LinuxLists.cc - [PATCH] perf tools: add compatibility with libelf 0.8 and autodetect

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

* Marti Raudsepp <[email protected]> wrote:

> The Makefile now automatically defines LIBELF_NO_MMAP when libelf 0.8 is
> detected. libelf 0.8 is still maintained and some distributions such as
> Arch Linux use it instead of elfutils.
>
> Signed-off-by: Marti Raudsepp <[email protected]>
> ---
> tools/perf/Makefile | 6 +++++-
> tools/perf/util/symbol.c | 12 ++++++++++++
> 2 files changed, 17 insertions(+), 1 deletions(-)

Nice fix!

Mind doing a small change:

> diff --git a/tools/perf/Makefile b/tools/perf/Makefile
> index 742a32e..46e877b 100644
> --- a/tools/perf/Makefile
> +++ b/tools/perf/Makefile
> @@ -422,7 +422,11 @@ 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 $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
> +ifeq ($(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
> index 47ea060..8d1df1e 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -413,7 +413,11 @@ static int dso__synthesize_plt_symbols(struct dso *self, int v)
> if (fd < 0)
> goto out;
>
> +#ifdef LIBELF_NO_MMAP
> + elf = elf_begin(fd, ELF_C_READ, NULL);
> +#else
> elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
> +#endif
> if (elf == NULL)
> goto out_close;
>
> @@ -533,7 +537,11 @@ static int dso__load_sym(struct dso *self, int fd, const char *name,
> Elf *elf;
> int nr = 0, kernel = !strcmp("[kernel]", self->name);
>
> +#ifdef LIBELF_NO_MMAP
> + elf = elf_begin(fd, ELF_C_READ, NULL);
> +#else
> elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
> +#endif
> if (elf == NULL) {
> if (v)
> fprintf(stderr, "%s: cannot read %s ELF file.\n",
> @@ -675,7 +683,11 @@ static char *dso__read_build_id(struct dso *self, int v)
> if (fd < 0)
> goto out;
>
> +#ifdef LIBELF_NO_MMAP
> + elf = elf_begin(fd, ELF_C_READ, NULL);
> +#else
> elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
> +#endif
> if (elf == NULL) {
> if (v)
> fprintf(stderr, "%s: cannot read %s ELF file.\n",

I think we want a small cleanup here: a perf_elf_begin() wrapper in a
header file to hide this #ifdef. (That's how Git wraps environmental
libraries as well.)

Also, this would be an urgent fix for v2.6.32 too, to make perf build on
Arch Linux, agreed?

Ingo

2009-10-23 21:49:17

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

On Sat, Oct 24, 2009 at 12:02 AM, Ingo Molnar <[email protected]> wrote:
> Mind doing a small change:
>
> I think we want a small cleanup here: a perf_elf_begin() wrapper in a
> header file to hide this #ifdef. (That's how Git wraps environmental
> libraries as well.)

Ok, does this patch do what you had in mind? I wasn't quite sure how to
implement; changing the cmd behind someone's back might be considered
surprising.

Another take would be to #define our own ELF_C_READ_MMAP, but that would be
lying, too...

> Also, this would be an urgent fix for v2.6.32 too, to make perf build on
> Arch Linux, agreed?

Hopefully :)

Regards,
Marti

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

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

Signed-off-by: Marti Raudsepp <[email protected]>
---
tools/perf/Makefile | 6 +++++-
tools/perf/util/symbol.c | 9 +++++----
tools/perf/util/symbol.h | 11 +++++++++++
3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 742a32e..46e877b 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -422,7 +422,11 @@ 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 $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
+ifeq ($(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
index 47ea060..ec69c42 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -5,7 +5,6 @@

#include "debug.h"

-#include <libelf.h>
#include <gelf.h>
#include <elf.h>

@@ -413,7 +412,8 @@ static int dso__synthesize_plt_symbols(struct dso *self, int v)
if (fd < 0)
goto out;

- elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+ elf = perf_elf_begin(fd, ELF_C_READ, NULL);
+
if (elf == NULL)
goto out_close;

@@ -533,7 +533,8 @@ static int dso__load_sym(struct dso *self, int fd, const char *name,
Elf *elf;
int nr = 0, kernel = !strcmp("[kernel]", self->name);

- elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+ elf = perf_elf_begin(fd, ELF_C_READ, NULL);
+
if (elf == NULL) {
if (v)
fprintf(stderr, "%s: cannot read %s ELF file.\n",
@@ -675,7 +676,7 @@ static char *dso__read_build_id(struct dso *self, int v)
if (fd < 0)
goto out;

- elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+ elf = perf_elf_begin(fd, ELF_C_READ, 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
index 6e84907..50750e9 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -8,6 +8,8 @@
#include "module.h"
#include "event.h"

+#include <libelf.h>
+
#ifdef HAVE_CPLUS_DEMANGLE
extern char *cplus_demangle(const char *, int);

@@ -27,6 +29,15 @@ static inline char *bfd_demangle(void __used *v, const char __used *c,
#endif
#endif

+static inline Elf *perf_elf_begin(int fd, Elf_Cmd cmd, Elf *ref)
+{
+#ifndef LIBELF_NO_MMAP
+ if (cmd == ELF_C_READ)
+ cmd = ELF_C_READ_MMAP;
+#endif
+ return elf_begin(fd, cmd, ref);
+}
+
#ifndef DMGL_PARAMS
#define DMGL_PARAMS (1 << 0) /* Include function args */
#define DMGL_ANSI (1 << 1) /* Include const, volatile, etc */
--
1.6.5.1

2009-10-23 21:52:45

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

* Marti Raudsepp <[email protected]> wrote:

> On Sat, Oct 24, 2009 at 12:02 AM, Ingo Molnar <[email protected]> wrote:
> > Mind doing a small change:
> >
> > I think we want a small cleanup here: a perf_elf_begin() wrapper in a
> > header file to hide this #ifdef. (That's how Git wraps environmental
> > libraries as well.)
>
> Ok, does this patch do what you had in mind? I wasn't quite sure how to
> implement; changing the cmd behind someone's back might be considered
> surprising.
>
> Another take would be to #define our own ELF_C_READ_MMAP, but that would be
> lying, too...
>
> > Also, this would be an urgent fix for v2.6.32 too, to make perf build on
> > Arch Linux, agreed?
>
> Hopefully :)
>
> Regards,
> Marti
>
>
> [PATCH] perf tools: add compatibility with libelf 0.8 and autodetect
>
> The Makefile now automatically defines LIBELF_NO_MMAP when libelf 0.8 is
> detected. libelf 0.8 is still maintained and some distributions such as
> Arch Linux use it instead of elfutils.
>
> Signed-off-by: Marti Raudsepp <[email protected]>
> ---
> tools/perf/Makefile | 6 +++++-
> tools/perf/util/symbol.c | 9 +++++----
> tools/perf/util/symbol.h | 11 +++++++++++
> 3 files changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/Makefile b/tools/perf/Makefile
> index 742a32e..46e877b 100644
> --- a/tools/perf/Makefile
> +++ b/tools/perf/Makefile
> @@ -422,7 +422,11 @@ 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 $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
> +ifeq ($(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
> index 47ea060..ec69c42 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -5,7 +5,6 @@
>
> #include "debug.h"
>
> -#include <libelf.h>
> #include <gelf.h>
> #include <elf.h>
>
> @@ -413,7 +412,8 @@ static int dso__synthesize_plt_symbols(struct dso *self, int v)
> if (fd < 0)
> goto out;
>
> - elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
> + elf = perf_elf_begin(fd, ELF_C_READ, NULL);
> +
> if (elf == NULL)
> goto out_close;
>
> @@ -533,7 +533,8 @@ static int dso__load_sym(struct dso *self, int fd, const char *name,
> Elf *elf;
> int nr = 0, kernel = !strcmp("[kernel]", self->name);
>
> - elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
> + elf = perf_elf_begin(fd, ELF_C_READ, NULL);
> +
> if (elf == NULL) {
> if (v)
> fprintf(stderr, "%s: cannot read %s ELF file.\n",
> @@ -675,7 +676,7 @@ static char *dso__read_build_id(struct dso *self, int v)
> if (fd < 0)
> goto out;
>
> - elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
> + elf = perf_elf_begin(fd, ELF_C_READ, 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
> index 6e84907..50750e9 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -8,6 +8,8 @@
> #include "module.h"
> #include "event.h"
>
> +#include <libelf.h>
> +
> #ifdef HAVE_CPLUS_DEMANGLE
> extern char *cplus_demangle(const char *, int);
>
> @@ -27,6 +29,15 @@ static inline char *bfd_demangle(void __used *v, const char __used *c,
> #endif
> #endif
>
> +static inline Elf *perf_elf_begin(int fd, Elf_Cmd cmd, Elf *ref)
> +{
> +#ifndef LIBELF_NO_MMAP
> + if (cmd == ELF_C_READ)
> + cmd = ELF_C_READ_MMAP;
> +#endif
> + return elf_begin(fd, cmd, ref);
> +}
> +
> #ifndef DMGL_PARAMS
> #define DMGL_PARAMS (1 << 0) /* Include function args */
> #define DMGL_ANSI (1 << 1) /* Include const, volatile, etc */

