On 06/20/2014 01:38 PM, Lukasz Sokol wrote:
Is it possible to call about any syscall (timing included) through (32bit)
exising vdso ?
I understand that is what "__kernel_vsyscall" is supplied for (and I
don't understand why it is nit supplied in 64 Bit).
And measure how it goes vs 'normal' way of doing it via library chain?
In fact that is not in my agenda.
I suppose for normal syscalls there will be no significant difference,
as the switch to Kernel-mode and back will take the greatest amount of
latency. But there might be certain syscalls that in fact are handled
completely in user mode by the vDSO variant and hence will perform better.
I did not yet actually _call_ any vDSO function right now. I only
checked how to find the vDSO ELF structure and dumped it's content on
the screen so that I can see, what functions are implemented.
I did not yet try to do code that analyzes the ELF structure itself to
find the procedure entry points.
If you want do do some tests yourself, I can send you my pure-pascal
source code (no C-library calls ) that is able to locate the ELF
structure (as well 32 as 64 Bits), so that you can enhance it.
-Michael
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