[tip:perf/core] objtool: Add fallback from ELF_C_READ_MMAP to ELF_C_READ

[tip-bot for Arnaldo Carvalho de Melo]

Commit-ID:  774bec3fddcccb0b36f319c6d6e8148dc5e8c937
Gitweb:     http://git.kernel.org/tip/774bec3fddcccb0b36f319c6d6e8148dc5e8c937
Author:     Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
AuthorDate: Wed, 13 Jul 2016 15:28:51 -0300
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Wed, 13 Jul 2016 15:38:50 -0300

objtool: Add fallback from ELF_C_READ_MMAP to ELF_C_READ

Not all libelf implementations have this "Please, ELF_C_READ, but use
mmap if possible" elf_begin() cmd, so provide a fallback to plain old
ELF_C_READ.

Case in point: Alpine Linux 3.4.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-1fctuknrawgoi5xqon4mu9dv@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/objtool/elf.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index e11f6b6..0d7983a 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -30,6 +30,13 @@
 #include "elf.h"
 #include "warn.h"
 
+/*
+ * Fallback for systems without this "read, mmaping if possible" cmd.
+ */
+#ifndef ELF_C_READ_MMAP
+#define ELF_C_READ_MMAP ELF_C_READ
+#endif
+
 struct section *find_section_by_name(struct elf *elf, const char *name)
 {
 	struct section *sec;