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From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH 01/23] all: syscall wrappers: add documentation
Date: Wed, 25 May 2016 13:50:39 -0700 (PDT)
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From: Arnd Bergmann <arnd@arndb.de>
Date: Wed, 25 May 2016 22:47:33 +0200

> If we use the normal calling conventions, we could remove these overrides
> along with the respective special-case handling in glibc. None of them
> look particularly performance-sensitive, but I could be wrong there.

You could set the lowest bit in the system call entry pointer to indicate
the upper-half clears should be elided.