Re: [PATCH 1/1 perf-tools-next] tools features: Don't check for libunwind devel files by default

[Ian Rogers]

On Tue, Dec 3, 2024 at 1:08 PM Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> wrote:
>
> Since 13e17c9ff49119aa ("perf build: Make libunwind opt-in rather than
> opt-out"), so we shouldn't by default be testing for its availability at
> build time in tools/build/features/test-all.c.
>
> That test was designed to test the features we expect to be the most
> common ones in most builds, so if we test build just that file, then we
> assume the features there are present and will not test one by one.
>
> Removing it from test-all.c gets rid of the first impediment for
> test-all.c to build successfully:
>
>   $ cat /tmp/build/perf-tools-next/feature/test-all.make.output
>   In file included from test-all.c:62:
>   test-libunwind.c:2:10: fatal error: libunwind.h: No such file or directory
>       2 | #include <libunwind.h>
>         |          ^~~~~~~~~~~~~
>   compilation terminated.
>   $
>
> We then get to:
>
>   $ cat /tmp/build/perf-tools-next/feature/test-all.make.output
>   /usr/bin/ld: cannot find -lunwind-x86_64: No such file or directory
>   /usr/bin/ld: cannot find -lunwind: No such file or directory
>   collect2: error: ld returned 1 exit status
>   $
>
> So make all the logic related to setting CFLAGS, LDFLAGS, etc for
> libunwind to be conditional on NO_LIBWUNWIND=1, which is now the
> default, now we get a faster build:
>
>   $ cat /tmp/build/perf-tools-next/feature/test-all.make.output
>   $ ldd /tmp/build/perf-tools-next/feature/test-all.bin
>         linux-vdso.so.1 (0x00007fef04cde000)
>         libdw.so.1 => /lib64/libdw.so.1 (0x00007fef04a49000)
>         libpython3.12.so.1.0 => /lib64/libpython3.12.so.1.0 (0x00007fef04478000)
>         libm.so.6 => /lib64/libm.so.6 (0x00007fef04394000)
>         libtraceevent.so.1 => /lib64/libtraceevent.so.1 (0x00007fef0436c000)
>         libtracefs.so.1 => /lib64/libtracefs.so.1 (0x00007fef04345000)
>         libcrypto.so.3 => /lib64/libcrypto.so.3 (0x00007fef03e95000)
>         libz.so.1 => /lib64/libz.so.1 (0x00007fef03e72000)
>         libelf.so.1 => /lib64/libelf.so.1 (0x00007fef03e56000)
>         libnuma.so.1 => /lib64/libnuma.so.1 (0x00007fef03e48000)
>         libslang.so.2 => /lib64/libslang.so.2 (0x00007fef03b65000)
>         libperl.so.5.38 => /lib64/libperl.so.5.38 (0x00007fef037c6000)
>         libc.so.6 => /lib64/libc.so.6 (0x00007fef035d5000)
>         liblzma.so.5 => /lib64/liblzma.so.5 (0x00007fef035a0000)
>         libzstd.so.1 => /lib64/libzstd.so.1 (0x00007fef034e1000)
>         libbz2.so.1 => /lib64/libbz2.so.1 (0x00007fef034cd000)
>         /lib64/ld-linux-x86-64.so.2 (0x00007fef04ce0000)
>         libcrypt.so.2 => /lib64/libcrypt.so.2 (0x00007fef03495000)
>   $
>
> Fixes: 13e17c9ff49119aa ("perf build: Make libunwind opt-in rather than opt-out")
> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Cc: Ian Rogers <irogers@xxxxxxxxxx>
> Cc: James Clark <james.clark@xxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
> ---
>  tools/build/feature/test-all.c |  5 --
>  tools/perf/Makefile.config     | 83 ++++++++++++++++++++--------------
>  2 files changed, 49 insertions(+), 39 deletions(-)
>
> diff --git a/tools/build/feature/test-all.c b/tools/build/feature/test-all.c
> index 59ef3d7fe6a4e771..80ac297f81967171 100644
> --- a/tools/build/feature/test-all.c
> +++ b/tools/build/feature/test-all.c
> @@ -58,10 +58,6 @@
>  # include "test-libelf-getshdrstrndx.c"
>  #undef main
>
> -#define main main_test_libunwind
> -# include "test-libunwind.c"
> -#undef main
> -
>  #define main main_test_libslang
>  # include "test-libslang.c"
>  #undef main
> @@ -184,7 +180,6 @@ int main(int argc, char *argv[])
>         main_test_libelf_getphdrnum();
>         main_test_libelf_gelf_getnote();
>         main_test_libelf_getshdrstrndx();
> -       main_test_libunwind();
>         main_test_libslang();
>         main_test_libbfd();
>         main_test_libbfd_buildid();
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 2916d59c88cd08b2..0e4f6a860ae25339 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -43,7 +43,9 @@ endif
>  # Additional ARCH settings for ppc
>  ifeq ($(SRCARCH),powerpc)
>    CFLAGS += -I$(OUTPUT)arch/powerpc/include/generated
> -  LIBUNWIND_LIBS := -lunwind -lunwind-ppc64
> +  ifndef NO_LIBUNWIND
> +    LIBUNWIND_LIBS := -lunwind -lunwind-ppc64
> +  endif

