The ENDBRANCH Instruction Sequence

ENDBRANCH isn’t the newest thing in the world, but it’s still one of the many things to do with your CPU. Aside from being one of the x86’s many processors, it’s also a security feature that can detect the presence of a malformed jump instruction. If you don’t follow the proper protocol, you could be subjected to a nasty hardware lockup. It’s a good idea to keep this in mind when you’re debugging.

The most important part of this sequence is the sub rsp, which allocates a whopping 32 bytes of stack space. The rest of the sequence enumerates the main ingredients: a function, a call, a stack, and a couple of variables. The function is the most important, as it will be used to execute the call.

In the x86 world, it’s a good idea to avoid oversizing the number of variables involved, especially when it comes to stack sizes. This is especially important for high-performance applications that require large amounts of memory. This is why the DWARF (Dual Window Address Recognition Facility) feature is a must-have, as it allows you to manage all your stacks under one roof. In addition, a good debugger can be a valuable aid when it comes to ensuring that your code isn’t buggy, as it will be able to tell you which code paths are being used most often. You could also consider using a virtualization solution to prevent your program from leaking out of your main memory. Luckily, this is a relatively inexpensive alternative.

The endbr64 is actually a no-op on many processors, which is why you might be seeing this particular instruction appear on a more modern processor with a better code-compiling environment.

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