Messages in this thread | | | Date | Thu, 26 May 2022 11:36:41 +0800 | Subject | Re: [PATCH -next v4 3/7] arm64: add support for machine check error safe | From | Tong Tiangen <> |
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在 2022/5/25 16:30, Mark Rutland 写道: > On Thu, May 19, 2022 at 02:29:54PM +0800, Tong Tiangen wrote: >> >> >> 在 2022/5/13 23:26, Mark Rutland 写道: >>> On Wed, Apr 20, 2022 at 03:04:14AM +0000, Tong Tiangen wrote: >>>> During the processing of arm64 kernel hardware memory errors(do_sea()), if >>>> the errors is consumed in the kernel, the current processing is panic. >>>> However, it is not optimal. >>>> >>>> Take uaccess for example, if the uaccess operation fails due to memory >>>> error, only the user process will be affected, kill the user process >>>> and isolate the user page with hardware memory errors is a better choice. >>> >>> Conceptually, I'm fine with the idea of constraining what we do for a >>> true uaccess, but I don't like the implementation of this at all, and I >>> think we first need to clean up the arm64 extable usage to clearly >>> distinguish a uaccess from another access. >> >> OK,using EX_TYPE_UACCESS and this extable type could be recover, this is >> more reasonable. > > Great. > >> For EX_TYPE_UACCESS_ERR_ZERO, today we use it for kernel accesses in a >> couple of cases, such as >> get_user/futex/__user_cache_maint()/__user_swpX_asm(), > > Those are all user accesses. > > However, __get_kernel_nofault() and __put_kernel_nofault() use > EX_TYPE_UACCESS_ERR_ZERO by way of __{get,put}_mem_asm(), so we'd need to > refactor that code to split the user/kernel cases higher up the callchain. > >> your suggestion is: >> get_user continues to use EX_TYPE_UACCESS_ERR_ZERO and the other cases use >> new type EX_TYPE_FIXUP_ERR_ZERO? > > Yes, that's the rough shape. We could make the latter EX_TYPE_KACCESS_ERR_ZERO > to be clearly analogous to EX_TYPE_UACCESS_ERR_ZERO, and with that I susepct we > could remove EX_TYPE_FIXUP. > > Thanks, > Mark. According to your suggestion, i think the definition is like this:
#define EX_TYPE_NONE 0 #define EX_TYPE_FIXUP 1 --> delete #define EX_TYPE_BPF 2 #define EX_TYPE_UACCESS_ERR_ZERO 3 #define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4 #define EX_TYPE_UACCESS xx --> add #define EX_TYPE_KACCESS_ERR_ZERO xx --> add [The value defined by the macro here is temporary]
There are two points to modify:
1、_get_kernel_nofault() and __put_kernel_nofault() using EX_TYPE_KACCESS_ERR_ZERO, Other positions using EX_TYPE_UACCESS_ERR_ZERO keep unchanged.
2、delete EX_TYPE_FIXUP.
There is no doubt about others. As for EX_TYPE_FIXUP, I think it needs to be retained, _cond_extable(EX_TYPE_FIXUP) is still in use in assembler.h.
Thanks, Tong.
> .
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