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

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Date:   Wed, 13 Apr 2022 22:41:23 +0800
From:   Tong Tiangen <tongtiangen@...wei.com>
To:     Kefeng Wang <wangkefeng.wang@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Ingo Molnar" <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Robin Murphy <robin.murphy@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Catalin Marinas" <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        "Alexander Viro" <viro@...iv.linux.org.uk>, <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        Xie XiuQi <xiexiuqi@...wei.com>
Subject: Re: [RFC PATCH -next V3 3/6] arm64: add support for machine check
 error safe



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++;
> .