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|
.:: Runtime ld ::.
--------------------------------------------------------------------------------
# toc
------
|ld_so|
|load_init_order|
# ld.so(8) *ld_so*
===========
env:
LD_PRELOAD=<l_so> colon separated list of libso's to be pre loaded
LD_DEBUG=<opts> comman separated list of debug options
=help list available options
=libs show library search path
=files processing of input files
=symbols show search path for symbol lookup
=bindings show against which definition a symbol is bound
## LD_PRELOAD load & init order *load_init_order*
> ldd ./main
>> libc.so.6 => /usr/lib/libc.so.6
> LD_PRELOAD=liba.so:libb.so ./main
-->
preloaded in this order
<--
initialized in this order
- preload order determines the order libs are inserted into the link map
- resulting link map:
+------+ +------+ +------+ +------+
| main | -> | liba | -> | libb | -> | libc |
+------+ +------+ +------+ +------+
- see preload and init order in action
> LD_DEBUG=files LD_PRELOAD=liba.so:libb.so ./main
# load order (-> determines link map)
>> file=liba.so [0]; generating link map
>> file=libb.so [0]; generating link map
>> file=libc.so.6 [0]; generating link map
# init order
>> calling init: /usr/lib/libc.so.6
>> calling init: <path>/libb.so
>> calling init: <path>/liba.so
>> initialize program: ./main
- see the symbol lookup in action and therefore the link map order
> LD_DEBUG=symbols,bindings LD_PRELOAD=liba.so:libb.so ./main
>> symbol=memcpy; lookup in file=./main [0]
>> symbol=memcpy; lookup in file=<path>/liba.so [0]
>> symbol=memcpy; lookup in file=<path>/libb.so [0]
>> symbol=memcpy; lookup in file=/usr/lib/libc.so.6 [0]
>> binding file ./main [0] to /usr/lib/libc.so.6 [0]: normal symbol
`memcpy' [GLIBC_2.14]
--------------------------------------------------------------------------------
vim:sts=2:et:tw=80:cc=80:fo+=t:ft=help
|
