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Message-ID: <b12c9088-f86c-60a2-6cf8-54823867e8fd@huawei.com>
Date: Thu, 19 May 2022 15:09:23 +0800
From: Tong Tiangen <tongtiangen@...wei.com>
To: Mark Rutland <mark.rutland@....com>
CC: 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>,
Michael Ellerman <mpe@...erman.id.au>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>, <x86@...nel.org>,
"H . Peter Anvin" <hpa@...or.com>, <linuxppc-dev@...ts.ozlabs.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
Kefeng Wang <wangkefeng.wang@...wei.com>,
Xie XiuQi <xiexiuqi@...wei.com>,
Guohanjun <guohanjun@...wei.com>
Subject: Re: [PATCH -next v4 6/7] arm64: add {get, put}_user to machine check
safe
在 2022/5/13 23:39, Mark Rutland 写道:
> On Wed, Apr 20, 2022 at 03:04:17AM +0000, Tong Tiangen wrote:
>> Add {get, put}_user() to machine check safe.
>>
>> If get/put fail due to hardware memory error, only the relevant processes
>> are affected, so killing the user process and isolate the user page with
>> hardware memory errors is a more reasonable choice than kernel panic.
>>
>> Add new extable type EX_TYPE_UACCESS_MC_ERR_ZERO which can be used for
>> uaccess that can be recovered from hardware memory errors. The difference
>> from EX_TYPE_UACCESS_MC is that this type also sets additional two target
>> register which save error code and value needs to be set zero.
>
> Why does this need to be in any way distinct from the existing
> EX_TYPE_UACCESS_ERR_ZERO ?
>
> Other than the case where we currently (ab)use that for
> copy_{to,from}_kernel_nofault(), where do we *not* want to use
> EX_TYPE_UACCESS_ERR_ZERO and *not* recover from a memory error?
>
> Thanks,
> Mark.
There are some cases (futex/__user_cache_maint()/__user_swpX_asm())
using EX_TYPE_UACCESS_ERR_ZERO, for these cases, whether to restore is
not yet determined, let's discuss in patch 3/7.
Thanks,
Tong.
>
>>
>> Signed-off-by: Tong Tiangen <tongtiangen@...wei.com>
>> ---
>> arch/arm64/include/asm/asm-extable.h | 14 ++++++++++++++
>> arch/arm64/include/asm/uaccess.h | 4 ++--
>> arch/arm64/mm/extable.c | 4 ++++
>> 3 files changed, 20 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h
>> index 75b2c00e9523..80410899a9ad 100644
>> --- a/arch/arm64/include/asm/asm-extable.h
>> +++ b/arch/arm64/include/asm/asm-extable.h
>> @@ -13,6 +13,7 @@
>>
>> /* _MC indicates that can fixup from machine check errors */
>> #define EX_TYPE_UACCESS_MC 5
>> +#define EX_TYPE_UACCESS_MC_ERR_ZERO 6
>>
>> #ifdef __ASSEMBLY__
>>
>> @@ -78,6 +79,15 @@
>> #define EX_DATA_REG(reg, gpr) \
>> "((.L__gpr_num_" #gpr ") << " __stringify(EX_DATA_REG_##reg##_SHIFT) ")"
>>
>> +#define _ASM_EXTABLE_UACCESS_MC_ERR_ZERO(insn, fixup, err, zero) \
>> + __DEFINE_ASM_GPR_NUMS \
>> + __ASM_EXTABLE_RAW(#insn, #fixup, \
>> + __stringify(EX_TYPE_UACCESS_MC_ERR_ZERO), \
>> + "(" \
>> + EX_DATA_REG(ERR, err) " | " \
>> + EX_DATA_REG(ZERO, zero) \
>> + ")")
>> +
>> #define _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, zero) \
>> __DEFINE_ASM_GPR_NUMS \
>> __ASM_EXTABLE_RAW(#insn, #fixup, \
>> @@ -90,6 +100,10 @@
>> #define _ASM_EXTABLE_UACCESS_ERR(insn, fixup, err) \
>> _ASM_EXTABLE_UACCESS_ERR_ZERO(insn, fixup, err, wzr)
>>
>> +
>> +#define _ASM_EXTABLE_UACCESS_MC_ERR(insn, fixup, err) \
>> + _ASM_EXTABLE_UACCESS_MC_ERR_ZERO(insn, fixup, err, wzr)
>> +
>> #define EX_DATA_REG_DATA_SHIFT 0
>> #define EX_DATA_REG_DATA GENMASK(4, 0)
>> #define EX_DATA_REG_ADDR_SHIFT 5
>> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
>> index e8dce0cc5eaa..e41b47df48b0 100644
>> --- a/arch/arm64/include/asm/uaccess.h
>> +++ b/arch/arm64/include/asm/uaccess.h
>> @@ -236,7 +236,7 @@ static inline void __user *__uaccess_mask_ptr(const void __user *ptr)
>> asm volatile( \
>> "1: " load " " reg "1, [%2]\n" \
>> "2:\n" \
>> - _ASM_EXTABLE_UACCESS_ERR_ZERO(1b, 2b, %w0, %w1) \
>> + _ASM_EXTABLE_UACCESS_MC_ERR_ZERO(1b, 2b, %w0, %w1) \
>> : "+r" (err), "=&r" (x) \
>> : "r" (addr))
>>
>> @@ -325,7 +325,7 @@ do { \
>> asm volatile( \
>> "1: " store " " reg "1, [%2]\n" \
>> "2:\n" \
>> - _ASM_EXTABLE_UACCESS_ERR(1b, 2b, %w0) \
>> + _ASM_EXTABLE_UACCESS_MC_ERR(1b, 2b, %w0) \
>> : "+r" (err) \
>> : "r" (x), "r" (addr))
>>
>> diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c
>> index 525876c3ebf4..1023ccdb2f89 100644
>> --- a/arch/arm64/mm/extable.c
>> +++ b/arch/arm64/mm/extable.c
>> @@ -88,6 +88,7 @@ bool fixup_exception(struct pt_regs *regs)
>> case EX_TYPE_BPF:
>> return ex_handler_bpf(ex, regs);
>> case EX_TYPE_UACCESS_ERR_ZERO:
>> + case EX_TYPE_UACCESS_MC_ERR_ZERO:
>> return ex_handler_uaccess_err_zero(ex, regs);
>> case EX_TYPE_LOAD_UNALIGNED_ZEROPAD:
>> return ex_handler_load_unaligned_zeropad(ex, regs);
>> @@ -107,6 +108,9 @@ bool fixup_exception_mc(struct pt_regs *regs)
>> switch (ex->type) {
>> case EX_TYPE_UACCESS_MC:
>> return ex_handler_uaccess_type(ex, regs, FIXUP_TYPE_MC);
>> + case EX_TYPE_UACCESS_MC_ERR_ZERO:
>> + return ex_handler_uaccess_err_zero(ex, regs);
>> +
>> }
>>
>> return false;
>> --
>> 2.25.1
>>
> .
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