arm64: add machine check safe sysctl interface

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5GB28
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: NTong Tiangen <tongtiangen@huawei.com>

Documentation/admin-guide/sysctl/kernel.rst

@@ -478,6 +478,27 @@ 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)
+================================
+
+Controls the kernel's behaviour when an hardware memory error is
+encountered in the following scenarios:
+
+=  ===================
+1  cow
+2  copy_mc_to_kernel
+3  copy_from_user
+4  copy_to_user
+5  get_user
+6  put_user
+=  ===================
+
+Correspondence between sysctl value and behavior:
+
+= =======================
+0 Kernel panic
+1 Kill related processes
+= =======================
 
 modprobe
 ========

arch/arm64/include/asm/processor.h

@@ -88,6 +88,8 @@
 #define STACK_TOP		STACK_TOP_MAX
 #endif /* CONFIG_COMPAT */
 
+extern int sysctl_machine_check_safe;
+
 #ifndef CONFIG_ARM64_FORCE_52BIT
 #define arch_get_mmap_end(addr) ((addr > DEFAULT_MAP_WINDOW) ? TASK_SIZE :\
 				DEFAULT_MAP_WINDOW)

arch/arm64/mm/fault.c

@@ -40,6 +40,8 @@
 #include <asm/tlbflush.h>
 #include <asm/traps.h>
 
+int sysctl_machine_check_safe = 1;
+
 struct fault_info {
 	int	(*fn)(unsigned long addr, unsigned int esr,
 		      struct pt_regs *regs);
@@ -640,6 +642,9 @@ static bool arm64_do_kernel_sea(void __user *addr, unsigned int esr,
 	if (!IS_ENABLED(CONFIG_ARCH_HAS_COPY_MC))
 		return false;
 
+	if (!sysctl_machine_check_safe)
+		return false;
+
 	if (user_mode(regs))
 		return false;
 

kernel/sysctl.c

@@ -2726,6 +2726,17 @@ static struct ctl_table kern_table[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_ONE,
 	},
+#endif
+#if defined(CONFIG_ARM64) && defined(CONFIG_ARCH_HAS_COPY_MC)
+	{
+		.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,
+	},
 #endif
 	{ }
 };