perf build: Make libunwind opt-in rather than opt-out

Having multiple unwinding libraries makes the perf code harder to
understand and we have unused/untested code paths.

Perf made BPF support an opt-out rather than opt-in feature. As libbpf
has a libelf dependency, elfutils that provides libelf will also
provide libdw. When libdw is present perf will use libdw unwinding
rather than libunwind unwinding even if libunwind support is compiled
in.

Rather than have libunwind built into perf and never used, explicitly
disable the support and make it opt-in.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20241028193619.247727-1-irogers@google.com
Closes: https://lore.kernel.org/linux-perf-users/CAP-5=fUXkp-d7gkzX4eF+nbjb2978dZsiHZ9abGHN=BN1qAcbg@mail.gmail.com/
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 8da6d91b7ad516f5dc3a863a6e1b675187b3d27d..e68f0be259a19ecd47de4781a3e14b05e6ce5a75 100644 (file)
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -95,6 +95,10 @@ ifneq ($(SRCARCH),$(filter $(SRCARCH),x86 arm arm64 powerpc s390 csky riscv loon
   NO_LIBDW_DWARF_UNWIND := 1
 endif
 
+ifneq ($(LIBUNWIND),1)
+  NO_LIBUNWIND := 1
+endif
+
 ifeq ($(LIBUNWIND_LIBS),)
   NO_LIBUNWIND := 1
 endif

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index b4dee7c20ed158fb5b4f3fe83a0bc7d2d317a16c..d74241a151313bd09101aabb5d765a5a0a6efc84 100644 (file)
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -52,7 +52,7 @@ include ../scripts/utilities.mak
 #
 # Define NO_LIBELF if you do not want libelf dependency (e.g. cross-builds)
 #
-# Define NO_LIBUNWIND if you do not want libunwind dependency for dwarf
+# Define LIBUNWIND if you do not want libunwind dependency for dwarf
 # backtrace post unwind.
 #
 # Define NO_BACKTRACE if you do not want stack backtrace debug feature

diff --git a/tools/perf/tests/make b/tools/perf/tests/make
index a5040772043f63c4af13c9001cfb4571103eb8c6..a7fcbd589752a90459815bd21075528c6dfa4d94 100644 (file)
--- a/tools/perf/tests/make
+++ b/tools/perf/tests/make
@@ -81,7 +81,7 @@ make_no_gtk2        := NO_GTK2=1
 make_no_ui          := NO_SLANG=1 NO_GTK2=1
 make_no_demangle    := NO_DEMANGLE=1
 make_no_libelf      := NO_LIBELF=1
-make_no_libunwind   := NO_LIBUNWIND=1
+make_libunwind      := LIBUNWIND=1
 make_no_libdw_dwarf_unwind := NO_LIBDW_DWARF_UNWIND=1
 make_no_backtrace   := NO_BACKTRACE=1
 make_no_libcapstone := NO_CAPSTONE=1
@@ -121,7 +121,7 @@ make_static         := LDFLAGS=-static NO_PERF_READ_VDSO32=1 NO_PERF_READ_VDSOX3
 
 # all the NO_* variable combined
 make_minimal        := NO_LIBPERL=1 NO_LIBPYTHON=1 NO_GTK2=1
-make_minimal        += NO_DEMANGLE=1 NO_LIBELF=1 NO_LIBUNWIND=1 NO_BACKTRACE=1
+make_minimal        += NO_DEMANGLE=1 NO_LIBELF=1 NO_BACKTRACE=1
 make_minimal        += NO_LIBNUMA=1 NO_LIBAUDIT=1 NO_LIBBIONIC=1
 make_minimal        += NO_LIBDW_DWARF_UNWIND=1 NO_AUXTRACE=1 NO_LIBBPF=1
 make_minimal        += NO_LIBCRYPTO=1 NO_SDT=1 NO_JVMTI=1 NO_LIBZSTD=1
@@ -153,7 +153,7 @@ run += make_no_gtk2
 run += make_no_ui
 run += make_no_demangle
 run += make_no_libelf
-run += make_no_libunwind
+run += make_libunwind
 run += make_no_libdw_dwarf_unwind
 run += make_no_backtrace
 run += make_no_libcapstone