[PATCH bpf-next v7 7/9] selftests/bpf: extract BPF skeleton generation into a helper script

Mykola Lysenko <[email protected]>
Newsgroups org.kernel.vger.bpf
Message-ID <[email protected]> 
The four skeleton generation recipes (regular, light, signed light and
linked) are near-identical pipelines - link via "bpftool gen
object" three times, compare the second and third results as a
regression test for bpftool's determinism, generate the skeleton (and
possibly subskeleton), remove intermediates - duplicated with small
variations inside DEFINE_TEST_RUNNER_RULES, where every line pays the
double-expansion escaping tax.

Move the pipeline into gen_bpf_skel.sh; the differences between the
four variants become the --lskel, --sign and --subskel flags. Signing
takes the key and certificate from $PRIVATE_KEY and $VERIFICATION_CERT
in the environment, like the bpftool binary comes from $BPFTOOL; the
script checks for both up front, before any intermediate exists. The
distinct linked/llinked intermediate infixes are kept but derived
inside the script (its header says why they matter). The intermediates
are now named after the output header rather than the input object
(foo.linked1.o instead of foo.bpf.linked1.o for the single-object
variants; the linked-skeleton variant already used that form), which
keeps the stems distinct just the same.

The permissive-mode missing-input checks at the top of the recipes -
when the object's compile already failed and was skipped, skip the
skeleton quietly instead of running bpftool against a missing file -
are kept, factored into a skip_if_missing helper.
The build-log messages stay folded behind the guard as in the original
recipes, so a skipped skeleton prints SKIP-SKEL and nothing else. What
does change is the failure path: the script removes the intermediates
it created (the recipes left them behind), the determinism check
reports through cmp plus one message instead of a diff listing, and
the linked-skeleton recipe prints its GEN-SKEL line before the link
rather than after it, like the other three always did.

Suggested-by: Eduard Zingerman <[email protected]>
Assisted-by: Claude:claude-fable-5 shellcheck
Signed-off-by: Mykola Lysenko <[email protected]>
Acked-by: Eduard Zingerman <[email protected]>
---
 tools/testing/selftests/bpf/Makefile        | 93 ++++++++-----------
 tools/testing/selftests/bpf/gen_bpf_skel.sh | 99 +++++++++++++++++++++
 2 files changed, 136 insertions(+), 56 deletions(-)
 create mode 100755 tools/testing/selftests/bpf/gen_bpf_skel.sh

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 9f18dd291736..8ac6c8844d4a 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -56,6 +56,17 @@ PERMISSIVE := $(filter 0,$(BPF_STRICT_BUILD))
 skip_on_fail = $(if $(PERMISSIVE),|| { $(RM) $@ $(2); \
 	printf '  %-12s %s\n' 'SKIP-$(1)' '$(notdir $@)$(if $(3), $(3))' 1>&2; })
 
+# Permissive-mode recipe prefix: when a prerequisite object is missing
+# (its compile failed and was skipped), remove the target and $(3),
+# emit a SKIP marker and report success without running the rest of
+# the recipe.
+# $(1) - SKIP tag
+# $(2) - input files to check
+# $(3) - optional extra files to remove alongside the target
+skip_if_missing = $(if $(PERMISSIVE),for f in $(2); do [ -f $$f ] || { \
+	$(RM) $@ $(3); \
+	printf '  %-12s %s\n' 'SKIP-$(1)' '$(notdir $@)' 1>&2; exit 0; }; done;)
+
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(CURDIR)))
 srctree := $(patsubst %/,%,$(dir $(srctree)))
@@ -564,7 +575,6 @@ HEADERS_FOR_BPF_OBJS := $(wildcard $(BPFDIR)/*.bpf.h)		\
 # $2 - test runner extra "flavor" (e.g., no_alu32, cpuv4, bpf_gcc, etc)
 define DEFINE_TEST_RUNNER
 
-LSKEL_SIGN := -S -k $(PRIVATE_KEY) -i $(VERIFICATION_CERT)
 TRUNNER_OUTPUT := $(OUTPUT)$(if $2,/)$2
 TRUNNER_BINARY := $1$(if $2,-)$2
 TRUNNER_TEST_OBJS := $$(patsubst %.c,$$(TRUNNER_OUTPUT)/%.test.o,	\
@@ -624,70 +634,41 @@ $(TRUNNER_BPF_OBJS): $(TRUNNER_OUTPUT)/%.bpf.o:				\
 					  $$($$<-CFLAGS)		\
 					  $$($$<-$2-CFLAGS),$(TRUNNER_BINARY))
 
