RFR: 8339480: Build static-jdk image with a statically linked launcher

[Jiangli Zhou]

On Tue, 3 Sep 2024 12:50:01 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> As a prerequisite for Hermetic Java, we need a statically linked `java` launcher. It should behave like the normal, dynamically linked `java` launcher, except that all JDK native libraries should be statically, not dynamically, linked.
> 
> This patch is the first step towards this goal. It will generate a `static-jdk` image with a statically linked launcher. This launcher is missing several native libs, however, and does therefore not behave like a proper dynamic java. One of the reasons for this is that local symbol hiding in static libraries are not implemented yet, which causes symbol clashes when linking all static libraries together. This will be addressed in an upcoming patch. 
> 
> All changes in the `src` directory are copied from, or inspired by, changes made in [the hermetic-java-runtime branch in Project Leyden](https://github.com/openjdk/leyden/tree/hermetic-java-runtime).

make/StaticLibs.gmk line 1:

> 1: #

Perhaps also consider adopting StaticLink.gmk file name from the https://github.com/openjdk/leyden/tree/hermetic-java-runtime/ branch, as we are mostly doing the static linking here. Creating the static libs is handled elsewhere.

make/StaticLibs.gmk line 71:

> 69:   # libsspi_bridge has name conflicts with sunmscapi
> 70:   BROKEN_STATIC_LIBS += sspi_bridge
> 71:   # These libs define DllMain which conflict with Hotspot

I'm not aware of the DllMain issue with static linking these libs. Could you please explain? The libawt.a and libdt_socket.a are statically linked with `javastatic` in https://github.com/openjdk/leyden/tree/hermetic-java-runtime/ branch.

make/StaticLibs.gmk line 74:

> 72:   BROKEN_STATIC_LIBS += awt dt_shmem dt_socket javaaccessbridge
> 73:   # These libs are dependent on any of the above disabled libs
> 74:   BROKEN_STATIC_LIBS += fontmanager jawt lcms net nio

Which specific dependent cause these libs being excluded? In https://github.com/openjdk/leyden/tree/hermetic-java-runtime/ branch, these JDK libs (except `libjawt.a`) are statically linked into `javastatic`.

make/StaticLibs.gmk line 118:

> 116:     OPTIMIZATION := HIGH, \
> 117:     STATIC_LAUNCHER := true, \
> 118:     LDFLAGS := $(JAVASTATIC_LINK_LDFLAGS), \

I could be missing something, but I don't see where is $JAVASTATIC_LINK_LDFLAGS defined.

On a related notes, I think we need to include $JVM_LDFLAGS when linking the static "java". See https://bugs.openjdk.org/browse/JDK-8339522?focusedId=14702923&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-14702923.

make/modules/java.desktop/lib/AwtLibraries.gmk line 176:

> 174: 
> 175:   ifneq ($(ENABLE_HEADLESS_ONLY), true)
> 176:     # We cannot link with both awt_headless and awt_xawt at the same time

Just a note on that. It's doable to link with both awt_headless and awt_xawt with some work. I did some quick experiments on that during the initial investigation for hermetic/static Java.

src/java.base/unix/native/libjli/java_md.c line 300:

> 298:                            char jvmcfg[],  jint so_jvmcfg) {
> 299:     /* Compute/set the name of the executable. This is needed for macOS. */
> 300:     SetExecname(*pargv);

Why is `SetExecname()` needed for the static case?

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PR Review Comment: https://git.openjdk.org/jdk/pull/20837#discussion_r1744614583
PR Review Comment: https://git.openjdk.org/jdk/pull/20837#discussion_r1744604685
PR Review Comment: https://git.openjdk.org/jdk/pull/20837#discussion_r1744603414
PR Review Comment: https://git.openjdk.org/jdk/pull/20837#discussion_r1744611776
PR Review Comment: https://git.openjdk.org/jdk/pull/20837#discussion_r1744616878
PR Review Comment: https://git.openjdk.org/jdk/pull/20837#discussion_r1744620611