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. 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 -- 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
