Commit 4601082c authored by Tong Tiangen's avatar Tong Tiangen
Browse files

arm64: add machine check safe sysctl interface 

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9GCZS


CVE: NA

-------------------------------

Add /proc/sys/kernel/machine_check_safe_enable. Set 1(default value) to
enable machine check safe support. Set 0(default) to disable machine
check safe support.

Signed-off-by: default avatarTong Tiangen <tongtiangen@huawei.com>
parent b991780c

Documentation/admin-guide/sysctl/kernel.rst

+14 −0
Original line number Diff line number Diff line
@@ -540,6 +540,20 @@ if leaking kernel pointer values to unprivileged users is a concern. 
When ``kptr_restrict`` is set to 2, kernel pointers printed using

%pK will be replaced with 0s regardless of privileges.



machine_check_safe (arm64 only)

================================



This indicates whether the Machine Check safe memory copy feature enabled

or not，which only exists on arm64 when ARCH_HAS_COPY_MC enabled.



The value in this file determines the behaviour of the kernel when

synchronous exception from memory copy.



= ===================================================================

0 the kernel will panic immediately.

1 the kernel will recover since a memcpy-variant provided which can

  safely fail when accessing to hwpoison.

= ===================================================================



modprobe

========

arch/arm64/mm/fault.c

+29 −1
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
#include <linux/perf_event.h>

#include <linux/preempt.h>

#include <linux/hugetlb.h>

#include <linux/sysctl.h>



#include <asm/acpi.h>

#include <asm/bug.h>
@@ -43,6 +44,31 @@ 
#include <asm/tlbflush.h>

#include <asm/traps.h>



static int sysctl_machine_check_safe = IS_ENABLED(CONFIG_ARCH_HAS_COPY_MC);



#ifdef CONFIG_ARCH_HAS_COPY_MC

static struct ctl_table machine_check_safe_sysctl_table[] = {

	{

		.procname       = "machine_check_safe",

		.data           = &sysctl_machine_check_safe,

		.maxlen         = sizeof(sysctl_machine_check_safe),

		.mode           = 0644,

		.proc_handler   = proc_dointvec_minmax,

		.extra1         = SYSCTL_ZERO,

		.extra2         = SYSCTL_ONE,

	},

};



static int __init machine_check_safe_sysctl_init(void)

{

	if (!register_sysctl("kernel", machine_check_safe_sysctl_table))

		return -EINVAL;

	return 0;

}



core_initcall(machine_check_safe_sysctl_init);

#endif



struct fault_info {

	int	(*fn)(unsigned long far, unsigned long esr,

		      struct pt_regs *regs);
@@ -742,7 +768,9 @@ static bool do_apei_claim_sea(struct pt_regs *regs) 
		if (!apei_claim_sea(regs))

			return true;

	} else if (IS_ENABLED(CONFIG_ARCH_HAS_COPY_MC)) {

		if (fixup_exception_me(regs) && !apei_claim_sea(regs))

		if (sysctl_machine_check_safe &&

		    fixup_exception_me(regs) &&

		    !apei_claim_sea(regs))

			return true;

	}