ARC: pt_regs update #2: Remove unused gutter at start of pt_regs

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

4 files changed, 15 insertions, 26 deletions

diff --git a/arch/arc/include/asm/entry.h b/arch/arc/include/asm/entry.h
index 2b274fa9c5a7..5ff7b8dd3d5b 100644
--- a/arch/arc/include/asm/entry.h
+++ b/arch/arc/include/asm/entry.h
@@ -432,9 +432,6 @@
         st.a    r9, [sp, -4]
         lr      r9, [erbta]
         st.a    r9, [sp, -4]
-
-        /* move up by 1 word to "create" pt_regs->"stack_place_holder" */
-        sub sp, sp, 4
 .endm
 
 /*--------------------------------------------------------------
@@ -474,9 +471,6 @@
  * by hardware and that is not good.
  *-------------------------------------------------------------*/
 .macro RESTORE_ALL_SYS
-
-        add sp, sp, 4       /* hop over unused "pt_regs->stack_place_holder" */
-
         ld.ab   r9, [sp, 4]
         sr      r9, [erbta]
         ld.ab   r9, [sp, 4]
@@ -530,9 +524,6 @@
         st.a    r9, [sp, -4]
         lr      r9, [bta_l1]
         st.a    r9, [sp, -4]
-
-        /* move up by 1 word to "create" pt_regs->"stack_place_holder" */
-        sub sp, sp, 4
 .endm
 
 .macro SAVE_ALL_INT2
@@ -561,9 +552,6 @@
         st.a    r9, [sp, -4]
         lr      r9, [bta_l2]
         st.a    r9, [sp, -4]
-
-        /* move up by 1 word to "create" pt_regs->"stack_place_holder" */
-        sub sp, sp, 4
 .endm
 
 /*--------------------------------------------------------------
@@ -577,8 +565,6 @@
  *-------------------------------------------------------------*/
 
 .macro RESTORE_ALL_INT1
-        add sp, sp, 4       /* hop over unused "pt_regs->stack_place_holder" */
-
         ld.ab   r9, [sp, 4] /* Actual reg file */
         sr      r9, [bta_l1]
         ld.ab   r9, [sp, 4]
@@ -601,8 +587,6 @@
 .endm
 
 .macro RESTORE_ALL_INT2
-        add sp, sp, 4       /* hop over unused "pt_regs->stack_place_holder" */
-
         ld.ab   r9, [sp, 4]
         sr      r9, [bta_l2]
         ld.ab   r9, [sp, 4]
diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h
index f82a3a2201b5..7491bb7428bd 100644
--- a/arch/arc/include/asm/ptrace.h
+++ b/arch/arc/include/asm/ptrace.h
@@ -17,12 +17,6 @@
 /* THE pt_regs: Defines how regs are saved during entry into kernel */
 
 struct pt_regs {
-        /*
-         * 1 word gutter after reg-file has been saved
-         * Technically not needed, Since SP always points to a "full" location
-         * (vs. "empty"). But pt_regs is shared with tools....
-         */
-        long res;
 
         /* Real registers */
         long bta;       /* bta_l1, bta_l2, erbta */
diff --git a/arch/arc/include/uapi/asm/ptrace.h b/arch/arc/include/uapi/asm/ptrace.h
index 30333cec0fef..e0e8403f181f 100644
--- a/arch/arc/include/uapi/asm/ptrace.h
+++ b/arch/arc/include/uapi/asm/ptrace.h
@@ -20,16 +20,19 @@
  *
  * 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 {
 
+        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;
diff --git a/arch/arc/kernel/ptrace.c b/arch/arc/kernel/ptrace.c
index c6a81c58d0f3..6e467e3585b0 100644
--- a/arch/arc/kernel/ptrace.c
+++ b/arch/arc/kernel/ptrace.c
@@ -40,6 +40,13 @@ static int genregs_get(struct task_struct *target,
                         offsetof(struct user_regs_struct, LOC), \
                         offsetof(struct user_regs_struct, LOC) + 4);
 
+#define REG_O_ZERO(LOC)         \
+        if (!ret)               \
+                ret = user_regset_copyout_zero(&pos, &count, &kbuf, &ubuf, \
+                        offsetof(struct user_regs_struct, LOC), \
+                        offsetof(struct user_regs_struct, LOC) + 4);
+
+        REG_O_ZERO(pad);
         REG_O_CHUNK(scratch, callee, ptregs);
         REG_O_CHUNK(callee, efa, cregs);
         REG_O_CHUNK(efa, stop_pc, &target->thread.fault_address);
@@ -88,6 +95,7 @@ static int genregs_set(struct task_struct *target,
                         offsetof(struct user_regs_struct, LOC), \
                         offsetof(struct user_regs_struct, LOC) + 4);
 
+        REG_IGNORE_ONE(pad);
         /* TBD: disallow updates to STATUS32, orig_r8 etc*/
         REG_IN_CHUNK(scratch, callee, ptregs);  /* pt_regs[bta..orig_r8] */
         REG_IN_CHUNK(callee, efa, cregs);       /* callee_regs[r25..r13] */