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I'm trying to establish if my linux kernel is using sysenter/sysexit instructions to initiate and terminate system calls from user space.

The kernel I'm running is "2.6.31.12-174.2.3.fc12.x86_64".

Any Ideas?

M.

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3 Answers 3

sysenter/sysexit depends more on your CPU than the kernel - Linux has utilized it since the early 2.5 days. Linux picks either SYSENTER, SYSCALL or legacy int 80 methods depending on what type of CPU it is running on.

Not sure how you could confirm that it's actually being used. I don't think Systemtap or LTT will look at a low enough level. Maybe you could instrument the kernel and add some tracepoints in the vDSO code...

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You might consider looking into SystemTap. With that, you should be able to write a script that triggers an action whenever an event of your liking, including system calls, occurs.

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Only suggestion I can think of would be to use the Linux Trace Toolkit to create a kernel dump and dig through the system calls.

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