Looks nice!

Mind adding a comment as well to document the version dependency?

Also, there's a few probably unintended whitespaces in the patch not
matching surrounding style (which is the kernel coding style) - please
run the patch through scripts/checkpatch.pl.

Ingo

2009-10-23 21:56:35

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

(sorry, Ingo, forgot to reply-all)

On Fri, Oct 23, 2009 at 19:02, Ingo Molnar <[email protected]> wrote:
> Also, this would be an urgent fix for v2.6.32 too, to make perf build on
> Arch Linux, agreed?
>
If the fix is as simple as this patch, and will not cause any other
problems, may it be sent to -stable as well?

To make perf build on Arch is also possible to install elfutils from
AUR (http://aur.archlinux.org/packages.php?ID=5300) and I've made a
request some months ago to switch to this library instead of using
libelf but got no answers.

I think it's Arch's fault to continue using an unmaintained library
when there's an easy replacement, but if the "fix" is easy, why not?

Lucas De Marchi

2009-10-23 21:59:38

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

On Sat, Oct 24, 2009 at 12:56 AM, Lucas De Marchi
<[email protected]> wrote:
> I think it's Arch's fault to continue using an unmaintained library
> when there's an easy replacement, but if the "fix" is easy, why not?

As far as I can tell, libelf is still maintained; the latest release
is from July 2009.

Regards,
Marti

2009-10-23 22:10:53

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

On Sat, Oct 24, 2009 at 12:52 AM, Ingo Molnar <[email protected]> wrote:
> Mind adding a comment as well to document the version dependency?

Sure

> Also, there's a few probably unintended whitespaces

Fixed

--
perf tools: add compatibility with libelf 0.8 and autodetect

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

Signed-off-by: Marti Raudsepp <[email protected]>
---
tools/perf/Makefile | 6 +++++-
tools/perf/util/symbol.c | 9 +++++----
tools/perf/util/symbol.h | 16 ++++++++++++++++
3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 742a32e..46e877b 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -422,7 +422,11 @@ 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 $(ALL_LDFLAGS) > /dev/null 2>&1 && echo y"), y)
+ifeq ($(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
index 47ea060..ec69c42 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -5,7 +5,6 @@

#include "debug.h"

-#include <libelf.h>
#include <gelf.h>
#include <elf.h>

@@ -413,7 +412,8 @@ static int dso__synthesize_plt_symbols(struct dso *self, int v)
if (fd < 0)
goto out;

- elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+ elf = perf_elf_begin(fd, ELF_C_READ, NULL);
+
if (elf == NULL)
goto out_close;

@@ -533,7 +533,8 @@ static int dso__load_sym(struct dso *self, int fd, const char *name,
Elf *elf;
int nr = 0, kernel = !strcmp("[kernel]", self->name);

- elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+ elf = perf_elf_begin(fd, ELF_C_READ, NULL);
+
if (elf == NULL) {
if (v)
fprintf(stderr, "%s: cannot read %s ELF file.\n",
@@ -675,7 +676,7 @@ static char *dso__read_build_id(struct dso *self, int v)
if (fd < 0)
goto out;

- elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+ elf = perf_elf_begin(fd, ELF_C_READ, 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
index 6e84907..38bc832 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -8,6 +8,8 @@
#include "module.h"
#include "event.h"

+#include <libelf.h>
+
#ifdef HAVE_CPLUS_DEMANGLE
extern char *cplus_demangle(const char *, int);

@@ -27,6 +29,20 @@ static inline char *bfd_demangle(void __used *v, const char __used *c,
#endif
#endif

+static inline Elf *perf_elf_begin(int fd, Elf_Cmd cmd, Elf *ref)
+{
+#ifndef LIBELF_NO_MMAP
+ /*
+ * libelf 0.8 and earlier do not support ELF_C_READ_MMAP; for newer
+ * versions we can use mmap to reduce memory usage
+ */
+
+ if (cmd == ELF_C_READ)
+ cmd = ELF_C_READ_MMAP;
+#endif
+ return elf_begin(fd, cmd, ref);
+}
+
#ifndef DMGL_PARAMS
#define DMGL_PARAMS (1 << 0) /* Include function args */
#define DMGL_ANSI (1 << 1) /* Include const, volatile, etc */
--
1.6.5.1

2009-10-23 22:16:31

[permalink] [raw]

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

On Fri, Oct 23, 2009 at 19:59, Marti Raudsepp <[email protected]> wrote:
> On Sat, Oct 24, 2009 at 12:56 AM, Lucas De Marchi
> <[email protected]> wrote:
>> I think it's Arch's fault to continue using an unmaintained library
>> when there's an easy replacement, but if the "fix" is easy, why not?
>
> As far as I can tell, libelf is still maintained; the latest release
> is from July 2009.
>

humn... I was looking at FSF site
(http://directory.fsf.org/project/libelf/) where version was not
updated anymore.

Lucas De Marchi

2009-10-24 01:07:58

[permalink] [raw]

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

On Fri, Oct 23, 2009 at 19:48, Marti Raudsepp <[email protected]> wrote:
> On Sat, Oct 24, 2009 at 12:02 AM, Ingo Molnar <[email protected]> wrote:
>> Mind doing a small change:
>>
>> I think we want a small cleanup here: a perf_elf_begin() wrapper in a
>> header file to hide this #ifdef. (That's how Git wraps environmental
>> libraries as well.)
>
Why don't you do something like?:

#ifdef LIBELF_NO_MMAP
#define ELF_C_READ_MMAP ELF_C_READ
#endif
+ changes to Makefile

or:

#ifndef ELF_C_READ_MMAP
#define ELF_C_READ_MMAP ELF_C_READ
#endif

2009-10-24 01:19:15

[permalink] [raw]

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

On Sat, Oct 24, 2009 at 4:07 AM, Lucas De Marchi
<[email protected]> wrote:
> Why don't you do something like?:
>
> #ifdef LIBELF_NO_MMAP
> #define ELF_C_READ_MMAP ELF_C_READ
> #endif

Seemed like bad programming practice to redefine enum constants from
third-party include files. But you are right, it would significantly
simplify the patch. Can we get a third opinion?

