![]() Different compilers may have different uses for the registers, the ones listed below are used in Microsoft’s compiler: Register Intel assembly has 8 general purpose and 2 special purpose 32-bit register. No specific uses, often set to a commonly used value in a function to speed up calculations. Occasionally used as a function parameter and often used as a loop counter. Occasionally used as a function parameter, also used for storing short-term variables in a function. Used as a pointer, points to the source of instructions that require a source and destination. Points to the destination of instructions that require a source and destination. Has two uses depending on compile settings, it is either the frame pointer or a general purpose register for storing of data used in calculations.Ī special register that stores a pointer to the top of the stack (virtually under the end of the stack). Stores a pointer to the address of the instruction that the program is currently executing.Īfter each instruction, a value equal to the its size is added to EIP, meaning it points at the machine code for the next instruction. Stores meta-information about the results of previous operations i.e. whether it overflowed the register or whether the operands were equal.Ī pointer is, a variable that stores a memory address as its value, which will correspond to a certain instruction the program will have to perform. The value of the memory address can be obtained by “dereferencing” the pointer. They are used in buffer overflow attacks to redirect the execution flow to malicious code through a pointer that points at a JMP instruction. This section covers some of the most common assembly instructions, their purpose in a program and some example uses: Instruction Type VIMR STORING BUFFERS FOR NO REASON CODE Since registers simply store values, they may or may not be used as pointers, depending on on the information stored. If being used as a pointer, registers can be dereferenced, retrieving the value stored at the address being pointed to. The NOP instruction, short for “no operation”, simply does nothing. Some are simple arithmetic operations and some are complex calculations. Used mainly to perform jumps to certain memory locations, it stores the address to jump to. Used for adding and removing data from the stack. ![]() VIMR STORING BUFFERS FOR NO REASON FREEįinding & Testing a JMP ESP Instruction Address.Fuzzing the Application to Replicate the Crash.Stack Buffer Overflow ProcessĪlthough applications require a custom exploit to be crafted in order to gain remote access, most stack buffer overflow exploitation, at a high level, involve the following phases: Some of these instructions are used during the practical example in order to gain remote access to the victim machine. ![]() VIMR STORING BUFFERS FOR NO REASON CODE. ![]()
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