Merge tag 'perf-tools-fixes-for-v6.11-2024-07-30' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools

Pull perf tools fixes from Namhyung Kim:
 "Some more build fixes and a random crash fix:

   - Fix cross-build by setting pkg-config env according to the arch

   - Fix static build for missing library dependencies

   - Fix Segfault when callchain has no symbols"

* tag 'perf-tools-fixes-for-v6.11-2024-07-30' of git://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools:
  perf docs: Document cross compilation
  perf: build: Link lib 'zstd' for static build
  perf: build: Link lib 'lzma' for static build
  perf: build: Only link libebl.a for old libdw
  perf: build: Set Python configuration for cross compilation
  perf: build: Setup PKG_CONFIG_LIBDIR for cross compilation
  perf tool: fix dereferencing NULL al->maps

Author: torvalds

tools/build/feature/Makefile

@@ -82,7 +82,30 @@ FILES=                                          \
 
 FILES := $(addprefix $(OUTPUT),$(FILES))
 
-PKG_CONFIG ?= $(CROSS_COMPILE)pkg-config
+# Some distros provide the command $(CROSS_COMPILE)pkg-config for
+# searching packges installed with Multiarch. Use it for cross
+# compilation if it is existed.
+ifneq (, $(shell which $(CROSS_COMPILE)pkg-config))
+  PKG_CONFIG ?= $(CROSS_COMPILE)pkg-config
+else
+  PKG_CONFIG ?= pkg-config
+
+  # PKG_CONFIG_PATH or PKG_CONFIG_LIBDIR, alongside PKG_CONFIG_SYSROOT_DIR
+  # for modified system root, are required for the cross compilation.
+  # If these PKG_CONFIG environment variables are not set, Multiarch library
+  # paths are used instead.
+  ifdef CROSS_COMPILE
+    ifeq ($(PKG_CONFIG_LIBDIR)$(PKG_CONFIG_PATH)$(PKG_CONFIG_SYSROOT_DIR),)
+      CROSS_ARCH = $(shell $(CC) -dumpmachine)
+      PKG_CONFIG_LIBDIR := /usr/local/$(CROSS_ARCH)/lib/pkgconfig/
+      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/local/lib/$(CROSS_ARCH)/pkgconfig/
+      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/lib/$(CROSS_ARCH)/pkgconfig/
+      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/local/share/pkgconfig/
+      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/share/pkgconfig/
+      export PKG_CONFIG_LIBDIR
+    endif
+  endif
+endif
 
 all: $(FILES)
 
@@ -147,7 +170,17 @@ $(OUTPUT)test-libopencsd.bin:
 
 DWARFLIBS := -ldw
 ifeq ($(findstring -static,${LDFLAGS}),-static)
-DWARFLIBS += -lelf -lebl -lz -llzma -lbz2
+  DWARFLIBS += -lelf -lz -llzma -lbz2 -lzstd
+
+  LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw)
+  LIBDW_VERSION_1 := $(word 1, $(subst ., ,$(LIBDW_VERSION)))
+  LIBDW_VERSION_2 := $(word 2, $(subst ., ,$(LIBDW_VERSION)))
+
+  # Elfutils merged libebl.a into libdw.a starting from version 0.177,
+  # Link libebl.a only if libdw is older than this version.
+  ifeq ($(shell test $(LIBDW_VERSION_2) -lt 177; echo $$?),0)
+    DWARFLIBS += -lebl
+  endif
 endif
 
 $(OUTPUT)test-dwarf.bin:
@@ -178,27 +211,27 @@ $(OUTPUT)test-numa_num_possible_cpus.bin:
 	$(BUILD) -lnuma
 
 $(OUTPUT)test-libunwind.bin:
-	$(BUILD) -lelf
+	$(BUILD) -lelf -llzma
 
 $(OUTPUT)test-libunwind-debug-frame.bin:
-	$(BUILD) -lelf
+	$(BUILD) -lelf -llzma
 $(OUTPUT)test-libunwind-x86.bin:
-	$(BUILD) -lelf -lunwind-x86
+	$(BUILD) -lelf -llzma -lunwind-x86
 
