Learning link:
http://www.xuetangx.com/courses/course-v1:TsinghuaX+30240243X+sp/courseware/1d95cdf6f0e943448801e538b039300a/263a269e19884fa48b1a139e04ff7016/
system call
Programming interface for operating system services
Usually written in a high-level language
Program access is usually through high-level APIs rather than direct system calls
The three most commonly used application programming interfaces (APIs)
win32 API
POSIX API
JAVA API
Difference between system call and function call
system call
INT and IRET instructions are used for operating system calls
During system calls, stack switching and privilege level conversion
function call
CALL and RET for regular calls
No stack switching for regular calls