问题
I installed openjdk-devel and openjdk-devel-debuginfo of the same major/minor version for an architecture in RedHat Linux Server 8+. I would like to make sure that the OpenJDK runtime has symbols for debugging. After installation, I ran the followings:
[root@localhost bin]# objdump --syms /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-0.el8_1.x86_64/jre/bin/java
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-0.el8_1.x86_64/jre/bin/java: file format elf64-x86-64
SYMBOL TABLE:
0000000000000270 l d .interp 0000000000000000 .interp
0000000000000290 l d .note.gnu.property 0000000000000000 .note.gnu.property
00000000000002b0 l d .note.ABI-tag 0000000000000000 .note.ABI-tag
00000000000002d0 l d .note.gnu.build-id 0000000000000000 .note.gnu.build-id
00000000000002f8 l d .hash 0000000000000000 .hash
0000000000000348 l d .gnu.hash 0000000000000000 .gnu.hash
0000000000000370 l d .dynsym 0000000000000000 .dynsym
....
....
....
[root@localhost etc]# file /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-0.el8_1.x86_64/jre/bin/java
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-0.el8_1.x86_64/jre/bin/java:
ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=613871d1514ba05fa2914c22c10f1dfe01d3d2e8, not stripped
[root@localhost bin]# objdump --syms /usr/lib/debug/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-0.el8_1.x86_64/bin/java-1.8.0.242.b08-0.el8_1.x86_64.debug
/usr/lib/debug/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-0.el8_1.x86_64/bin/java-1.8.0.242.b08-0.el8_1.x86_64.debug: file format elf64-x86-64
SYMBOL TABLE:
no symbols
[root@localhost bin]# file /usr/lib/debug/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-0.el8_1.x86_64/bin/java-1.8.0.242.b08-0.el8_1.x86_64.debug
/usr/lib/debug/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-0.el8_1.x86_64/bin/java-1.8.0.242.b08-0.el8_1.x86_64.debug:
ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter \004, for GNU/Linux 3.2.0, BuildID[sha1]=613871d1514ba05fa2914c22c10f1dfe01d3d2e8, with debug_info, not stripped
As the above suggests, I see the objdump for java prints out some sort of symbol table, but I had read that one should also look for .debug* in the output, which I'm not seeing in the remaining of SYMBOL TABLE section (a few dozens of lines omitted from above output for brevity).
I see the file for /usr/lib/debug/..../java...debug says with debug_info, but I need confirmation that the Java installation does have symbols.
回答1:
java executable is just a simple launcher. You won't find JVM symbols there.
To see if JVM has debug symbols, check libjvm.so instead:
nm /usr/lib/jvm/jre/lib/amd64/server/libjvm.so
My ultimate goal is to load a malloc profiler alongside my server and try to trace the native memory allocations. In this case, if the calls are traced back to JVM, I need to know which method is getting called.
Well, if you'd started with this question, you wouldn't have fallen into XY problem trap.
Even with JVM debug symbols, native memory profilers (e.g. jemalloc) cannot show Java methods. They simply don't know how to unwind Java stack, so the traces will likely break at some random hex addresses, like in this question.
I'd suggest to try async-profiler to profile malloc, mprotect and mmap calls. This tool can show mixed Java+native stack traces. Here is an example of using async-profiler to profile native allocations. This video also demonstrates how async-profiler can help in finding native memory leaks.
来源：https://stackoverflow.com/questions/61626400/how-to-determine-whether-openjdk-installed-with-debugging-symbols