This problem will give you a chance to reverse engineer a switch statement from
ID: 3890714 • Letter: T
Question
This problem will give you a chance to reverse engineer a switch statement from machine code. In the following procedure, the body of the switch statement has been removed:
The disassembled machine code for the procedure is shown below. Recall parameter x is passed in register %rdi and parameter n is passed in register %rsi. The jump table resides in a different area of memory. We can see from the mov at address 0x040065e that the jump table begins at address 0x0400798. Using the gdb debugger, we can examine the ten 8-byte words of memory comprising the jump table with the command x/10x 0x400798. gdb prints the following:
Explanation / Answer
Not sure what needs to be answered here, but to test your disassembly, you could test your solution by writing a driver program like below -
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#include <stdio.h>
long switch_prob(long x, long n) ;
int main () {
printf("%d ", switch_prob(100, 200));
return 0;
}
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Now you can compile the assembly code -
gcc -Wall questiontest.c test-assembly-switch.s
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Now you can edit your questiontest.c file and match the argumnents you passed in the driver program, to see if it actually holds.