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From:   David Laight <David.Laight@ACULAB.COM>
To:     "'kpark3469@gmail.com'" <kpark3469@gmail.com>,
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Subject: RE: [PATCH v3 3/3] x86: usercopy: reimplement
 arch_within_stack_frames with unwinder
Thread-Topic: [PATCH v3 3/3] x86: usercopy: reimplement
 arch_within_stack_frames with unwinder
Thread-Index: AQHTz/sSAuKS/MpI00yCw1px+eBQn6P4ZtyQ
Date:   Mon, 9 Apr 2018 13:14:58 +0000
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From: kpark3469@gmail.com
> Sent: 09 April 2018 12:59
>
> The old arch_within_stack_frames which used the frame pointer is
> now reimplemented to use frame pointer unwinder apis. So the main
> functionality is same as before.

How much slower does this make the code?
Following stack frames using %bp is reasonably quick.
I can't imagine some of the other unwinder APIs being any where
near that fast.
While fine for fault tracebacks, using them during usercopy
is likely to have measurable performance impact.

	David