arm64: Make the user fault reporting more specific

For user space faults the kernel reports "unhandled page fault" and it
gives the ESR value. With this patch the error message looked up in the
fault info array to give a better description.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/mm/fault.c

@@ -36,6 +36,8 @@
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 
+static const char *fault_name(unsigned int esr);
+
 /*
  * Dump out the page tables associated with 'addr' in mm 'mm'.
  */
@@ -112,8 +114,9 @@ static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
 	struct siginfo si;
 
 	if (show_unhandled_signals) {
-		pr_info("%s[%d]: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
-			tsk->comm, task_pid_nr(tsk), sig, addr, esr);
+		pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n",
+			tsk->comm, task_pid_nr(tsk), fault_name(esr), sig,
+			addr, esr);
 		show_pte(tsk->mm, addr);
 		show_regs(regs);
 	}
@@ -450,6 +453,12 @@ static struct fault_info {
 	{ do_bad,		SIGBUS,  0,		"unknown 63"			},
 };
 
+static const char *fault_name(unsigned int esr)
+{
+	const struct fault_info *inf = fault_info + (esr & 63);
+	return inf->name;
+}
+
 /*
  * Dispatch a data abort to the relevant handler.
  */