Ch 5: Why both kernel headers?

Kevin P. Fleming kpfleming at
Wed Sep 15 14:18:28 PDT 2004

Ian Molton wrote:

> userspace uses *software* interrupts to communicate with the kernel,
> which behave in a very similar manner but arent triggered by hadrware
> IRQ lines.

Well, it did :-)

I believe now with the 2.6 kernel on an x86/x86-64 CPU and recent glibc 
(in other words, LFS testing/unstable), userspace is using the vDSO to 
talk to the kernel on any CPUs that support SYSENTER/SYSCALL. That would 
be all modern P3s, P4s, Athlons, etc.

The claim when this was being developed was that it is much faster than 
using software interrupts. I can't say from personal experience, though :-)

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