Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 2 Sep 2022 18:59:37 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Andrew Jones <ajones@ventanamicro.com>
Cc:     linux-riscv@lists.infradead.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: fix a nasty sigreturn bug...
Message-ID: <YxJEiSq/CGaL6Gm9@ZenIV>
References: <YU0wDzeS/jXwkAca@zeniv-ca.linux.org.uk>
 <20220902092245.ande6fvievnbn35h@kamzik>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220902092245.ande6fvievnbn35h@kamzik>
Sender: Al Viro <viro@ftp.linux.org.uk>
Precedence: bulk

On Fri, Sep 02, 2022 at 11:22:45AM +0200, Andrew Jones wrote:

> So, for riscv, where in do_signal and handle_signal syscall restarting
> is avoided when regs->cause != EXC_SYSCALL and it's common to set cause
> to -1 to avoid it, then it makes sense to set regs->cause != EXEC_SYSCALL
> in rt_sigreturn or in restore_sigcontext, which rt_sigreturn calls, as
> well.
> 
> So the only question I have is whether or not the cause assignment
> is better in restore_sigcontext() like other architectures? At least,
> since rt_sigreturn is the only caller of restore_sigcontext, it can't
> break anything putting it there atm...

	The only reason for doing that in restore_sigcontext() is that for
old architectures there'd been separate sigreturn(2) and rt_sigreturn(2).
Doing that in the helper shared by both avoided duplication; since
there's no such thing on riscv...

	Matter of taste, really - I have a slight preference for doing that
closer to the syscall surface, but it's no more than that.