 $(OUTPUT)test-libunwind-x86_64.bin:
-	$(BUILD) -lelf -lunwind-x86_64
+	$(BUILD) -lelf -llzma -lunwind-x86_64
 
 $(OUTPUT)test-libunwind-arm.bin:
-	$(BUILD) -lelf -lunwind-arm
+	$(BUILD) -lelf -llzma -lunwind-arm
 
 $(OUTPUT)test-libunwind-aarch64.bin:
-	$(BUILD) -lelf -lunwind-aarch64
+	$(BUILD) -lelf -llzma -lunwind-aarch64
 
 $(OUTPUT)test-libunwind-debug-frame-arm.bin:
-	$(BUILD) -lelf -lunwind-arm
+	$(BUILD) -lelf -llzma -lunwind-arm
 
 $(OUTPUT)test-libunwind-debug-frame-aarch64.bin:
-	$(BUILD) -lelf -lunwind-aarch64
+	$(BUILD) -lelf -llzma -lunwind-aarch64
 
 $(OUTPUT)test-libaudit.bin:
 	$(BUILD) -laudit

tools/perf/Documentation/Build.txt

@@ -71,3 +71,31 @@ supported by GCC. UBSan detects undefined behaviors of programs at runtime.
   $ UBSAN_OPTIONS=print_stacktrace=1 ./perf record -a
 
 If UBSan detects any problem at runtime, it outputs a “runtime error:” message.
+
+4) Cross compilation
+====================
+As Multiarch is commonly supported in Linux distributions, we can install
+libraries for multiple architectures on the same system and then cross-compile
+Linux perf. For example, Aarch64 libraries and toolchains can be installed on
+an x86_64 machine, allowing us to compile perf for an Aarch64 target.
+
+Below is the command for building the perf with dynamic linking.
+
+  $ cd /path/to/Linux
+  $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -C tools/perf
+
+For static linking, the option `LDFLAGS="-static"` is required.
+
+  $ make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
+    LDFLAGS="-static" -C tools/perf
+
+In the embedded system world, a use case is to explicitly specify the package
+configuration paths for cross building:
+
+  $ PKG_CONFIG_SYSROOT_DIR="/path/to/cross/build/sysroot" \
+    PKG_CONFIG_LIBDIR="/usr/lib/:/usr/local/lib" \
+    make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -C tools/perf
+
+In this case, the variable PKG_CONFIG_SYSROOT_DIR can be used alongside the
+variable PKG_CONFIG_LIBDIR or PKG_CONFIG_PATH to prepend the sysroot path to
+the library paths for cross compilation.

tools/perf/Makefile.config

@@ -152,7 +152,17 @@ ifdef LIBDW_DIR
 endif
 DWARFLIBS := -ldw
 ifeq ($(findstring -static,${LDFLAGS}),-static)
-  DWARFLIBS += -lelf -lebl -ldl -lz -llzma -lbz2
+  DWARFLIBS += -lelf -ldl -lz -llzma -lbz2 -lzstd
+
+  LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw)
+  LIBDW_VERSION_1 := $(word 1, $(subst ., ,$(LIBDW_VERSION)))
+  LIBDW_VERSION_2 := $(word 2, $(subst ., ,$(LIBDW_VERSION)))
+
+  # Elfutils merged libebl.a into libdw.a starting from version 0.177,
+  # Link libebl.a only if libdw is older than this version.
+  ifeq ($(shell test $(LIBDW_VERSION_2) -lt 177; echo $$?),0)
+    DWARFLIBS += -lebl
+  endif
 endif
 FEATURE_CHECK_CFLAGS-libdw-dwarf-unwind := $(LIBDW_CFLAGS)
 FEATURE_CHECK_LDFLAGS-libdw-dwarf-unwind := $(LIBDW_LDFLAGS) $(DWARFLIBS)
@@ -296,6 +306,11 @@ endif
 
