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

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Message-ID: <4C24B03B.8090504@picochip.com>
Date:	Fri, 25 Jun 2010 14:33:47 +0100
From:	Jamie Iles <jamie.iles@...ochip.com>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.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

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.

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
-- 
1.7.0.1

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