1. assembly basics
1.1. memory
1.1.1. ram
1.1.2. binary
1.1.3. function frames
1.2. registers
1.2.1. sizes
1.2.2. common x86 registers
1.3. stack
1.3.1. push
1.3.2. pop
1.4. syntax
1.4.1. intel
1.4.2. AT&T
1.5. Instruction
1.5.1. mov
1.5.2. sub / add
1.5.3. ret
1.5.4. leave
1.5.5. call
1.5.6. jmp
1.6. Functions
1.6.1. prolog
1.6.2. epilog
1.7. Buffer
1.8. Jump tables
0xffff ffff ffff ffff
Memory can be addressed using some number:
0x00000000000000000000
...
*memory*
...
0xffffffffffffffffffff
Somewhere in memory lies the binary:
0x??? .text
initialized data
.bss
heap
|
v
...
...
^
|
stack
cmd line args
0x???
On the stack:
...
locals |
base pointer | line function
ret addr |
parameters |
locals |
base pointer | rectangle function
ret addr |
parameters |
64 | 32 | 16 | 8 | 0 |
v v v v v
rax: ................................................................
eax: ................................
ax: ................
ah ........
al ........
r?x: 64 bit
e?x: 32 bit
?x: 16 bit
?h: "high" 8 bit
?l: "low" 8 bit
- stack
- rsp (stack pointer)
- rbp (base pointer)
- function arguments
- rdi
- rsi
- rdx
- rcx
- return value
- rax
- intruction pointer
- rip
Stack: ___ ___ ___
push "a"
Stack: _a_ ___ ___
push "b"
Stack: _a_ _b_ ___
push "c"
Stack: _a_ _b_ _c_
Stack: _a_ _b_ _c_
rax: ___
rbx: ___
rcx: ___
pop "rax"
Stack: _a_ _b_ ___
rax: _c_
rbx: ___
rcx: ___
pop "rbx"
Stack: _a_ ___ ___
rax: _c_
rbx: _b_
rcx: ___
pop "rcx"
Stack: ___ ___ ___
rax: _c_
rbx: _b_
rcx: _a_
mov rax, rbx
mov %rax, %rbx
mov dst, src
values in square brackets dereference pointers, so the following:
mov rbx, [rax]
sould move the value the pointer that is stored in rax points to into rbx.
subtrace or add to the provided value
sub rax, 0x100
add rdx, [rax]
jne: jump if not equal
jnz: jump if not zero
- group of instructions
- execute function by preparing registers, jumping to code, execution code and returning to original code
- function arguments passed depending on arch:
- 32: stack
- 64: registers (rdi, rsi, rdx, rcx, r8, r9)
push rip
push rbp
mov rbp, rsp
mov rsp, rbp
pop rbp
pop rip
char str[16];
_ _ _ _
_ _ _ _
_ _ _ _
_ _ _ _
^
| stack grows up
| buffer get's written in the other dir
v
gets(str);
*input 16 "A"*
A A A A
A A A A
A A A A
A A A A
_ _ _ _ <- old rbp
_ _ _ _ <- old rip
*input 4 "B"*
A A A A
A A A A
A A A A
A A A A
B B B B <- old rbp
_ _ _ _ <- old rip
emile - 1731525159.880668s - generated using vokobe "0.1.3"
