[PATCH 0/2] objtool: xxhash dependency improvements

[PATCH 0/2] objtool: xxhash dependency improvements

[Josh Poimboeuf]

Set the minimum xxhash version to 0.8, and soften the xxhash dependency
a bit so that it's only needed when running klp-build rather than doing
a normal kernel build.

For tip/objtool/core.

Josh Poimboeuf (2):
  objtool: Set minimum xxhash version to 0.8
  objtool/klp: Only enable --checksum when needed

 arch/x86/boot/startup/Makefile | 2 +-
 scripts/Makefile.lib           | 1 -
 scripts/livepatch/klp-build    | 4 ++++
 tools/objtool/Makefile         | 2 +-
 tools/objtool/builtin-check.c  | 2 +-
 5 files changed, 7 insertions(+), 4 deletions(-)

-- 
2.51.1

[PATCH 1/2] objtool: Set minimum xxhash version to 0.8

[Josh Poimboeuf]

XXH3 is only supported starting with xxhash 0.8.  Enforce that.

Fixes: 0d83da43b1e1 ("objtool/klp: Add --checksum option to generate per-function checksums")
Reported-by: Michael Kelley <mhklinux@outlook.com>
Closes: https://lore.kernel.org/SN6PR02MB41579B83CD295C9FEE40EED6D4FCA@SN6PR02MB4157.namprd02.prod.outlook.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 tools/objtool/Makefile        | 2 +-
 tools/objtool/builtin-check.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
index 48928c9bebef..021f55b7bd87 100644
--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -12,7 +12,7 @@ ifeq ($(SRCARCH),loongarch)
 endif
 
 ifeq ($(ARCH_HAS_KLP),y)
-	HAVE_XXHASH = $(shell echo "int main() {}" | \
+	HAVE_XXHASH = $(shell printf "$(pound)include <xxhash.h>\nXXH3_state_t *state;int main() {}" | \
 		      $(HOSTCC) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)
 	ifeq ($(HAVE_XXHASH),y)
 		BUILD_KLP	 := y
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 1e1ea8396eb3..aab7fa9c7e00 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -164,7 +164,7 @@ static bool opts_valid(void)
 
 #ifndef BUILD_KLP
 	if (opts.checksum) {
-		ERROR("--checksum not supported; install xxhash-devel/libxxhash-dev and recompile");
+		ERROR("--checksum not supported; install xxhash-devel/libxxhash-dev (version >= 0.8) and recompile");
 		return false;
 	}
 #endif
-- 
2.51.1

[PATCH 2/2] objtool/klp: Only enable --checksum when needed

[Josh Poimboeuf]

With CONFIG_KLP_BUILD enabled, checksums are only needed during a
klp-build run.  There's no need to enable them for normal kernel builds.

This also has the benefit of softening the xxhash dependency.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/boot/startup/Makefile | 2 +-
 scripts/Makefile.lib           | 1 -
 scripts/livepatch/klp-build    | 4 ++++
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/boot/startup/Makefile b/arch/x86/boot/startup/Makefile
index e8fdf020b422..5e499cfb29b5 100644
--- a/arch/x86/boot/startup/Makefile
+++ b/arch/x86/boot/startup/Makefile
@@ -36,7 +36,7 @@ $(patsubst %.o,$(obj)/%.o,$(lib-y)): OBJECT_FILES_NON_STANDARD := y
 # relocations, even if other objtool actions are being deferred.
 #
 $(pi-objs): objtool-enabled	= 1
-$(pi-objs): objtool-args	= $(if $(delay-objtool),,$(objtool-args-y)) --noabs
+$(pi-objs): objtool-args	= $(if $(delay-objtool),--dry-run,$(objtool-args-y)) --noabs
 
 #
 # Confine the startup code by prefixing all symbols with __pi_ (for position
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index f4b33919ec37..28a1c08e3b22 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -173,7 +173,6 @@ ifdef CONFIG_OBJTOOL
 
 objtool := $(objtree)/tools/objtool/objtool
 
-objtool-args-$(CONFIG_KLP_BUILD)			+= --checksum
 objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
 objtool-args-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
 objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake
diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
index 881e052e7fae..882272120c9e 100755
--- a/scripts/livepatch/klp-build
+++ b/scripts/livepatch/klp-build
@@ -489,8 +489,11 @@ clean_kernel() {
 
 build_kernel() {
 	local log="$TMP_DIR/build.log"
+	local objtool_args=()
 	local cmd=()
 
+	objtool_args=("--checksum")
+
 	cmd=("make")
 
 	# When a patch to a kernel module references a newly created unexported
@@ -513,6 +516,7 @@ build_kernel() {
 	cmd+=("$VERBOSE")
 	cmd+=("-j$JOBS")
 	cmd+=("KCFLAGS=-ffunction-sections -fdata-sections")
+	cmd+=("OBJTOOL_ARGS=${objtool_args[*]}")
 	cmd+=("vmlinux")
 	cmd+=("modules")
 
-- 
2.51.1

RE: [PATCH 1/2] objtool: Set minimum xxhash version to 0.8

[Michael Kelley]

