| Message ID | 20220406091311.3354723-4-tongtiangen@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: add machine check safe support | expand |
On Wed, Apr 06, 2022 at 09:13:07AM +0000, Tong Tiangen wrote: > In arm64 kernel hardware memory errors process(do_sea()), if the errors > is consumed in the kernel, the current processing is panic. However, > it is not optimal. In some case, the page accessed in kernel is a user > page (such as copy_from_user/get_user), kill the user process and > isolate the user page with hardware memory errors is a better choice. > > Consistent with PPC/x86, it is implemented by CONFIG_ARCH_HAS_COPY_MC. Why do we need new helpers for this, rather than doing this for *any* uaccess? I understand this is consistent with PPC & X86, but *why* is it done that way today? e.g. are there cases where we access memroy where we do not expect the situation to be recoverable? > This patch only enable machine error check framework, it add exception > fixup before kernel panic in do_sea() and only limit the consumption of > hardware memory errors in kernel mode triggered by user mode processes. > If fixup successful, there is no need to panic. > > Also add _asm_extable_mc macro used for add extable entry to help > fixup. > > Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> > --- > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/asm-extable.h | 13 ++++++++++++ > arch/arm64/include/asm/esr.h | 5 +++++ > arch/arm64/include/asm/extable.h | 2 +- > arch/arm64/kernel/probes/kprobes.c | 2 +- > arch/arm64/mm/extable.c | 20 ++++++++++++++++++- > arch/arm64/mm/fault.c | 30 +++++++++++++++++++++++++++- > include/linux/uaccess.h | 8 ++++++++ > 8 files changed, 77 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index d9325dd95eba..012e38309955 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -19,6 +19,7 @@ config ARM64 > select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2 > select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE > select ARCH_HAS_CACHE_LINE_SIZE > + select ARCH_HAS_COPY_MC if ACPI_APEI_GHES > select ARCH_HAS_CURRENT_STACK_POINTER > select ARCH_HAS_DEBUG_VIRTUAL > select ARCH_HAS_DEBUG_VM_PGTABLE > diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h > index c39f2437e08e..74d1db74fd86 100644 > --- a/arch/arm64/include/asm/asm-extable.h > +++ b/arch/arm64/include/asm/asm-extable.h > @@ -8,6 +8,11 @@ > #define EX_TYPE_UACCESS_ERR_ZERO 3 > #define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4 > > +/* _MC indicates that can fixup from machine check errors */ > +#define EX_TYPE_FIXUP_MC 5 > + > +#define IS_EX_TYPE_MC(type) (type == EX_TYPE_FIXUP_MC) If we need this, I'd strongly prefer that we have a EX_TYPE_UACCESS_MC or EX_TYPE_UACCESS_MC_ERR_ZERO for the uaccess cases, so that we can clearly distinguish those from non-uaccess cases. AFAICT the only remaining raw EX_TYPE_FIXUP cases we have today are in some cache maintenance routines, and we should be able to convert those to a new EX_TYPE_FIXUP_UACCESS, or EX_TYPE_UACCESS_ERR_ZERO. > + > #ifdef __ASSEMBLY__ > > #define __ASM_EXTABLE_RAW(insn, fixup, type, data) \ > @@ -27,6 +32,14 @@ > __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0) > .endm > > +/* > + * Create an exception table entry for `insn`, which will branch to `fixup` > + * when an unhandled fault(include sea fault) is taken. > + */ > + .macro _asm_extable_mc, insn, fixup > + __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP_MC, 0) > + .endm > + > /* > * Create an exception table entry for `insn` if `fixup` is provided. Otherwise > * do nothing. > diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h > index d52a0b269ee8..11fcfc002654 100644 > --- a/arch/arm64/include/asm/esr.h > +++ b/arch/arm64/include/asm/esr.h > @@ -330,6 +330,11 @@ > #ifndef __ASSEMBLY__ > #include <asm/types.h> > > +static inline bool esr_is_sea(u32 esr) > +{ > + return (esr & ESR_ELx_FSC) == ESR_ELx_FSC_EXTABT; > +} > + > static inline bool esr_is_data_abort(u32 esr) > { > const u32 ec = ESR_ELx_EC(esr); > diff --git a/arch/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h > index 72b0e71cc3de..f7835b0f473b 100644 > --- a/arch/arm64/include/asm/extable.h > +++ b/arch/arm64/include/asm/extable.h > @@ -45,5 +45,5 @@ bool ex_handler_bpf(const struct exception_table_entry *ex, > } > #endif /* !CONFIG_BPF_JIT */ > > -bool fixup_exception(struct pt_regs *regs); > +bool fixup_exception(struct pt_regs *regs, unsigned int esr); > #endif > diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c > index d9dfa82c1f18..16a069e8eec3 100644 > --- a/arch/arm64/kernel/probes/kprobes.c > +++ b/arch/arm64/kernel/probes/kprobes.c > @@ -285,7 +285,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) > * In case the user-specified fault handler returned > * zero, try to fix up. > */ > - if (fixup_exception(regs)) > + if (fixup_exception(regs, fsr)) > return 1; > } > return 0; > diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c > index 489455309695..f1134c88e849 100644 > --- a/arch/arm64/mm/extable.c > +++ b/arch/arm64/mm/extable.c > @@ -9,6 +9,7 @@ > > #include <asm/asm-extable.h> > #include <asm/ptrace.h> > +#include <asm/esr.h> > > static inline unsigned long > get_ex_fixup(const struct exception_table_entry *ex) > @@ -23,6 +24,18 @@ static bool ex_handler_fixup(const struct exception_table_entry *ex, > return true; > } > > +static bool ex_handler_fixup_mc(const struct exception_table_entry *ex, > + struct pt_regs *regs, unsigned int esr) > +{ > + if (esr_is_sea(esr)) > + regs->regs[0] = 0; > + else > + regs->regs[0] = 1; This needs more explanation. Why does this hard-code an assumption that we can alter x0? Why is the x0 value distinct for SEA or non-SEA? What is this meant to represent specifically? What if this SEA was taken for a reason other than a memory error? > + > + regs->pc = get_ex_fixup(ex); > + return true; > +} > + > static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex, > struct pt_regs *regs) > { > @@ -63,7 +76,7 @@ ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, > return true; > } > > -bool fixup_exception(struct pt_regs *regs) > +bool fixup_exception(struct pt_regs *regs, unsigned int esr) > { > const struct exception_table_entry *ex; > > @@ -71,9 +84,14 @@ bool fixup_exception(struct pt_regs *regs) > if (!ex) > return false; > > + if (esr_is_sea(esr) && !IS_EX_TYPE_MC(ex->type)) > + return false; I don't think this check belongs here. Either this should be folded into ex_handler_fixup_mc(), or we should make the judgement earlier in the fault handling path, and have a separate fixup_exception_mc() that we can call specifically in the case of a memory error. > + > switch (ex->type) { > case EX_TYPE_FIXUP: > return ex_handler_fixup(ex, regs); > + case EX_TYPE_FIXUP_MC: > + return ex_handler_fixup_mc(ex, regs, esr); > case EX_TYPE_BPF: > return ex_handler_bpf(ex, regs); > case EX_TYPE_UACCESS_ERR_ZERO: > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 77341b160aca..ffdfab2fdd60 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -361,7 +361,7 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr, > * Are we prepared to handle this kernel fault? > * We are almost certainly not prepared to handle instruction faults. > */ > - if (!is_el1_instruction_abort(esr) && fixup_exception(regs)) > + if (!is_el1_instruction_abort(esr) && fixup_exception(regs, esr)) > return; > > if (WARN_RATELIMIT(is_spurious_el1_translation_fault(addr, esr, regs), > @@ -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; > + > + if (!fixup_exception(regs, esr)) > + 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; > + > 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) > +{ > + return raw_copy_to_user(dst, src, cnt); > +} ... this isn't using the new EX_TYPE_FIXUP_MC type, so isn't this just broken as of this patch? Thanks, Mark. > +#endif > + > static __always_inline void pagefault_disabled_inc(void) > { > current->pagefault_disabled++; > -- > 2.18.0.huawei.25 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
