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On Linux, I have a C++ application that is using dlopen() to load some shared libraries, but I'm suspicious that the version of the shared library being loaded is not the one I expect because my debugging trace code does not appear to be executed.
Is there a way to check a running process to query all the shared libraries it currently has open and the path to each of those libraries? In other words, something akin to ldd but that works on a running executable and lists runtime loaded libraries as well.
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We know that a shared library is a library that can be linked to any program at runtime. In order to view all the shared libraries used by an executable we make use of the Linux command utility known as ldd. We can easily locate the shared libraries on a Linux machine, as they usually start with lib* prefix.
You can use readelf to explore the ELF headers. readelf -d will list the direct dependencies as NEEDED sections. $ readelf -d elfbin Dynamic section at offset 0xe30 contains 22 entries: Tag Type Name/Value 0x0000000000000001 (NEEDED) Shared library: [libssl. so.
Shared code is loaded into memory once in the shared library segment and shared by all processes that reference it. The advantages of shared libraries are: Less disk space is used because the shared library code is not included in the executable programs.
In this standard, folders /lib, /usr/lib and /usr/local/lib are the default folders to store shared libraries. The /lib folder has libraries used during the boot time of the system but also used by programs in the /bin folder. Similarly, the/usr/lib folder has libraries used by programs in the /usr/bin folder.
If you want to know the library files a program have opened, you can try pmap. For example, if we want to know the libraries that bash process 3860 have opened, the result could be:
3860: bash
08048000 880K r-x-- /bin/bash
08124000 4K r---- /bin/bash
08125000 20K rw--- /bin/bash
0812a000 20K rw--- [ anon ]
099ae000 348K rw--- [ anon ]
b715c000 44K r-x-- /lib/i386-linux-gnu/libnss_files-2.15.so
b7167000 4K r---- /lib/i386-linux-gnu/libnss_files-2.15.so
b7168000 4K rw--- /lib/i386-linux-gnu/libnss_files-2.15.so
b7169000 88K r-x-- /lib/i386-linux-gnu/libnsl-2.15.so
b717f000 4K r---- /lib/i386-linux-gnu/libnsl-2.15.so
b7180000 4K rw--- /lib/i386-linux-gnu/libnsl-2.15.so
b7181000 8K rw--- [ anon ]
b7183000 28K r-x-- /lib/i386-linux-gnu/libnss_compat-2.15.so
b718a000 4K r---- /lib/i386-linux-gnu/libnss_compat-2.15.so
b718b000 4K rw--- /lib/i386-linux-gnu/libnss_compat-2.15.so
b71a1000 4K r---- /usr/lib/locale/locale-archive
b71a2000 1428K r---- /usr/lib/locale/locale-archive
b7307000 2048K r---- /usr/lib/locale/locale-archive
b7507000 4K rw--- [ anon ]
b7508000 1676K r-x-- /lib/i386-linux-gnu/libc-2.15.so
b76ab000 8K r---- /lib/i386-linux-gnu/libc-2.15.so
b76ad000 4K rw--- /lib/i386-linux-gnu/libc-2.15.so
b76ae000 16K rw--- [ anon ]
b76b2000 12K r-x-- /lib/i386-linux-gnu/libdl-2.15.so
b76b5000 4K r---- /lib/i386-linux-gnu/libdl-2.15.so
b76b6000 4K rw--- /lib/i386-linux-gnu/libdl-2.15.so
b76b7000 112K r-x-- /lib/i386-linux-gnu/libtinfo.so.5.9
b76d3000 8K r---- /lib/i386-linux-gnu/libtinfo.so.5.9
b76d5000 4K rw--- /lib/i386-linux-gnu/libtinfo.so.5.9
b76d8000 28K r--s- /usr/lib/i386-linux-gnu/gconv/gconv-modules.cache
b76df000 40K r-x-- /lib/i386-linux-gnu/libnss_nis-2.15.so
b76e9000 4K r---- /lib/i386-linux-gnu/libnss_nis-2.15.so
b76ea000 4K rw--- /lib/i386-linux-gnu/libnss_nis-2.15.so
b76eb000 8K rw--- [ anon ]
b76ed000 4K r-x-- [ anon ]
b76ee000 128K r-x-- /lib/i386-linux-gnu/ld-2.15.so
b770e000 4K r---- /lib/i386-linux-gnu/ld-2.15.so
b770f000 4K rw--- /lib/i386-linux-gnu/ld-2.15.so
bfbbf000 132K rw--- [ stack ]
total 7152K
Wish it would be of help for you.
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