--- zzzz-none-000/linux-3.10.107/arch/arc/kernel/process.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/arch/arc/kernel/process.c	2021-02-04 17:41:59.000000000 +0000
@@ -44,23 +44,27 @@
 void arch_cpu_idle(void)
 {
 	/* sleep, but enable all interrupts before committing */
-	__asm__("sleep 0x3");
+	__asm__ __volatile__(
+		"sleep %0	\n"
+		:
+		:"I"(ISA_SLEEP_ARG)); /* can't be "r" has to be embedded const */
 }
 
 asmlinkage void ret_from_fork(void);
 
-/* Layout of Child kernel mode stack as setup at the end of this function is
+/*
+ * Copy architecture-specific thread state
+ *
+ * Layout of Child kernel mode stack as setup at the end of this function is
  *
  * |     ...        |
  * |     ...        |
  * |    unused      |
  * |                |
- * ------------------  <==== top of Stack (thread.ksp)
- * |   UNUSED 1 word|
  * ------------------
- * |     r25        |
+ * |     r25        |   <==== top of Stack (thread.ksp)
  * ~                ~
- * |    --to--      |   (CALLEE Regs of user mode)
+ * |    --to--      |   (CALLEE Regs of kernel mode)
  * |     r13        |
  * ------------------
  * |     fp         |
@@ -76,11 +80,14 @@
  * |    --to--      |   (scratch Regs of user mode)
  * |     r0         |
  * ------------------
- * |   UNUSED 1 word|
+ * |      SP        |
+ * |    orig_r0     |
+ * |    event/ECR   |
+ * |    user_r25    |
  * ------------------  <===== END of PAGE
  */
 int copy_thread(unsigned long clone_flags,
-		unsigned long usp, unsigned long arg,
+		unsigned long usp, unsigned long kthread_arg,
 		struct task_struct *p)
 {
 	struct pt_regs *c_regs;        /* child's pt_regs */
@@ -111,7 +118,7 @@
 	if (unlikely(p->flags & PF_KTHREAD)) {
 		memset(c_regs, 0, sizeof(struct pt_regs));
 
-		c_callee->r13 = arg; /* argument to kernel thread */
+		c_callee->r13 = kthread_arg;
 		c_callee->r14 = usp;  /* function */
 
 		return 0;
@@ -150,6 +157,26 @@
 }
 
 /*
+ * Do necessary setup to start up a new user task
+ */
+void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
+{
+	regs->sp = usp;
+	regs->ret = pc;
+
+	/*
+	 * [U]ser Mode bit set
+	 * [L] ZOL loop inhibited to begin with - cleared by a LP insn
+	 * Interrupts enabled
+	 */
+	regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
+
+	/* bogus seed values for debugging */
+	regs->lp_start = 0x10;
+	regs->lp_end = 0x80;
+}
+
+/*
  * Some archs flush debug and FPU info here
  */
 void flush_thread(void)
@@ -168,35 +195,15 @@
 	return 0;
 }
 
-/*
- * API: expected by schedular Code: If thread is sleeping where is that.
- * What is this good for? it will be always the scheduler or ret_from_fork.
- * So we hard code that anyways.
- */
-unsigned long thread_saved_pc(struct task_struct *t)
-{
-	struct pt_regs *regs = task_pt_regs(t);
-	unsigned long blink = 0;
-
-	/*
-	 * If the thread being queried for in not itself calling this, then it
-	 * implies it is not executing, which in turn implies it is sleeping,
-	 * which in turn implies it got switched OUT by the schedular.
-	 * In that case, it's kernel mode blink can reliably retrieved as per
-	 * the picture above (right above pt_regs).
-	 */
-	if (t != current && t->state != TASK_RUNNING)
-		blink = *((unsigned int *)regs - 1);
-
-	return blink;
-}
-
 int elf_check_arch(const struct elf32_hdr *x)
 {
 	unsigned int eflags;
 
-	if (x->e_machine != EM_ARCOMPACT)
+	if (x->e_machine != EM_ARC_INUSE) {
+		pr_err("ELF not built for %s ISA\n",
+			is_isa_arcompact() ? "ARCompact":"ARCv2");
 		return 0;
+	}
 
 	eflags = x->e_flags;
 	if ((eflags & EF_ARC_OSABI_MSK) < EF_ARC_OSABI_CURRENT) {