-$(TRUNNER_BPF_SKELS): %.skel.h: %.bpf.o $(BPFTOOL) | $(TRUNNER_OUTPUT)
-	$(Q)$(if $(PERMISSIVE),if [ ! -f $$< ]; then			\
-		$$(RM) $$@ $$(@:.skel.h=.subskel.h);			\
-		printf '  %-12s %s\n' 'SKIP-SKEL' '$$(notdir $$@)' 1>&2; \
-		exit 0;							\
-	fi;)								\
+$(TRUNNER_BPF_SKELS): %.skel.h: %.bpf.o $(BPFTOOL) gen_bpf_skel.sh | $(TRUNNER_OUTPUT)
+	$(Q)$$(call skip_if_missing,SKEL,$$<,$$(@:.skel.h=.subskel.h))	\
 	printf '  %-12s %s\n' 'GEN-SKEL' '[$(TRUNNER_BINARY)] $$(notdir $$@)' 1>&2; \
-	$$(BPFTOOL) gen object $$(<:.o=.linked1.o) $$< &&		\
-	$$(BPFTOOL) gen object $$(<:.o=.linked2.o) $$(<:.o=.linked1.o) && \
-	$$(BPFTOOL) gen object $$(<:.o=.linked3.o) $$(<:.o=.linked2.o) && \
-	diff $$(<:.o=.linked2.o) $$(<:.o=.linked3.o) &&		\
-	$$(BPFTOOL) gen skeleton $$(<:.o=.linked3.o) name $$(notdir $$(<:.bpf.o=)) > $$@ && \
-	$$(BPFTOOL) gen subskeleton $$(<:.o=.linked3.o) name $$(notdir $$(<:.bpf.o=)) > $$(@:.skel.h=.subskel.h) $$(call skip_on_fail,SKEL,$$(@:.skel.h=.subskel.h)) && \
-	rm -f $$(<:.o=.linked1.o) $$(<:.o=.linked2.o) $$(<:.o=.linked3.o)
-
-$(TRUNNER_BPF_LSKELS): %.lskel.h: %.bpf.o $(BPFTOOL) | $(TRUNNER_OUTPUT)
-	$(Q)$(if $(PERMISSIVE),if [ ! -f $$< ]; then			\
-		$$(RM) $$@;						\
-		printf '  %-12s %s\n' 'SKIP-SKEL' '$$(notdir $$@)' 1>&2; \
-		exit 0;							\
-	fi;)								\
+	BPFTOOL=$$(BPFTOOL) ./gen_bpf_skel.sh					\
+		--name $$(notdir $$(<:.bpf.o=))					\
+		--skel $$@ --subskel $$(@:.skel.h=.subskel.h) $$< $$(call skip_on_fail,SKEL,$$(@:.skel.h=.subskel.h))
+
+$(TRUNNER_BPF_LSKELS): %.lskel.h: %.bpf.o $(BPFTOOL) gen_bpf_skel.sh | $(TRUNNER_OUTPUT)
+	$(Q)$$(call skip_if_missing,SKEL,$$<)					\
 	printf '  %-12s %s\n' 'GEN-SKEL' '[$(TRUNNER_BINARY)] $$(notdir $$@)' 1>&2; \
-	$$(BPFTOOL) gen object $$(<:.o=.llinked1.o) $$< &&		\
-	$$(BPFTOOL) gen object $$(<:.o=.llinked2.o) $$(<:.o=.llinked1.o) && \
-	$$(BPFTOOL) gen object $$(<:.o=.llinked3.o) $$(<:.o=.llinked2.o) && \
-	diff $$(<:.o=.llinked2.o) $$(<:.o=.llinked3.o) &&		\
-	$$(BPFTOOL) gen skeleton -L $$(<:.o=.llinked3.o) name $$(notdir $$(<:.bpf.o=_lskel)) > $$@ $$(call skip_on_fail,SKEL) && \
-	rm -f $$(<:.o=.llinked1.o) $$(<:.o=.llinked2.o) $$(<:.o=.llinked3.o)
-
-$(TRUNNER_BPF_LSKELS_SIGNED): %.lskel.h: %.bpf.o $(BPFTOOL) | $(TRUNNER_OUTPUT)
-	$(Q)$(if $(PERMISSIVE),if [ ! -f $$< ]; then			\
-		$$(RM) $$@;						\
-		printf '  %-12s %s\n' 'SKIP-SKEL' '$$(notdir $$@)' 1>&2; \
-		exit 0;							\
-	fi;)								\
+	BPFTOOL=$$(BPFTOOL) ./gen_bpf_skel.sh					\
+		--name $$(notdir $$(<:.bpf.o=_lskel)) --lskel			\
+		--skel $$@ $$< $$(call skip_on_fail,SKEL)
+
+$(TRUNNER_BPF_LSKELS_SIGNED): %.lskel.h: %.bpf.o $(BPFTOOL) gen_bpf_skel.sh | $(TRUNNER_OUTPUT)
+	$(Q)$$(call skip_if_missing,SKEL,$$<)					\
 	printf '  %-12s %s\n' 'GEN-SKEL' '[$(TRUNNER_BINARY) (signed)] $$(notdir $$@)' 1>&2; \
-	$$(BPFTOOL) gen object $$(<:.o=.llinked1.o) $$< &&		\
-	$$(BPFTOOL) gen object $$(<:.o=.llinked2.o) $$(<:.o=.llinked1.o) && \
-	$$(BPFTOOL) gen object $$(<:.o=.llinked3.o) $$(<:.o=.llinked2.o) && \
-	diff $$(<:.o=.llinked2.o) $$(<:.o=.llinked3.o) &&		\
-	$$(BPFTOOL) gen skeleton $(LSKEL_SIGN) $$(<:.o=.llinked3.o) name $$(notdir $$(<:.bpf.o=_lskel)) > $$@ $$(call skip_on_fail,SKEL) && \
-	rm -f $$(<:.o=.llinked1.o) $$(<:.o=.llinked2.o) $$(<:.o=.llinked3.o)
+	BPFTOOL=$$(BPFTOOL) PRIVATE_KEY=$(PRIVATE_KEY)				\
+		VERIFICATION_CERT=$(VERIFICATION_CERT)				\
+		./gen_bpf_skel.sh --sign					\
+		--name $$(notdir $$(<:.bpf.o=_lskel))				\
+		--skel $$@ $$< $$(call skip_on_fail,SKEL)
 