在 2022/4/6 18:58, Mark Rutland 写道: > On Wed, Apr 06, 2022 at 09:13:07AM +0000, Tong Tiangen wrote: >> In arm64 kernel hardware memory errors process(do_sea()), if the errors >> is consumed in the kernel, the current processing is panic. However, >> it is not optimal. In some case, the page accessed in kernel is a user >> page (such as copy_from_user/get_user), kill the user process and >> isolate the user page with hardware memory errors is a better choice. >> >> Consistent with PPC/x86, it is implemented by CONFIG_ARCH_HAS_COPY_MC. > > Why do we need new helpers for this, rather than doing this for *any* uaccess > > I understand this is consistent with PPC & X86, but *why* is it done that way > today? e.g. are there cases where we access memroy where we do not expect the > situation to be recoverable? Here[1] i explain why not all uaccess needs to be recoverable. [1]https://lore.kernel.org/lkml/bdf67ff6-9eb8-c2b4-2c2f-b160d4f879cd@huawei.com/ > >> This patch only enable machine error check framework, it add exception >> fixup before kernel panic in do_sea() and only limit the consumption of >> hardware memory errors in kernel mode triggered by user mode processes. >> If fixup successful, there is no need to panic. >> >> Also add _asm_extable_mc macro used for add extable entry to help >> fixup. >> >> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> >> --- >> arch/arm64/Kconfig | 1 + >> arch/arm64/include/asm/asm-extable.h | 13 ++++++++++++ >> arch/arm64/include/asm/esr.h | 5 +++++ >> arch/arm64/include/asm/extable.h | 2 +- >> arch/arm64/kernel/probes/kprobes.c | 2 +- >> arch/arm64/mm/extable.c | 20 ++++++++++++++++++- >> arch/arm64/mm/fault.c | 30 +++++++++++++++++++++++++++- >> include/linux/uaccess.h | 8 ++++++++ >> 8 files changed, 77 insertions(+), 4 deletions(-) >> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index d9325dd95eba..012e38309955 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -19,6 +19,7 @@ config ARM64 >> select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2 >> select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE >> select ARCH_HAS_CACHE_LINE_SIZE >> + select ARCH_HAS_COPY_MC if ACPI_APEI_GHES >> select ARCH_HAS_CURRENT_STACK_POINTER >> select ARCH_HAS_DEBUG_VIRTUAL >> select ARCH_HAS_DEBUG_VM_PGTABLE >> diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h >> index c39f2437e08e..74d1db74fd86 100644 >> --- a/arch/arm64/include/asm/asm-extable.h >> +++ b/arch/arm64/include/asm/asm-extable.h >> @@ -8,6 +8,11 @@ >> #define EX_TYPE_UACCESS_ERR_ZERO 3 >> #define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4 >> >> +/* _MC indicates that can fixup from machine check errors */ >> +#define EX_TYPE_FIXUP_MC 5 >> + >> +#define IS_EX_TYPE_MC(type) (type == EX_TYPE_FIXUP_MC) > > If we need this, I'd strongly prefer that we have a EX_TYPE_UACCESS_MC or > EX_TYPE_UACCESS_MC_ERR_ZERO for the uaccess cases, so that we can clearly > distinguish those from non-uaccess cases. Agreed. > > AFAICT the only remaining raw EX_TYPE_FIXUP cases we have today are in some > cache maintenance routines, and we should be able to convert those to a new > EX_TYPE_FIXUP_UACCESS, or EX_TYPE_UACCESS_ERR_ZERO. I will redesign this part. The general idea is not to use x0 to save exception information. At that time, it may be merged into raw EX_TYPE_FIXUP processing. > >> + >> #ifdef __ASSEMBLY__ >> >> #define __ASM_EXTABLE_RAW(insn, fixup, type, data) \ >> @@ -27,6 +32,14 @@ >> __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0) >> .endm >> >> +/* >> + * Create an exception table entry for `insn`, which will branch to `fixup` >> + * when an unhandled fault(include sea fault) is taken. >> + */ >> + .macro _asm_extable_mc, insn, fixup >> + __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP_MC, 0) >> + .endm >> + >> /* >> * Create an exception table entry for `insn` if `fixup` is provided. Otherwise >> * do nothing. >> diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h >> index d52a0b269ee8..11fcfc002654 100644 >> --- a/arch/arm64/include/asm/esr.h >> +++ b/arch/arm64/include/asm/esr.h >> @@ -330,6 +330,11 @@ >> #ifndef __ASSEMBLY__ >> #include <asm/types.h> >> >> +static inline bool esr_is_sea(u32 esr) >> +{ >> + return (esr & ESR_ELx_FSC) == ESR_ELx_FSC_EXTABT; >> +} >> + >> static inline bool esr_is_data_abort(u32 esr) >> { >> const u32 ec = ESR_ELx_EC(esr); >> diff --git a/arch/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h >> index 72b0e71cc3de..f7835b0f473b 100644 >> --- a/arch/arm64/include/asm/extable.h >> +++ b/arch/arm64/include/asm/extable.h >> @@ -45,5 +45,5 @@ bool ex_handler_bpf(const struct exception_table_entry *ex, >> } >> #endif /* !CONFIG_BPF_JIT */ >> >> -bool fixup_exception(struct pt_regs *regs); >> +bool fixup_exception(struct pt_regs *regs, unsigned int esr); >> #endif >> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c >> index d9dfa82c1f18..16a069e8eec3 100644 >> --- a/arch/arm64/kernel/probes/kprobes.c >> +++ b/arch/arm64/kernel/probes/kprobes.c >> @@ -285,7 +285,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) >> * In case the user-specified fault handler returned >> * zero, try to fix up. >> */ >> - if (fixup_exception(regs)) >> + if (fixup_exception(regs, fsr)) >> return 1; >> } >> return 0; >> diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c >> index 489455309695..f1134c88e849 100644 >> --- a/arch/arm64/mm/extable.c >> +++ b/arch/arm64/mm/extable.c >> @@ -9,6 +9,7 @@ >> >> #include <asm/asm-extable.h> >> #include <asm/ptrace.h> >> +#include <asm/esr.h> >> >> static inline unsigned long >> get_ex_fixup(const struct exception_table_entry *ex) >> @@ -23,6 +24,18 @@ static bool ex_handler_fixup(const struct exception_table_entry *ex, >> return true; >> } >> >> +static bool ex_handler_fixup_mc(const struct exception_table_entry *ex, >> + struct pt_regs *regs, unsigned int esr) >> +{ >> + if (esr_is_sea(esr)) >> + regs->regs[0] = 0; >> + else >> + regs->regs[0] = 1; > > This needs more explanation. > > Why does this hard-code an assumption that we can alter x0? > > Why is the x0 value distinct for SEA or non-SEA? What is this meant to > represent specifically? > > What if this SEA was taken for a reason other than a memory error? There is a problem with the design of this place and it needs to be modified. The value in x0 cannot be overwritten. will be fixed in next version. > >> + >> + regs->pc = get_ex_fixup(ex); >> + return true; >> +} >> + >> static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex, >> struct pt_regs *regs) >> { >> @@ -63,7 +76,7 @@ ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, >> return true; >> } >> >> -bool fixup_exception(struct pt_regs *regs) >> +bool fixup_exception(struct pt_regs *regs, unsigned int esr) >> { >> const struct exception_table_entry *ex; >> >> @@ -71,9 +84,14 @@ bool fixup_exception(struct pt_regs *regs) >> if (!ex) >> return false; >> >> + if (esr_is_sea(esr) && !IS_EX_TYPE_MC(ex->type)) >> + return false; > > I don't think this check belongs here. > > Either this should be folded into ex_handler_fixup_mc(), or we should make the > judgement earlier in the fault handling path, and have a separate > fixup_exception_mc() that we can call specifically in the case of a memory > error. Agreed, Maybe it's better to use