Sorry for missing this patch. Given this, and below, are just
declaring a variable making it NO_LIBUNWIND conditional feels like
clutter. I'd suggest just keeping the variable unconditionally and
making the uses conditional (which of course the patch does).

Other than this:
Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

>  endif
>
>  # Additional ARCH settings for x86
> @@ -53,25 +55,35 @@ ifeq ($(SRCARCH),x86)
>    ifeq (${IS_64_BIT}, 1)
>      CFLAGS += -DHAVE_ARCH_X86_64_SUPPORT
>      ARCH_INCLUDE = ../../arch/x86/lib/memcpy_64.S ../../arch/x86/lib/memset_64.S
> -    LIBUNWIND_LIBS = -lunwind-x86_64 -lunwind -llzma
> +    ifndef NO_LIBUNWIND
> +      LIBUNWIND_LIBS = -lunwind-x86_64 -lunwind -llzma
> +    endif
>      $(call detected,CONFIG_X86_64)
>    else
> -    LIBUNWIND_LIBS = -lunwind-x86 -llzma -lunwind
> +    ifndef NO_LIBUNWIND
> +      LIBUNWIND_LIBS = -lunwind-x86 -llzma -lunwind
> +    endif
>    endif
>  endif
>
>  ifeq ($(SRCARCH),arm)
> -  LIBUNWIND_LIBS = -lunwind -lunwind-arm
> +  ifndef NO_LIBUNWIND
> +    LIBUNWIND_LIBS = -lunwind -lunwind-arm
> +  endif
>  endif
>
>  ifeq ($(SRCARCH),arm64)
>    CFLAGS += -I$(OUTPUT)arch/arm64/include/generated
> -  LIBUNWIND_LIBS = -lunwind -lunwind-aarch64
> +  ifndef NO_LIBUNWIND
> +    LIBUNWIND_LIBS = -lunwind -lunwind-aarch64
> +  endif
>  endif
>
>  ifeq ($(SRCARCH),loongarch)
>    CFLAGS += -I$(OUTPUT)arch/loongarch/include/generated
> -  LIBUNWIND_LIBS = -lunwind -lunwind-loongarch64
> +  ifndef NO_LIBUNWIND
> +    LIBUNWIND_LIBS = -lunwind -lunwind-loongarch64
> +  endif
>  endif
>
>  ifeq ($(ARCH),s390)
> @@ -80,7 +92,9 @@ endif
>
>  ifeq ($(ARCH),mips)
>    CFLAGS += -I$(OUTPUT)arch/mips/include/generated
> -  LIBUNWIND_LIBS = -lunwind -lunwind-mips
> +  ifndef NO_LIBUNWIND
> +    LIBUNWIND_LIBS = -lunwind -lunwind-mips
> +  endif
>  endif
>
>  ifeq ($(ARCH),riscv)
> @@ -121,16 +135,18 @@ ifdef LIBUNWIND_DIR
>    $(foreach libunwind_arch,$(LIBUNWIND_ARCHS),$(call libunwind_arch_set_flags,$(libunwind_arch)))
>  endif
>
> -# Set per-feature check compilation flags
> -FEATURE_CHECK_CFLAGS-libunwind = $(LIBUNWIND_CFLAGS)
> -FEATURE_CHECK_LDFLAGS-libunwind = $(LIBUNWIND_LDFLAGS) $(LIBUNWIND_LIBS)
> -FEATURE_CHECK_CFLAGS-libunwind-debug-frame = $(LIBUNWIND_CFLAGS)
> -FEATURE_CHECK_LDFLAGS-libunwind-debug-frame = $(LIBUNWIND_LDFLAGS) $(LIBUNWIND_LIBS)
> -
> -FEATURE_CHECK_LDFLAGS-libunwind-arm += -lunwind -lunwind-arm
> -FEATURE_CHECK_LDFLAGS-libunwind-aarch64 += -lunwind -lunwind-aarch64
