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What does SYSENTER do?
Executes a fast call to a level 0 system procedure or routine. SYSENTER is a companion instruction to SYSEXIT. When executed in IA-32e mode, the SYSENTER instruction transitions the logical processor to 64-bit mode; otherwise, the logical processor remains in protected mode.
What is x86_64 in Linux?
Linux x86_64 (64-bit) is a Unix-like and mostly POSIX-compliant computer operating system (OS) assembled under the model of free and open-source software development and distribution. Using host OS (Mac OS X or Linux 64-bit) you can build native application for Linux x86_64 platform.
What is Syscall instruction?
syscall is an instruction in x86-64, and is used as part of the ABI for making system calls. (The 32-bit ABI uses int 80h or sysenter , and is also available in 64-bit mode, but using the 32-bit ABI from 64-bit code is a bad idea, especially for calls with pointer arguments.)
What is system call stub?
A stub in distributed computing is a piece of code that converts parameters passed between client and server during a remote procedure call (RPC). Stubs perform the conversion of the parameters, so a remote procedure call looks like a local function call for the remote computer.
What is int 0x80 Assembly?
int 0x80 is the assembly language instruction that is used to invoke system calls in Linux on x86 (i.e., Intel-compatible) processors. An assembly language is a human-readable notation for the machine language that a specific type of processor (also called a central processing unit or CPU) uses.
What is the purpose of writing stub routines?
A stub may simulate the behavior of existing code (such as a procedure on a remote machine; such methods are often called mocks) or be a temporary substitute for yet-to-be-developed code. Stubs are therefore most useful in porting, distributed computing as well as general software development and testing.
How a system call works in Linux?
A system call is implemented by a “software interrupt” that transfers control to kernel code; in Linux/i386 this is “interrupt 0x80”. The specific system call being invoked is stored in the EAX register, abd its arguments are held in the other processor registers.