 $(LINKED_BPF_OBJS): %: $(TRUNNER_OUTPUT)/%
 
 # .SECONDEXPANSION here allows to correctly expand %-deps variables as prerequisites
 .SECONDEXPANSION:
-$(TRUNNER_BPF_SKELS_LINKED): $(TRUNNER_OUTPUT)/%: $$$$(%-deps) $(BPFTOOL) | $(TRUNNER_OUTPUT)
-	$(Q)$(if $(PERMISSIVE),for f in $$(addprefix $(TRUNNER_OUTPUT)/,$$($$(@F)-deps)); do \
-		if [ ! -f $$$$f ]; then						\
-			$$(RM) $$@ $$(@:.skel.h=.subskel.h);		\
-			printf '  %-12s %s\n' 'SKIP-SKEL' '$$(notdir $$@)' 1>&2; \
-			exit 0;							\
-		fi;								\
-	done;)									\
+$(TRUNNER_BPF_SKELS_LINKED): $(TRUNNER_OUTPUT)/%: $$$$(%-deps) $(BPFTOOL) gen_bpf_skel.sh | $(TRUNNER_OUTPUT)
+	$(Q)$$(call skip_if_missing,SKEL,$$(addprefix $(TRUNNER_OUTPUT)/,$$($$(@F)-deps)),$$(@:.skel.h=.subskel.h)) \
 	printf '  %-12s %s\n' 'LINK-BPF' '[$(TRUNNER_BINARY)] $$(notdir $$(@:.skel.h=.bpf.o))' 1>&2; \
-	$$(BPFTOOL) gen object $$(@:.skel.h=.linked1.o) $$(addprefix $(TRUNNER_OUTPUT)/,$$($$(@F)-deps)) && \
-	$$(BPFTOOL) gen object $$(@:.skel.h=.linked2.o) $$(@:.skel.h=.linked1.o) && \
-	$$(BPFTOOL) gen object $$(@:.skel.h=.linked3.o) $$(@:.skel.h=.linked2.o) && \
-	diff $$(@:.skel.h=.linked2.o) $$(@:.skel.h=.linked3.o) &&	\
-	printf '  %-12s %s\n' 'GEN-SKEL' '[$(TRUNNER_BINARY)] $$(notdir $$@)' 1>&2 && \
-	$$(BPFTOOL) gen skeleton $$(@:.skel.h=.linked3.o) name $$(notdir $$(@:.skel.h=)) > $$@ && \
-	$$(BPFTOOL) gen subskeleton $$(@:.skel.h=.linked3.o) name $$(notdir $$(@:.skel.h=)) > $$(@:.skel.h=.subskel.h) $$(call skip_on_fail,SKEL,$$(@:.skel.h=.subskel.h)) &&									\
-	rm -f $$(@:.skel.h=.linked1.o) $$(@:.skel.h=.linked2.o) $$(@:.skel.h=.linked3.o)
+	printf '  %-12s %s\n' 'GEN-SKEL' '[$(TRUNNER_BINARY)] $$(notdir $$@)' 1>&2; \
+	BPFTOOL=$$(BPFTOOL) ./gen_bpf_skel.sh					\
+		--name $$(notdir $$(@:.skel.h=))				\
+		--skel $$@ --subskel $$(@:.skel.h=.subskel.h)			\
+		$$(addprefix $(TRUNNER_OUTPUT)/,$$($$(@F)-deps)) $$(call skip_on_fail,SKEL,$$(@:.skel.h=.subskel.h))
 
