From db1adc86580361e6acda632515756df0f0528e70 Mon Sep 17 00:00:00 2001
From: Andrey Ignatov <rdna@fb.com>
Date: Tue, 2 Apr 2019 18:07:41 -0700
Subject: [PATCH] Add symlinks for DSO

Add symlinks with version suffix in a way similar to how it's done in
kernel tree.

The differences with kernel tree version:

* LIBS is used to handle both files and targets w/o separation;

* Version symlink is created in corresponding target as opposed to do
  everything in libbpf.so.$(LIBBPF_VERSION).

Example:

  % OBJDIR=build DESTDIR=root make install
  ...
  % find root/ ! -type d -exec ls -l {} +
  -rw-r--r--. 1 rdna users   6046 Apr  2 18:09 root/usr/include/bpf/bpf.h
  -rw-r--r--. 1 rdna users   3485 Apr  2 18:09 root/usr/include/bpf/btf.h
  -rw-r--r--. 1 rdna users  16454 Apr  2 18:09 root/usr/include/bpf/libbpf.h
  -rw-r--r--. 1 rdna users 602030 Apr  2 18:09 root/usr/lib64/libbpf.a
  lrwxrwxrwx. 1 rdna users     11 Apr  2 18:09 root/usr/lib64/libbpf.so -> libbpf.so.0
  lrwxrwxrwx. 1 rdna users     15 Apr  2 18:09 root/usr/lib64/libbpf.so.0 -> libbpf.so.0.0.2
  -rwxr-xr-x. 1 rdna users 377640 Apr  2 18:09 root/usr/lib64/libbpf.so.0.0.2
  -rw-r--r--. 1 rdna users    241 Apr  2 18:09 root/usr/lib64/pkgconfig/libbpf.pc

Signed-off-by: Andrey Ignatov <rdna@fb.com>
---
 src/Makefile | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/Makefile b/src/Makefile
index 9bd670d..1014ce3 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -38,7 +38,9 @@ OBJS := $(addprefix $(OBJDIR)/,bpf.o btf.o libbpf.o libbpf_errno.o netlink.o \
 
 LIBS := $(OBJDIR)/libbpf.a
 ifndef BUILD_STATIC_ONLY
-	LIBS += $(OBJDIR)/libbpf.so
+	LIBS += $(OBJDIR)/libbpf.so \
+		$(OBJDIR)/libbpf.so.$(VERSION) \
+		$(OBJDIR)/libbpf.so.$(LIBBPF_VERSION)
 	VERSION_SCRIPT := libbpf.map
 endif
 
@@ -68,7 +70,13 @@ all: $(LIBS) $(PC_FILE)
 $(OBJDIR)/libbpf.a: $(OBJS)
 	$(AR) rcs $@ $^
 
-$(OBJDIR)/libbpf.so: $(OBJS)
+$(OBJDIR)/libbpf.so: $(OBJDIR)/libbpf.so.$(VERSION)
+	ln -sf $(^F) $@
+
+$(OBJDIR)/libbpf.so.$(VERSION): $(OBJDIR)/libbpf.so.$(LIBBPF_VERSION)
+	ln -sf $(^F) $@
+
+$(OBJDIR)/libbpf.so.$(LIBBPF_VERSION): $(OBJS)
 	$(CC) -shared $(ALL_LDFLAGS) -Wl,--version-script=$(VERSION_SCRIPT) \
 				     $^ -o $@
 
@@ -88,8 +96,16 @@ define do_install
 	$(INSTALL) $1 $(if $3,-m $3,) '$(DESTDIR)$2'
 endef
 
+# Preserve symlinks at installation.
+define do_s_install
+	if [ ! -d '$(DESTDIR)$2' ]; then		\
+		$(INSTALL) -d -m 755 '$(DESTDIR)$2';	\
+	fi;						\
+	cp -fpR $1 '$(DESTDIR)$2'
+endef
+
 install: all install_headers install_pkgconfig
-	$(call do_install,$(LIBS),$(LIBDIR))
+	$(call do_s_install,$(LIBS),$(LIBDIR))
 
 install_headers:
 	$(call do_install,$(HEADERS),$(INCLUDEDIR)/bpf,644)
@@ -103,4 +119,4 @@ install_pkgconfig: $(PC_FILE)
 	$(call do_install,$(PC_FILE),$(LIBDIR)/pkgconfig,644)
 
 clean:
-	rm -f *.o *.a *.so *.pc
+	rm -f *.o *.a *.so *.so.* *.pc