a separate fixup_exception_mc(). > >> + >> switch (ex->type) { >> case EX_TYPE_FIXUP: >> return ex_handler_fixup(ex, regs); >> + case EX_TYPE_FIXUP_MC: >> + return ex_handler_fixup_mc(ex, regs, esr); >> case EX_TYPE_BPF: >> return ex_handler_bpf(ex, regs); >> case EX_TYPE_UACCESS_ERR_ZERO: >> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c >> index 77341b160aca..ffdfab2fdd60 100644 >> --- a/arch/arm64/mm/fault.c >> +++ b/arch/arm64/mm/fault.c >> @@ -361,7 +361,7 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr, >> * Are we prepared to handle this kernel fault? >> * We are almost certainly not prepared to handle instruction faults. >> */ >> - if (!is_el1_instruction_abort(esr) && fixup_exception(regs)) >> + if (!is_el1_instruction_abort(esr) && fixup_exception(regs, esr)) >> return; >> >> if (WARN_RATELIMIT(is_spurious_el1_translation_fault(addr, esr, regs), >> @@ -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; >> + >> + if (!fixup_exception(regs, esr)) >> + 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; >> + >> 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) >> +{ >> + return raw_copy_to_user(dst, src, cnt); >> +} > > ... this isn't using the new EX_TYPE_FIXUP_MC type, so isn't this just broken > as of this patch? > > Thanks, > Mark. It is useful in the later patch (adding specific scenarios to use this framework), here just add helper. Great thanks, Tong. > >> +#endif >> + >> static __always_inline void pagefault_disabled_inc(void) >> { >> current->pagefault_disabled++; >> -- >> 2.18.0.huawei.25 >> >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > .
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index d9325dd95eba..012e38309955 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -19,6 +19,7 @@ config ARM64 select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2 select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE select ARCH_HAS_CACHE_LINE_SIZE + select ARCH_HAS_COPY_MC if ACPI_APEI_GHES select ARCH_HAS_CURRENT_STACK_POINTER select ARCH_HAS_DEBUG_VIRTUAL select ARCH_HAS_DEBUG_VM_PGTABLE diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h index c39f2437e08e..74d1db74fd86 100644 --- a/arch/arm64/include/asm/asm-extable.h +++ b/arch/arm64/include/asm/asm-extable.h @@ -8,6 +8,11 @@ #define EX_TYPE_UACCESS_ERR_ZERO 3 #define EX_TYPE_LOAD_UNALIGNED_ZEROPAD 4 +/* _MC indicates that can fixup from machine check errors */ +#define EX_TYPE_FIXUP_MC 5 + +#define IS_EX_TYPE_MC(type) (type == EX_TYPE_FIXUP_MC) + #ifdef __ASSEMBLY__ #define __ASM_EXTABLE_RAW(insn, fixup, type, data) \ @@ -27,6 +32,14 @@ __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP, 0) .endm +/* + * Create an exception table entry for `insn`, which will branch to `fixup` + * when an unhandled fault(include sea fault) is taken. + */ + .macro _asm_extable_mc, insn, fixup + __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_FIXUP_MC, 0) + .endm + /* * Create an exception table entry for `insn` if `fixup` is provided. Otherwise * do nothing. diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h index d52a0b269ee8..11fcfc002654 100644 --- a/arch/arm64/include/asm/esr.h +++ b/arch/arm64/include/asm/esr.h @@ -330,6 +330,11 @@ #ifndef __ASSEMBLY__ #include <asm/types.h> +static inline bool esr_is_sea(u32 esr) +{ + return (esr & ESR_ELx_FSC) == ESR_ELx_FSC_EXTABT; +} + static inline bool esr_is_data_abort(u32 esr) { const u32 ec = ESR_ELx_EC(esr); diff --git a/arch/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h index 72b0e71cc3de..f7835b0f473b 100644 --- a/arch/arm64/include/asm/extable.h +++ b/arch/arm64/include/asm/extable.h @@ -45,5 +45,5 @@ bool ex_handler_bpf(const struct exception_table_entry *ex, } #endif /* !CONFIG_BPF_JIT */ -bool fixup_exception(struct pt_regs *regs); +bool fixup_exception(struct pt_regs *regs, unsigned