On Mon, Jan 29, 2024 at 09:46:48PM +0800, Tong Tiangen wrote:
> For the arm64 kernel, when it processes hardware memory errors for
> synchronize notifications(do_sea()), if the errors is consumed within 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. Killing the user process and
> isolating the corrupt page is a better choice.
>
> This patch only enable machine error check framework and adds an exception
> fixup before the kernel panic in do_sea().
>
> Signed-off-by: Tong Tiangen <tongtiangen@xxxxxxxxxx>
> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/include/asm/extable.h | 1 +
> arch/arm64/mm/extable.c | 16 ++++++++++++++++
> arch/arm64/mm/fault.c | 29 ++++++++++++++++++++++++++++-
> 4 files changed, 46 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index aa7c1d435139..2cc34b5e7abb 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -20,6 +20,7 @@ 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 228d681a8715..478e639f8680 100644
> --- a/arch/arm64/mm/extable.c
> +++ b/arch/arm64/mm/extable.c
> @@ -76,3 +76,19 @@ bool fixup_exception(struct pt_regs *regs)
>
> BUG();
> }
> +
> +bool fixup_exception_mc(struct pt_regs *regs)
Can we please replace 'mc' with something like 'memory_error' ?
There's no "machine check" on arm64, and 'mc' is opaque regardless.
> +{
> + const struct exception_table_entry *ex;
> +
> + ex = search_exception_tables(instruction_pointer(regs));
> + if (!ex)
> + return false;
> +
> + /*
> + * This is not complete, More Machine check safe extable type can
> + * be processed here.
> + */
> +
> + return false;
> +}
As with my comment on the subsequenty patch, I'd much prefer that we handle
EX_TYPE_UACCESS_ERR_ZERO from the outset.
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index 55f6455a8284..312932dc100b 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -730,6 +730,31 @@ static int do_bad(unsigned long far, unsigned long esr, struct pt_regs *regs)
> return 1; /* "fault" */
> }
>
> +static bool arm64_do_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))
> + return false;
This function is called "arm64_do_kernel_sea"; surely the caller should *never*
call this for a SEA taken from user mode?
> +
> + if (apei_claim_sea(regs) < 0)
> + return false;
> +
> + if (!fixup_exception_mc(regs))
> + return false;
> +
> + if (current->flags & PF_KTHREAD)
> + return true;
I think this needs a comment; why do we allow kthreads to go on, yet kill user
threads? What about helper threads (e.g. for io_uring)?
> +
> + set_thread_esr(0, esr);
Why do we set the ESR to 0?
Mark.
> + arm64_force_sig_fault(sig, code, addr,
> + "Uncorrected memory error on access to user memory\n");
> +
> + return true;
> +}
> +
> static int do_sea(unsigned long far, unsigned long esr, struct pt_regs *regs)
> {
> const struct fault_info *inf;
> @@ -755,7 +780,9 @@ static int do_sea(unsigned long far, unsigned long esr, struct pt_regs *regs)
> */
> siaddr = untagged_addr(far);
> }
> - arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr);
> +
> + if (!arm64_do_kernel_sea(siaddr, esr, regs, inf->sig, inf->code))
> + arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr);
>
> return 0;
> }
> --
> 2.25.1
>
