sync: sync veristat.c and set up initial Makefile

Sync upstream veristat.c and set up Makefile to build veristat tool.
Also record upstream commit that was used as a reference for current
veristat.c source code.

Signed-off-by: Andrii Nakryiko <[email protected]>

Author: anakryiko

UPSTREAM-COMMIT

@@ -0,0 +1 @@
+041ec0f96f7d ("veristat: avoid using kernel-internal headers")

src/.gitignore

@@ -0,0 +1,3 @@
+/.output
+/veristat
+/.gdb_history

src/Makefile

@@ -0,0 +1,84 @@
+# SPDX-License-Identifier: BSD-2-Clause
+VERISTAT_VERSION ?= 0.1
+DEBUG ?=
+
+OUTPUT := .output
+LIBBPF_SRC := $(abspath ../../libbpf/src)
+LIBBPF_OBJ := $(abspath $(OUTPUT)/libbpf.a)
+# Use our own libbpf API headers and Linux UAPI headers distributed with
+# libbpf to avoid dependency on system-wide headers, which could be missing or
+# outdated
+INCLUDES := -I$(OUTPUT) -I../../libbpf/include/uapi
+CFLAGS := -g -Wall -DVERISTAT_VERSION=\"$(VERISTAT_VERSION)\" -O$(if $(DEBUG),0,2)
+ALL_CFLAGS := $(CFLAGS) $(EXTRA_LDFLAGS)
+ALL_LDFLAGS := $(LDFLAGS) $(EXTRA_LDFLAGS)
+
+export VERISTAT_VERSION
+
+ifeq ($(V),1)
+	Q =
+	msg =
+else
+	Q = @
+	msg = @printf '  %-8s %s%s\n'					\
+		      "$(1)"						\
+		      "$(patsubst $(abspath $(OUTPUT))/%,%,$(2))"	\
+		      "$(if $(3), $(3))";
+	MAKEFLAGS += --no-print-directory
+endif
+
+define allow-override
+  $(if $(or $(findstring environment,$(origin $(1))),\
+            $(findstring command line,$(origin $(1)))),,\
+    $(eval $(1) = $(2)))
+endef
+
+$(call allow-override,CC,$(CROSS_COMPILE)cc)
+$(call allow-override,LD,$(CROSS_COMPILE)ld)
+
+# for installation
+INSTALL := install
+prefix := /usr/local
+bindir := $(prefix)/bin
+
+.PHONY: all
+all: veristat
+
+.PHONY: clean
+clean:
+	$(call msg,CLEAN)
+	$(Q)rm -rf $(OUTPUT) veristat
+
+.PHONY: install
+install: all
+	mkdir -p $(DESTDIR)$(bindir)/
+	$(INSTALL) -pt $(DESTDIR)$(bindir)/ veristat
+
+$(OUTPUT) $(OUTPUT)/libbpf:
+	$(call msg,MKDIR,$@)
+	$(Q)mkdir -p $@
+
+# Build libbpf
+$(LIBBPF_OBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(OUTPUT)/libbpf
+	$(call msg,LIB,$@)
+	$(Q)$(MAKE) -C $(LIBBPF_SRC) BUILD_STATIC_ONLY=1		      \
+		    OBJDIR=$(dir $@)/libbpf DESTDIR=$(dir $@)		      \
+		    INCLUDEDIR= LIBDIR= UAPIDIR=			      \
+		    EXTRA_CFLAGS="-g -O$(if $(DEBUG),0,2)"		      \
+		    install
+
+# Build .c files
+$(OUTPUT)/%.o: %.c $(wildcard %.h) | $(OUTPUT)
+	$(call msg,CC,$@)
+	$(Q)$(CC) $(ALL_CFLAGS) $(INCLUDES) -c $(filter %.c,$^) -o $@
+
+# Build application binary
+veristat: $(OUTPUT)/veristat.o $(LIBBPF_OBJ) | $(OUTPUT)
+	$(call msg,BINARY,$@)
+	$(Q)$(CC) $(ALL_CFLAGS) $^ $(ALL_LDFLAGS) -lelf -lz -o $@
+
+# delete failed targets
+.DELETE_ON_ERROR:
+
+# keep intermediate (.skel.h, .bpf.o, etc) targets
+.SECONDARY: