Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210226135156.1081606-1-figiel@google.com> <192824546.8190.1614353555831.JavaMail.zimbra@efficios.com>
In-Reply-To: <192824546.8190.1614353555831.JavaMail.zimbra@efficios.com>
From:   =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <emmir@google.com>
Date:   Fri, 26 Feb 2021 17:04:25 +0100
Message-ID: <CABb0KFFhbxU0xq0A=m2FO83j04vrzwVa2-JwKJi1mtRhu_0kSg@mail.gmail.com>
Subject: Re: [PATCH v2] ptrace: add PTRACE_GET_RSEQ_CONFIGURATION request
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc:     Piotr Figiel <figiel@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        paulmck <paulmck@kernel.org>, Boqun Feng <boqun.feng@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        Florian Weimer <fweimer@redhat.com>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andrei Vagin <avagin@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Peter Oskolkov <posk@google.com>,
        Kamil Yurtsever <kyurtsever@google.com>,
        Chris Kennelly <ckennelly@google.com>,
        Paul Turner <pjt@google.com>,
        linux-man <linux-man@vger.kernel.org>,
        linux-api <linux-api@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Fri, 26 Feb 2021 at 16:32, Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
> ----- On Feb 26, 2021, at 8:51 AM, Piotr Figiel figiel@google.com wrote:
> [...]
> > ---
> > v2:
> > Applied review comments:
> > - changed return value from the ptrace request to the size of the
> >   configuration structure
> > - expanded configuration structure with the flags field and
> >   the rseq abi structure size
> >
> [...]
> > +#define PTRACE_GET_RSEQ_CONFIGURATION        0x420f
> > +
> > +struct ptrace_rseq_configuration {
> > +     __u64 rseq_abi_pointer;
> > +     __u32 rseq_abi_size;
> > +     __u32 signature;
> > +     __u32 flags;
> > +     __u32 pad;
> > +};
> > +
> [...]
> > +#ifdef CONFIG_RSEQ
> > +static long ptrace_get_rseq_configuration(struct task_struct *task,
> > +                                       unsigned long size, void __user=
 *data)
> > +{
> > +     struct ptrace_rseq_configuration conf =3D {
> > +             .rseq_abi_pointer =3D (u64)(uintptr_t)task->rseq,
> > +             .rseq_abi_size =3D sizeof(*task->rseq),
> > +             .signature =3D task->rseq_sig,
> > +             .flags =3D 0,
> > +     };
> > +
> > +     size =3D min_t(unsigned long, size, sizeof(conf));
> > +     if (copy_to_user(data, &conf, size))
> > +             return -EFAULT;
> > +     return sizeof(conf);
> > +}
>
> I think what Florian was after would be:
>
> struct ptrace_rseq_configuration {
>         __u32 size;  /* size of struct ptrace_rseq_configuration */
>         __u32 flags;
>         __u64 rseq_abi_pointer;
>         __u32 signature;
>         __u32 pad;
> };
>
> where:
>
>     .size =3D sizeof(struct ptrace_rseq_configuration),
>
> This way, the configuration structure can be expanded in the future. The
> rseq ABI structure is by definition fixed-size, so there is no point in
> having its size here.
>
> Florian, did I understand your request correctly, or am I missing your po=
int ?

In this case returning sizeof(conf) would serve the same purpose, wouldn't =
it?

Best Regards
Micha=C5=82 Miros=C5=82aw

[Resent because of HTML mail misfeature...]