[RFC PATCH for 4.18 08/16] powerpc: Add support for restartable sequences

[RFC PATCH for 4.18 08/16] powerpc: Add support for restartable sequences

[Mathieu Desnoyers]

From: Boqun Feng <boqun.feng@gmail.com>

Call the rseq_handle_notify_resume() function on return to userspace if
TIF_NOTIFY_RESUME thread flag is set.

Perform fixup on the pre-signal when a signal is delivered on top of a
restartable sequence critical section.

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/Kconfig         | 1 +
 arch/powerpc/kernel/signal.c | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c32a181a7cbb..ed21a777e8c6 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -223,6 +223,7 @@ config PPC
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_VIRT_CPU_ACCOUNTING
 	select HAVE_IRQ_TIME_ACCOUNTING
+	select HAVE_RSEQ
 	select IRQ_DOMAIN
 	select IRQ_FORCED_THREADING
 	select MODULES_USE_ELF_RELA
diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
index 61db86ecd318..d3bb3aaaf5ac 100644
--- a/arch/powerpc/kernel/signal.c
+++ b/arch/powerpc/kernel/signal.c
@@ -133,6 +133,8 @@ static void do_signal(struct task_struct *tsk)
 	/* Re-enable the breakpoints for the signal stack */
 	thread_change_pc(tsk, tsk->thread.regs);
 
+	rseq_signal_deliver(tsk->thread.regs);
+
 	if (is32) {
         	if (ksig.ka.sa.sa_flags & SA_SIGINFO)
 			ret = handle_rt_signal32(&ksig, oldset, tsk);
@@ -164,6 +166,7 @@ void do_notify_resume(struct pt_regs *regs, unsigned long thread_info_flags)
 	if (thread_info_flags & _TIF_NOTIFY_RESUME) {
 		clear_thread_flag(TIF_NOTIFY_RESUME);
 		tracehook_notify_resume(regs);
+		rseq_handle_notify_resume(regs);
 	}
 
 	user_enter();
-- 
2.11.0

[RFC PATCH for 4.18 09/16] powerpc: Add syscall detection for restartable sequences

[Mathieu Desnoyers]

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(+)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index eb8d01bae8c6..973577f2141c 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -365,6 +365,13 @@ 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 */
+	stw	r3,GPR3(r1)
+	addi    r3,r1,STACK_FRAME_OVERHEAD
+	bl      rseq_syscall
+	lwz	r3,GPR3(r1)
+#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 51695608c68b..1c374387656a 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -184,6 +184,14 @@ system_call:			/* label this so stack traces look sane */
 
 .Lsyscall_exit:
 	std	r3,RESULT(r1)
+
+#ifdef CONFIG_DEBUG_RSEQ
+	/* Check whether the syscall is issued inside a restartable sequence */
+	addi    r3,r1,STACK_FRAME_OVERHEAD
+	bl      rseq_syscall
+	ld	r3,RESULT(r1)
+#endif
+
 	CURRENT_THREAD_INFO(r12, r1)
 
 	ld	r8,_MSR(r1)
-- 
2.11.0

[RFC PATCH for 4.18 10/16] powerpc: Wire up restartable sequences system call

[Mathieu Desnoyers]

From: Boqun Feng <boqun.feng@gmail.com>

Wire up the rseq system call on powerpc.

This provides an ABI improving the speed of a user-space getcpu
operation on powerpc by skipping the getcpu system call on the fast
path, as well as improving the speed of user-space operations on per-cpu
data compared to using load-reservation/store-conditional atomics.