int esr); #endif diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index d9dfa82c1f18..16a069e8eec3 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -285,7 +285,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr) * In case the user-specified fault handler returned * zero, try to fix up. */ - if (fixup_exception(regs)) + if (fixup_exception(regs, fsr)) return 1; } return 0; diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c index 489455309695..f1134c88e849 100644 --- a/arch/arm64/mm/extable.c +++ b/arch/arm64/mm/extable.c @@ -9,6 +9,7 @@ #include <asm/asm-extable.h> #include <asm/ptrace.h> +#include <asm/esr.h> static inline unsigned long get_ex_fixup(const struct exception_table_entry *ex) @@ -23,6 +24,18 @@ static bool ex_handler_fixup(const struct exception_table_entry *ex, return true; } +static bool ex_handler_fixup_mc(const struct exception_table_entry *ex, + struct pt_regs *regs, unsigned int esr) +{ + if (esr_is_sea(esr)) + regs->regs[0] = 0; + else + regs->regs[0] = 1; + + regs->pc = get_ex_fixup(ex); + return true; +} + static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex, struct pt_regs *regs) { @@ -63,7 +76,7 @@ ex_handler_load_unaligned_zeropad(const struct exception_table_entry *ex, return true; } -bool fixup_exception(struct pt_regs *regs) +bool fixup_exception(struct pt_regs *regs, unsigned int esr) { const struct exception_table_entry *ex; @@ -71,9 +84,14 @@ bool fixup_exception(struct pt_regs *regs) if (!ex) return false; + if (esr_is_sea(esr) && !IS_EX_TYPE_MC(ex->type)) + return false; + switch (ex->type) { case EX_TYPE_FIXUP: return ex_handler_fixup(ex, regs); + case EX_TYPE_FIXUP_MC: + return ex_handler_fixup_mc(ex, regs, esr); case EX_TYPE_BPF: return ex_handler_bpf(ex, regs); case EX_TYPE_UACCESS_ERR_ZERO: diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 77341b160aca..ffdfab2fdd60 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -361,7 +361,7 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr, * Are we prepared to handle this kernel fault? * We are almost certainly not prepared to handle instruction faults. */ - if (!is_el1_instruction_abort(esr) && fixup_exception(regs)) + if (!is_el1_instruction_abort(esr) && fixup_exception(regs, esr)) return; if (WARN_RATELIMIT(is_spurious_el1_translation_fault(addr, esr, regs), @@ -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; + + if (!fixup_exception(regs, esr)) + 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; + 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) +{ + return raw_copy_to_user(dst, src, cnt); +} +#endif + static __always_inline void pagefault_disabled_inc(void) { current->pagefault_disabled++;
In arm64 kernel hardware memory errors process(do_sea()), if the errors is consumed in the kernel, the current processing is panic. However, it is not optimal. In some case, the page accessed in kernel is a user page (such as copy_from_user/get_user), kill the user process and isolate the user page with hardware memory errors is a better choice. Consistent with PPC/x86, it is implemented by CONFIG_ARCH_HAS_COPY_MC. This patch only enable machine error check framework, it add exception fixup before kernel panic in do_sea() and only limit the consumption of hardware memory errors in kernel mode triggered by user mode processes. If fixup successful, there is no need to panic. Also add _asm_extable_mc macro used for add extable entry to help fixup. Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/asm-extable.h | 13 ++++++++++++ arch/arm64/include/asm/esr.h | 5 +++++ arch/arm64/include/asm/extable.h | 2 +- arch/arm64/kernel/probes/kprobes.c | 2 +- arch/arm64/mm/extable.c | 20 ++++++++++++++++++- arch/arm64/mm/fault.c | 30 +++++++++++++++++++++++++++- include/linux/uaccess.h | 8 ++++++++ 8 files changed, 77 insertions(+), 4 deletions(-)