linux-kernel - Re: pt_regs leak into userspace (was Re: [PATCH v3 20/71] ARC: Signal handling)

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Message-ID: <CACM3HyExw6WDtF6gtFrmLjyvPDTAKodSerChaoqUNZsSyD+b2g@mail.gmail.com>
Date:	Fri, 15 Feb 2013 08:23:44 +0100
From:	Jonas Bonn <jonas.bonn@...il.com>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: pt_regs leak into userspace (was Re: [PATCH v3 20/71] ARC: Signal handling)

On 11 February 2013 15:07, Al Viro <viro@...iv.linux.org.uk> wrote:

> I'd suggest asking itanic folks; they do *not* put callee-saved stuff into
> sigcontext.  AFAICS, they don't have setcontext() implemented as a syscall
> at all - it's done as sigprocmask() + doing to callee-saved registers what
> longjmp() does.


Just to round off this discussion, after giving it some more thought I
agree that the case where you would need callee-saved registers
restored is probably rather pathological.  Any sane use of
get/set/swapcontext is manageable without this.

So, Vineet, I'm now convinced your approach is sound.  I will probably
amend the OpenRISC arch to behave similarly.  Consider your entire
patch Acked now.

/Jonas
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