From: Mathieu Desnoyers <mathieu.desnoyers@efficios•com>
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 <catalin.marinas@arm•com>,
Michael Kerrisk <mtk.manpages@gmail•com>,
Joel Fernandes <joelaf@google•com>,
Benjamin Herrenschmidt <benh@kernel•crashing.org>,
Paul Mackerras <paulus@samba•org>,
Michael Ellerman <mpe@ellerman•id.au>,
linuxppc-dev <linuxppc-dev@lists•ozlabs.org>
Subject: Re: [PATCH 07/14] powerpc: Add support for restartable sequences
Date: Wed, 23 May 2018 16:14:39 -0400 (EDT) [thread overview]
Message-ID: <1928158599.1541.1527106479862.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20180520140811.GB1121@tardis>
----- On May 20, 2018, at 10:08 AM, Boqun Feng boqun.feng@gmail•com wrote:
> On Fri, May 18, 2018 at 02:17:17PM -0400, Mathieu Desnoyers wrote:
>> ----- 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.
>>
>
> Good point.
>
>> Would you like to implement and test an updated patch adding those calls for ppc
>> 32 and 64 ?
>>
>
> I'd like to help, but I don't have a handy ppc environment for test...
> So I made the below patch which has only been build-tested, hope it
> could be somewhat helpful.
Hi Boqun,
I tried your patch in a ppc64 le environment, and it does not survive boot
with CONFIG_DEBUG_RSEQ=y. init gets killed right away.
Moreover, I'm not sure that the r3 register don't contain something worth
saving before the call on ppc32. Just after there is a "mr" instruction
which AFAIU takes r3 as input register.
Can you look into it ?
Thanks,
Mathieu
>
> Regards,
> Boqun
>
> --------------------------------->8
> Subject: [PATCH] powerpc: Add syscall detection for restartable sequences
>
> 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.
>
> Signed-off-by: Boqun Feng <boqun.feng@gmail•com>
> ---
> arch/powerpc/kernel/entry_32.S | 5 +++++
> arch/powerpc/kernel/entry_64.S | 5 +++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index eb8d01bae8c6..2f134eebe7ed 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -365,6 +365,11 @@ syscall_dotrace_cont:
> blrl /* Call handler */
> .globl ret_from_syscall
> ret_from_syscall:
> +#ifdef CONFIG_DEBUG_RSEQ
> + /* Check whether the syscall is issued inside a restartable sequence */
> + addi r3,r1,STACK_FRAME_OVERHEAD
> + bl rseq_syscall
> +#endif
> mr r6,r3
> CURRENT_THREAD_INFO(r12, r1)
> /* disable interrupts so current_thread_info()->flags can't change */
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 2cb5109a7ea3..2e2d59bb45d0 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -204,6 +204,11 @@ system_call: /* label this so stack traces look sane */
> * This is blacklisted from kprobes further below with _ASM_NOKPROBE_SYMBOL().
> */
> system_call_exit:
> +#ifdef CONFIG_DEBUG_RSEQ
> + /* Check whether the syscall is issued inside a restartable sequence */
> + addi r3,r1,STACK_FRAME_OVERHEAD
> + bl rseq_syscall
> +#endif
> /*
> * Disable interrupts so current_thread_info()->flags can't change,
> * and so that we don't get interrupted after loading SRR0/1.
> --
> 2.16.2
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2018-05-23 20:14 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20180430224433.17407-1-mathieu.desnoyers@efficios.com>
2018-04-30 22:44 ` [PATCH 07/14] powerpc: Add support for restartable sequences Mathieu Desnoyers
2018-05-16 16:18 ` Peter Zijlstra
2018-05-16 20:13 ` Mathieu Desnoyers
2018-05-17 1:19 ` Boqun Feng
2018-05-17 7:43 ` Peter Zijlstra
2018-05-17 15:28 ` Mathieu Desnoyers
2018-05-17 23:50 ` Boqun Feng
2018-05-18 18:17 ` Mathieu Desnoyers
2018-05-20 14:08 ` Boqun Feng
2018-05-23 20:14 ` Mathieu Desnoyers [this message]
2018-05-23 20:46 ` Paul E. McKenney
2018-05-23 21:29 ` Mathieu Desnoyers
2018-05-24 1:03 ` Michael Ellerman
2018-05-28 7:00 ` Mathieu Desnoyers
2018-05-18 12:38 ` Michael Ellerman
2018-04-30 22:44 ` [PATCH 08/14] powerpc: Wire up restartable sequences system call Mathieu Desnoyers
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1928158599.1541.1527106479862.JavaMail.zimbra@efficios.com \
--to=mathieu.desnoyers@efficios$(echo .)com \
--cc=ahh@google$(echo .)com \
--cc=akpm@linux-foundation$(echo .)org \
--cc=andi@firstfloor$(echo .)org \
--cc=benh@kernel$(echo .)crashing.org \
--cc=bmaurer@fb$(echo .)com \
--cc=boqun.feng@gmail$(echo .)com \
--cc=catalin.marinas@arm$(echo .)com \
--cc=cl@linux$(echo .)com \
--cc=davejwatson@fb$(echo .)com \
--cc=hpa@zytor$(echo .)com \
--cc=joelaf@google$(echo .)com \
--cc=josh@joshtriplett$(echo .)org \
--cc=linux-api@vger$(echo .)kernel.org \
--cc=linux-kernel@vger$(echo .)kernel.org \
--cc=linux@arm$(echo .)linux.org.uk \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
--cc=luto@amacapital$(echo .)net \
--cc=mingo@redhat$(echo .)com \
--cc=mpe@ellerman$(echo .)id.au \
--cc=mtk.manpages@gmail$(echo .)com \
--cc=paulmck@linux$(echo .)vnet.ibm.com \
--cc=paulus@samba$(echo .)org \
--cc=peterz@infradead$(echo .)org \
--cc=pjt@google$(echo .)com \
--cc=rostedt@goodmis$(echo .)org \
--cc=tglx@linutronix$(echo .)de \
--cc=torvalds@linux-foundation$(echo .)org \
--cc=will.deacon@arm$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox