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A comment on OpenBSD system-call-origin verification. Parent comment

Re:OpenBSD system-call-origin verification by saagarjha on Sunday December 22, 2019 @08:21PM (#21860832)
> We should have a VDSO for every system call.

This doesn't really make sense; the vDSO only works for system calls that do nothing but read a value from the kernel and return it to userspace.

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Re:OpenBSD system-call-origin verification by quotemstr on Sunday December 22, 2019 @08:25PM (#21860854)
Not the case. Some VDSOs just forward to regular system calls. Try clock_gettime with CLOCK_BOOTTIME sometime. (I need to send a patch to fix this. Maybe over Christmas.)

Requiring that every system call go through a VDSO would be great because it would give us a "hook" for changing system behavior before entering the kernel, which is a good thing, because in the age of speculative execution mitigations, entering the kernel is expensive, just like in the days of yore.

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Re:OpenBSD system-call-origin verification by saagarjha on Sunday December 22, 2019 @08:46PM (#21860926)
On my computer I ended up going through a rdtsc instead of a syscall…
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