Difference between revisions of "X86 64 Register and Instruction Quick Start"
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[[Category:Assembly Language]] | [[Category:Assembly Language]] | ||
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| + | This page contains very basic information on the x86_64 architecture: the [[Register|register]] layout and naming and the some basic instructions. | ||
| + | |||
== Registers == | == Registers == | ||
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* 8-bit registers using 'l' ("low byte" of 16 bits) suffix (original registers - bits 0-7: _l) or 'b' suffix (added registers: r__b): al, bl, r15b | * 8-bit registers using 'l' ("low byte" of 16 bits) suffix (original registers - bits 0-7: _l) or 'b' suffix (added registers: r__b): al, bl, r15b | ||
| − | Usage during syscall/function call: | + | Usage during [[Syscalls|syscall]]/function call: |
| − | * First six arguments are in rdi, rsi, rdx, rcx, r8d, r9d; remaining arguments are on the stack | + | * First six arguments are in rdi, rsi, rdx, rcx, r8d, r9d; remaining arguments are on the stack. |
| − | * For syscalls, the syscall number is in rax | + | * For syscalls, the syscall number is in rax. For procedure calls, rax should be set to 0. |
| − | * Return value is in rax | + | * Return value is in rax. |
| − | * The called routine is expected to | + | * The called routine is expected to preserve rsp,rbp, rbx, r12, r13, r14, and r15 but may trample any other registers. |
=== Floating-Point and SIMD Registers === | === Floating-Point and SIMD Registers === | ||
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These instructions are sufficient to complete the [[SPO600 Assembler Lab]] (GAS syntax): | These instructions are sufficient to complete the [[SPO600 Assembler Lab]] (GAS syntax): | ||
| − | add %r10,%r11 | + | add %r10,%r11 // add r10 and r11, put result in r11 |
| − | cmp %r10,%r11 | + | add $5,%r10 // add 5 to r10, put result in r10 |
| − | cmp $99,%r11 | + | call ''label'' // call a subroutine / function / procedure |
| − | div | + | cmp %r10,%r11 // compare register r10 with register r11. The comparison sets flags in the processor status register which affect conditional jumps. |
| − | inc %r10 | + | cmp $99,%r11 // compare the number 99 with register r11. The comparison sets flags in the processor status register which affect conditional jumps. |
| − | jmp ''label'' | + | div %r10 // divide rax by the given register (r10), places quotient into rax and remainder into rdx (rdx must be zero before this instruction) |
| − | + | inc %r10 // increment r10 | |
| − | jne ''label'' | + | jmp ''label'' // jump to label |
| − | jl ''label'' | + | je ''label'' // jump to label if equal |
| − | jg ''label'' | + | jne ''label'' // jump to label if not equal |
| − | mov %r10,%r11 | + | jl ''label'' // jump to label if less |
| − | mov $99,%r10 | + | jg ''label'' // jump to label if greater |
| − | mov %r10,(%r11) | + | mov %r10,%r11 // move data from r10 to r11 |
| − | mov (%r10),%r11 | + | mov $99,%r10 // put the immediate value 99 into r10 |
| − | mul | + | mov %r10,(%r11) // move data from r10 to address pointed to by r11 |
| − | push %r10 | + | mov (%r10),%r11 // move data from address pointed to by r10 to r10 |
| − | pop %r10 | + | mul %r10 // multiplies rax by r10, places result in rax and overflow in rdx |
| − | syscall | + | push %r10 // push r10 onto the stack |
| + | pop %r10 // pop r10 off the stack | ||
| + | ret // routine from subroutine (counterpart to call) | ||
| + | syscall // invoke a syscall (in 32-bit mode, use "int $0x80" instead) | ||
| + | |||
| + | Note the syntax: | ||
| + | * [[Register]] names are prefixed by % | ||
| + | * [[Immediate Value|Immediate values]] are prefixed by $ | ||
| + | * Indirect memory access is indicated by (parenthesis). | ||
| + | * Hexadecimal values are indicated by a 0x prefix. | ||
| + | * Character values are indicated by quotation marks. Escapes (such as '\n') are permitted. | ||
| + | * Data sources are given as the first argument (mov %r10,%r11 moves FROM r10 INTO r11). | ||
| + | |||
| + | For the MOV instruction: | ||
| + | * You can append a suffix indicating the amount of data to be moved -- e.g., q for quadword (64 bits), d for doubleword (32 bits), w for word (16 bits), or b for byte (8 bits). | ||
| − | == | + | == Resources == |
* CPU Instruction Set and Software Developer Manuals | * CPU Instruction Set and Software Developer Manuals | ||
| − | ** AMD: | + | ** AMD: https://developer.amd.com/resources/developer-guides-manuals/ (see the AMD64 Architecture section, particularly the ''AMD64 Architecture Programmer’s Manual Volume 3: General Purpose and System Instructions'') |
** Intel: http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html | ** Intel: http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html | ||
| + | * Web sites | ||
| + | ** http://ref.x86asm.net/ | ||
| + | ** http://sandpile.org/ | ||
* GAS Manual - Using as, The GNU Assembler: https://sourceware.org/binutils/docs/as/ | * GAS Manual - Using as, The GNU Assembler: https://sourceware.org/binutils/docs/as/ | ||
Latest revision as of 08:41, 18 February 2022
This page contains very basic information on the x86_64 architecture: the register layout and naming and the some basic instructions.
