linux-kernel - [PATCH 4.6 080/100] objtool: Allow building with older libelf

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Message-Id: <20160530204911.012628482@linuxfoundation.org>
Date:	Mon, 30 May 2016 13:50:15 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Jan Beulich <jbeulich@...e.com>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jan Beulich <JBeulich@...e.com>, Jiri Olsa <jolsa@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vince Weaver <vincent.weaver@...ne.edu>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.6 080/100] objtool: Allow building with older libelf

4.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Beulich <JBeulich@...e.com>

commit 2e51f26245701cb28f154552836b7807159088a8 upstream.

The switch to elf_getshdr{num,strndx} post-dates the oldest tool chain
the kernel is supposed to be able to build with, so try to cope with
such an environment.

Signed-off-by: Jan Beulich <jbeulich@...e.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jan Beulich <JBeulich@...e.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vince Weaver <vincent.weaver@...ne.edu>
Link: http://lkml.kernel.org/r/732dae6872b7ff187d94f22bb699a12849d3fe04.1463430618.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 tools/objtool/Makefile |    4 ++++
 tools/objtool/elf.h    |    5 +++++
 2 files changed, 9 insertions(+)

--- a/tools/objtool/Makefile
+++ b/tools/objtool/Makefile
@@ -30,6 +30,10 @@ INCLUDES := -I$(srctree)/tools/include
 CFLAGS   += -Wall -Werror $(EXTRA_WARNINGS) -fomit-frame-pointer -O2 -g $(INCLUDES)
 LDFLAGS  += -lelf $(LIBSUBCMD)
 
+# Allow old libelf to be used:
+elfshdr := $(shell echo '\#include <libelf.h>' | $(CC) $(CFLAGS) -x c -E - | grep elf_getshdr)
+CFLAGS += $(if $(elfshdr),,-DLIBELF_USE_DEPRECATED)
+
 AWK = awk
 export srctree OUTPUT CFLAGS ARCH AWK
 include $(srctree)/tools/build/Makefile.include
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -23,6 +23,11 @@
 #include <linux/list.h>
 #include <linux/hashtable.h>
 
+#ifdef LIBELF_USE_DEPRECATED
+# define elf_getshdrnum    elf_getshnum
+# define elf_getshdrstrndx elf_getshstrndx
+#endif
+
 struct section {
 	struct list_head list;
 	GElf_Shdr sh;