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Re: V2 [PATCH] ucontext.h: Add __INDIRECT_RETURN

From: Florian Weimer <fw at deneb dot enyo dot de>
To: "H.J. Lu" <hjl dot tools at gmail dot com>
Cc: GNU C Library <libc-alpha at sourceware dot org>
Date: Thu, 19 Jul 2018 14:21:46 +0200
Subject: Re: V2 [PATCH] ucontext.h: Add __INDIRECT_RETURN
References: <20180718173558.GA18109@intel.com> <87y3e8ckzc.fsf@mid.deneb.enyo.de> <CAMe9rOqWwt0wmktv7EmixbxMfWYB330x6Mzu5RRA7g6OvdBQbA@mail.gmail.com> <20180719121841.GA7226@gmail.com>

* H. J. Lu:

> +/* On x86, swapcontext returns via indirect branch when the shadow stack
> +   is enabled.  Define __INDIRECT_RETURN to indicate whether swapcontext
> +   returns via indirect branch.  */
> +#if defined __CET__ && (__CET__ & 2) != 0
> +/* Note: Functions returned via indirect branch returns once.  Without
> +   indirect_return attribute, use returns_twice attribute.  */

I still don't understand the first sentence of the second comment.

Follow-Ups:
- V3 [PATCH] ucontext.h: Add __INDIRECT_RETURN
  - From: H.J. Lu

References:
- [PATCH] ucontext.h: Add __INDIRECT_RETURN
  - From: H.J. Lu
- Re: [PATCH] ucontext.h: Add __INDIRECT_RETURN
  - From: Florian Weimer
- Re: [PATCH] ucontext.h: Add __INDIRECT_RETURN
  - From: H.J. Lu
- V2 [PATCH] ucontext.h: Add __INDIRECT_RETURN
  - From: H.J. Lu

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