Messages in this thread | | | Date | Thu, 19 May 2022 15:09:23 +0800 | Subject | Re: [PATCH -next v4 6/7] arm64: add {get, put}_user to machine check safe | From | Tong Tiangen <> |
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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@huawei.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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