From: Will Deacon <will.deacon@arm.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Boqun Feng <boqun.feng@gmail.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>
Subject: Re: [PATCH 03/14] arm: Add restartable sequences support
Date: Thu, 17 May 2018 14:32:31 +0100 [thread overview]
Message-ID: <20180517133230.GA2688@arm.com> (raw)
In-Reply-To: <670368504.1912.1526501593893.JavaMail.zimbra@efficios.com>
On Wed, May 16, 2018 at 04:13:13PM -0400, Mathieu Desnoyers wrote:
> ----- On May 16, 2018, at 12:18 PM, Peter Zijlstra peterz@infradead.org wrote:
>
> > On Mon, Apr 30, 2018 at 06:44:22PM -0400, Mathieu Desnoyers wrote:
> >> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> >> index a7f8e7f4b88f..4f5c386631d4 100644
> >> --- a/arch/arm/Kconfig
> >> +++ b/arch/arm/Kconfig
> >> @@ -91,6 +91,7 @@ config ARM
> >> select HAVE_PERF_USER_STACK_DUMP
> >> select HAVE_RCU_TABLE_FREE if (SMP && ARM_LPAE)
> >> select HAVE_REGS_AND_STACK_ACCESS_API
> >> + select HAVE_RSEQ
> >> select HAVE_SYSCALL_TRACEPOINTS
> >> select HAVE_UID16
> >> select HAVE_VIRT_CPU_ACCOUNTING_GEN
> >> diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
> >> index bd8810d4acb3..5879ab3f53c1 100644
> >> --- a/arch/arm/kernel/signal.c
> >> +++ b/arch/arm/kernel/signal.c
> >> @@ -541,6 +541,12 @@ static void handle_signal(struct ksignal *ksig, struct
> >> pt_regs *regs)
> >> int ret;
> >>
> >> /*
> >> + * Increment event counter and perform fixup for the pre-signal
> >> + * frame.
> >> + */
> >> + rseq_signal_deliver(regs);
> >> +
> >> + /*
> >> * Set up the stack frame
> >> */
> >> if (ksig->ka.sa.sa_flags & SA_SIGINFO)
> >> @@ -660,6 +666,7 @@ do_work_pending(struct pt_regs *regs, unsigned int
> >> thread_flags, int syscall)
> >> } else {
> >> clear_thread_flag(TIF_NOTIFY_RESUME);
> >> tracehook_notify_resume(regs);
> >> + rseq_handle_notify_resume(regs);
> >> }
> >> }
> >> local_irq_disable();
> >
> > I think you forgot to hook up rseq_syscall() checking.
>
> Considering that rseq_syscall is implemented as follows:
>
> +void rseq_syscall(struct pt_regs *regs)
> +{
> + unsigned long ip = instruction_pointer(regs);
> + struct task_struct *t = current;
> + struct rseq_cs rseq_cs;
> +
> + if (!t->rseq)
> + return;
> + if (!access_ok(VERIFY_READ, t->rseq, sizeof(*t->rseq)) ||
> + rseq_get_rseq_cs(t, &rseq_cs) || in_rseq_cs(ip, &rseq_cs))
> + force_sig(SIGSEGV, t);
> +}
>
> and that x86 calls it from syscall_return_slowpath() (which AFAIU is
> now used in the fast-path since KPTI), I wonder where we should call
> this on ARM ? I was under the impression that ARM return to userspace
> fast-path was not calling C code unless work flags were set, but I might
> be wrong.
>
> Thoughts ?
Since this only matters for CONFIG_DEBUG_RSEQ, can we just force the
slowpath for rseq tasks when that option is set?
Will
next prev parent reply other threads:[~2018-05-17 13:32 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-30 22:44 [RFC PATCH for 4.18 00/14] Restartable Sequences Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 01/14] uapi headers: Provide types_32_64.h (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 02/14] rseq: Introduce restartable sequences system call (v13) Mathieu Desnoyers
2018-05-16 16:24 ` Peter Zijlstra
2018-05-16 20:18 ` Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 03/14] arm: Add restartable sequences support Mathieu Desnoyers
2018-05-16 16:18 ` Peter Zijlstra
2018-05-16 20:13 ` Mathieu Desnoyers
2018-05-17 13:32 ` Will Deacon [this message]
2018-05-17 15:30 ` Mathieu Desnoyers
2018-05-22 18:19 ` Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 04/14] arm: Wire up restartable sequences system call Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 05/14] x86: Add support for restartable sequences (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 06/14] x86: Wire up restartable sequence system call Mathieu Desnoyers
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
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
2018-04-30 22:44 ` [PATCH 09/14] selftests: lib.mk: Introduce OVERRIDE_TARGETS Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 10/14] rseq: selftests: Provide rseq library (v5) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 11/14] rseq: selftests: Provide basic test Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 12/14] rseq: selftests: Provide basic percpu ops test (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 13/14] rseq: selftests: Provide parametrized tests (v2) Mathieu Desnoyers
2018-04-30 22:44 ` [PATCH 14/14] rseq: selftests: Provide Makefile, scripts, gitignore (v2) Mathieu Desnoyers
2018-05-02 3:53 ` [RFC PATCH for 4.18 00/14] Restartable Sequences Daniel Colascione
2018-05-02 8:43 ` Peter Zijlstra
2018-05-02 16:03 ` Mathieu Desnoyers
2018-05-02 16:07 ` Daniel Colascione
2018-05-02 16:42 ` Steven Rostedt
2018-05-02 16:55 ` Daniel Colascione
2018-05-03 16:12 ` Mathieu Desnoyers
2018-05-03 16:22 ` Daniel Colascione
2018-05-03 18:04 ` Mathieu Desnoyers
2018-05-03 16:48 ` Joel Fernandes
2018-05-03 17:18 ` Daniel Colascione
2018-05-03 17:46 ` Joel Fernandes
2018-05-04 22:17 ` Ben Maurer
2018-05-02 17:22 ` Peter Zijlstra
2018-05-02 18:27 ` Daniel Colascione
2018-05-02 20:22 ` Peter Zijlstra
2018-05-02 20:37 ` Daniel Colascione
2018-05-03 1:15 ` Steven Rostedt
2018-05-03 8:49 ` Peter Zijlstra
2018-05-06 10:03 ` Thomas Gleixner
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