[RFC PATCH v2 3/7] perf build: Add MINIMAL=1 to build without optional features

[Sasha Levin]

Turning off every optional feature takes a long list of NO_* variables,
and the list has to follow features as they are added and renamed. The
one in tests/make for make_minimal has fallen behind: it leaves
libtraceevent, jevents, slang, AIO, LZMA, zlib, libLLVM and Rust to be
detected, so a make_minimal build still needs libtraceevent and python.

Add MINIMAL=1, which turns off every optional feature, the BPF skeletons
and the shellcheck run. perf then builds, natively or cross, with no
library beyond the C library and without python, pkg-config, clang or
rustc, and the result does not depend on what is installed on the build
machine.

A MINIMAL=1 build also leaves out the notices that post unwind and
python support are disabled, which it asked for, and the one about the
pkg-config search path for cross builds, as pkg-config is not needed
then.

It is handled in Makefile.perf rather than Makefile.config, as
Makefile.config is included after the pkg-config and shellcheck setup.

Use it for make_minimal in tests/make.

Suggested-by: Ian Rogers <irogers@xxxxxxxxxx>
Link: https://lore.kernel.org/r/CAP-5=fWFY-tpJz2vcBZvurwdZY5gwd8cuTemE9q1rtZ0Vi0dng@xxxxxxxxxxxxxx
Assisted-by: LLM
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 tools/perf/Makefile.config |  8 ++++++--
 tools/perf/Makefile.perf   | 40 ++++++++++++++++++++++++++++++++++++--
 tools/perf/tests/make      |  8 +-------
 3 files changed, 45 insertions(+), 11 deletions(-)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 4d5993da9f945..137c9e120670b 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -742,7 +742,9 @@ dwarf-post-unwind-text := BUG
 # setup DWARF post unwinder
 ifdef NO_LIBUNWIND
   ifdef NO_LIBDW
-    $(warning Disabling post unwind, no support found.)
+    ifneq ($(MINIMAL),1)
+      $(warning Disabling post unwind, no support found.)
+    endif
     dwarf-post-unwind := 0
   else
     dwarf-post-unwind-text := libdw
@@ -828,7 +830,9 @@ endef
 
 PYTHON_EXTENSION_SUFFIX := '.so'
 ifdef NO_LIBPYTHON
-  $(call disable-python,Python support disabled by user)
+  ifneq ($(MINIMAL),1)
+    $(call disable-python,Python support disabled by user)
+  endif
 else
 
   ifndef PYTHON
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 29cfd44c427f3..c770077e7d392 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -129,6 +129,9 @@ include ../scripts/utilities.mak
 # Define GEN_VMLINUX_H to generate vmlinux.h from the BTF.
 #
 # Define NO_SHELLCHECK if you do not want to run shellcheck during build
+#
+# Define MINIMAL=1 to build without any optional feature, needing only a C
+# compiler and library, flex and bison
 
 # As per kernel Makefile, avoid funny character set dependencies
 unexport LC_ALL
@@ -174,6 +177,37 @@ endef
 
 LD += $(EXTRA_LDFLAGS)
 
+# MINIMAL=1 is handled here rather than in Makefile.config, which is included
+# after the pkg-config and shellcheck setup below
+ifeq ($(MINIMAL),1)
+  NO_LIBELF := 1
+  NO_LIBDW := 1
+  NO_LIBTRACEEVENT := 1
+  NO_JEVENTS := 1
+  NO_LIBPYTHON := 1
+  NO_LIBBPF := 1
+  BUILD_BPF_SKEL := 0
+  NO_SLANG := 1
+  NO_DEMANGLE := 1
+  NO_BACKTRACE := 1
+  NO_AIO := 1
+  NO_ZLIB := 1
+  NO_LZMA := 1
+  NO_LIBZSTD := 1
+  NO_LIBNUMA := 1
+  NO_LIBLLVM := 1
+  NO_CAPSTONE := 1
+  NO_LIBPFM4 := 1
+  NO_LIBDEBUGINFOD := 1
+  NO_BABELTRACE2 := 1
+  NO_SDT := 1
+  NO_JVMTI := 1
+  NO_RUST := 1
+  NO_PERF_READ_VDSO32 := 1
+  NO_PERF_READ_VDSOX32 := 1
+  NO_SHELLCHECK := 1
+endif
+
 # Some distros provide the command $(CROSS_COMPILE)pkg-config for
 # searching packges installed with Multiarch. Use it for cross
 # compilation if it is existed.
@@ -195,8 +229,10 @@ else
       PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/local/share/pkgconfig/
       PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/share/pkgconfig/
       export PKG_CONFIG_LIBDIR
-      $(warning Missing PKG_CONFIG_LIBDIR, PKG_CONFIG_PATH and PKG_CONFIG_SYSROOT_DIR for cross compilation,)
-      $(warning set PKG_CONFIG_LIBDIR for using Multiarch libs.)
+      ifneq ($(MINIMAL),1)
+        $(warning Missing PKG_CONFIG_LIBDIR, PKG_CONFIG_PATH and PKG_CONFIG_SYSROOT_DIR for cross compilation,)
+        $(warning set PKG_CONFIG_LIBDIR for using Multiarch libs.)
+      endif
     endif
   endif
 endif
diff --git a/tools/perf/tests/make b/tools/perf/tests/make
index d2c2f526e1db0..dbbc971a144b2 100644
--- a/tools/perf/tests/make
+++ b/tools/perf/tests/make
@@ -115,13 +115,7 @@ make_install_prefix       := install prefix=/tmp/krava
 make_install_prefix_slash := install prefix=/tmp/krava/
 make_static         := LDFLAGS=-static NO_PERF_READ_VDSO32=1 NO_PERF_READ_VDSOX32=1 NO_JVMTI=1 NO_LIBTRACEEVENT=1 NO_LIBELF=1
 
-# all the NO_* variable combined
-make_minimal        := NO_LIBPYTHON=1
-make_minimal        += NO_DEMANGLE=1 NO_LIBELF=1 NO_BACKTRACE=1
-make_minimal        += NO_LIBNUMA=1 NO_LIBBIONIC=1 NO_LIBDW=1
-make_minimal        += NO_LIBBPF=1
-make_minimal        += NO_SDT=1 NO_JVMTI=1 NO_LIBZSTD=1
-make_minimal        += NO_CAPSTONE=1
+make_minimal        := MINIMAL=1
 
 # binutils 2_42 and newer have bfd_thread_init()
 new_libbfd := $(shell echo '#include <bfd.h>' | $(CC) -E -x c - | grep bfd_thread_init)
-- 
2.53.0