----- On May 20, 2018, at 10:08 AM, Boqun Feng boqun.f...@gmail.com 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.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.
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 ? 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.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 -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com
