Messages in this thread Patch in this message | | | Date | Wed, 16 May 2018 16:13:13 -0400 (EDT) | From | Mathieu Desnoyers <> | Subject | Re: [PATCH 03/14] arm: Add restartable sequences support |
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----- On May 16, 2018, at 12:18 PM, Peter Zijlstra peterz@infradead.org wrote:
> On Mon, Apr 30, 2018 at 06:44:22PM -0400, Mathieu Desnoyers wrote: >> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig >> index a7f8e7f4b88f..4f5c386631d4 100644 >> --- a/arch/arm/Kconfig >> +++ b/arch/arm/Kconfig >> @@ -91,6 +91,7 @@ config ARM >> select HAVE_PERF_USER_STACK_DUMP >> select HAVE_RCU_TABLE_FREE if (SMP && ARM_LPAE) >> select HAVE_REGS_AND_STACK_ACCESS_API >> + select HAVE_RSEQ >> select HAVE_SYSCALL_TRACEPOINTS >> select HAVE_UID16 >> select HAVE_VIRT_CPU_ACCOUNTING_GEN >> diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c >> index bd8810d4acb3..5879ab3f53c1 100644 >> --- a/arch/arm/kernel/signal.c >> +++ b/arch/arm/kernel/signal.c >> @@ -541,6 +541,12 @@ static void handle_signal(struct ksignal *ksig, struct >> pt_regs *regs) >> int ret; >> >> /* >> + * Increment event counter and perform fixup for the pre-signal >> + * frame. >> + */ >> + rseq_signal_deliver(regs); >> + >> + /* >> * Set up the stack frame >> */ >> if (ksig->ka.sa.sa_flags & SA_SIGINFO) >> @@ -660,6 +666,7 @@ do_work_pending(struct pt_regs *regs, unsigned int >> thread_flags, int syscall) >> } else { >> clear_thread_flag(TIF_NOTIFY_RESUME); >> tracehook_notify_resume(regs); >> + rseq_handle_notify_resume(regs); >> } >> } >> local_irq_disable(); > > I think you forgot to hook up rseq_syscall() checking.
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 ARM ? I was under the impression that ARM 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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