- On linux, /usr/include/asm/unistd_32.h and /usr/include/asm/unistd_64.h for the Linux ABI call numbers.
- [A Whirlwind Tutorial on Creating Really Teensy ELF Executables for Linux](https://www.muppetlabs.com/~breadbox/software/tiny/teensy.html): Note, use -sn or -sN with `ld` today to avoid page alignment bloat.
- [Official docs](https://www.nasm.us/xdoc/2.15.05/html/nasmdoc2.html)
+- [Interfacing with Linux](https://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_Linux)
- [x86_64 NASM Cheat Sheet](https://www.cs.uaf.edu/2017/fall/cs301/reference/x86_64.html)
- [x86 Cheat Sheet](https://www.bencode.net/blob/nasmcheatsheet.pdf (x86))
-- [Interfacing with Linux](https://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_Linux)
Thanks to muurkha and #swhack on libera for help.
[x86 Cheat Sheet](https://www.bencode.net/blob/nasmcheatsheet.pdf (x86))
## x86-64 reference
-TODO: Registers, mov
-[x86_64 NASM Cheat Sheet](https://www.cs.uaf.edu/2017/fall/cs301/reference/x86_64.html)
+TODO: mov
+
+|Name | asm notes | C ABI | C ABI | Linux ABI | Linux ABI | 32-bit | 16-bit | 8-bit |
+|-----|-----------------|-----------|-------|-----------|-----------|--------|--------|-------|
+|rax | values returned | scratch | ret | scratch | ret | eax | ax | ah al |
+|rcx | can be counter | scratch | arg 4 | scratch | | ecx | cx | ch cl |
+|rdx | | scratch | arg 3 | preserved | arg 3 | edx | dx | dh dl |
+|rbx | | preserved | | preserved | | ebx | bx | bh bl |
+|rsp | top of stack | preserved | | preserved | | esp | sp | spl |
+|rbp | (old sp) | preserved | | preserved | | ebp | bp | bpl |
+|rsi | | scratch | arg 2 | preserved | arg 2 | esi | si | sil |
+|rdi | | scratch | arg 1 | preserved | arg 1 | edi | di | dil |
+|r8 | | scratch | arg 5 | preserved | arg 5 | r8d | r8w | r8b |
+|r9 | | scratch | arg 6 | preserved | arg 6 | r9d | r9w | r9b |
+|r10 | | scratch | | preserved | arg 4 | r10d | r10w | r10b |
+|r11 | | scratch | | scratch | | r11d | r11w | r11b |
+|r12 | | preserved | | preserved | | r12d | r12w | r12b |
+|r13 | | preserved | | preserved | | r13d | r13w | r13b |
+|r14 | | preserved | | preserved | | r14d | r14w | r14b |
+|r15 | | preserved | | preserved | | r15d | r15w | r15b |
+
+Parts of a 64-bit register
+
+```
+[76543210 76543210 76543210 76543210 76543210 76543210 76543210 76543210] bits
+[ RAX ]
+ [ EAX ]
+ [ AX ]
+ [ AH ][ AL ]
+```
+
+Register sizes
+
+| C datatype | Bits | Bytes | Register | NASM allocate |
+|------------|------|-------|----------|---------------|
+| char | 8 | 1 | al | db |
+| short | 16 | 2 | ax | dw |
+| int | 32 | 4 | eax | dd |
+| long | 64 | 8 | rax | dq |
+
+Register moves
+
+| from | to 64 bit rcx | to 32 bit ecx | to 16 bit cx | to 8 bit cl | Notes
+|------------|---------------|---------------|--------------|-------------|
+| 64 bit rax | mov rax,rcx | movsxd rax,ecx| movsx rax,cx | movsx rax,cl| Writes to whole register
+| 32 bit eax | mov eax,ecx | mov eax,ecx | movsx eax,cx | movsx eax,cl| Top half of destination gets zeroed
+| 16 bit ax | mov ax,cx | mov ax,cx | mov ax,cx | movsx ax,cl | Only affects low 16 bits, rest unchanged
+| 8 bit al | mov al,cl | mov al,cl | mov al,cl | mov al,cl | Only affects low 8 bits, rest unchanged
+
+Linux syscall
+
+| system call number | 1st param | 2nd param | 3rd param | 4th param | 5th param | 6th param | result |
+|--------------------|-----------|-----------|-----------|-----------|-----------|-----------|--------|
+| rax | rdi | rsi | rdx | r10 | r8 | r9 | rax |
+
+Linux C ABI (integers)
+
+| 1st param | 2nd param | 3rd param | 4th param | 5th param | 6th param | 7+ params | result |
+|-----------|-----------|-----------|-----------|-----------|-----------|-----------|--------|
+| rdi | rsi | rdx | rcx | r8 | r9 | stack | rax |
+
+| instruction | result |
+|-------------|--------|
+| MOV dest,src| dest = src
+| CALL func | call a function
+| RET | return from a function
+| SYSCALL | call an OS function
+| PUSH src | push onto stack
+| POP dest | pop from stack
+| ADD a,b | a = a + b
+| MUL a,b | a = a * b
+| AND a,b | a = a & b
+| OR a,b | a = a & b
+| DIV src | Divide rax by src. Put the quotient in rax, and the remainder in rdx. rdx MUST be zero on call or you get SIGFPE
+| SHR val,bits| val = val >> bits; bits can also be rcx (only)
+| CMP a,b | Compare a and b. Used for conditional jumps
+| JMP label | Unconditional jump
+| JL label | Jump if less than (signed)
+| JLE label | Jump if less than or equal (signed)
+| JG label | Jump if greater than (signed)
+| JGE label | Jump if greater than or equal (signed)
+| JNE label | Jump if not equal
+| JE label | Jump if equal
+| RDRAND | random number (16,32,64-bit only)
## x86 and x86-64 ISA
instructions - are they that different? combine maybe
### Chapter 12: Writing 64-bit Code (Unix, Win64)
**C ABI for Unix**
+- Stack should be 16-byte aligned
- The first six arguments are passed in RDI, RSI, RDX, RCX, R8, and R9.
- All the above, plus RAX, R10, and R11 are "scratch" registers destroyed by function calls and don't need to be saved.
- Additional arguments are passed on the stack.
projects / za3k.git / commitdiff