From: Alexey Brodkin <[email protected]> Commit 5ef7bbb09f7b ("perf tools: Allow to specify custom linker command") was meant to enable usage non $(CROSS_COMPILE)ld linker during perf building.
But implementation didn't take into account the fact that LD is a pre-defined variable in GNU Make. I.e. it is always defined. Which means there's no point to check "LD ?= ..." because it will never succeed. And so LD will be either that explicitly passed to make like this: ------->8------- make LD=path_to_my_ld ... ------->8------- or default value, which is host's "ld". Latter leads to failure of cross-linkage because instead of cross linker "$(CROSS_COMPILE)ld" host's "ld" is used. Fortunately there's a way to do correct substitution of $(CROSS_COMPILE)ld with user defined LD on command-line. As a reference was used implementation in "tools/lib/traceevent/Makefile". Build tested for x86_64 and ARC. Thanks Jiri for this hint. Signed-off-by: Alexey Brodkin <[email protected]> Fixes: 5ef7bbb09f7b ("perf tools: Allow to specify custom linker command") Cc: Aaro Koskinen <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Vineet Gupta <[email protected]> Cc: Vineet Gupta <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Arnaldo Carvalho de Melo <[email protected]> --- tools/perf/Makefile.perf | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf index 7a4b549214e3..bba34636b733 100644 --- a/tools/perf/Makefile.perf +++ b/tools/perf/Makefile.perf @@ -109,9 +109,22 @@ $(OUTPUT)PERF-VERSION-FILE: ../../.git/HEAD $(Q)$(SHELL_PATH) util/PERF-VERSION-GEN $(OUTPUT) $(Q)touch $(OUTPUT)PERF-VERSION-FILE -CC = $(CROSS_COMPILE)gcc -LD ?= $(CROSS_COMPILE)ld -AR = $(CROSS_COMPILE)ar +# Makefiles suck: This macro sets a default value of $(2) for the +# variable named by $(1), unless the variable has been set by +# environment or command line. This is necessary for CC and AR +# because make sets default values, so the simpler ?= approach +# won't work as expected. +define allow-override + $(if $(or $(findstring environment,$(origin $(1))),\ + $(findstring command line,$(origin $(1)))),,\ + $(eval $(1) = $(2))) +endef + +# Allow setting CC and AR and LD, or setting CROSS_COMPILE as a prefix. +$(call allow-override,CC,$(CROSS_COMPILE)gcc) +$(call allow-override,AR,$(CROSS_COMPILE)ar) +$(call allow-override,LD,$(CROSS_COMPILE)ld) + PKG_CONFIG = $(CROSS_COMPILE)pkg-config RM = rm -f -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
