perf: Auto-detect libelf

Adds autodetection for libelf as well, and simplifies the
libbfd code. Furthermore, fail make with an error when libelf
is not found and warn about the lack of libbfd.

Also provide an option to build a 32bit version even though you
might be running a 64bit kernel.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/Makefile

@@ -158,8 +158,10 @@ uname_P := $(shell sh -c 'uname -p 2>/dev/null || echo not')
 uname_V := $(shell sh -c 'uname -v 2>/dev/null || echo not')
 
 # If we're on a 64-bit kernel, use -m64
-ifneq ($(patsubst %64,%,$(uname_M)),$(uname_M))
+ifndef NO_64BIT
+	ifneq ($(patsubst %64,%,$(uname_M)),$(uname_M))
 	  M64 := -m64
+	endif
 endif
 
 # CFLAGS and LDFLAGS are for the users to override from the command line.
@@ -373,19 +375,24 @@ ifeq ($(uname_S),Darwin)
 	PTHREAD_LIBS =
 endif
 
+ifneq ($(shell sh -c "(echo '\#include <libelf.h>'; echo 'int main(void) { Elf * elf = elf_begin(0, ELF_C_READ_MMAP, 0); return (long)elf; }') | $(CC) -x c - $(ALL_CFLAGS) -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -o /dev/null $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
+	msg := $(error No libelf.h/libelf found, please install libelf-dev/elfutils-libelf-devel);
+endif
+
 ifdef NO_DEMANGLE
 	BASIC_CFLAGS += -DNO_DEMANGLE
 else
 
-	has_bfd := $(shell sh -c "(echo '\#include <stdio.h>'; echo '\#include <bfd.h>'; echo '\#ifndef DMGL_PARAMS'; echo '\#define DMGL_PARAMS (1 << 0)'; echo '\#define DMGL_ANSI (1 << 1)'; echo '\#endif'; echo 'int main(int argc, char **argv) { bfd_demangle(NULL, argv[0], DMGL_PARAMS | DMGL_ANSI); return 0; }') | gcc -x c - -lbfd > /dev/null 2>&1 && echo y")
+	has_bfd := $(shell sh -c "(echo '\#include <bfd.h>'; echo 'int main(void) { bfd_demangle(0, 0, 0); return 0; }') | $(CC) -x c - $(ALL_CFLAGS) -o /dev/null $(ALL_LDFLAGS) -lbfd > /dev/null 2>&1 && echo y")
 
-	has_bfd_iberty := $(shell sh -c "(echo '\#include <stdio.h>'; echo '\#include <bfd.h>'; echo '\#ifndef DMGL_PARAMS'; echo '\#define DMGL_PARAMS (1 << 0)'; echo '\#define DMGL_ANSI (1 << 1)'; echo '\#endif'; echo 'int main(int argc, char **argv) { bfd_demangle(NULL, argv[0], DMGL_PARAMS | DMGL_ANSI); return 0; }') | gcc -x c - -lbfd -liberty > /dev/null 2>&1 && echo y")
+	has_bfd_iberty := $(shell sh -c "(echo '\#include <bfd.h>'; echo 'int main(void) { bfd_demangle(0, 0, 0); return 0; }') | $(CC) -x c - $(ALL_CFLAGS) -o /dev/null $(ALL_LDFLAGS) -lbfd -liberty > /dev/null 2>&1 && echo y")
 
 	ifeq ($(has_bfd),y)
 		EXTLIBS += -lbfd
 	else ifeq ($(has_bfd_iberty),y)
 		EXTLIBS += -lbfd -liberty
 	else
+		msg := $(warning No bfd.h/libbfd found, install binutils-dev[el] to gain symbol demangling)
 		BASIC_CFLAGS += -DNO_DEMANGLE
 	endif
 endif