Apr 26, 2017 · As x86(_64) is a CISC processor, it has a big instruction set, but the compilers, unless you are optimizing, only use a "small" subset of it. You can check that disassembling binaries with objdump or your preferred disassembler.

Dec 14, 2021 · On the x86 processor, instructions are variable-sized, so disassembling backward is an exercise in pattern matching. To disassemble backward from an address, you should start disassembling at a point further back than you really want to go, then look forward until the instructions start making sense.

This handout only mentions a small subset of the rich possibilities provided by the x86-64 instruction set and architecture. For a more complete (but still readable) introduction, consult The AMD64 Architecture Programmer’s Manual, Volume 1: Application Programming. Registers

CS107 x86-64 Reference Sheet Common instructions mov src, dst dst = src movsbl src, dst byte to int, sign-extend movzbl src, dst byte to int, zero-fill cmov src, reg reg = src when condition holds, using same condition suffixes as jmp lea addr, dst dst = addr ZF add src, dst dst += src sub src, dst dst -= src imul src, dst dst *= src neg dst dst = -dst (arith inverse)

A 64 bit linux machine passes function parameters in rdi, rsi, rdx, rcx, r8, and r9. Any additional parameters get pushed on the stack. OS X in 64 bit uses the same parameter scheme. Example function call: extern putchar mov rdi,'H' ; function parameter: one char to print call putchar Windows in 64 bit is quite different:

Aug 6, 2021 · The x86-64 instruction set defines many opcodes and many ways to encode them, depending on several factors. Legacy opcodes Legacy (and x87) opcodes consist of, in this order: mandatory prefix; REX prefix; opcode. Mandatory prefix

A shift is underway to a 64-bit version of the Intel instruction set. Originally developed by Advanced Micro Devices (AMD) and named x86-64, it is now supported by high end processors from AMD (who now call it AMD64) and by Intel, who refer to it as EM64T. Most people still refer to it as “x86-64,” and we follow this convention.

May 25, 2020 · 1 Answer Sorted by: 2 To compile 32-bit code on a 64-bit system, use the option -m32 to gcc. -mtune=i386 is not correct. Share Follow answered May 25, 2020 at 19:12 Nate Eldredge 44.1k 6 51 74 Add a comment Your Answer Post Your Answer By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

It details the instruction set and the microcode formats native to this family of processors that are accessible to programmers and compilers. The document specifies the instructions (include the format of each type of instruction) and the relevant program state (including how the program state interacts with the instructions).

x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999.It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging mode.. With 64-bit mode and the new paging mode, it supports vastly larger amounts of virtual memory and physical memory than was …

The table below compares basic information about instruction set architectures. Notes: Usually the number of registers is a power of two, e.g. 8, 16, 32.In some cases a hardwired-to-zero pseudo-register is included, as "part" of register files of architectures, mostly to simplify indexing modes. The column "Registers" only counts the integer "registers" usable by general …

this a thorny issue. To explain why the instruction set is so complex requires a bit of x86 history and an overview of the resulting layout of instructions. 2.2 x86 History Why is the x86-64 instruction set so hard to describe? For historical reasons. Intel (and AMD) have long attempted to

Jun 3, 2022 · The steps for enabling long mode are: Disable paging. Set the PAE enable bit in CR4. Load CR3 with the physical address of the PML4 (Level 4 Page Map) Enable long mode by setting the LME flag (bit 8) in MSR 0xC0000080 (aka EFER) Enable paging. Reference: Intel 64 and IA-32 Architectures Software Developer's Manual, Section 9.8.5.