Executing binaries without execve?

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http://stackoverflow.com – I saw somewhere mentioned that one can "emulate" execve (primarily with open and mmap) in order to load some other binary (without actual "execve" syscall). Are there any already implemented examples for it? Can we load both static and dynamic binaries? Can it be done portably? Such feature may be useful for delegating work to arbitrary binaries ignoring filesystem bits or with seccomp policy installed not allowing actual execve. (HowTos)