Re: [PATCH 06/10] perf probe: Check if dwarf_getlocations() is available

[Masami Hiramatsu <mhiramat@kernel.org>]

On Thu, 12 May 2016 17:03:51 -0300
Arnaldo Carvalho de Melo <acme@kernel.org> wrote:

> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> 
> If not, tell the user that:
> 
>   config/Makefile:273: Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157
> 
> And return -ENOTSUPP in die_get_var_range(), failing features that
> need it, like the one pointed out above.
> 
> This fixes the build on older systems, such as Ubuntu 12.04.5.
> 

Hmm, would we better to use similar technique for dwarf_cfi_addrframe?
the commit 7752f1b096e1
("perf probe: Don't compile CFI related code if elfutils is old")
uses _ELFUTILS_PREREQ() macro for checking the elfutils version directly.

Anyway, this looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: David Ahern <dsahern@gmail.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Vinson Lee <vlee@freedesktop.org>
> Cc: Wang Nan <wangnan0@huawei.com>
> Link: http://lkml.kernel.org/n/tip-9l7luqkq4gfnx7vrklkq4obs@git.kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  tools/build/Makefile.feature                  |  2 ++
>  tools/build/feature/Makefile                  |  4 ++++
>  tools/build/feature/test-all.c                |  5 +++++
>  tools/build/feature/test-dwarf_getlocations.c | 12 ++++++++++++
>  tools/perf/config/Makefile                    |  6 ++++++
>  tools/perf/util/dwarf-aux.c                   |  9 +++++++++
>  6 files changed, 38 insertions(+)
>  create mode 100644 tools/build/feature/test-dwarf_getlocations.c
> 
> diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
> index 6b7707270aa3..9f878619077a 100644
> --- a/tools/build/Makefile.feature
> +++ b/tools/build/Makefile.feature
> @@ -30,6 +30,7 @@ endef
>  FEATURE_TESTS_BASIC :=			\
>  	backtrace			\
>  	dwarf				\
> +	dwarf_getlocations		\
>  	fortify-source			\
>  	sync-compare-and-swap		\
>  	glibc				\
> @@ -78,6 +79,7 @@ endif
>  
>  FEATURE_DISPLAY ?=			\
>  	dwarf				\
> +	dwarf_getlocations		\
>  	glibc				\
>  	gtk2				\
>  	libaudit			\
> diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
> index c5f4c417428d..4ae94dbfdab9 100644
> --- a/tools/build/feature/Makefile
> +++ b/tools/build/feature/Makefile
> @@ -3,6 +3,7 @@ FILES=					\
>  	test-backtrace.bin		\
>  	test-bionic.bin			\
>  	test-dwarf.bin			\
> +	test-dwarf_getlocations.bin	\
>  	test-fortify-source.bin		\
>  	test-sync-compare-and-swap.bin	\
>  	test-glibc.bin			\
> @@ -82,6 +83,9 @@ endif
>  $(OUTPUT)test-dwarf.bin:
>  	$(BUILD) $(DWARFLIBS)
>  
> +$(OUTPUT)test-dwarf_getlocations.bin:
> +	$(BUILD) $(DWARFLIBS)
> +
>  $(OUTPUT)test-libelf-mmap.bin:
>  	$(BUILD) -lelf
>  
> diff --git a/tools/build/feature/test-all.c b/tools/build/feature/test-all.c
> index e499a36c1e4a..a282e8cb84f3 100644
> --- a/tools/build/feature/test-all.c
> +++ b/tools/build/feature/test-all.c
> @@ -41,6 +41,10 @@
>  # include "test-dwarf.c"
>  #undef main
>  
> +#define main main_test_dwarf_getlocations
> +# include "test-dwarf_getlocations.c"
> +#undef main
> +
>  #define main main_test_libelf_getphdrnum
>  # include "test-libelf-getphdrnum.c"
>  #undef main
> @@ -143,6 +147,7 @@ int main(int argc, char *argv[])
>  	main_test_libelf_mmap();
>  	main_test_glibc();
>  	main_test_dwarf();
> +	main_test_dwarf_getlocations();
>  	main_test_libelf_getphdrnum();
>  	main_test_libunwind();
>  	main_test_libaudit();
> diff --git a/tools/build/feature/test-dwarf_getlocations.c b/tools/build/feature/test-dwarf_getlocations.c
> new file mode 100644
> index 000000000000..70162699dd43
> --- /dev/null
> +++ b/tools/build/feature/test-dwarf_getlocations.c
> @@ -0,0 +1,12 @@
> +#include <stdlib.h>
> +#include <elfutils/libdw.h>
> +
> +int main(void)
> +{
> +	Dwarf_Addr base, start, end;
> +	Dwarf_Attribute attr;
> +	Dwarf_Op *op;
> +        size_t nops;
> +	ptrdiff_t offset = 0;
> +        return (int)dwarf_getlocations(&attr, offset, &base, &start, &end, &op, &nops);
> +}
> diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
> index f7d7f5a1cad5..6f8f6430f2bf 100644
> --- a/tools/perf/config/Makefile
> +++ b/tools/perf/config/Makefile
> @@ -268,6 +268,12 @@ else
>      ifneq ($(feature-dwarf), 1)
>        msg := $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev);
>        NO_DWARF := 1
> +    else
> +      ifneq ($(feature-dwarf_getlocations), 1)
> +        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157);
> +      else
> +        CFLAGS += -DHAVE_DWARF_GETLOCATIONS
> +      endif # dwarf_getlocations
>      endif # Dwarf support
>    endif # libelf support
>  endif # NO_LIBELF
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index 577e600c8eb1..aea189b41cc8 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -959,6 +959,7 @@ int die_get_varname(Dwarf_Die *vr_die, struct strbuf *buf)
>  	return 0;
>  }
>  
> +#ifdef HAVE_DWARF_GETLOCATIONS
>  /**
>   * die_get_var_innermost_scope - Get innermost scope range of given variable DIE
>   * @sp_die: a subprogram DIE
> @@ -1080,3 +1081,11 @@ int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die, struct strbuf *buf)
>  
>  	return ret;
>  }
> +#else
> +int die_get_var_range(Dwarf_Die *sp_die __maybe_unused,
> +		      Dwarf_Die *vr_die __maybe_unused,
> +		      struct strbuf *buf __maybe_unused)
> +{
> +	return -ENOTSUP;
> +}
> +#endif
> -- 
> 2.5.5
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>