Re: [PATCH] perf tools: allow cross compiling with DWARF support

[Masami Hiramatsu]

Jamie Iles wrote:
> The path to elfutils was previously hardcoded as /usr/include/elfutils
> which does not work with cross compilers. If CROSS_COMPILE is set, try
> to set an include path from GCC's sysroot if GCC was built with sysroot
> support, if sysroot support isn't enabled, don't specify a path for
> elfutils allowing the user to set it with EXTRA_CFLAGS.

Hmm, I'm not so sure about cross compiling. I just thought
if there is no sysroot support, we should warn user instead of
just failing to find elfutils.

Thank you,

> 
> Signed-off-by: Jamie Iles <jamie.iles@xxxxxxxxxxxx>
> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> ---
>  tools/perf/Makefile |   14 ++++++++++++--
>  1 files changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/Makefile b/tools/perf/Makefile
> index 6aa2fe3..6217839 100644
> --- a/tools/perf/Makefile
> +++ b/tools/perf/Makefile
> @@ -503,8 +503,18 @@ PERFLIBS = $(LIB_FILE)
>  -include config.mak.autogen
>  -include config.mak
>  
> +ifndef CROSS_COMPILE
> +ELFUTILS_INCLUDE = -I/usr/include/elfutils
> +else
> +# See if the compiler has been built with sysroot support
> +SYSROOT_PATH = $(shell $(CC) -print-sysroot 2> /dev/null || echo "")
> +ifneq ($(SYSROOT_PATH),)
> +ELFUTILS_INCLUDE := -I$(SYSROOT_PATH)/usr/include/elfutils
> +endif
> +endif
> +
>  ifndef NO_DWARF
> -FLAGS_DWARF=$(ALL_CFLAGS) -I/usr/include/elfutils -ldw -lelf $(ALL_LDFLAGS) $(EXTLIBS)
> +FLAGS_DWARF=$(ALL_CFLAGS) $(ELFUTILS_INCLUDE) -ldw -lelf $(ALL_LDFLAGS) $(EXTLIBS)
>  ifneq ($(call try-cc,$(SOURCE_DWARF),$(FLAGS_DWARF)),y)
>  	msg := $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev);
>  	NO_DWARF := 1
> @@ -551,7 +561,7 @@ ifndef NO_DWARF
>  ifeq ($(origin PERF_HAVE_DWARF_REGS), undefined)
>  	msg := $(warning DWARF register mappings have not been defined for architecture $(ARCH), DWARF support disabled);
>  else
> -	BASIC_CFLAGS += -I/usr/include/elfutils -DDWARF_SUPPORT
> +	BASIC_CFLAGS += $(ELFUTILS_INCLUDE) -DDWARF_SUPPORT
>  	EXTLIBS += -lelf -ldw
>  	LIB_OBJS += $(OUTPUT)util/probe-finder.o
>  endif # PERF_HAVE_DWARF_REGS

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