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

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Date:	Mon, 28 Jun 2010 10:34:34 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Jamie Iles <jamie.iles@...ochip.com>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] perf tools: allow cross compiling with DWARF support

Jamie Iles wrote:
> On 06/25/2010 01:03 PM, Masami Hiramatsu wrote:
>> Jamie Iles wrote:
>>> On Fri, Jun 25, 2010 at 08:16:55PM +0900, Masami Hiramatsu wrote:
>>>> 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.
> [...]
>> It seems that $ELFUTILS_INCLUDE become "" without sysroot support.
>> In that case, I guess that user have to set the elfutils header
>> path to  EXTRA_CFLAGS and, make will just show "No libdw.h found
>> or old libdw.h found ..." message. (I just guess, not so familier
>> with cross compile...)
>>
>> So, I just like to suggest adding a message like as;
>> "No sysroot support. Please set elfutils include path in EXTRA_CFLAGS."
>> Doesn't it make easier to find a problem?
>>
>> Other parts are OK for me.
> 
> Ok, how about this revised patch?
> 
> From: Jamie Iles <jamie.iles@...ochip.com>
> Date: Fri, 25 Jun 2010 13:59:44 +0100
> Subject: [PATCHv2] perf tools: allow cross compiling with DWARF support
> 
> 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.
> 
> v2: if we can't find libdw.h and there is no sysroot support but it
> would be useful, warn the user.

Nice! Looks good to me. :)

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

Thanks!

> 
> Signed-off-by: Jamie Iles <jamie.iles@...ochip.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> ---
>  tools/perf/Makefile |   19 +++++++++++++++++--
>  1 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/Makefile b/tools/perf/Makefile
> index 6aa2fe3..1c08b7b 100644
> --- a/tools/perf/Makefile
> +++ b/tools/perf/Makefile
> @@ -503,9 +503,24 @@ 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$(SYSROOT_PATH)/usr/include/elfutils
> +	else
> +		NO_SYSROOT := y
> +	endif
> +endif
> +
>  ifndef NO_DWARF
> -FLAGS_DWARF=$(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)
> +	ifdef NO_SYSROOT
> +		msg := $(warning No sysroot support. Set elfutils include path in EXTRA_CFLAGS for dwarf support)
> +	endif
>  	msg := $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev);
>  	NO_DWARF := 1
>  endif # Dwarf support
> @@ -551,7 +566,7 @@ ifndef NO_DWARF
>  ifeq ($(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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