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From: Michael Ellerman <mpe@ellerman.id.au>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Peter Zijlstra <peterz@infradead.org>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
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Subject: Re: [RFC PATCH for 4.18 09/16] powerpc: Add syscall detection for restartable sequences
In-Reply-To: <20180602124408.8430-10-mathieu.desnoyers@efficios.com>
References: <20180602124408.8430-1-mathieu.desnoyers@efficios.com> <20180602124408.8430-10-mathieu.desnoyers@efficios.com>
Date: Tue, 05 Jun 2018 15:21:28 +1000
Message-ID: <871sdlbyg7.fsf@concordia.ellerman.id.au>
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Mathieu Desnoyers <mathieu.desnoyers@efficios.com> writes:
> From: Boqun Feng <boqun.feng@gmail.com>
>
> Syscalls are not allowed inside restartable sequences, so add a call to
> rseq_syscall() at the very beginning of system call exiting path for
> CONFIG_DEBUG_RSEQ=y kernel. This could help us to detect whether there
> is a syscall issued inside restartable sequences.
>
> [ Tested on 64-bit powerpc kernel by Mathieu Desnoyers. Still needs to
>   be tested on 32-bit powerpc kernel. ]
>
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> CC: Paul Mackerras <paulus@samba.org>
> CC: Michael Ellerman <mpe@ellerman.id.au>
> CC: Peter Zijlstra <peterz@infradead.org>
> CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> CC: linuxppc-dev@lists.ozlabs.org
> ---
>  arch/powerpc/kernel/entry_32.S | 7 +++++++
>  arch/powerpc/kernel/entry_64.S | 8 ++++++++
>  2 files changed, 15 insertions(+)

I don't _love_ the #ifdefs in here, but they look correct and there's
not really a better option until we rewrite the syscall handler in C.

The rseq selftests passed for me with this applied and enabled. So if
you like here's some tags:

Tested-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>

cheers