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// IntegerRep.java: Dec, Bin, and Hex
 assembler.txt |
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assembler
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exit_shellcode.txt |
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Section .text
global _start
_start:
mov ebx,0
mov eax,1
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foobar.c |
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/* http://www.cgsecurity.org/Articles/1-MISC/Protections-1/ */
intel_reg.htm |
intel registers mnemonics examples
The following are 32 bit registers so each can hold one word == 0xAA like that.
| EAX |
Accumulator for operands and results data. | the function number is placed in EAX
mov $0xfc, %eax (syscall 252 == exit_group)
mov $0x1, %eax(syscal 1)
By putting somethign into %eax, we automatically set the value returned |
| EBX | Pointer to start/location in data in the DS segment.
one of the base registers-- to do with data addressing modes |
has historically been used for working with the stack
mv 0x4(%esp,1), %ebx ("an instruction that loads the argument to our exit syscal into EBX")
mov eax, [ebp+10h] (moves dword from16 bytes down the stack)
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| ECX |
Counter for string and loop operations. |
| EDX |
I/O pointer. |
| EBP |
Pointer to start of stack (in the SS segment).
one of the base registers-- to do with data addressing modes
also called the frame pointer (== start of the stack) |
| ESI |
Pointer to data in the segment pointed to by the DS register; source
pointer for string operations. |
| EDI |
Pointer to data (or destination) in the segment pointed to by the ES
register; destination pointer for string operations. |
| ESP |
Stack pointer (in the SS segment). |
points to the last address used by the stack
by subtracting from this value can overwrite the stack by overwriting that new address |
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sizeoflong.c |
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int main() {
stacks.txt |
direction assembly stack growth
*stack grows from higher to lower addresses *
"MIPS software allocates another register just for the stack: the stack pointer ($sp), used to save the registers needed by the callee. By historical precedent, stacks "grow" from higher addresses to lower addresses. This convention means that you push values onto the stack by subtracting from the stack pointer. Adding to the stack pointer shrinks the stack, thereby popping values off the stack." (page 80, hennessy).
he gives instruction like *addi, $sp, $sp, -12 # adjust stack to maek room for 3 items*
intel does the same thing.
push 1
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sum_array.txt |
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# introductory example; finds the sum of the elements of an array
.data # start of data segment
x:
.long 1
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wack.c |
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char shellcode[] = "\xbb\x00\x00\x00\x00"
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koziol