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javalinuxjvmsystem-callsjit

Does the JVM JIT generate syscall instructions?

I am wondering how does Java code make a syscall, does the JIT compiler generate syscall instructions directly, or that it just put calls to libc functions (or other basic library functions)?

Solution

  • The Hotspot JVM generates machine code for Java code (which doesn't support making syscalls).

    All code which makes syscalls is in a native method.

    So when Java wants to make a syscalls, you have to call some native code to do it for you.

    There are libraries you can use to wrap native calls. E.g. JNA and JNR-FFI. This allows you call c libraries without writhing native code.