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Re: [PATCH 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v10)
- From: Florian Weimer <fweimer at redhat dot com>
- To: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- Cc: carlos <carlos at redhat dot com>, Joseph Myers <joseph at codesourcery dot com>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, libc-alpha <libc-alpha at sourceware dot org>, Thomas Gleixner <tglx at linutronix dot de>, Ben Maurer <bmaurer at fb dot com>, Peter Zijlstra <peterz at infradead dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>, Boqun Feng <boqun dot feng at gmail dot com>, Will Deacon <will dot deacon at arm dot com>, Dave Watson <davejwatson at fb dot com>, Paul Turner <pjt at google dot com>, Rich Felker <dalias at libc dot org>, linux-kernel <linux-kernel at vger dot kernel dot org>, linux-api <linux-api at vger dot kernel dot org>
- Date: Fri, 14 Jun 2019 12:06:45 +0200
- Subject: Re: [PATCH 1/5] glibc: Perform rseq(2) registration at C startup and thread creation (v10)
- References: <20190503184219.19266-1-mathieu.desnoyers@efficios.com> <87muj2k4ov.fsf@oldenburg2.str.redhat.com> <1528929896.22217.1559326257155.JavaMail.zimbra@efficios.com> <87o93d4lqb.fsf@oldenburg2.str.redhat.com> <117220011.27079.1559663870037.JavaMail.zimbra@efficios.com> <87wohzorj0.fsf@oldenburg2.str.redhat.com> <c16c9785-7f8c-430b-a4df-a53e47bf1600@redhat.com> <914051741.43025.1560348011775.JavaMail.zimbra@efficios.com> <802638054.3032.1560506584705.JavaMail.zimbra@efficios.com>
* Mathieu Desnoyers:
> ----- On Jun 12, 2019, at 4:00 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.com wrote:
>
>> ----- On Jun 10, 2019, at 4:43 PM, carlos carlos@redhat.com wrote:
>>
>>> On 6/6/19 7:57 AM, Florian Weimer wrote:
>>>> Let me ask the key question again: Does it matter if code observes the
>>>> rseq area first without kernel support, and then with kernel support?
>>>> If we don't expect any problems immediately, we do not need to worry
>>>> much about the constructor ordering right now. I expect that over time,
>>>> fixing this properly will become easier.
>>>
>>> I just wanted to chime in and say that splitting this into:
>>>
>>> * Ownership (__rseq_handled)
>>>
>>> * Initialization (__rseq_abi)
>>>
>>> Makes sense to me.
>>>
>>> I agree we need an answer to this question of ownership but not yet
>>> initialized, to owned and initialized.
>>>
>>> I like the idea of having __rseq_handled in ld.so.
>>
>> Very good, so I'll implement this approach. Sorry for the delayed
>> feedback, I am traveling this week.
>
> I had issues with cases where application or LD_PRELOAD library also
> define the __rseq_handled symbol. They appear not to see the same
> address as the one initialized by ld.so.
What exactly did you do? How did you determine the addresses? How is
__rseq_handled defined in ld.so?
Thanks,
Florian