[PATCH v3 4/4] perf build: Filter out BTF sources without a .BTF section

Ian Rogers
2023-06-09T04:33:20Z

If generating vmlinux.h, make the code to generate it more tolerant by
filtering out paths to kernels that lack a .BTF section.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/Makefile.perf | 29 ++++++++++++++++++++++++++---
1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index f1840af195c0..e440793fc6ca 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -193,6 +193,7 @@ FLEX ?= flex
BISON ?= bison
STRIP = strip
AWK = awk
+READELF ?= readelf

# include Makefile.config by default and rule out
# non-config cases
@@ -1080,12 +1081,34 @@ $(BPFTOOL): | $(SKEL_TMP_OUT)
$(Q)CFLAGS= $(MAKE) -C ../bpf/bpftool \
OUTPUT=$(SKEL_TMP_OUT)/ bootstrap

-VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux) \
+# Paths to search for a kernel to generate vmlinux.h from.
+VMLINUX_BTF_ELF_PATHS ?= $(if $(O),$(O)/vmlinux) \
$(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux) \
../../vmlinux \
- /sys/kernel/btf/vmlinux \
/boot/vmlinux-$(shell uname -r)
-VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+
+# Paths to BTF information.
+VMLINUX_BTF_BTF_PATHS ?= /sys/kernel/btf/vmlinux
+
+# Filter out kernels that don't exist or without a BTF section.
+VMLINUX_BTF_ELF_ABSPATHS ?= $(abspath $(wildcard $(VMLINUX_BTF_ELF_PATHS)))
+VMLINUX_BTF_PATHS ?= $(shell for file in $(VMLINUX_BTF_ELF_ABSPATHS); \
+ do \
+ if [ -f $$file ] && ($(READELF) -S "$$file" | grep -q .BTF); \
+ then \
+ echo "$$file"; \
+ fi; \
+ done) \
+ $(wildcard $(VMLINUX_BTF_BTF_PATHS))
+
+# Select the first as the source of vmlinux.h.
+VMLINUX_BTF ?= $(firstword $(VMLINUX_BTF_PATHS))
+
+ifeq ($(VMLINUX_H),)
+ ifeq ($(VMLINUX_BTF),)
+ $(error Missing bpftool input for generating vmlinux.h)
+ endif
+endif

$(SKEL_OUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
ifeq ($(VMLINUX_H),)