> -FEATURE_CHECK_LDFLAGS-libunwind-x86 += -lunwind -llzma -lunwind-x86
> -FEATURE_CHECK_LDFLAGS-libunwind-x86_64 += -lunwind -llzma -lunwind-x86_64
> +ifndef NO_LIBUNWIND
> +  # Set per-feature check compilation flags
> +  FEATURE_CHECK_CFLAGS-libunwind = $(LIBUNWIND_CFLAGS)
> +  FEATURE_CHECK_LDFLAGS-libunwind = $(LIBUNWIND_LDFLAGS) $(LIBUNWIND_LIBS)
> +  FEATURE_CHECK_CFLAGS-libunwind-debug-frame = $(LIBUNWIND_CFLAGS)
> +  FEATURE_CHECK_LDFLAGS-libunwind-debug-frame = $(LIBUNWIND_LDFLAGS) $(LIBUNWIND_LIBS)
> +
> +  FEATURE_CHECK_LDFLAGS-libunwind-arm += -lunwind -lunwind-arm
> +  FEATURE_CHECK_LDFLAGS-libunwind-aarch64 += -lunwind -lunwind-aarch64
> +  FEATURE_CHECK_LDFLAGS-libunwind-x86 += -lunwind -llzma -lunwind-x86
> +  FEATURE_CHECK_LDFLAGS-libunwind-x86_64 += -lunwind -llzma -lunwind-x86_64
> +endif
>
>  FEATURE_CHECK_LDFLAGS-libcrypto = -lcrypto
>
> @@ -734,26 +750,25 @@ ifeq ($(dwarf-post-unwind),1)
>    $(call detected,CONFIG_DWARF_UNWIND)
>  endif
>
> -ifndef NO_LOCAL_LIBUNWIND
> -  ifeq ($(SRCARCH),$(filter $(SRCARCH),arm arm64))
> -    $(call feature_check,libunwind-debug-frame)
> -    ifneq ($(feature-libunwind-debug-frame), 1)
> -      $(warning No debug_frame support found in libunwind)
> +ifndef NO_LIBUNWIND
> +  ifndef NO_LOCAL_LIBUNWIND
> +    ifeq ($(SRCARCH),$(filter $(SRCARCH),arm arm64))
> +      $(call feature_check,libunwind-debug-frame)
> +      ifneq ($(feature-libunwind-debug-frame), 1)
> +        $(warning No debug_frame support found in libunwind)
> +        CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME
> +      endif
> +    else
> +      # non-ARM has no dwarf_find_debug_frame() function:
>        CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME
>      endif
> -  else
> -    # non-ARM has no dwarf_find_debug_frame() function:
> -    CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME
> +    EXTLIBS += $(LIBUNWIND_LIBS)
> +    LDFLAGS += $(LIBUNWIND_LIBS)
> +  endif
> +  ifeq ($(findstring -static,${LDFLAGS}),-static)
> +    # gcc -static links libgcc_eh which contans piece of libunwind
> +    LIBUNWIND_LDFLAGS += -Wl,--allow-multiple-definition
>    endif
> -  EXTLIBS += $(LIBUNWIND_LIBS)
> -  LDFLAGS += $(LIBUNWIND_LIBS)
> -endif
> -ifeq ($(findstring -static,${LDFLAGS}),-static)
> -  # gcc -static links libgcc_eh which contans piece of libunwind
> -  LIBUNWIND_LDFLAGS += -Wl,--allow-multiple-definition
> -endif
> -
> -ifndef NO_LIBUNWIND
>    CFLAGS  += -DHAVE_LIBUNWIND_SUPPORT
>    CFLAGS  += $(LIBUNWIND_CFLAGS)
>    LDFLAGS += $(LIBUNWIND_LDFLAGS)
> --
> 2.47.0
>