Reporting from linux kernel land,
Starting with version 2.5, linux kernel introduced a new system call entry mechanism on Pentium II+ processors. Why this new mechanism? Well, somebody reported performances issues with system calls on Pentium IV processors. Apparently, the system call mechanism based on software interrupts was responsible for this performance lag. Linux, or Linus more specifically, responded by implementing an alternative system call mechanism.
This mechanism made use of SYSENTER/SYSEXIT instructions available on Pentium II+ processors to implement system call entry and exit. This articles explores this new mechanism. If I have made any general statement, i.e. not mentioned specific architecture, please make a mental note that I am talking about Pentium processors. Also, all source code listings are based on the kernel i.e. 220.127.116.11 (that's the kernel on backtrack v1.0).
Here is the link:
I explored this mechanism for awareness and of course, for fun ;) I wrote this article as a reference for other explorers. You can send me a note (manugarg at gmail dot com) if you find this article of any use.
"Journey is the destination of life"
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