 ifdef PYTHON_CONFIG
   PYTHON_EMBED_LDOPTS := $(shell $(PYTHON_CONFIG_SQ) $(PYTHON_CONFIG_LDFLAGS) 2>/dev/null)
+  # Update the python flags for cross compilation
+  ifdef CROSS_COMPILE
+    PYTHON_NATIVE := $(shell echo $(PYTHON_EMBED_LDOPTS) | sed 's/\(-L.*\/\)\(.*-linux-gnu\).*/\2/')
+    PYTHON_EMBED_LDOPTS := $(subst $(PYTHON_NATIVE),$(shell $(CC) -dumpmachine),$(PYTHON_EMBED_LDOPTS))
+  endif
   PYTHON_EMBED_LDFLAGS := $(call strip-libs,$(PYTHON_EMBED_LDOPTS))
   PYTHON_EMBED_LIBADD := $(call grep-libs,$(PYTHON_EMBED_LDOPTS)) -lutil
   PYTHON_EMBED_CCOPTS := $(shell $(PYTHON_CONFIG_SQ) --includes 2>/dev/null)
@@ -897,6 +912,9 @@ else
          PYTHON_SETUPTOOLS_INSTALLED := $(shell $(PYTHON) -c 'import setuptools;' 2> /dev/null && echo "yes" || echo "no")
          ifeq ($(PYTHON_SETUPTOOLS_INSTALLED), yes)
            PYTHON_EXTENSION_SUFFIX := $(shell $(PYTHON) -c 'from importlib import machinery; print(machinery.EXTENSION_SUFFIXES[0])')
+           ifdef CROSS_COMPILE
+             PYTHON_EXTENSION_SUFFIX := $(subst $(PYTHON_NATIVE),$(shell $(CC) -dumpmachine),$(PYTHON_EXTENSION_SUFFIX))
+           endif
            LANG_BINDINGS += $(obj-perf)python/perf$(PYTHON_EXTENSION_SUFFIX)
 	 else
            $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent)

tools/perf/Makefile.perf

@@ -193,7 +193,32 @@ HOSTLD  ?= ld
 HOSTAR  ?= ar
 CLANG   ?= clang
 
-PKG_CONFIG = $(CROSS_COMPILE)pkg-config
+# Some distros provide the command $(CROSS_COMPILE)pkg-config for
+# searching packges installed with Multiarch. Use it for cross
+# compilation if it is existed.
+ifneq (, $(shell which $(CROSS_COMPILE)pkg-config))
+  PKG_CONFIG ?= $(CROSS_COMPILE)pkg-config
+else
+  PKG_CONFIG ?= pkg-config
+
+  # PKG_CONFIG_PATH or PKG_CONFIG_LIBDIR, alongside PKG_CONFIG_SYSROOT_DIR
+  # for modified system root, is required for the cross compilation.
+  # If these PKG_CONFIG environment variables are not set, Multiarch library
+  # paths are used instead.
+  ifdef CROSS_COMPILE
+    ifeq ($(PKG_CONFIG_LIBDIR)$(PKG_CONFIG_PATH)$(PKG_CONFIG_SYSROOT_DIR),)
+      CROSS_ARCH = $(shell $(CC) -dumpmachine)
+      PKG_CONFIG_LIBDIR := /usr/local/$(CROSS_ARCH)/lib/pkgconfig/
+      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/local/lib/$(CROSS_ARCH)/pkgconfig/
+      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/lib/$(CROSS_ARCH)/pkgconfig/
+      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.)
+    endif
+  endif
+endif
 
 RM      = rm -f
 LN      = ln -f

tools/perf/util/callchain.c

@@ -1141,7 +1141,7 @@ int hist_entry__append_callchain(struct hist_entry *he, struct perf_sample *samp
 int fill_callchain_info(struct addr_location *al, struct callchain_cursor_node *node,
 			bool hide_unresolved)
 {
-	struct machine *machine = maps__machine(node->ms.maps);
+	struct machine *machine = node->ms.maps ? maps__machine(node->ms.maps) : NULL;
 
 	maps__put(al->maps);
 	al->maps = maps__get(node->ms.maps);