Intel x86 assembly reference manual

The segment register instructions load far pointers segment addresses into the segment registers. The instructions documented in this section provide a number of useful functions. Data Transfer Instructions The data transfer instructions move data between memory and the general-purpose and segment registers, and perform operations such as conditional moves, stack access, and data conversion.

The image above depicts the contents of the stack during the execution of a subroutine with three parameters and three local variables. The cells depicted in the stack are bit wide memory locations, thus the memory addresses of the cells are 4 bytes apart.

The first parameter resides at an offset of 8 bytes from the base pointer. Above the parameters on the stack and below the base pointer , the call instruction placed the return address, thus leading to an extra 4 bytes of offset from the base pointer to the first parameter.

When the ret instruction is used to return from the subroutine, it will jump to the return address stored on the stack. Caller Rules To make a subrouting call, the caller should: Before calling a subroutine, the caller should save the contents of certain registers that are designated caller-saved. Since the called subroutine is allowed to modify these registers, if the caller relies on their values after the subroutine returns, the caller must push the values in these registers onto the stack so they can be restore after the subroutine returns.

To pass parameters to the subroutine, push them onto the stack before the call. The parameters should be pushed in inverted order i. Since the stack grows down, the first parameter will be stored at the lowest address this inversion of parameters was historically used to allow functions to be passed a variable number of parameters.

To call the subroutine, use the call instruction. This instruction places the return address on top of the parameters on the stack, and branches to the subroutine code. This invokes the subroutine, which should follow the callee rules below.

After the subroutine returns immediately following the call instruction , the caller can expect to find the return value of the subroutine in the register EAX. To restore the machine state, the caller should: Remove the parameters from stack. This restores the stack to its state before the call was performed. The caller can assume that no other registers were modified by the subroutine. Example The code below shows a function call that follows the caller rules.

First parameter is in EAX, the second parameter is the constant ; the third parameter is in memory location var. Thus, to get rid of the parameters, we can simply add 12 to the stack pointer. If the caller uses them after the call, it would have needed to save them on the stack before the call and restore them after it.

Callee Rules The definition of the subroutine should adhere to the following rules at the beginning of the subroutine: Push the value of EBP onto the stack, and then copy the value of ESP into EBP using the following instructions: push ebp mov ebp, esp This initial action maintains the base pointer , EBP. The base pointer is used by convention as a point of reference for finding parameters and local variables on the stack.

When a subroutine is executing, the base pointer holds a copy of the stack pointer value from when the subroutine started executing. Parameters and local variables will always be located at known, constant offsets away from the base pointer value.

A computer cannot really understand an assembly program directly. Tiny C Compiler Reference Documentation. This manual documents version 0. Pass command line to the Optimizing subroutines in assembly language: An optimization guide for x86 platforms This is an optimization manual for advanced assembly language programmers and compiler makers.

Linking optimized assembly subroutines into high level language programs. The leading enterprise Linux operating system, certified on hundreds of clouds and with thousands of vendors.

Learn more. An enterprise-ready Kubernetes container platform with full-stack automated operations to manage hybrid cloud and multicloud deployments. Assembly language syntax. Assembly language uses a mnemonic to represent, e. Some of the mnemonics may be built in and some user defined. Many operations require one or more operands in order to form a complete instruction. Most assemblers permit named … NASM is an awesome assembler, but assembly language is complex. Logic responsible for managing coherency, managing access to the DIMMs, managing power distribution and sleep states, and so forth.

Most of these components provide similar performance monitoring capabilities. Speculative Execution Side Channel Mitigations This document provides a detailed explanation of the security vulnerabilities and possible mitigations. The document provides an overview of x86 hybrid architecture, hybrid core usage with Windows, and provides details on how software applications and drivers can ensure optimal core usage.

This document is a work in progress and is subject to change based on customer feedback and internal analysis. Secure Access of Performance Monitoring Unit by User Space Profilers This paper proposes a software mechanism targeting performance profilers which would run at user space privilege to access performance monitoring hardware.

The latter requires privileged access in kernel mode, in a secure manner without causing unintended interference to the software stack. Product and Performance Information 1 Performance varies by use, configuration and other factors. Give Feedback.

This document contains the full instruction set reference, A-Z, in one volume. This document contains the full system programming guide, parts 1, 2, 3, and 4, in one volume. Describes the format of the instruction and provides reference pages for instructions from A to L.