On 06/03/2015 11:04 AM, H. Peter Anvin wrote:
> On 06/03/2015 10:22 AM, Andy Lutomirski wrote:
>>
>> I'm convinced. If "entry" means entry into code provided by the
>> kernel as opposed to entry via hardware-provided entry mechanism, then
>> the vdso is indeed a pile of entries into the kernel.
>>
>
> No, it isn't. It is user space code provided by the kernel. It is a
> very different beast, and this is highly and unnecessarily confusing. I
> am thrilled we finally have managed to get the vdso code separated out,
> this just muddles the situation.
>
So let me clarify this: vdso code is really a kind of system calls, that
just happen to be executed in user space, thus *bypassing* kernel entry.
We don't want to put all the system call code (or even the x86-specific
ones) in entry/ as that would completely eliminate the point and we have
once again re-invented the kernel/ catch-all.
-hpa
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