Re: [RFC PATCH -next V3 3/6] arm64: add support for machine check error safe

[Tong Tiangen]

在 2022/4/12 21:08, Kefeng Wang 写道:
[...]
> > +
> > +bool fixup_exception_mc(struct pt_regs *regs)
> > +{
> > +    const struct exception_table_entry *ex;
> > +
> > +    ex = search_exception_tables(instruction_pointer(regs));
> > +    if (!ex)
> > +        return false;
> > +
> > +    switch (ex->type) {
> > +    case EX_TYPE_UACCESS_MC:
> > +        return ex_handler_fixup(ex, regs);
> > +    }
> > +
> > +    return false;
> > +}
>
> The definition of EX_TYPE_UACCESS_MC is in patch4, please fix it, and if 
> arm64 exception table

ok, will do next version.

> is sorted by exception type, we could drop fixup_exception_mc(), right?

In sort_relative_table_with_data(), it seems sorted by insn and data.

> > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> > index 77341b160aca..56b13cf8bf1d 100644
> > --- a/arch/arm64/mm/fault.c
> > +++ b/arch/arm64/mm/fault.c
> > @@ -695,6 +695,30 @@ static int do_bad(unsigned long far, unsigned int 
> > esr, struct pt_regs *regs)
> >       return 1; /* "fault" */
> >   }
> > +static bool arm64_process_kernel_sea(unsigned long addr, unsigned int 
> > esr,
> > +                     struct pt_regs *regs, int sig, int code)
> > +{
> > +    if (!IS_ENABLED(CONFIG_ARCH_HAS_COPY_MC))
> > +        return false;
> > +
> > +    if (user_mode(regs) || !current->mm)
> > +        return false;
> > +
> > +    if (apei_claim_sea(regs) < 0)
> > +        return false;
> > +
> > +    current->thread.fault_address = 0;
> > +    current->thread.fault_code = esr;
> > +
> Use set_thread_esr(0, esr) and move it after fixup_exception_mc();
> > +    if (!fixup_exception_mc(regs))
> > +        return false;
> > +
> > +    arm64_force_sig_fault(sig, code, addr,
> > +        "Uncorrected hardware memory error in kernel-access\n");
> > +
> > +    return true;
> > +}
> > +
> >   static int do_sea(unsigned long far, unsigned int esr, struct 
> > pt_regs *regs)
> >   {
> >       const struct fault_info *inf;
> > @@ -720,6 +744,10 @@ static int do_sea(unsigned long far, unsigned int 
> > esr, struct pt_regs *regs)
> >            */
> >           siaddr  = untagged_addr(far);
> >       }
> > +
> > +    if (arm64_process_kernel_sea(siaddr, esr, regs, inf->sig, 
> > inf->code))
> > +        return 0;
> > +
>
> Rename arm64_process_kernel_sea() to arm64_do_kernel_sea() 
>
> if (!arm64_do_kernel_sea())
>
>      arm64_notify_die();

Agreed, will do next version.

> >       arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, 
> > esr);
> >       return 0;
> > diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
> > index 546179418ffa..dd952aeecdc1 100644
> > --- a/include/linux/uaccess.h
> > +++ b/include/linux/uaccess.h
> > @@ -174,6 +174,14 @@ copy_mc_to_kernel(void *dst, const void *src, 
> > size_t cnt)
> >   }
> >   #endif
> > +#ifndef copy_mc_to_user
> > +static inline unsigned long __must_check
> > +copy_mc_to_user(void *dst, const void *src, size_t cnt)
> > +{
> Add check_object_size(cnt, src, true);  which could make 
> HARDENED_USERCOPY works.

Agreed, will do next version.

Thanks KeFeng,
Tong.

> > +    return raw_copy_to_user(dst, src, cnt);
> > +}
> > +#endif
> > +
> >   static __always_inline void pagefault_disabled_inc(void)
> >   {
> >       current->pagefault_disabled++;
> .