-goog
>

Sorry, I forgot to cc linux-kbuild@xxxxxxxxxxxxxxx as well. Adding
now. The original patch is at
https://lore.kernel.org/lkml/20260303010340.306164-1-elsk@xxxxxxxxxx