From 8b2782a1f250f58aafe38b2cd718aa3dc8ad58ed Mon Sep 17 00:00:00 2001
From: Andrii Nakryiko <andriin@fb.com>
Date: Mon, 30 Sep 2019 20:41:39 -0700
Subject: [PATCH] makefile: support libbpf symbol versioning in shared library
 mode

Similarly to Linux's 1bd63524593b ("libbpf: handle symbol versioning properly
for libbpf.a"), add necessary changes to build static and shared object
files separately with extra shared library flags. This allows to
properly handle symbol versioning in shared library mode, while still
having statically linkable library.

Cc: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 src/.gitignore |  2 ++
 src/Makefile   | 44 +++++++++++++++++++++++++++-----------------
 2 files changed, 29 insertions(+), 17 deletions(-)

diff --git a/src/.gitignore b/src/.gitignore
index fddb29b..0473afb 100644
--- a/src/.gitignore
+++ b/src/.gitignore
@@ -2,3 +2,5 @@
 *.a
 /libbpf.pc
 /libbpf.so*
+/staticobjs
+/sharedobjs
diff --git a/src/Makefile b/src/Makefile
index 3f4d2b1..57510ca 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -15,9 +15,7 @@ ifneq ($(FEATURE_REALLOCARRAY),)
 	ALL_CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
 endif
 
-ifndef BUILD_STATIC_ONLY
-	ALL_CFLAGS += -fPIC -fvisibility=hidden
-endif
+SHARED_CFLAGS += -fPIC -fvisibility=hidden -DSHARED
 
 CFLAGS ?= -g -O2 -Werror -Wall
 ALL_CFLAGS += $(CFLAGS)
@@ -31,22 +29,25 @@ else
 endif
 
 OBJDIR ?= .
-
-OBJS := $(addprefix $(OBJDIR)/,bpf.o btf.o libbpf.o libbpf_errno.o netlink.o \
+SHARED_OBJDIR := $(OBJDIR)/sharedobjs
+STATIC_OBJDIR := $(OBJDIR)/staticobjs
+OBJS := bpf.o btf.o libbpf.o libbpf_errno.o netlink.o \
 	nlattr.o str_error.o libbpf_probes.o bpf_prog_linfo.o xsk.o \
-	btf_dump.o hashmap.o)
+	btf_dump.o hashmap.o
+SHARED_OBJS := $(addprefix $(SHARED_OBJDIR)/,$(OBJS))
+STATIC_OBJS := $(addprefix $(STATIC_OBJDIR)/,$(OBJS))
 
-LIBS := $(OBJDIR)/libbpf.a
+STATIC_LIBS := $(OBJDIR)/libbpf.a
 ifndef BUILD_STATIC_ONLY
-	LIBS += $(OBJDIR)/libbpf.so \
-		$(OBJDIR)/libbpf.so.$(LIBBPF_MAJOR_VERSION) \
-		$(OBJDIR)/libbpf.so.$(LIBBPF_VERSION)
+	SHARED_LIBS := $(OBJDIR)/libbpf.so \
+		       $(OBJDIR)/libbpf.so.$(LIBBPF_MAJOR_VERSION) \
+		       $(OBJDIR)/libbpf.so.$(LIBBPF_VERSION)
 	VERSION_SCRIPT := libbpf.map
 endif
 
 HEADERS := bpf.h libbpf.h btf.h xsk.h libbpf_util.h
-UAPI_HEADERS := $(addprefix $(TOPDIR)/include/uapi/linux/,bpf.h bpf_common.h \
-	btf.h)
+UAPI_HEADERS := $(addprefix $(TOPDIR)/include/uapi/linux/,\
+			    bpf.h bpf_common.h btf.h)
 
 PC_FILE := $(OBJDIR)/libbpf.pc
 
@@ -65,9 +66,9 @@ LIBDIR ?= $(PREFIX)/$(LIBSUBDIR)
 INCLUDEDIR ?= $(PREFIX)/include
 UAPIDIR ?= $(PREFIX)/include
 
-all: $(LIBS) $(PC_FILE)
+all: $(STATIC_LIBS) $(SHARED_LIBS) $(PC_FILE)
 
-$(OBJDIR)/libbpf.a: $(OBJS)
+$(OBJDIR)/libbpf.a: $(STATIC_OBJS)
 	$(AR) rcs $@ $^
 
 $(OBJDIR)/libbpf.so: $(OBJDIR)/libbpf.so.$(LIBBPF_MAJOR_VERSION)
@@ -76,7 +77,7 @@ $(OBJDIR)/libbpf.so: $(OBJDIR)/libbpf.so.$(LIBBPF_MAJOR_VERSION)
 $(OBJDIR)/libbpf.so.$(LIBBPF_MAJOR_VERSION): $(OBJDIR)/libbpf.so.$(LIBBPF_VERSION)
 	ln -sf $(^F) $@
 
-$(OBJDIR)/libbpf.so.$(LIBBPF_VERSION): $(OBJS)
+$(OBJDIR)/libbpf.so.$(LIBBPF_VERSION): $(SHARED_OBJS)
 	$(CC) -shared -Wl,--version-script=$(VERSION_SCRIPT) \
 		      -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \
 		      $^ $(ALL_LDFLAGS) -o $@
@@ -87,9 +88,18 @@ $(OBJDIR)/libbpf.pc:
 		-e "s|@VERSION@|$(LIBBPF_VERSION)|" \
 		< libbpf.pc.template > $@
 
-$(OBJDIR)/%.o: %.c
+$(STATIC_OBJDIR):
+	mkdir -p $(STATIC_OBJDIR)
+
+$(SHARED_OBJDIR):
+	mkdir -p $(SHARED_OBJDIR)
+
+$(STATIC_OBJDIR)/%.o: %.c | $(STATIC_OBJDIR)
 	$(CC) $(ALL_CFLAGS) $(CPPFLAGS) -c $< -o $@
 
+$(SHARED_OBJDIR)/%.o: %.c | $(SHARED_OBJDIR)
+	$(CC) $(ALL_CFLAGS) $(SHARED_CFLAGS) $(CPPFLAGS) -c $< -o $@
+
 define do_install
 	if [ ! -d '$(DESTDIR)$2' ]; then		\
 		$(INSTALL) -d -m 755 '$(DESTDIR)$2';	\
@@ -120,4 +130,4 @@ install_pkgconfig: $(PC_FILE)
 	$(call do_install,$(PC_FILE),$(LIBDIR)/pkgconfig,644)
 
 clean:
-	rm -f *.o *.a *.so *.so.* *.pc
+	rm -rf *.o *.a *.so *.so.* *.pc $(SHARED_OBJDIR) $(STATIC_OBJDIR)