Marti

2009-10-24 08:30:45

[permalink] [raw]

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

* Lucas De Marchi <[email protected]> wrote:

> On Fri, Oct 23, 2009 at 19:48, Marti Raudsepp <[email protected]> wrote:
> > On Sat, Oct 24, 2009 at 12:02 AM, Ingo Molnar <[email protected]> wrote:
> >> Mind doing a small change:
> >>
> >> I think we want a small cleanup here: a perf_elf_begin() wrapper in a
> >> header file to hide this #ifdef. (That's how Git wraps environmental
> >> libraries as well.)
> >
> Why don't you do something like?:
>
> #ifdef LIBELF_NO_MMAP
> #define ELF_C_READ_MMAP ELF_C_READ
> #endif
> + changes to Makefile
>
> or:
>
> #ifndef ELF_C_READ_MMAP
> #define ELF_C_READ_MMAP ELF_C_READ
> #endif

Makes sense - i'd suggest to prefix it with PERF_ in that case, to make
sure all callsites are aware of the wrapped nature of this constant.

I.e. something like this:

/*
* libelf 0.8 and earlier do not support ELF_C_READ_MMAP;
* for newer versions we can use mmap to reduce memory usage:
*/
#ifndef ELF_C_READ_MMAP
# define PERF_ELF_C_READ_MMAP ELF_C_READ
#endif

Ingo

2009-10-24 13:26:49

[permalink] [raw]

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

On Sat, Oct 24, 2009 at 06:30, Ingo Molnar <[email protected]> wrote:
> I.e. something like this:
>
> /*
> ?* libelf 0.8 and earlier do not support ELF_C_READ_MMAP;
> ?* for newer versions we can use mmap to reduce memory usage:
> ?*/
> #ifndef ELF_C_READ_MMAP
> # define PERF_ELF_C_READ_MMAP ELF_C_READ
> #endif

In this case you should define PERF_ELF_C_READ_MMAP as ELF_C_READ_MMAP
when using elftutils:
#ifndef ELF_C_READ_MMAP
# define PERF_ELF_C_READ_MMAP ELF_C_READ
#else
# define PERF_ELF_C_READ_MMAP ELF_C_READ_MMAP
#endif

and change all places to use PERF_ELF_C_READ_MMAP

I think the comment is wrong. I downloaded the latest version of
libelf, i.e. 0.8.12 at http://www.mr511.de/software/english.html, and
there's no support to ELF_C_READ_MMAP. It's a elfutils' feature only.

2009-10-24 15:13:17

[permalink] [raw]

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

On Sat, 2009-10-24 at 11:26 -0200, Lucas De Marchi wrote:
> In this case you should define PERF_ELF_C_READ_MMAP as ELF_C_READ_MMAP
> when using elftutils:
> #ifndef ELF_C_READ_MMAP
> # define PERF_ELF_C_READ_MMAP ELF_C_READ
> #else
> # define PERF_ELF_C_READ_MMAP ELF_C_READ_MMAP
> #endif

That's what I wanted to do at first, but it doesn't work because
ELF_C_READ_MMAP is an enum constant -- not a #define

But defining our own PERF_ELF_C_READ_MMAP is a good idea and much
cleaner than the earlier mess. Thanks

> I think the comment is wrong. I downloaded the latest version of
> libelf, i.e. 0.8.12 at http://www.mr511.de/software/english.html, and
> there's no support to ELF_C_READ_MMAP. It's a elfutils' feature only.

I guess the comment was confusing. With "libelf 0.8" I meant the whole
0.8.x series.

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 <[email protected]>
---
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 */

2009-10-24 15:19:25

[permalink] [raw]

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

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 <[email protected]>
---
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 */

2009-10-24 15:42:04

[permalink] [raw]

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

* Marti Raudsepp <[email protected]> wrote:

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

The patch got whitespace damaged (tabs are spaces, etc.) - please see
Documentation/email-clients.txt.

Ingo

2009-10-24 16:10:39