Contents
Registers
General-Purpose Registers
The 64-bit versions of the 'original' x86 registers are named:
- rax - register a extended
- rbx - register b extended
- rcx - register c extended
- rdx - register d extended
- rbp - register base pointer (start of stack)
- rsp - register stack pointer (current location in stack, growing downwards)
- rsi - register source index (source for data copies)
- rdi - register destination index (destination for data copies)
The registers added for 64-bit mode are named:
- r8 - register 8
- r9 - register 9
- r10 - register 10
- r11 - register 11
- r12 - register 12
- r13 - register 13
- r14 - register 14
- r15 - register 15
These may be accessed as:
- 64-bit registers using the 'r' prefix: rax, r15
- 32-bit registers using the 'e' prefix (original registers: e_x) or 'd' suffix (added registers: r__d): eax, r15d
- 16-bit registers using no prefix (original registers: _x) or a 'w' suffix (added registers: r__w): ax, r15w
- 8-bit registers using 'h' ("high byte" of 16 bits) suffix (original registers - bits 8-15: _h): ah, bh
- 8-bit registers using 'l' ("low byte" of 16 bits) suffix (original registers - bits 0-7: _l) or 'b' suffix (added registers: r__b): al, bl, r15b
Usage during syscall/function call:
- First six arguments are in rdi, rsi, rdx, rcx, r8d, r9d; remaining arguments are on the stack.
- For syscalls, the syscall number is in rax. For procedure calls, rax should be set to 0.
- Return value is in rax.
- The called routine is expected to preserve rsp,rbp, rbx, r12, r13, r14, and r15 but may trample any other registers.
Floating-Point and SIMD Registers
x86_64 also defines a set of large registers for floating-point and single-instruction/multiple-data (SIMD) operations. For details, refer to the Intel or AMD documentation.
Instructions
Starter Kit
These instructions are sufficient to complete the SPO600 Assembler Lab (GAS syntax):
add %r10,%r11 // add r10 and r11, put result in r11 add $5,%r10 // add 5 to r10, put result in r10 call label // call a subroutine / function / procedure cmp %r10,%r11 // compare register r10 with register r11. The comparison sets flags in the processor status register which affect conditional jumps. cmp $99,%r11 // compare the number 99 with register r11. The comparison sets flags in the processor status register which affect conditional jumps. div %r10 // divide rax by the given register (r10), places quotient into rax and remainder into rdx (rdx must be zero before this instruction) inc %r10 // increment r10 jmp label // jump to label je label // jump to label if equal jne label // jump to label if not equal jl label // jump to label if less jg label // jump to label if greater mov %r10,%r11 // move data from r10 to r11 mov $99,%r10 // put the immediate value 99 into r10 mov %r10,(%r11) // move data from r10 to address pointed to by r11 mov (%r10),%r11 // move data from address pointed to by r10 to r10 mul %r10 // multiplies rax by r10, places result in rax and overflow in rdx push %r10 // push r10 onto the stack pop %r10 // pop r10 off the stack ret // routine from subroutine (counterpart to call) syscall // invoke a syscall (in 32-bit mode, use "int $0x80" instead)
Note the syntax:
- Register names are prefixed by %
- Immediate values are prefixed by $
- Indirect memory access is indicated by (parenthesis).
- Hexadecimal values are indicated by a 0x prefix.
- Character values are indicated by quotation marks. Escapes (such as '\n') are permitted.
- Data sources are given as the first argument (mov %r10,%r11 moves FROM r10 INTO r11).
For the MOV instruction:
- You can append a suffix indicating the amount of data to be moved -- e.g., q for quadword (64 bits), d for doubleword (32 bits), w for word (16 bits), or b for byte (8 bits).
Resources
- CPU Instruction Set and Software Developer Manuals
- AMD: https://developer.amd.com/resources/developer-guides-manuals/ (see the AMD64 Architecture section, particularly the AMD64 Architecture Programmer’s Manual Volume 3: General Purpose and System Instructions)
- Intel: http://www.intel.com/content/www/us/en/processors/architectures-software-developer-manuals.html
- Web sites
- GAS Manual - Using as, The GNU Assembler: https://sourceware.org/binutils/docs/as/
