[PATCH v3 1/2] RISC-V: Add support for restartable sequence

[Vincent Chen]

On Thu, Mar 3, 2022 at 12:29 AM Mathieu Desnoyers
<mathieu.desnoyers at efficios.com> wrote:
>
> ----- On Mar 1, 2022, at 9:30 PM, Vincent Chen vincent.chen at sifive.com wrote:
>
> > Add calls to rseq_signal_deliver() and rseq_syscall() to introduce RSEQ
> > support.
> >
> > 1. Call the rseq_signal_deliver() function to fixup on the pre-signal
> >   frame when a signal is delivered on top of a restartable sequence
> >   critical section.
> >
> > 2. Check that system calls are not invoked from within rseq critical
> >   sections by invoking rseq_signal() from ret_from_syscall(). With
> >   CONFIG_DEBUG_RSEQ, such behavior results in termination of the
> >   process with SIGSEGV.
> >
> > Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
>
> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
>
> Will it be picked by by riscv maintainers ?
>
Hi Mathieu,
Thank you very much for reviewing it.
Yes, I hope it can be picked up by riscv maintainers.

Thanks,
Vincent

> Thanks,
>
> Mathieu
>
> > ---
> > arch/riscv/Kconfig         | 1 +
> > arch/riscv/kernel/entry.S  | 4 ++++
> > arch/riscv/kernel/signal.c | 2 ++
> > 3 files changed, 7 insertions(+)
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index 5adcbd9b5e88..67a671b099b6 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -101,6 +101,7 @@ config RISCV
> >       select HAVE_FUNCTION_ARG_ACCESS_API
> >       select HAVE_STACKPROTECTOR
> >       select HAVE_SYSCALL_TRACEPOINTS
> > +     select HAVE_RSEQ
> >       select IRQ_DOMAIN
> >       select IRQ_FORCED_THREADING
> >       select MODULES_USE_ELF_RELA if MODULES
> > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> > index ed29e9c8f660..56ada2a583fa 100644
> > --- a/arch/riscv/kernel/entry.S
> > +++ b/arch/riscv/kernel/entry.S
> > @@ -225,6 +225,10 @@ ret_from_syscall:
> >        * (If it was configured with SECCOMP_RET_ERRNO/TRACE)
> >        */
> > ret_from_syscall_rejected:
> > +#ifdef CONFIG_DEBUG_RSEQ
> > +     move a0, sp
> > +     call rseq_syscall
> > +#endif
> >       /* Trace syscalls, but only if requested by the user. */
> >       REG_L t0, TASK_TI_FLAGS(tp)
> >       andi t0, t0, _TIF_SYSCALL_WORK
> > diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
> > index c2d5ecbe5526..16da3c3b53a1 100644
> > --- a/arch/riscv/kernel/signal.c
> > +++ b/arch/riscv/kernel/signal.c
> > @@ -258,6 +258,8 @@ static void handle_signal(struct ksignal *ksig, struct
> > pt_regs *regs)
> >               }
> >       }
> >
> > +     rseq_signal_deliver(ksig, regs);
> > +
> >       /* Set up the stack frame */
> >       ret = setup_rt_frame(ksig, oldset, regs);
> >
> > --
> > 2.17.1
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com