Provide a way to opt into searching the default image for symbols #147
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headius
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May 8, 2020
This addresses the issue in jruby/jruby#6202 where patch libraries loaded via LD_PRELOAD on Linux or DYLD_INSERT_LIBRARIES on MacOS would not be seen, since we go directly to the system libc and acquire all symbols from there. The patch utilizes the work in jnr/jnr-ffi#204 to unconditionally add a default search to the library bootstrapping. This is part of work to implement jnr#147. Note that this does not provide a way to opt-out of searching the default image due to the static native of how the POSIX LibC library wrapper gets set up. A larger change will be needed to allow configuring this behavior.
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Moved to 3.0.57 because there's currently no way to configure the POSIX you get, other than asking for native vs non-native. The root issue in jruby/jruby#6202 will be fixed by modifying jnr-posix to always search the default image, which is a behavior change but more in line with how C programs would work in the absence of dlopen/dlsym reflection. We'll need more work here to make this an optional behavior of jnr-posix. We may also want to examine the other jnr libraries and see if they should likewise opt into the default image search. |
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In jruby/jruby#6202 we learned that the jnr-posix bootstrapping does not honor preloaded libraries as from LD_PRELOAD on Linux and DYLD_INSERT_LIBRARIES on MacOS. This prevents patch libraries like libfaketime, which hooks the standard POSIX time functions to alter their output.
A discussion of the issue is provided in wolfcw/libfaketime#255. There is no bug in libfaketime, and the current functionality of jnr-posix is not really incorrect, but it provides no way to "soften" the symbol search to try simply loading the symbol from the current process as if using RTLD_DEFAULT.
The functionality to search the default image will be provided when fixing jnr/jnr-ffi#203.
The additional work required here is to add a way to acquire a native POSIX with or without the default image being included in the symbol search.
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