--- zzzz-none-000/linux-3.10.107/arch/arc/mm/fault.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/arch/arc/mm/fault.c	2021-02-04 17:41:59.000000000 +0000
@@ -14,9 +14,18 @@
 #include <linux/ptrace.h>
 #include <linux/uaccess.h>
 #include <linux/kdebug.h>
+#include <linux/perf_event.h>
 #include <asm/pgalloc.h>
+#include <asm/mmu.h>
 
-static int handle_vmalloc_fault(unsigned long address)
+/*
+ * kernel virtual address is required to implement vmalloc/pkmap/fixmap
+ * Refer to asm/processor.h for System Memory Map
+ *
+ * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
+ * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
+ */
+noinline static int handle_kernel_vaddr_fault(unsigned long address)
 {
 	/*
 	 * Synchronize this task's top level page-table
@@ -51,14 +60,14 @@
 	return 1;
 }
 
-void do_page_fault(struct pt_regs *regs, int write, unsigned long address,
-		   unsigned long cause_code)
+void do_page_fault(unsigned long address, struct pt_regs *regs)
 {
 	struct vm_area_struct *vma = NULL;
 	struct task_struct *tsk = current;
 	struct mm_struct *mm = tsk->mm;
 	siginfo_t info;
 	int fault, ret;
+	int write = regs->ecr_cause & ECR_C_PROTV_STORE;  /* ST/EX */
 	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 
 	/*
@@ -70,8 +79,8 @@
 	 * only copy the information from the master page table,
 	 * nothing more.
 	 */
-	if (address >= VMALLOC_START && address <= VMALLOC_END) {
-		ret = handle_vmalloc_fault(address);
+	if (address >= VMALLOC_START) {
+		ret = handle_kernel_vaddr_fault(address);
 		if (unlikely(ret))
 			goto bad_area_nosemaphore;
 		else
@@ -84,7 +93,7 @@
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
-	if (in_atomic() || !mm)
+	if (faulthandler_disabled() || !mm)
 		goto no_context;
 
 	if (user_mode(regs))
@@ -110,7 +119,8 @@
 
 	/* Handle protection violation, execute on heap or stack */
 
-	if (cause_code == ((ECR_V_PROTV << 16) | ECR_C_PROTV_INST_FETCH))
+	if ((regs->ecr_vec == ECR_V_PROTV) &&
+	    (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
 		goto bad_area;
 
 	if (write) {
@@ -137,13 +147,20 @@
 			return;
 	}
 
+	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+
 	if (likely(!(fault & VM_FAULT_ERROR))) {
 		if (flags & FAULT_FLAG_ALLOW_RETRY) {
 			/* To avoid updating stats twice for retry case */
-			if (fault & VM_FAULT_MAJOR)
+			if (fault & VM_FAULT_MAJOR) {
 				tsk->maj_flt++;
-			else
+				perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
+					      regs, address);
+			} else {
 				tsk->min_flt++;
+				perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
+					      regs, address);
+			}
 
 			if (fault & VM_FAULT_RETRY) {
 				flags &= ~FAULT_FLAG_ALLOW_RETRY;
@@ -157,7 +174,6 @@
 		return;
 	}
 
-	/* TBD: switch to pagefault_out_of_memory() */
 	if (fault & VM_FAULT_OOM)
 		goto out_of_memory;
 	else if (fault & VM_FAULT_SIGSEGV)
@@ -179,7 +195,6 @@
 	/* User mode accesses just cause a SIGSEGV */
 	if (user_mode(regs)) {
 		tsk->thread.fault_address = address;
-		tsk->thread.cause_code = cause_code;
 		info.si_signo = SIGSEGV;
 		info.si_errno = 0;
 		/* info.si_code has been set above */
@@ -200,7 +215,7 @@
 	if (fixup_exception(regs))
 		return;
 
-	die("Oops", regs, address, cause_code);
+	die("Oops", regs, address);
 
 out_of_memory:
 	up_read(&mm->mmap_sem);
@@ -219,7 +234,6 @@
 		goto no_context;
 
 	tsk->thread.fault_address = address;
-	tsk->thread.cause_code = cause_code;
 	info.si_signo = SIGBUS;
 	info.si_errno = 0;
 	info.si_code = BUS_ADRERR;