Messages in this thread | | | Date | Sat, 18 Jun 2022 17:27:45 +0800 | Subject | Re: [PATCH -next v5 7/8] arm64: add uaccess to machine check safe | From | Tong Tiangen <> |
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在 2022/6/17 17:06, Mark Rutland 写道: > On Sat, May 28, 2022 at 06:50:55AM +0000, Tong Tiangen wrote: >> If user access fail due to hardware memory error, only the relevant >> processes are affected, so killing the user process and isolate the >> error page with hardware memory errors is a more reasonable choice >> than kernel panic. >> >> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> > >> --- >> arch/arm64/lib/copy_from_user.S | 8 ++++---- >> arch/arm64/lib/copy_to_user.S | 8 ++++---- > > All of these changes are to the *kernel* accesses performed as part of copy > to/from user, and have nothing to do with userspace, so it does not make sense > to mark these as UACCESS.
You have a point. so there is no need to modify copy_from/to_user.S in this patch set.
> > Do we *actually* need to recover from failues on these accesses? Looking at > _copy_from_user(), the kernel will immediately follow this up with a memset() > to the same address which will be fatal anyway, so this is only punting the > failure for a few instructions.
If recovery success, The task will be killed and there will be no subsequent memset().
> > If we really need to recover from certain accesses to kernel memory we should > add a new EX_TYPE_KACCESS_ERR_ZERO_MC or similar, but we need a strong > rationale as to why that's useful. As things stand I do not beleive it makes > sense for copy to/from user specifically. > >> arch/arm64/mm/extable.c | 8 ++++---- >> 3 files changed, 12 insertions(+), 12 deletions(-) >> >> diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S >> index 34e317907524..402dd48a4f93 100644 >> --- a/arch/arm64/lib/copy_from_user.S >> +++ b/arch/arm64/lib/copy_from_user.S >> @@ -25,7 +25,7 @@ >> .endm >> >> .macro strb1 reg, ptr, val >> - strb \reg, [\ptr], \val >> + USER(9998f, strb \reg, [\ptr], \val) >> .endm >> >> .macro ldrh1 reg, ptr, val >> @@ -33,7 +33,7 @@ >> .endm >> >> .macro strh1 reg, ptr, val >> - strh \reg, [\ptr], \val >> + USER(9998f, strh \reg, [\ptr], \val) >> .endm >> >> .macro ldr1 reg, ptr, val >> @@ -41,7 +41,7 @@ >> .endm >> >> .macro str1 reg, ptr, val >> - str \reg, [\ptr], \val >> + USER(9998f, str \reg, [\ptr], \val) >> .endm >> >> .macro ldp1 reg1, reg2, ptr, val >> @@ -49,7 +49,7 @@ >> .endm >> >> .macro stp1 reg1, reg2, ptr, val >> - stp \reg1, \reg2, [\ptr], \val >> + USER(9998f, stp \reg1, \reg2, [\ptr], \val) >> .endm >> >> end .req x5 >> diff --git a/arch/arm64/lib/copy_to_user.S b/arch/arm64/lib/copy_to_user.S >> index 802231772608..4134bdb3a8b0 100644 >> --- a/arch/arm64/lib/copy_to_user.S >> +++ b/arch/arm64/lib/copy_to_user.S >> @@ -20,7 +20,7 @@ >> * x0 - bytes not copied >> */ >> .macro ldrb1 reg, ptr, val >> - ldrb \reg, [\ptr], \val >> + USER(9998f, ldrb \reg, [\ptr], \val) >> .endm >> >> .macro strb1 reg, ptr, val >> @@ -28,7 +28,7 @@ >> .endm >> >> .macro ldrh1 reg, ptr, val >> - ldrh \reg, [\ptr], \val >> + USER(9998f, ldrh \reg, [\ptr], \val) >> .endm >> >> .macro strh1 reg, ptr, val >> @@ -36,7 +36,7 @@ >> .endm >> >> .macro ldr1 reg, ptr, val >> - ldr \reg, [\ptr], \val >> + USER(9998f, ldr \reg, [\ptr], \val) >> .endm >> >> .macro str1 reg, ptr, val >> @@ -44,7 +44,7 @@ >> .endm >> >> .macro ldp1 reg1, reg2, ptr, val >> - ldp \reg1, \reg2, [\ptr], \val >> + USER(9998f, ldp \reg1, \reg2, [\ptr], \val) >> .endm >> >> .macro stp1 reg1, reg2, ptr, val >> diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c >> index c301dcf6335f..8ca8d9639f9f 100644 >> --- a/arch/arm64/mm/extable.c >> +++ b/arch/arm64/mm/extable.c >> @@ -86,10 +86,10 @@ bool fixup_exception_mc(struct pt_regs *regs) >> if (!ex) >> return false; >> >> - /* >> - * This is not complete, More Machine check safe extable type can >> - * be processed here. >> - */ >> + switch (ex->type) { >> + case EX_TYPE_UACCESS_ERR_ZERO: >> + return ex_handler_uaccess_err_zero(ex, regs); >> + } > > This addition specifically makes sense to me, so can you split this into a separate patch?
According to my understanding of the above, only the modification of extable.c is retained.
So what do you mean which part is made into a separate patch?
Thanks, Tong. > > Thanks, > Mark. > > .
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