gcc patch to modify function prologue and epilogue

[Abhinav Srivastava]

Hi there,

In my project, I am trying to develop a shadow stack where I can protect return addresses from getting modified. I want to do this by modifying function prologue and epilogue so that it could save return address on the call to a protected stack. And, verify the control flow during the return.
Is there any gcc patch exist that I can use for this purpose? If I have to create this my own, could you please give me some pointer how to do that?

Any help in this regard would be appreciated.

Thanks,
Abhinav