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/include/asm/systbl.h      | 1 +
 arch/powerpc/include/asm/unistd.h      | 2 +-
 arch/powerpc/include/uapi/asm/unistd.h | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/systbl.h b/arch/powerpc/include/asm/systbl.h
index d61f9c96d916..45d4d37495fd 100644
--- a/arch/powerpc/include/asm/systbl.h
+++ b/arch/powerpc/include/asm/systbl.h
@@ -392,3 +392,4 @@ SYSCALL(statx)
 SYSCALL(pkey_alloc)
 SYSCALL(pkey_free)
 SYSCALL(pkey_mprotect)
+SYSCALL(rseq)
diff --git a/arch/powerpc/include/asm/unistd.h b/arch/powerpc/include/asm/unistd.h
index daf1ba97a00c..1e9708632dce 100644
--- a/arch/powerpc/include/asm/unistd.h
+++ b/arch/powerpc/include/asm/unistd.h
@@ -12,7 +12,7 @@
 #include <uapi/asm/unistd.h>
 
 
-#define NR_syscalls		387
+#define NR_syscalls		388
 
 #define __NR__exit __NR_exit
 
diff --git a/arch/powerpc/include/uapi/asm/unistd.h b/arch/powerpc/include/uapi/asm/unistd.h
index 389c36fd8299..ac5ba55066dd 100644
--- a/arch/powerpc/include/uapi/asm/unistd.h
+++ b/arch/powerpc/include/uapi/asm/unistd.h
@@ -398,5 +398,6 @@
 #define __NR_pkey_alloc		384
 #define __NR_pkey_free		385
 #define __NR_pkey_mprotect	386
+#define __NR_rseq		387
 
 #endif /* _UAPI_ASM_POWERPC_UNISTD_H_ */
-- 
2.11.0

Re: [RFC PATCH for 4.18 10/16] powerpc: Wire up restartable sequences system call

[Michael Ellerman]

Mathieu Desnoyers <mathieu.desnoyers@efficios.com> writes:

> From: Boqun Feng <boqun.feng@gmail.com>
>
> Wire up the rseq system call on powerpc.
>
> This provides an ABI improving the speed of a user-space getcpu
> operation on powerpc by skipping the getcpu system call on the fast
> path, as well as improving the speed of user-space operations on per-cpu
> data compared to using load-reservation/store-conditional atomics.
>
> 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/include/asm/systbl.h      | 1 +
>  arch/powerpc/include/asm/unistd.h      | 2 +-
>  arch/powerpc/include/uapi/asm/unistd.h | 1 +
>  3 files changed, 3 insertions(+), 1 deletion(-)

Looks fine to me.

I don't have any other new syscalls in my next, so this should not
conflict with anything for 4.18.

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)


cheers

Re: [RFC PATCH for 4.18 09/16] powerpc: Add syscall detection for restartable sequences

[Michael Ellerman]

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

Re: [RFC PATCH for 4.18 09/16] powerpc: Add syscall detection for restartable sequences

[Mathieu Desnoyers]

----- On Jun 5, 2018, at 1:21 AM, Michael Ellerman mpe@ellerman.id.au wrote:

> 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>
> 

Adding you ack to the series.

Thanks!

Mathieu

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

Re: [RFC PATCH for 4.18 10/16] powerpc: Wire up restartable sequences system call

[Mathieu Desnoyers]

----- On Jun 5, 2018, at 1:18 AM, Michael Ellerman mpe@ellerman.id.au wrote:

> Mathieu Desnoyers <mathieu.desnoyers@efficios.com> writes:
> 
>> From: Boqun Feng <boqun.feng@gmail.com>
>>
>> Wire up the rseq system call on powerpc.
>>
>> This provides an ABI improving the speed of a user-space getcpu
>> operation on powerpc by skipping the getcpu system call on the fast
>> path, as well as improving the speed of user-space operations on per-cpu
>> data compared to using load-reservation/store-conditional atomics.
>>
>> 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/include/asm/systbl.h      | 1 +
>>  arch/powerpc/include/asm/unistd.h      | 2 +-
>>  arch/powerpc/include/uapi/asm/unistd.h | 1 +
>>  3 files changed, 3 insertions(+), 1 deletion(-)
> 
> Looks fine to me.
> 
> I don't have any other new syscalls in my next, so this should not
> conflict with anything for 4.18.
> 
> Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

Added your ack to the series, thanks!

Mathieu

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