From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [PATCH 07/14] powerpc: Add support for restartable sequences
Date: Fri, 18 May 2018 14:17:17 -0400 (EDT)
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To: Boqun Feng <boqun.feng@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>, Peter Zijlstra <peterz@infradead.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Andy Lutomirski <luto@amacapital.net>, Dave Watson <davejwatson@fb.com>, linux-kernel <linux-kernel@vger.kernel.org>, linux-api <linux-api@vger.kernel.org>, Paul Turner <pjt@google.com>, Andrew Morton <akpm@linux-foundation.org>, Russell King <linux@arm.linux.org.uk>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Andrew Hunter <ahh@google.com>, Andi Kleen <andi@firstfloor.org>, Chris Lameter <cl@linux.com>, Ben Maurer <bmaurer@fb.com>, rostedt <rostedt@goodmis.org>, Josh Triplett <josh@joshtriplett.org>, Linus Torvalds <torvalds@linux-foundation.org>, Catalin Marinas <cata>
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----- On May 17, 2018, at 7:50 PM, Boqun Feng boqun.feng@gmail.com wrote:
[...]
>> > I think you're right. So we have to introduce callsite to rseq_syscall()
>> > in syscall path, something like:
>> > 
>> > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
>> > index 51695608c68b..a25734a96640 100644
>> > --- a/arch/powerpc/kernel/entry_64.S
>> > +++ b/arch/powerpc/kernel/entry_64.S
>> > @@ -222,6 +222,9 @@ system_call_exit:
>> > 	mtmsrd	r11,1
>> > #endif /* CONFIG_PPC_BOOK3E */
>> > 
>> > +	addi    r3,r1,STACK_FRAME_OVERHEAD
>> > +	bl	rseq_syscall
>> > +
>> > 	ld	r9,TI_FLAGS(r12)
>> > 	li	r11,-MAX_ERRNO
>> > 	andi.
>> > 		r0,r9,(_TIF_SYSCALL_DOTRACE|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)
>> > 

By the way, I think this is not the right spot to call rseq_syscall, because
interrupts are disabled. I think we should move this hunk right after system_call_exit.

Would you like to implement and test an updated patch adding those calls for ppc 32 and 64 ?

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com