From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Piotr Figiel <figiel@google.com>
Cc: 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>, emmir <emmir@google.com>,
linux-man <linux-man@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>
Subject: Re: [PATCH v2] ptrace: add PTRACE_GET_RSEQ_CONFIGURATION request
Date: Wed, 3 Mar 2021 13:55:39 -0500 (EST) [thread overview]
Message-ID: <1647666880.9529.1614797739047.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <YDkchUnCe5ctDwYB@google.com>
----- On Feb 26, 2021, at 11:06 AM, Piotr Figiel figiel@google.com wrote:
> Hi,
>
> On Fri, Feb 26, 2021 at 10:32:35AM -0500, Mathieu Desnoyers wrote:
>> > +static long ptrace_get_rseq_configuration(struct task_struct *task,
>> > + unsigned long size, void __user *data)
>> > +{
>> > + struct ptrace_rseq_configuration conf = {
>> > + .rseq_abi_pointer = (u64)(uintptr_t)task->rseq,
>> > + .rseq_abi_size = sizeof(*task->rseq),
>> > + .signature = task->rseq_sig,
>> > + .flags = 0,
>> > + };
>> > +
>> > + size = 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 = 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.
>
> Still rseq syscall accepts the rseq ABI structure size as a paremeter.
> I think this way the information returned from ptrace is consistent with
> the userspace view of the rseq state and allows expansion in case the
> ABI structure would have to be extended (in spite of it's current
> definition).
>
> The configuration structure still can be expanded as its size is
> reported to userspace as return value from the request (in line with
> Dmitry's comments).
Fair enough. And now with the reply from Florian I see that I misunderstood his
point.
Thanks,
Mathieu
>
> Best regards, Piotr.
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2021-03-03 20:59 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-26 13:51 [PATCH v2] ptrace: add PTRACE_GET_RSEQ_CONFIGURATION request Piotr Figiel
2021-02-26 15:32 ` Mathieu Desnoyers
2021-02-26 16:04 ` Michał Mirosław
2021-02-26 16:41 ` Mathieu Desnoyers
2021-02-26 16:06 ` Piotr Figiel
2021-03-03 18:55 ` Mathieu Desnoyers [this message]
2021-03-03 17:10 ` Florian Weimer
2021-03-10 18:50 ` Oleg Nesterov
2021-03-11 14:51 ` Mathieu Desnoyers
2021-03-11 16:51 ` Peter Zijlstra
2021-03-11 17:24 ` Mathieu Desnoyers
2021-03-17 13:13 ` [tip: sched/core] rseq, ptrace: Add " tip-bot2 for Piotr Figiel
2021-03-17 15:19 ` tip-bot2 for Piotr Figiel
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