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Subject[PATCH 17/19] ARC: entry.S: [arcompact] simplify SWITCH_TO_KERNEL_STK
Date
Previously this macro was overloaded with stack switching, saving SP at right
slot in pt_regs, saving/setup of r25 and setting SP baseline to where
pt_regs->sp is saved (vs. bottom of pt_regs)

Now it only does SP switch, and leaves SP pointing to bottom of pt_regs.

r25 saving is no longer done here to allow for future reordering of
regfile in pt_regs w/o touching this macro

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
arch/arc/include/asm/entry-compact.h | 71 ++++++++++++++++++------------------
1 file changed, 35 insertions(+), 36 deletions(-)

diff --git a/arch/arc/include/asm/entry-compact.h b/arch/arc/include/asm/entry-compact.h
index 8b65eb36655a..8d0dd4d1001c 100644
--- a/arch/arc/include/asm/entry-compact.h
+++ b/arch/arc/include/asm/entry-compact.h
@@ -39,8 +39,8 @@
* Switch to Kernel Mode stack if SP points to User Mode stack
*
* Entry : r9 contains pre-IRQ/exception/trap status32
- * Exit : SP is set to kernel mode stack pointer
- * If CURR_IN_REG, r25 set to "current" task pointer
+ * Exit : SP set to K mode stack
+ * SP at the time of entry (K/U) saved @ pt_regs->sp
* Clobbers: r9
*-------------------------------------------------------------*/

@@ -80,12 +80,11 @@

#endif

- /* Save Pre Intr/Exception KERNEL MODE SP on kernel stack
- * safe-keeping not really needed, but it keeps the epilogue code
- * (SP restore) simpler/uniform.
- */
+ /*------Intr/Ecxp happened in kernel mode, SP already setup ------ */
+ /* save it nevertheless @ pt_regs->sp for uniformity */
+
b.d 66f
- mov r9, sp
+ st sp, [sp, PT_sp - SZ_PT_REGS]

88: /*------Intr/Ecxp happened in user mode, "switch" stack ------ */

@@ -94,30 +93,12 @@
/* With current tsk in r9, get it's kernel mode stack base */
GET_TSK_STACK_BASE r9, r9

-66:
-#ifdef CONFIG_ARC_CURR_IN_REG
- /*
- * Treat r25 as scratch reg, save it on stack first
- * Load it with current task pointer
- */
- st r25, [r9, -4]
- GET_CURR_TASK_ON_CPU r25
-#endif
-
- /* Save Pre Intr/Exception User SP on kernel stack */
- st.a sp, [r9, -16] ; Make room for orig_r0, ECR, user_r25
-
- /* CAUTION:
- * SP should be set at the very end when we are done with everything
- * In case of 2 levels of interrupt we depend on value of SP to assume
- * that everything else is done (loading r25 etc)
- */
-
- /* set SP to point to kernel mode stack */
- mov sp, r9
-
- /* ----- Stack Switched to kernel Mode, Now save REG FILE ----- */
+ /* save U mode SP @ pt_regs->sp */
+ st sp, [r9, PT_sp - SZ_PT_REGS]

+ /* final SP switch */
+ mov sp, r9
+66:
.endm

/*------------------------------------------------------------
@@ -181,11 +162,21 @@
/* ARC700 doesn't provide auto-stack switching */
SWITCH_TO_KERNEL_STK

- st r0, [sp, 4] /* orig_r0, needed only for sys calls */
+#ifdef CONFIG_ARC_CURR_IN_REG
+ /* Treat r25 as scratch reg (save it on stack) and load with "current" */
+ PUSH r25
+ GET_CURR_TASK_ON_CPU r25
+#else
+ sub sp, sp, 4
+#endif
+
+ st.a r0, [sp, -8] /* orig_r0 needed for syscall (skip ECR slot) */
+ sub sp, sp, 4 /* skip pt_regs->sp, already saved above */

/* Restore r9 used to code the early prologue */
PROLOG_RESTORE_REG r9, @ex_saved_reg1

+ /* now we are ready to save the regfile */
SAVE_R0_TO_R12
PUSH gp
PUSH fp
@@ -245,12 +236,20 @@

SWITCH_TO_KERNEL_STK

- /* restore original r9 */
- PROLOG_RESTORE_REG r9, @int\LVL\()_saved_reg
+#ifdef CONFIG_ARC_CURR_IN_REG
+ /* Treat r25 as scratch reg (save it on stack) and load with "current" */
+ PUSH r25
+ GET_CURR_TASK_ON_CPU r25
+#else
+ sub sp, sp, 4
+#endif

- /* now we are ready to save the remaining context */
- st 0x003\LVL\()abcd, [sp, 8] /* Dummy ECR */
- st 0, [sp, 4] /* orig_r0 , N/A for IRQ */
+ PUSH 0x003\LVL\()abcd /* Dummy ECR */
+ sub sp, sp, 8 /* skip orig_r0 (not needed)
+ skip pt_regs->sp, already saved above */
+
+ /* Restore r9 used to code the early prologue */
+ PROLOG_RESTORE_REG r9, @int\LVL\()_saved_reg

SAVE_R0_TO_R12
PUSH gp
--
1.9.1


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