Re: [PATCH] LoongArch: Fix missing fcsr in ptrace's fpr_set

[Qi Hu]

On 2022/7/14 21:12, Huacai Chen wrote:
> Hi,
>
> On Thu, Jul 14, 2022 at 2:26 PM Qi Hu <huqi@xxxxxxxxxxx> wrote:
> > In file ptrace.c, function fpr_set does not copy fcsr data from ubuf
> > to kbuf. That's the reason why fcsr cannot be modified by ptrace.
> >
> > This patch fixs this problem and allows users using ptrace to modify
> > the fcsr.
> >
> > Signed-off-by: Qi Hu <huqi@xxxxxxxxxxx>
> > Signed-off-by: Xu Li <lixu@xxxxxxxxxxx>
> > ---
> >   arch/loongarch/kernel/ptrace.c | 12 +++++++-----
> >   1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/loongarch/kernel/ptrace.c b/arch/loongarch/kernel/ptrace.c
> > index e6ab87948e1d..dc2b82ea894c 100644
> > --- a/arch/loongarch/kernel/ptrace.c
> > +++ b/arch/loongarch/kernel/ptrace.c
> > @@ -193,7 +193,7 @@ static int fpr_set(struct task_struct *target,
> >                     const void *kbuf, const void __user *ubuf)
> >   {
> >          const int fcc_start = NUM_FPU_REGS * sizeof(elf_fpreg_t);
> > -       const int fcc_end = fcc_start + sizeof(u64);
> > +       const int fcsr_start = fcc_start + sizeof(u64);
> >          int err;
> >
> >          BUG_ON(count % sizeof(elf_fpreg_t));
> > @@ -209,10 +209,12 @@ static int fpr_set(struct task_struct *target,
> >          if (err)
> >                  return err;
> >
> > -       if (count > 0)
> > -               err |= user_regset_copyin(&pos, &count, &kbuf, &ubuf,
> > -                                         &target->thread.fpu.fcc,
> > -                                         fcc_start, fcc_end);
> > +       err |= user_regset_copyin(&pos, &count, &kbuf, &ubuf,
> > +                                 &target->thread.fpu.fcc, fcc_start,
> > +                                 fcc_start + sizeof(u64));
> > +       err |= user_regset_copyin(&pos, &count, &kbuf, &ubuf,
> > +                                 &target->thread.fpu.fcsr, fcsr_start,
> > +                                 fcsr_start + sizeof(u32));
> You shouldn't remove (count > 0) here, because  the above
> user_regset_copyin() will modify count inside, and so "count == 0" is
> possible.
>
> Huacai

Yes, the "count" should be considered. But the "count" is checked at the 
beginning of the "user_regset_copyin()".

So "count > 0" is useless, i think.

Also like riscv, "count" is not checked in "riscv_fpr_set()".

> >          return err;
> >   }
> > --
> > 2.37.0