linux-kernel - Re: [PATCH] riscv: fix a nasty sigreturn bug...

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Date:   Fri, 2 Sep 2022 18:59:37 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Andrew Jones <ajones@...tanamicro.com>
Cc:     linux-riscv@...ts.infradead.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] riscv: fix a nasty sigreturn bug...

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.