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From:   Andy Lutomirski <luto@kernel.org>
Date:   Tue, 11 Aug 2020 11:50:23 -0700
Message-ID: <CALCETrVOW+L-SuLrb8KwxWS=ZeDdt5qPv8dALHh6Rmcp1KxU0Q@mail.gmail.com>
Subject: Re: [PATCH v5 3/9] x86: vdso: Expose sigreturn address on vdso to the kernel
To:     Gabriel Krisman Bertazi <krisman@collabora.com>
Cc:     Andrew Lutomirski <luto@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Kees Cook <keescook@chromium.org>, X86 ML <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>, Shuah Khan <shuah@kernel.org>,
        kernel@collabora.com
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On Mon, Aug 10, 2020 at 4:26 PM Gabriel Krisman Bertazi
<krisman@collabora.com> wrote:
>
> Syscall user redirection requires the signal trampoline code to not be
> captured, in order to support returning with a locked selector while
> avoiding recursion back into the signal handler.  For ia-32, which has
> the trampoline in the vDSO, expose the entry points to the kernel, such
> that it can avoid dispatching syscalls from that region to userspace.

Almost looks good.

> +int arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)

If you make that bool instead of int, feel free to add:

Acked-by: Andy Lutomirski <luto@kernel.org>