On Fri, May 18, 2018 at 02:17:17PM -0400, Mathieu Desnoyers wrote:
> ----- On May 17, 2018, at 7:50 PM, Boqun Feng boqun.f...@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.
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.f...@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
