How Can I Execute a Binary Directly from Memory in C on Linux?

Executing In-Memory Binaries

Developers often need to execute binaries as part of their applications. However, the traditional approach of saving the binary to disk and then calling "exec" or "fork" can be inefficient. This article explores a method for executing binaries directly from memory, eliminating the need for disk writes.

Background

In the provided code snippet, the binary data is stored in a variable named "myExec." The goal is to execute this binary without writing it back to the file system.

Solution in C and Linux

In C, the mprotect() system call allows you to modify the protection of a memory region. This means you can convert a data region into a code region. Once this conversion is done, you can execute the memory region by jumping into it.

Here's an example of how this could be done:

#include <sys/mman.h>

int main() {
  // Assume we have an array of bytes representing the binary data.
  char myExec[] = {'s', 'o', 'm', 'e', ' ', 'b', 'y', 't', 'e', 's'};
  
  // Convert the data region into a code region.
  mprotect(myExec, sizeof(myExec), PROT_READ | PROT_WRITE | PROT_EXEC);
  
  // Execute the code.
  ((void (*)())myExec)();
  
  return 0;
}

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