Hooking functions located in the executable (not in shared libraries)

Question

Let's say I have a function foo in ./elf . I want to hook it with foo_hook which is located in my shared object. foo is not exported from ./elf .

LD_PRELOAD is useful for hooking functions in shared objects, but is there a generic way to hook functions in the executable? I consider injecting with ptrace not very generic.

Also, foo_hook doesn't have to be in a shared object, if there is some other simple way (instead of writing shellcode) it is acceptable.

I prefer not to patch ./elf , but that is not a necessity. Changing the dynamic linker/RPATH is also ok. Rebuilding ./elf is not possible.

Answer 1

is there a generic way to hook functions in the executable?

No.