[Buildroot] [PATCH/2020.02.x 1/1] package/openjdk: fix installation with merged usr directories

[aduskett at gmail.com]

From: Adam Duskett <Aduskett at gmail.com>

Currently, Buildroot installs the jre libraries using
cp -dprf /build/linux-*-release/images/jre/lib/* $(TARGET_DIR)/usr/lib/

However, if a system has a merged /usr directory, and there is a
built kernel before installing OpenJDK, the installation fails because
jre/lib has binary modules file, which causes the following error:
cp: cannot overwrite directory '/usr/lib/modules with non-directory

The obvious fix is to install the modules to /usr/lib/jvm/ and set the
appropriate rpaths via the --with-extra-ldflags conf option. However, this fix
does not work because the binaries themselves do not link against libjava.so
and instead search for libjava.so with hardcoded paths in the following
directories:
  - /usr/lib
  - /usr/jre/lib
  - $(dirname $0)/../lib

As such, most distributions such as Redhat create the directory
/usr/lib/jvm/java-$(JAVA_VERSION)/ and install all directories and files
found in images/jre to that directory, and then symlink the binaries to
/usr/bin.

However, because Buildroot does not need to support multiple versions of java
concurrently, there is no need for the java-$(JAVA_VERSION) directory.

To fix the above error, perform the following changes:
  - Introduce the variable "OPENJDK_INSTALL_BASE" which points to usr/lib/jvm
  - Set the --with-extra-ldflags conf_opt to
      "-Wl,-rpath,/$(OPENJDK_INSTALL_BASE)/lib,-rpath,
      /$(OPENJDK_INSTALL_BASE)/lib/$(OPENJDK_JVM_VARIANT)"
  - Run "mkdir -p $(TARGET_DIR)/usr/lib/jvm" in the INSTALL_TARGET_CMDS step.
  - Copy both the lib and bin directories to /usr/lib/jvm/
  - Symlink the binaries in /usr/lib/jvm/bin/ to /usr/bin.

Fixes: https://bugs.busybox.net/show_bug.cgi?id=12751

Signed-off-by: Adam Duskett <Aduskett at gmail.com>
---
 package/openjdk/openjdk.mk | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/package/openjdk/openjdk.mk b/package/openjdk/openjdk.mk
index 030a205228..fba53f739a 100644
--- a/package/openjdk/openjdk.mk
+++ b/package/openjdk/openjdk.mk
@@ -46,6 +46,14 @@ OPENJDK_JVM_VARIANT = zero
 OPENJDK_DEPENDENCIES += libffi
 endif
 
+# Because jre/lib has a modules file, installation on a system with a merged
+# /usr directory, and a built Kernel before OpenJDK, the following error
+# occurs: "cp: cannot overwrite directory '/usr/lib/modules with non-directory"
+# To prevent this error, we follow what other distributions traditionally do:
+# Install the OpenJDK files in /usr/lib/jvm/ and symlink the binaries to
+# /usr/bin.
+OPENJDK_INSTALL_BASE=usr/lib/jvm
+
 # OpenJDK ignores some variables unless passed via the environment.
 # These variables are PATH, LD, CC, CXX, and CPP.
 # OpenJDK defaults ld to the ld binary but passes -Xlinker and -z as
@@ -75,6 +83,7 @@ OPENJDK_CONF_OPTS = \
 	--with-devkit=$(HOST_DIR) \
 	--with-extra-cflags="$(TARGET_CFLAGS)" \
 	--with-extra-cxxflags="$(TARGET_CXXFLAGS)" \
+	--with-extra-ldflags="-Wl,-rpath,/$(OPENJDK_INSTALL_BASE)/lib,-rpath,/$(OPENJDK_INSTALL_BASE)/lib/$(OPENJDK_JVM_VARIANT)" \
 	--with-giflib=system \
 	--with-jobs=$(PARALLEL_JOBS) \
 	--with-jvm-variants=$(OPENJDK_JVM_VARIANT) \
@@ -114,8 +123,12 @@ endef
 # Calling make install always builds and installs the JDK instead of the JRE,
 # which makes manual installation necessary.
 define OPENJDK_INSTALL_TARGET_CMDS
-	cp -dpfr $(@D)/build/linux-*-release/images/jre/bin/* $(TARGET_DIR)/usr/bin/
-	cp -dpfr $(@D)/build/linux-*-release/images/jre/lib/* $(TARGET_DIR)/usr/lib/
+	mkdir -p $(TARGET_DIR)/$(OPENJDK_INSTALL_BASE)
+	cp -dpfr $(@D)/build/linux-*-release/images/jre/bin/ \
+		$(TARGET_DIR)/$(OPENJDK_INSTALL_BASE)
+	cp -dpfr $(@D)/build/linux-*-release/images/jre/lib/ \
+		$(TARGET_DIR)/$(OPENJDK_INSTALL_BASE)
+	cd $(TARGET_DIR)/usr/bin && ln -snf ../../$(OPENJDK_INSTALL_BASE)/bin/* .
 endef
 
 $(eval $(generic-package))
-- 
2.25.2