Question

when passing procedure parameters on the stack, why are the following lines of code often necessary in a procedure? push ebp mov ebp, esp group of answer choices to preserve the original ebp register value for register indirect addressing. because the procedure might change the ebp register value. they are never necessary. to keep additional usage of the stack within the procedure from invalidating the stack offsets.

Answer 1

The code 'push ebp' and 'mov ebp, esp' are used when passing procedure parameters on the stack to set up a stack frame, preserve the original EBP value, and ensure register indirect addressing. This setup keeps the stack organized and makes access to variables and parameters reliable.

Step-by-step explanation:

When passing procedure parameters on the stack, the lines of code push ebp and mov ebp, esp are often necessary for a few reasons. These instructions are important in setting up what is known as a 'stack frame' for the procedure, which is used to manage the procedure's internal variables and passed parameters.

The push ebp instruction is used to preserve the original EBP register value. The Base Pointer (EBP) holds the address of the current stack frame, and it is essential to save this value so that when the procedure is finished, the previous stack frame can be restored.

Next, mov ebp, esp is used for register indirect addressing. The Stack Pointer (ESP) points to the top of the stack, and moving its value to EBP sets up a new stack frame. It ensures that any further stack operations within the procedure don't invalidate the offsets used to access parameters and local variables.

Thus, these instructions are not only necessary to preserve the EBP for the calling function but also to make the current function's stack manipulation safer and its variables easier to access.