Hermetic Java: dlopen() of objects in memory instead of on disk

[Magnus Ihse Bursie]

I noticed in the presentation[1] a discussion of using dynamic libraries 
in Hermetic Java, but this was hampered by glibc not allowing dlopen() 
from memory[2].

I just want to point out the idea proposed in a followup bug[3], to use 
dlopen("/proc/self/fd/" + file descriptor) to work around this 
limitation. It was a long time since I worked on these things, but I 
believe it is possible to get a file descriptor for mapped memory, and 
if so, the problem is solved.

With that said, I believe the second point about confusing tools is 
valid, and this is probably a worse approach than using static linking. 
But maybe it could be useful for users who want to build hermetic 
launchers of Java application which depends on native code for which 
they only have access to a dynamic library.

/Magnus

[1] https://cr.openjdk.org/~jiangli/hermetic_java.pdf
[2] https://sourceware.org/bugzilla/show_bug.cgi?id=11767
[3] https://sourceware.org/bugzilla/show_bug.cgi?id=30100#c33