Contains several prototypes for some kind of self-patching engine, which allows a running executable to update/modify some of it's functions/modules during runtime.

If not otherwise mentioned all tests were performed on standard Linux Kernel 3.2.0.

This prototype implements two functions export_func and import_func. export_func is used to write machine code of some function of the running executable into a file. import_func respectively can be used to restore a functions exported machine code by reading the binary file contents.

Both export_func and import_func work as expected but calling an imported function results in a segmentation violation on recent kernels (3.2.0). Though the provided test program did work on standard Linux running kernel 2.6.24.

$ cd asm_patching
$ make
$ ./main
 # sample output for imp_func != some_func
 some_func = 00000063
 main: ofp @ 080485a4
 main:  fp @ 0933d170
 imp_func size = 41
 imp_func:
	55 89 e5 83
	ec 10 c7 45
	f8 00 00 00
	00 c7 45 fc
	00 00 00 00
	eb 08 83 45
	f8 01 83 45
	fc 01 83 7d
	fc 62 76 f2
	8b 45 f8 c9
	c3 00 00 00
 imp_func = 000000c6

• static vars in imported func (prtinf( "Test\n" ) --> segfault)
• function calls from within imported func?
• memory protection in recent kernels forbids call to imported function?! --> segfault
• --> wrong approach

ToDo

ToDo

Both C and C++ version of the sample have identical usage. Only their outputs differ:

$ cd dynlib_patching/cpp/
$ make
$ ./main
 Foo::init: Hello World!
 ...
 <now modify code + replace .so>
 ...
 Foo::init: H3ll0 W0r1d!