diff mbox series

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

Message ID 20180602124408.8430-10-mathieu.desnoyers@efficios.com (mailing list archive)
State Not Applicable
Headers show
Series None | expand

Commit Message

Mathieu Desnoyers June 2, 2018, 12:44 p.m. UTC 
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(+)

Comments

Michael Ellerman June 5, 2018, 5:21 a.m. UTC | #1 
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
Mathieu Desnoyers June 5, 2018, 12:50 p.m. UTC | #2 
----- 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
diff mbox series

Patch

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)