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Custom Mach-O Image Loader. Tolerant to unsigned modules.

Purpose of this module

This is a simplified version of dynamic linker inherited from original Apple sources. The key difference is in a switched off signature check for loaded binaries. iOS platform doesn't provide mechanic to load unsigned binary, but you may need it for some developer purposes like benchmarking/testing code with real device. Using of this linker version let you get around this limitation.

This library exposes next symbols:

  • custom_dlopen
  • custom_dlclose
  • custom_dlsym
  • custom_dlerror

Use it instead of original Posix version.

Known limitations

  • Load only by absolute path
  • There is no recurrent dependencies loading (all required modules should be preloaded in process before)
  • Works only on system with enabled JIT permissions. Ex: iOS under debugger.
  • Only RTLD_LAZY mode is supported

Borrowed files

  • ImageLoader.h
  • ImageLoader.cpp
  • ImageLoaderMachO.h
  • ImageLoaderMachO.cpp
  • ImageLoaderMachOCompressed.h
  • ImageLoaderMachOCompressed.cpp

All specific changes of original Apple code are under conditional compilation with #if UNSIGN_TOLERANT macros. All classes are moved into namespace "isolator" to avoid intersection with original symbols from libdyld.

The file dyld_stubs.cpp contains some utils and other stub functions to make this code compilable. Most of them has no implementation, just for signature compatibility.

Link to original sources

https://opensource.apple.com/source/dyld/dyld-832.7.3

Licence

All source files and implementations are provided under an Apple Public Source License. API header file is provided under Apache License v2.