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ARC: entry.S: [arcompact] simplify SWITCH_TO_KERNEL_STK

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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>
This commit is contained in:
Vineet Gupta 2015-03-28 21:36:00 +05:30
parent c80417b612
commit 5a343b9fe2
1 changed files with 35 additions and 36 deletions
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71
arch/arc/include/asm/entry-compact.h
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@ -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
/* save U mode SP @ pt_regs->sp */
st sp, [r9, PT_sp - SZ_PT_REGS]
/* final SP switch */
mov sp, 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 ----- */
.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 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 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