linux-kernel - Is conditional calling of restore

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Message-ID: <c8ead7fd-9444-da25-74e9-f755da6296d5@synopsys.com>
Date:   Tue, 11 Oct 2016 11:04:41 -0700
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Al Viro <viro@...IV.linux.org.uk>
CC:     lkml <linux-kernel@...r.kernel.org>,
        arcml <linux-snps-arc@...ts.infradead.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: Is conditional calling of restore_altstack() correct for ARC

Hi Al,

I spotted a possible anomaly with ARC sigaltstack() handling and was wondering if
you could confirm if it was wrong (I don't have a test case to prove one way or
the other).

We have a micro-optimization which elides calling restore_altstack() in sigreturn
path, based on a "magic" value, set at the time of sigaction (SA_SIGINFO). So
essentially we only restore ss_{sp,size,flags} if SA_SIGINFO was set.

Do you think this needs to be done unconditionally like other ports do ?

Thx,
-Vineet