ARM: mm: Provide die_kernel_fault() helper

hulk inclusion
category: bugfix
bugzilla: 167379
CVE: NA

Reference: https://lore.kernel.org/linux-arm-kernel/20210610123556.171328-1-wangkefeng.wang@huawei.com/

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

Provide die_kernel_fault() helper to do the kernel fault reporting,
which with msg argument, it could report different message in different
scenes, and the later patch "ARM: mm: Fix PXN process with LPAE feature"
will use it.
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/arm/mm/fault.c

@@ -112,6 +112,21 @@ void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
 { }
 #endif					/* CONFIG_MMU */
 
+static void die_kernel_fault(const char *msg, struct mm_struct *mm,
+			     unsigned long addr, unsigned int fsr,
+			     struct pt_regs *regs)
+{
+	bust_spinlocks(1);
+	pr_alert("8<--- cut here ---\n");
+	pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
+		 msg, addr);
+
+	show_pte(KERN_ALERT, mm, addr);
+	die("Oops", regs, fsr);
+	bust_spinlocks(0);
+	do_exit(SIGKILL);
+}
+
 /*
  * Oops.  The kernel tried to access some page that wasn't present.
  */
@@ -119,6 +134,7 @@ static void
 __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 		  struct pt_regs *regs)
 {
+	const char *msg;
 	/*
 	 * Are we prepared to handle this kernel fault?
 	 */
@@ -128,16 +144,12 @@ __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 	/*
 	 * No handler, we'll have to terminate things with extreme prejudice.
 	 */
-	bust_spinlocks(1);
-	pr_alert("8<--- cut here ---\n");
-	pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
-		 (addr < PAGE_SIZE) ? "NULL pointer dereference" :
-		 "paging request", addr);
+	if (addr < PAGE_SIZE)
+		msg = "NULL pointer dereference";
+	else
+		msg = "paging request";
 
-	show_pte(KERN_ALERT, mm, addr);
-	die("Oops", regs, fsr);
-	bust_spinlocks(0);
-	do_exit(SIGKILL);
+	die_kernel_fault(msg, mm, addr, fsr, regs);
 }
 
 /*