Messages in this thread Patch in this message | | | Date | Tue, 12 Apr 2022 21:08:23 +0800 | Subject | Re: [RFC PATCH -next V3 3/6] arm64: add support for machine check error safe | From | Kefeng Wang <> |
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On 2022/4/12 15:25, 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. > > 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, panic can be avoided. > > Consistent with PPC/x86, it is implemented by CONFIG_ARCH_HAS_COPY_MC. > > Also add copy_mc_to_user() in include/linux/uaccess.h, this helper is > called when CONFIG_ARCH_HAS_COPOY_MC is open. > > Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> > --- > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/extable.h | 1 + > arch/arm64/mm/extable.c | 18 ++++++++++++++++++ > arch/arm64/mm/fault.c | 28 ++++++++++++++++++++++++++++ > include/linux/uaccess.h | 8 ++++++++ > 5 files changed, 56 insertions(+) > > 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/extable.h b/arch/arm64/include/asm/extable.h > index 72b0e71cc3de..f80ebd0addfd 100644 > --- a/arch/arm64/include/asm/extable.h > +++ b/arch/arm64/include/asm/extable.h > @@ -46,4 +46,5 @@ bool ex_handler_bpf(const struct exception_table_entry *ex, > #endif /* !CONFIG_BPF_JIT */ > > bool fixup_exception(struct pt_regs *regs); > +bool fixup_exception_mc(struct pt_regs *regs); > #endif > diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c > index 489455309695..5de256a25464 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) > @@ -73,6 +74,7 @@ bool fixup_exception(struct pt_regs *regs) > > switch (ex->type) { > case EX_TYPE_FIXUP: > + case EX_TYPE_UACCESS_MC: > return ex_handler_fixup(ex, regs); > case EX_TYPE_BPF: > return ex_handler_bpf(ex, regs); > @@ -84,3 +86,19 @@ bool fixup_exception(struct pt_regs *regs) > > BUG(); > } > + > +bool fixup_exception_mc(struct pt_regs *regs) > +{ > + const struct exception_table_entry *ex; > + > + ex = search_exception_tables(instruction_pointer(regs)); > + if (!ex) > + return false; > + > + switch (ex->type) { > + case EX_TYPE_UACCESS_MC: > + return ex_handler_fixup(ex, regs); > + } > + > + return false; > +}
The definition of EX_TYPE_UACCESS_MC is in patch4, please fix it, and if arm64 exception table
is sorted by exception type, we could drop fixup_exception_mc(), right?
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 77341b160aca..56b13cf8bf1d 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -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; > + Use set_thread_esr(0, esr) and move it after fixup_exception_mc(); > + if (!fixup_exception_mc(regs)) > + 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; > +
Rename arm64_process_kernel_sea() to arm64_do_kernel_sea() ?
if (!arm64_do_kernel_sea())
arm64_notify_die();
> 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) > +{ Add check_object_size(cnt, src, true); which could make HARDENED_USERCOPY works. > + return raw_copy_to_user(dst, src, cnt); > +} > +#endif > + > static __always_inline void pagefault_disabled_inc(void) > { > current->pagefault_disabled++;
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