From e0a43aa3e4a40fb88d3fa75397da0bf1e60a6c45 Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Fri, 30 Aug 2019 12:00:37 +0100 Subject: tools: bpftool: ignore make built-in rules for getting kernel version Bpftool calls the toplevel Makefile to get the kernel version for the sources it is built from. But when the utility is built from the top of the kernel repository, it may dump the following error message for certain architectures (including x86): $ make tools/bpf [...] make[3]: *** [checkbin] Error 1 [...] This does not prevent bpftool compilation, but may feel disconcerting. The "checkbin" arch-dependent target is not supposed to be called for target "kernelversion", which is a simple "echo" of the version number. It turns out this is caused by the make invocation in tools/bpf/bpftool, which attempts to find implicit rules to apply. Extract from debug output: Reading makefiles... Reading makefile 'Makefile'... Reading makefile 'scripts/Kbuild.include' (search path) (no ~ expansion)... Reading makefile 'scripts/subarch.include' (search path) (no ~ expansion)... Reading makefile 'arch/x86/Makefile' (search path) (no ~ expansion)... Reading makefile 'scripts/Makefile.kcov' (search path) (no ~ expansion)... Reading makefile 'scripts/Makefile.gcc-plugins' (search path) (no ~ expansion)... Reading makefile 'scripts/Makefile.kasan' (search path) (no ~ expansion)... Reading makefile 'scripts/Makefile.extrawarn' (search path) (no ~ expansion)... Reading makefile 'scripts/Makefile.ubsan' (search path) (no ~ expansion)... Updating makefiles.... Considering target file 'scripts/Makefile.ubsan'. Looking for an implicit rule for 'scripts/Makefile.ubsan'. Trying pattern rule with stem 'Makefile.ubsan'. [...] Trying pattern rule with stem 'Makefile.ubsan'. Trying implicit prerequisite 'scripts/Makefile.ubsan.o'. Looking for a rule with intermediate file 'scripts/Makefile.ubsan.o'. Avoiding implicit rule recursion. Trying pattern rule with stem 'Makefile.ubsan'. Trying rule prerequisite 'prepare'. Trying rule prerequisite 'FORCE'. Found an implicit rule for 'scripts/Makefile.ubsan'. Considering target file 'prepare'. File 'prepare' does not exist. Considering target file 'prepare0'. File 'prepare0' does not exist. Considering target file 'archprepare'. File 'archprepare' does not exist. Considering target file 'archheaders'. File 'archheaders' does not exist. Finished prerequisites of target file 'archheaders'. Must remake target 'archheaders'. Putting child 0x55976f4f6980 (archheaders) PID 31743 on the chain. To avoid that, pass the -r and -R flags to eliminate the use of make built-in rules (and while at it, built-in variables) when running command "make kernelversion" from bpftool's Makefile. Signed-off-by: Quentin Monnet Reviewed-by: Jakub Kicinski Signed-off-by: Daniel Borkmann --- tools/bpf/bpftool/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'tools/bpf') diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile index f284c207765a..cd0fc05464e7 100644 --- a/tools/bpf/bpftool/Makefile +++ b/tools/bpf/bpftool/Makefile @@ -24,7 +24,7 @@ endif LIBBPF = $(BPF_PATH)libbpf.a -BPFTOOL_VERSION := $(shell make --no-print-directory -sC ../../.. kernelversion) +BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion) $(LIBBPF): FORCE $(Q)$(MAKE) -C $(BPF_DIR) OUTPUT=$(OUTPUT) $(OUTPUT)libbpf.a -- cgit v1.2.3