ARC: pt_regs update #3: Remove unused gutter at start of callee_regs

This is trickier than prev two:

* context switching code saves kernel mode callee regs in the format of
  struct callee_regs thus needs adjustment. This also reduces the height
  of topmost kernel stack frame by 1 word.

* Since kernel stack unwinder is sensitive to height of topmost kernel
  stack frame, that needs a word of adjustment too.

ptrace needs a bit of updating since pt_regs now diverges from
user_regs_struct.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

4 files changed, 12 insertions, 16 deletions

diff --git a/arch/arc/include/asm/entry.h b/arch/arc/include/asm/entry.h
index 5ff7b8dd3d5b..820202af21a5 100644
--- a/arch/arc/include/asm/entry.h
+++ b/arch/arc/include/asm/entry.h
@@ -124,8 +124,6 @@
 	st.a    r25, [sp, -4]
 #endif
 
-	/* move up by 1 word to "create" callee_regs->"stack_place_holder" */
-	sub sp, sp, 4
 .endm
 
 /*--------------------------------------------------------------
@@ -148,10 +146,9 @@
 	st.a    r23, [sp, -4]
 	st.a    r24, [sp, -4]
 #ifdef CONFIG_ARC_CURR_IN_REG
-	sub     sp, sp, 8
+	sub     sp, sp, 4
 #else
 	st.a    r25, [sp, -4]
-	sub     sp, sp, 4
 #endif
 .endm
 
@@ -168,14 +165,11 @@
  *-------------------------------------------------------------*/
 .macro RESTORE_CALLEE_SAVED_KERNEL
 
-
 #ifdef CONFIG_ARC_CURR_IN_REG
-	add     sp, sp, 8  /* skip callee_reg gutter and user r25 placeholder */
+	add     sp, sp, 4  /* skip usual r25 placeholder */
 #else
-	add     sp, sp, 4   /* skip "callee_regs->stack_place_holder" */
 	ld.ab   r25, [sp, 4]
 #endif
-
 	ld.ab   r24, [sp, 4]
 	ld.ab   r23, [sp, 4]
 	ld.ab   r22, [sp, 4]
@@ -203,8 +197,6 @@
  *-------------------------------------------------------------*/
 .macro RESTORE_CALLEE_SAVED_USER
 
-	add     sp, sp, 4   /* skip "callee_regs->stack_place_holder" */
-
 #ifdef CONFIG_ARC_CURR_IN_REG
 	ld.ab   r12, [sp, 4]
 	st      r12, [r25, TASK_THREAD + THREAD_USER_R25]
@@ -230,7 +222,7 @@
  * Super FAST Restore callee saved regs by simply re-adjusting SP
  *-------------------------------------------------------------*/
 .macro DISCARD_CALLEE_SAVED_USER
-	add     sp, sp, 14 * 4
+	add     sp, sp, SZ_CALLEE_REGS
 .endm
 
 /*--------------------------------------------------------------
diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
index 81efbcae3839..8c77e623c4e5 100644
--- a/arch/arc/include/asm/processor.h
+++ b/arch/arc/include/asm/processor.h
@@ -19,6 +19,7 @@
 #ifndef __ASSEMBLY__
 
 #include <asm/arcregs.h>	/* for STATUS_E1_MASK et all */
+#include <asm/ptrace.h>
 
 /* Arch specific stuff which needs to be saved per task.
  * However these items are not so important so as to earn a place in
@@ -75,11 +76,15 @@ unsigned long thread_saved_pc(struct task_struct *t);
 
 /*
  * Where abouts of Task's sp, fp, blink when it was last seen in kernel mode.
- * These can't be derived from pt_regs as that would give correp user-mode val
+ * Look in process.c for details of kernel stack layout
  */
 #define KSTK_ESP(tsk)   (tsk->thread.ksp)
-#define KSTK_BLINK(tsk) (*((unsigned int *)((KSTK_ESP(tsk)) + (13+1+1)*4)))
-#define KSTK_FP(tsk)    (*((unsigned int *)((KSTK_ESP(tsk)) + (13+1)*4)))
+
+#define KSTK_REG(tsk, off)	(*((unsigned int *)(KSTK_ESP(tsk) + \
+					sizeof(struct callee_regs) + off)))
+
+#define KSTK_BLINK(tsk) KSTK_REG(tsk, 4)
+#define KSTK_FP(tsk)    KSTK_REG(tsk, 0)
 
 /*
  * Do necessary setup to start up a newly executed thread.
diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h
index 7491bb7428bd..47801ba135b3 100644
--- a/arch/arc/include/asm/ptrace.h
+++ b/arch/arc/include/asm/ptrace.h
@@ -59,7 +59,6 @@ struct pt_regs {
 /* Callee saved registers - need to be saved only when you are scheduled out */
 
 struct callee_regs {
-	long res;	/* Again this is not needed */
 	long r25;
 	long r24;
 	long r23;
diff --git a/arch/arc/include/uapi/asm/ptrace.h b/arch/arc/include/uapi/asm/ptrace.h
index e0e8403f181f..4599109f68f2 100644
--- a/arch/arc/include/uapi/asm/ptrace.h
+++ b/arch/arc/include/uapi/asm/ptrace.h
@@ -38,8 +38,8 @@ struct user_regs_struct {
 		long r12, r11, r10, r9, r8, r7, r6, r5, r4, r3, r2, r1, r0;
 		long sp;
 	} scratch;
+	long pad2;
 	struct {
-		long pad;
 		long r25, r24, r23, r22, r21, r20;
 		long r19, r18, r17, r16, r15, r14, r13;
 	} callee;