Reputation: 1726
I have a system "fsimage.so" that requires mkdirp, which just happens to live in libgen.so. But fsimage.so does not know this. For example:
# ldd /usr/lib/python2.4/vendor-packages/fsimage.so
libfsimage.so.1.0 => /usr/lib/libfsimage.so.1.0
libxml2.so.2 => /lib/libxml2.so.2
libgcc_s.so.1 => /usr/sfw/lib/libgcc_s.so.1
libpthread.so.1 => /lib/libpthread.so.1
libz.so.1 => /lib/libz.so.1
libm.so.2 => /lib/libm.so.2
libsocket.so.1 => /lib/libsocket.so.1
libnsl.so.1 => /lib/libnsl.so.1
libc.so.1 => /lib/libc.so.1
libmp.so.2 => /lib/libmp.so.2
libmd.so.1 => /lib/libmd.so.1
# ./test
Traceback (most recent call last):
File "./test", line 26, in ?
import fsimage
ImportError: ld.so.1: isapython2.4: fatal: relocation error: file /usr/lib/python2.4/vendor-packages/fsimage.so: symbol mkdirp: referenced symbol not found
# LD_PRELOAD=/usr/lib/libgen.so ./test
Usage: ./test
Naturally, if I had the sources etc, I could simply link it again, and add "-lgen", and it will add libgen.so as a dependency.
But as an exercise in hackery, say I do not have any sources, and simply wanted to add that fsimage.so needs to also load libgen.so. Using elfedit/objcopy etc, is this not possible? I don't suppose I can use "ld" to use .so as input, and write a new .so with extra library?
# elfdump /usr/lib/python2.4/vendor-packages/fsimage.so|grep NEEDED
[0] NEEDED 0x5187 libfsimage.so.1.0
[1] NEEDED 0x5152 libxml2.so.2
[2] NEEDED 0x5171 libgcc_s.so.1
First attempt at stackoverflow, go easy on me :)
Upvotes: 12
Views: 6161
Reputation: 765
You can use PatchELF. Release 0.9 is out since 29 Feb 2016 and lets you:
In your case:
$ patchelf --add-needed /usr/lib/libgen.so /usr/lib/python2.4/vendor-packages/fsimage.so
Upvotes: 4
Reputation: 213897
Not easily.
Most UNIX
systems (AIX
is a notable exception) consider *.so
a "final" link product, and it is not suitable as an input for any further link.
To add a new DT_NEEDED tag to the dynamic section of fsimage.so
, you would need to rewrite its .dynamic
section. Removing an entry from .dynamic
is relatively easy -- you can just "slide" the other entries up, and replace the last entry with DT_NULL
.
On the other hand, adding a new entry requires that you append a whole new .dynamic
section to the file, and then update all pointers (offsets) within fsimage.so
to point to the new section. This requires "deep" understanding of the ELF format.
There are existing tools to do this, e.g. rpath
but I've had mixed success with it.
Upvotes: 7
Reputation: 1726
Thank you "Employed Russian", you gave me the information needed to search deeper. Solaris already ships with "elfedit", so if others wants to know, these are the instructions
# elfedit libfsimage.so.1.0.0 libfsimage.so.1.0.0-new
> dyn:value DT_NEEDED
index tag value
[0] NEEDED 0x4f81 libpthread.so.1
[1] NEEDED 0x4fac libxml2.so.2
[2] NEEDED 0x4fc2 libgcc_s.so.1
> dyn:value -add -s DT_NEEDED libscf.so
index tag value
[35] NEEDED 0x500d libscf.so
> dyn:value DT_NEEDED
index tag value
[0] NEEDED 0x4f81 libpthread.so.1
[1] NEEDED 0x4fac libxml2.so.2
[2] NEEDED 0x4fc2 libgcc_s.so.1
[35] NEEDED 0x500d libscf.so
> :write
> :quit
# ldd libfsimage.so.1.0.0-new
libpthread.so.1 => /lib/libpthread.so.1
libxml2.so.2 => /lib/libxml2.so.2
libgcc_s.so.1 => /usr/sfw/lib/libgcc_s.so.1
libscf.so => /lib/libscf.so
libz.so.1 => /lib/libz.so.1
libm.so.2 => /lib/libm.so.2
libsocket.so.1 => /lib/libsocket.so.1
libnsl.so.1 => /lib/libnsl.so.1
libc.so.1 => /lib/libc.so.1
libuutil.so.1 => /lib/libuutil.so.1
libgen.so.1 => /lib/libgen.so.1
libnvpair.so.1 => /lib/libnvpair.so.1
libsmbios.so.1 => /usr/lib/libsmbios.so.1
libmp.so.2 => /lib/libmp.so.2
libmd.so.1 => /lib/libmd.so.1
Upvotes: 10