[PATCH 2/2] riscv: signal: fix signal_minsigstksz

[Yong-Xuan Wang]

Hi Andy,

On Thu, Dec 12, 2024 at 12:17 AM Andy Chiu <andybnac at gmail.com> wrote:
>
> Hi Yong-Xuan,
>
> Yong-Xuan Wang <yongxuan.wang at sifive.com> 於 2024年12月10日 週二 下午10:24寫道：
> >
> > The init_rt_signal_env() funciton is called before the alternative patch
> > is applied, so using the alternative-related API to check the availability
> > of an extension within this function doesn't have the intended effect.
> > Instead, the riscv_isa bitmap should be used to properly check whether
> > given extension is available. This patch also refactors the estimation of
> > signal_minsigstksz by extracting it from the get_rt_frame_size() funciton.
> >
> > Fixes: e92f469b0771 ("riscv: signal: Report signal frame size to userspace via auxv")
> > Signed-off-by: Yong-Xuan Wang <yongxuan.wang at sifive.com>
> > Reviewed-by: Zong Li <zong.li at sifive.com>
> > ---
> >  arch/riscv/kernel/signal.c | 40 ++++++++++++++++++++++++--------------
> >  1 file changed, 25 insertions(+), 15 deletions(-)
> >
> > diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
> > index c3c517b9eee5..85eac84719e9 100644
> > --- a/arch/riscv/kernel/signal.c
> > +++ b/arch/riscv/kernel/signal.c
> > @@ -203,22 +203,18 @@ static long restore_sigcontext(struct pt_regs *regs,
> >         return err;
> >  }
> >
> > -static size_t get_rt_frame_size(bool cal_all)
> > +static size_t get_rt_frame_size(struct pt_regs *regs)
> >  {
> >         struct rt_sigframe __user *frame;
> > -       size_t frame_size;
> > +       size_t frame_size = sizeof(*frame);
> >         size_t total_context_size = 0;
> >
> > -       frame_size = sizeof(*frame);
> > -
> > -       if (has_vector()) {
> > -               if (cal_all || riscv_v_vstate_query(task_pt_regs(current)))
> > -                       total_context_size += riscv_v_sc_size;
> > -       }
> > +       if (has_vector() && riscv_v_vstate_query(regs))
> > +               total_context_size += riscv_v_sc_size;
> >
> >         frame_size += total_context_size;
> > -
> >         frame_size = round_up(frame_size, 16);
> > +
> >         return frame_size;
> >  }
> >
> > @@ -228,7 +224,7 @@ SYSCALL_DEFINE0(rt_sigreturn)
> >         struct rt_sigframe __user *frame;
> >         struct task_struct *task;
> >         sigset_t set;
> > -       size_t frame_size = get_rt_frame_size(false);
> > +       size_t frame_size = get_rt_frame_size(regs);
> >
> >         /* Always make any pending restarted system calls return -EINTR */
> >         current->restart_block.fn = do_no_restart_syscall;
> > @@ -318,7 +314,7 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
> >         struct rt_sigframe __user *frame;
> >         long err = 0;
> >         unsigned long __maybe_unused addr;
> > -       size_t frame_size = get_rt_frame_size(false);
> > +       size_t frame_size = get_rt_frame_size(regs);
> >
> >         frame = get_sigframe(ksig, regs, frame_size);
> >         if (!access_ok(frame, frame_size))
> > @@ -465,19 +461,33 @@ void arch_do_signal_or_restart(struct pt_regs *regs)
> >  void init_rt_signal_env(void);
> >  void __init init_rt_signal_env(void)
> >  {
> > -       riscv_v_sc_size = sizeof(struct __riscv_ctx_hdr) +
> > -                         sizeof(struct __sc_riscv_v_state) + riscv_v_vsize;
> > +       struct rt_sigframe __user *frame;
> > +       size_t frame_size = sizeof(*frame);
> > +
> > +       /*
> > +        * init_rt_signal_env() is called before applying alternative patch. Do not use
> > +        * __riscv_has_extension_likely()/__riscv_has_extension_unlikely() to check the
> > +        * availiablity of an extension in this function.
> > +        */
> > +       if (__riscv_isa_extension_available(NULL, RISCV_ISA_EXT_v)) {
>
> This should also check for IS_ENABLED(CONFIG_RISCV_ISA_V). Another way
> to do this is to call init_rt_signal_env() after
> apply_boot_alternative(). This can make assumptions on different piece
> of code more coherent. What do you think?
>

Reorder the init_rt_signal_env() and apply_boot_alternative() is
better, I will fix it in the next version. Thank you!

Regards,
Yong-Xuan

>
> > +               riscv_v_sc_size = sizeof(struct __riscv_ctx_hdr) +
> > +                                 sizeof(struct __sc_riscv_v_state) + riscv_v_vsize;
> > +               frame_size += riscv_v_sc_size;
> > +       }
> > +
> > +       frame_size = round_up(frame_size, 16);
> > +
> >         /*
> >          * Determine the stack space required for guaranteed signal delivery.
> >          * The signal_minsigstksz will be populated into the AT_MINSIGSTKSZ entry
> >          * in the auxiliary array at process startup.
> >          */
> > -       signal_minsigstksz = get_rt_frame_size(true);
> > +       signal_minsigstksz = frame_size;
> >  }
> >
> >  #ifdef CONFIG_DYNAMIC_SIGFRAME
> >  bool sigaltstack_size_valid(size_t ss_size)
> >  {
> > -       return ss_size > get_rt_frame_size(false);
> > +       return ss_size > get_rt_frame_size(current_pt_regs());
> >  }
> >  #endif /* CONFIG_DYNAMIC_SIGFRAME */
> > --
> > 2.17.1
> >
>
> Thanks,
> Andy