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Instruction Set References
--------------------------
https://en.wikipedia.org/wiki/X86_instruction_listings
https://stackoverflow.com/questions/3818856/what-does-the-rep-stos-x86-assembly-instruction-sequence-do
https://stackoverflow.com/questions/6555094/what-does-cltq-do-in-assembly
Register Names / Sizes
----------------------
"Traditional" general-purpose registers:
rax, rbx, rcx, rdx, rsi, rdi, rbp, rsp
MSB LSB
+--------+--------+--------+--------+--------+--------+--------+--------+
| rax |
+--------+--------+--------+--------+--------+--------+--------+--------+
| eax |
+--------+--------+--------+--------+
| ax |
+--------+--------+
| ah | al |
+--------+--------+
Additional x86_64 general-purpose registers:
r8, r9, r10, r11, r12, r13, r14, r15
MSB LSB
+--------+--------+--------+--------+--------+--------+--------+--------+
| r8 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| r8d |
+--------+--------+--------+--------+
| r8w |
+--------+--------+
* Note: High byte of lower | r8b / |
16-bit word is inaccessible | r8l |
+--------+
Calling Conventions
-------------------
Passing function arguments is arch-dependent: see below. The caller return
address is pushed after any argument values.
Often, the called function will use the base pointer register to mark the stack
address at the bottom of the new stack frame and adjust the stack pointer
register to allocate space for the new frame in full. The old bp value is saved
on the stack above the return address. See below for an illustration of the
stack.
On return, the original base and stack pointer values are restored. Any pushed
argument values remain on the stack and are the responsibility of the caller.
The function return value is stored in the a register.
+----------------------------+ <- sp (register) top of stack
| | lower addresses
| space for local function |
| storage: variables, arrays |
| |
| |
+============================+ <- bp (register)
| saved base pointer |
+----------------------------+
| saved instruction pointer |
+============================+
| function argument ?? |
+----------------------------+
| function argument ?? |
+----------------------------+
| ... |
+----------------------------+
| |
| |
| |
| caller stack frame |
| |
| |
| |
+============================+ <- saved base pointer (on stack)
| caller saved base ptr |
.............................. higher addresses
32-bit (x86)
------------
All function arguments are pushed to the stack in reverse order, leaving the
first arguent on the top of the stack.
Stack pointer register: esp
Base pointer register: ebp
Return value in: eax
64-bit (x86_64)
---------------
The first six arguments are stored in registers. All remaining arguments
are pushed to the stack in reverse order.
Argument #1: rdi
Argument #2: rsi
Argument #3: rdx
Argument #4: rcx
Argument #5: r8
Argument #6: r9
Stack pointer register: rsp
Base pointer register: rbp
Return value in: rax
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