--- zzzz-none-000/linux-3.10.107/arch/arc/include/uapi/asm/ptrace.h	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/arch/arc/include/uapi/asm/ptrace.h	2021-02-04 17:41:59.000000000 +0000
@@ -21,28 +21,31 @@
  *
  * This is to decouple pt_regs from user-space ABI, to be able to change it
  * w/o affecting the ABI.
- * Although the layout (initial padding) is similar to pt_regs to have some
- * optimizations when copying pt_regs to/from user_regs_struct.
+ *
+ * The intermediate pad,pad2 are relics of initial layout based on pt_regs
+ * for optimizations when copying pt_regs to/from user_regs_struct.
+ * We no longer need them, but can't be changed as they are part of ABI now.
  *
  * Also, sigcontext only care about the scratch regs as that is what we really
- * save/restore for signal handling.
+ * save/restore for signal handling. However gdb also uses the same struct
+ * hence callee regs need to be in there too.
 */
 struct user_regs_struct {
 
+	unsigned long pad;
 	struct {
-		long pad;
-		long bta, lp_start, lp_end, lp_count;
-		long status32, ret, blink, fp, gp;
-		long r12, r11, r10, r9, r8, r7, r6, r5, r4, r3, r2, r1, r0;
-		long sp;
+		unsigned long bta, lp_start, lp_end, lp_count;
+		unsigned long status32, ret, blink, fp, gp;
+		unsigned long r12, r11, r10, r9, r8, r7, r6, r5, r4, r3, r2, r1, r0;
+		unsigned long sp;
 	} scratch;
+	unsigned long pad2;
 	struct {
-		long pad;
-		long r25, r24, r23, r22, r21, r20;
-		long r19, r18, r17, r16, r15, r14, r13;
+		unsigned long r25, r24, r23, r22, r21, r20;
+		unsigned long r19, r18, r17, r16, r15, r14, r13;
 	} callee;
-	long efa;	/* break pt addr, for break points in delay slots */
-	long stop_pc;	/* give dbg stop_pc directly after checking orig_r8 */
+	unsigned long efa;	/* break pt addr, for break points in delay slots */
+	unsigned long stop_pc;	/* give dbg stop_pc after ensuring brkpt trap */
 };
 #endif /* !__ASSEMBLY__ */