 # When the compiler generates a %.d file, only skel basenames (not
 # full paths) are specified as prerequisites for corresponding %.o
diff --git a/tools/testing/selftests/bpf/gen_bpf_skel.sh b/tools/testing/selftests/bpf/gen_bpf_skel.sh
new file mode 100755
index 000000000000..e43ccf095575
--- /dev/null
+++ b/tools/testing/selftests/bpf/gen_bpf_skel.sh
@@ -0,0 +1,99 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Link BPF object file(s) with "bpftool gen object" and generate a
+# skeleton (or light skeleton) header from the result.
+#
+# Usage:
+#   BPFTOOL=<bpftool> gen_bpf_skel.sh --name NAME --skel OUT [options] OBJ...
+#
+#   --name NAME       skeleton object name ("name NAME" for bpftool)
+#   --skel OUT        output header ("foo.skel.h" or "foo.lskel.h")
+#   --subskel OUT     also generate a subskeleton header into OUT
+#   --lskel           generate a light skeleton (bpftool gen skeleton -L)
+#   --sign            sign the (light) skeleton, with the key and
+#                     certificate taken from $PRIVATE_KEY and
+#                     $VERIFICATION_CERT
+#
+# The inputs are linked three times and the 2nd and 3rd results
+# compared, as a regression test for the determinism of "bpftool gen
+# object".
+#
+# Intermediate files are named after the output header with a "linked"
+# infix - "llinked" for light or signed skeletons, so generating a
+# .skel.h and a .lskel.h from the same .bpf.o in parallel never races
+# on the intermediates.
+#
+# The bpftool binary is taken from $BPFTOOL (default: bpftool from PATH).
+# On failure all outputs and intermediates are removed and the script
+# exits non-zero; permissive-mode skipping is the caller's business
+# (see skip_on_fail in the Makefile).
+
+set -u
+
+bpftool=${BPFTOOL:-bpftool}
+name='' skel='' subskel=''
+lskel=0 sign=0
+
+while [ $# -gt 0 ]; do
+	case "$1" in
+	--name)		name=$2; shift 2 ;;
+	--skel)		skel=$2; shift 2 ;;
+	--subskel)	subskel=$2; shift 2 ;;
+	--lskel)	lskel=1; shift ;;
+	--sign)		sign=1; shift ;;
+	--)		shift; break ;;
+	-*)		echo "$0: unknown option: $1" >&2; exit 1 ;;
+	*)		break ;;
+	esac
+done
+
+if [ -z "$name" ] || [ -z "$skel" ] || [ $# -eq 0 ]; then
+	echo "usage: $0 --name NAME --skel OUT [options] OBJ..." >&2
+	exit 1
+fi
+
+infix=linked
+if [ "$lskel" -eq 1 ] || [ "$sign" -eq 1 ]; then
+	infix=llinked
+fi
+
+if [ "$sign" -eq 1 ] && { [ -z "${PRIVATE_KEY-}" ] || [ -z "${VERIFICATION_CERT-}" ]; }; then
+	echo "$0: --sign requires PRIVATE_KEY and VERIFICATION_CERT in the environment" >&2
+	exit 1
+fi
+
+base=${skel%.skel.h}
+base=${base%.lskel.h}
+t1=$base.${infix}1.o
+t2=$base.${infix}2.o
+t3=$base.${infix}3.o
+
+fail() {
+	rm -f "$skel" ${subskel:+"$subskel"} "$t1" "$t2" "$t3"
+	exit 1
+}
+
+"$bpftool" gen object "$t1" "$@" || fail
+"$bpftool" gen object "$t2" "$t1" || fail
+"$bpftool" gen object "$t3" "$t2" || fail
+if ! cmp -s "$t2" "$t3"; then
+	echo "$0: bpftool gen object is not deterministic for $skel" >&2
+	fail
+fi
+
+args=()
+if [ "$sign" -eq 1 ]; then
+	args+=(-S -k "$PRIVATE_KEY" -i "$VERIFICATION_CERT")
+fi
+if [ "$lskel" -eq 1 ]; then
+	args+=(-L)
+fi
+"$bpftool" gen skeleton ${args[@]+"${args[@]}"} "$t3" name "$name" > "$skel" || fail
+
+if [ -n "$subskel" ]; then
+	"$bpftool" gen subskeleton "$t3" name "$name" > "$subskel" || fail
+fi
+
+rm -f "$t1" "$t2" "$t3"
+exit 0
-- 
2.43.0
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