Re: [PATCH] perf tools: add compatibility with libelf 0.8 and autodetect

[Marti Raudsepp <marti@juffo.org>]

Re-sending small fix; somehow I typed "elf_c_read_mmap" in lower case in
the comment.

Marti

--

perf tools: add compatibility with libelf 0.8.x and autodetect

The Makefile now automatically defines LIBELF_NO_MMAP when libelf 0.8.x is
detected. libelf 0.8.x is still maintained and some distributions such as
Arch Linux use it instead of elfutils.

Can't use #ifdef ELF_C_READ_MMAP because it's an enum constant not a
define.

Signed-off-by: Marti Raudsepp <marti@juffo.org>
---
 Makefile      |    6 +++++-
 util/symbol.c |    6 +++---
 util/symbol.h |   10 ++++++++++
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -422,7 +422,11 @@
        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 $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
+ifeq ($(shell sh -c "(echo '\#include <libelf.h>'; echo 'int main(void) { Elf * elf = elf_begin(0, ELF_C_READ, 0); return (long)elf; }') | $(CC) -x c - $(ALL_CFLAGS) -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -o /dev/null $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
+       ifneq ($(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)
+               BASIC_CFLAGS += -DLIBELF_NO_MMAP
+       endif
+else
        msg := $(error No libelf.h/libelf found, please install libelf-dev/elfutils-libelf-devel and glibc-dev[el]);
 endif
 
diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -413,7 +413,7 @@
        if (fd < 0)
                goto out;
 
-       elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+       elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        if (elf == NULL)
                goto out_close;
 
@@ -533,7 +533,7 @@
        Elf *elf;
        int nr = 0, kernel = !strcmp("[kernel]", self->name);
 
-       elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+       elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        if (elf == NULL) {
                if (v)
                        fprintf(stderr, "%s: cannot read %s ELF file.\n",
@@ -675,7 +675,7 @@
        if (fd < 0)
                goto out;
 
-       elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+       elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
        if (elf == NULL) {
                if (v)
                        fprintf(stderr, "%s: cannot read %s ELF file.\n",
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -27,6 +27,16 @@
 #endif
 #endif
 
+/*
+ * libelf 0.8.x and earlier do not support ELF_C_READ_MMAP; for newer versions
+ * we can use mmap to reduce memory usage
+ */
+#ifdef LIBELF_NO_MMAP
+# define PERF_ELF_C_READ_MMAP ELF_C_READ
+#else
+# define PERF_ELF_C_READ_MMAP ELF_C_READ_MMAP
+#endif
+
 #ifndef DMGL_PARAMS
 #define DMGL_PARAMS      (1 << 0)       /* Include function args */
 #define DMGL_ANSI        (1 << 1)       /* Include const, volatile, etc */