----- On May 16, 2018, at 12:18 PM, Peter Zijlstra peterz@xxxxxxxxxxxxx wrote:
> On Mon, Apr 30, 2018 at 06:44:26PM -0400, Mathieu Desnoyers wrote:
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index c32a181a7cbb..ed21a777e8c6 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -223,6 +223,7 @@ config PPC
>> select HAVE_SYSCALL_TRACEPOINTS
>> select HAVE_VIRT_CPU_ACCOUNTING
>> select HAVE_IRQ_TIME_ACCOUNTING
>> + select HAVE_RSEQ
>> select IRQ_DOMAIN
>> select IRQ_FORCED_THREADING
>> select MODULES_USE_ELF_RELA
>> diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
>> index 61db86ecd318..d3bb3aaaf5ac 100644
>> --- a/arch/powerpc/kernel/signal.c
>> +++ b/arch/powerpc/kernel/signal.c
>> @@ -133,6 +133,8 @@ static void do_signal(struct task_struct *tsk)
>> /* Re-enable the breakpoints for the signal stack */
>> thread_change_pc(tsk, tsk->thread.regs);
>>
>> + rseq_signal_deliver(tsk->thread.regs);
>> +
>> if (is32) {
>> if (ksig.ka.sa.sa_flags & SA_SIGINFO)
>> ret = handle_rt_signal32(&ksig, oldset, tsk);
>> @@ -164,6 +166,7 @@ void do_notify_resume(struct pt_regs *regs, unsigned long
>> thread_info_flags)
>> if (thread_info_flags & _TIF_NOTIFY_RESUME) {
>> clear_thread_flag(TIF_NOTIFY_RESUME);
>> tracehook_notify_resume(regs);
>> + rseq_handle_notify_resume(regs);
>> }
>>
>> user_enter();
>
> Again no rseq_syscall().
Same question for PowerPC as for ARM:
Considering that rseq_syscall is implemented as follows:
+void rseq_syscall(struct pt_regs *regs)
+{
+ unsigned long ip = instruction_pointer(regs);
+ struct task_struct *t = current;
+ struct rseq_cs rseq_cs;
+
+ if (!t->rseq)
+ return;
+ if (!access_ok(VERIFY_READ, t->rseq, sizeof(*t->rseq)) ||
+ rseq_get_rseq_cs(t, &rseq_cs) || in_rseq_cs(ip, &rseq_cs))
+ force_sig(SIGSEGV, t);
+}
and that x86 calls it from syscall_return_slowpath() (which AFAIU is
now used in the fast-path since KPTI), I wonder where we should call
this on PowerPC ? I was under the impression that PowerPC return to
userspace fast-path was not calling C code unless work flags were set,
but I might be wrong.
Thoughts ?
Thanks!
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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