From: Josh Poimboeuf <jpoimboe@kernel.org> Sent: Wednesday, November 12, 2025 3:33 PM
> 
> XXH3 is only supported starting with xxhash 0.8.  Enforce that.
> 
> Fixes: 0d83da43b1e1 ("objtool/klp: Add --checksum option to generate per-function checksums")
> Reported-by: Michael Kelley <mhklinux@outlook.com>
> Closes: https://lore.kernel.org/all/SN6PR02MB41579B83CD295C9FEE40EED6D4FCA@SN6PR02MB4157.namprd02.prod.outlook.com
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---
>  tools/objtool/Makefile        | 2 +-
>  tools/objtool/builtin-check.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
> index 48928c9bebef..021f55b7bd87 100644
> --- a/tools/objtool/Makefile
> +++ b/tools/objtool/Makefile
> @@ -12,7 +12,7 @@ ifeq ($(SRCARCH),loongarch)
>  endif
> 
>  ifeq ($(ARCH_HAS_KLP),y)
> -	HAVE_XXHASH = $(shell echo "int main() {}" | \
> +	HAVE_XXHASH = $(shell printf "$(pound)include <xxhash.h>\nXXH3_state_t *state;int main() {}" | \
>  		      $(HOSTCC) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)
>  	ifeq ($(HAVE_XXHASH),y)
>  		BUILD_KLP	 := y
> diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
> index 1e1ea8396eb3..aab7fa9c7e00 100644
> --- a/tools/objtool/builtin-check.c
> +++ b/tools/objtool/builtin-check.c
> @@ -164,7 +164,7 @@ static bool opts_valid(void)
> 
>  #ifndef BUILD_KLP
>  	if (opts.checksum) {
> -		ERROR("--checksum not supported; install xxhash-devel/libxxhash-dev and recompile");
> +		ERROR("--checksum not supported; install xxhash-devel/libxxhash-dev (version >= 0.8) and recompile");
>  		return false;
>  	}
>  #endif
> --
> 2.51.1

Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>

RE: [PATCH 2/2] objtool/klp: Only enable --checksum when needed

[Michael Kelley]

From: Josh Poimboeuf <jpoimboe@kernel.org> Sent: Wednesday, November 12, 2025 3:33 PM
> 
> With CONFIG_KLP_BUILD enabled, checksums are only needed during a
> klp-build run.  There's no need to enable them for normal kernel builds.
> 
> This also has the benefit of softening the xxhash dependency.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
> ---
>  arch/x86/boot/startup/Makefile | 2 +-
>  scripts/Makefile.lib           | 1 -
>  scripts/livepatch/klp-build    | 4 ++++
>  3 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/boot/startup/Makefile b/arch/x86/boot/startup/Makefile
> index e8fdf020b422..5e499cfb29b5 100644
> --- a/arch/x86/boot/startup/Makefile
> +++ b/arch/x86/boot/startup/Makefile
> @@ -36,7 +36,7 @@ $(patsubst %.o,$(obj)/%.o,$(lib-y)):
> OBJECT_FILES_NON_STANDARD := y
>  # relocations, even if other objtool actions are being deferred.
>  #
>  $(pi-objs): objtool-enabled	= 1
> -$(pi-objs): objtool-args	= $(if $(delay-objtool),,$(objtool-args-y)) --noabs
> +$(pi-objs): objtool-args	= $(if $(delay-objtool),--dry-run,$(objtool-args-y)) --noabs
> 
>  #
>  # Confine the startup code by prefixing all symbols with __pi_ (for position
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index f4b33919ec37..28a1c08e3b22 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -173,7 +173,6 @@ ifdef CONFIG_OBJTOOL
> 
>  objtool := $(objtree)/tools/objtool/objtool
> 
> -objtool-args-$(CONFIG_KLP_BUILD)			+= --checksum
>  objtool-args-$(CONFIG_HAVE_JUMP_LABEL_HACK)		+= --hacks=jump_label
>  objtool-args-$(CONFIG_HAVE_NOINSTR_HACK)		+= --hacks=noinstr
>  objtool-args-$(CONFIG_MITIGATION_CALL_DEPTH_TRACKING)	+= --hacks=skylake
> diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build
> index 881e052e7fae..882272120c9e 100755
> --- a/scripts/livepatch/klp-build
> +++ b/scripts/livepatch/klp-build
> @@ -489,8 +489,11 @@ clean_kernel() {
> 
>  build_kernel() {
>  	local log="$TMP_DIR/build.log"
> +	local objtool_args=()
>  	local cmd=()
> 
> +	objtool_args=("--checksum")
> +
>  	cmd=("make")
> 
>  	# When a patch to a kernel module references a newly created unexported
> @@ -513,6 +516,7 @@ build_kernel() {
>  	cmd+=("$VERBOSE")
>  	cmd+=("-j$JOBS")
>  	cmd+=("KCFLAGS=-ffunction-sections -fdata-sections")
> +	cmd+=("OBJTOOL_ARGS=${objtool_args[*]}")
>  	cmd+=("vmlinux")
>  	cmd+=("modules")
> 
> --
> 2.51.1

Did a normal linux-next kernel build on an Ubuntu 20.04 system, which by default
does not have xxhash installed. Previous error about needing to install libxxhash-dev
is no longer generated. Have not tested a klp-build.

Tested-by: Michael Kelley <mhklinux@outlook.com>