On Wed, May 23, 2018 at 04:14:39PM -0400, Mathieu Desnoyers wrote: > ----- On May 20, 2018, at 10:08 AM, Boqun Feng boqun.feng@xxxxxxxxx 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@xxxxxxxxx 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 ? Hello, Boqun, You can also request access to a ppc64 environment here: http://osuosl.org/services/powerdev/request_hosting/ Thanx, Paul > 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@xxxxxxxxx> > > --- > > 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 > -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
