From: Carlos O'Donell <codonell@redhat.com>
To: Tulio Magno Quites Machado Filho <tuliom@ascii.art.br>,
Florian Weimer <fweimer@redhat.com>,
Michael Meissner <meissner@linux.ibm.com>,
Alan Modra <amodra@gmail.com>,
Peter Bergner <bergner@vnet.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Paul Burton <paul.burton@mips.com>,
Will Deacon <will.deacon@arm.com>,
Boqun Feng <boqun.feng@gmail.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Russell King <linux@armlinux.org.uk>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>, carlos <carlos@redhat.com>,
Joseph Myers <joseph@codesourcery.com>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
libc-alpha <libc-alpha@sourceware.org>,
Thomas Gleixner <tglx@linutronix.de>, Ben Maurer <bmaurer@fb.com>,
Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Dave Watson <davejwatson@fb.com>, Paul Turner <pjt@google.com>,
Rich Felker <dalias@libc.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-api <linux-api@vger.kernel.org>
Subject: Re: [PATCH 1/4] glibc: Perform rseq(2) registration at C startup and thread creation (v7)
Date: Mon, 8 Apr 2019 17:45:41 -0400 [thread overview]
Message-ID: <ce9fbc66-5eb9-0fa9-99fa-5abfe00ddfc2@redhat.com> (raw)
In-Reply-To: <877ec4pam2.fsf@linux.ibm.com>
On 4/8/19 3:20 PM, Tulio Magno Quites Machado Filho wrote:
> Carlos O'Donell <codonell@redhat.com> writes:
>
>> On 4/5/19 5:16 AM, Florian Weimer wrote:
>>> * Carlos O'Donell:
>>>> It is valuable that it be a trap, particularly for constant pools because
>>>> it means that a jump into the constant pool will trap.
>>>
>>> Sorry, I don't understand why this matters in this context. Would you
>>> please elaborate?
>>
>> Sorry, I wasn't very clear.
>>
>> My point is only that any accidental jumps, either with off-by-one (like you
>> fixed in gcc/glibc's signal unwinding most recently), result in a process fault
>> rather than executing RSEQ_SIG as a valid instruction *and then* continuing
>> onwards to the handler.
>>
>> A process fault is achieved either by a trap, or an invalid instruction, or
>> a privileged insn (like suggested for MIPS in this thread).
>
> In that case, mtmsr (Move to Machine State Register) seems a good candidate.
>
> mtmsr is available both on 32 and 64 bits since their first implementations.
>
> It's a privileged instruction and should never appear in userspace
> code (causes SIGILL).
>
> Any comments?
That seems good to me.
Mathieu,
What's required to move this forward for POWER?
--
Cheers,
Carlos.
next prev parent reply other threads:[~2019-04-08 21:45 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190212194253.1951-1-mathieu.desnoyers@efficios.com>
2019-02-12 19:42 ` [PATCH 1/4] glibc: Perform rseq(2) registration at C startup and thread creation (v7) Mathieu Desnoyers
2019-03-22 20:09 ` Carlos O'Donell
2019-03-25 15:54 ` Mathieu Desnoyers
2019-03-27 9:16 ` Martin Schwidefsky
2019-03-27 20:01 ` Mathieu Desnoyers
2019-03-27 20:38 ` Carlos O'Donell
2019-03-28 7:49 ` Martin Schwidefsky
2019-03-28 15:42 ` Mathieu Desnoyers
2019-04-02 6:02 ` Michael Ellerman
2019-04-02 7:08 ` Florian Weimer
2019-04-04 20:32 ` Carlos O'Donell
2019-04-05 9:16 ` Florian Weimer
2019-04-05 15:40 ` Carlos O'Donell
2019-04-08 19:20 ` Tulio Magno Quites Machado Filho
2019-04-08 21:45 ` Carlos O'Donell [this message]
2019-04-09 4:23 ` Michael Ellerman
2019-04-09 9:29 ` Alan Modra
[not found] ` <871s2bp9f9.fsf@linux.ibm.com>
2019-04-09 14:13 ` Carlos O'Donell
2019-04-09 15:45 ` Mathieu Desnoyers
2019-04-18 15:31 ` Mathieu Desnoyers
2019-04-09 16:33 ` Mathieu Desnoyers
2019-04-04 20:15 ` Carlos O'Donell
2019-04-04 20:50 ` Carlos O'Donell
2019-04-04 21:41 ` Paul Burton
2019-04-09 16:40 ` Mathieu Desnoyers
2019-04-18 18:58 ` Mathieu Desnoyers
2019-04-24 15:05 ` Mathieu Desnoyers
2019-04-24 23:13 ` Paul Burton
2019-04-25 0:41 ` Maciej W. Rozycki
2019-02-12 19:42 ` [PATCH 2/4] glibc: sched_getcpu(): use rseq cpu_id TLS on Linux Mathieu Desnoyers
2019-03-22 20:13 ` Carlos O'Donell
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