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linux/arch/arc/include/asm/entry.h
Vineet Gupta ba3558c772 ARC: K/U SP saved from one location in stack switching macro 
This paves way for further simplifications.

There's an overhead of 1 insn for the non-common case of interrupt taken
from kernel mode.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
2013-06-22 19:23:25 +05:30

653 lines
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C
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/*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Vineetg: March 2009 (Supporting 2 levels of Interrupts)
* Stack switching code can no longer reliably rely on the fact that
* if we are NOT in user mode, stack is switched to kernel mode.
* e.g. L2 IRQ interrupted a L1 ISR which had not yet completed
* it's prologue including stack switching from user mode
*
* Vineetg: Aug 28th 2008: Bug #94984
* -Zero Overhead Loop Context shd be cleared when entering IRQ/EXcp/Trap
* Normally CPU does this automatically, however when doing FAKE rtie,
* we also need to explicitly do this. The problem in macros
* FAKE_RET_FROM_EXCPN and FAKE_RET_FROM_EXCPN_LOCK_IRQ was that this bit
* was being "CLEARED" rather then "SET". Actually "SET" clears ZOL context
*
* Vineetg: May 5th 2008
* -Modified CALLEE_REG save/restore macros to handle the fact that
* r25 contains the kernel current task ptr
* - Defined Stack Switching Macro to be reused in all intr/excp hdlrs
* - Shaved off 11 instructions from RESTORE_ALL_INT1 by using the
* address Write back load ld.ab instead of seperate ld/add instn
*
* Amit Bhor, Sameer Dhavale: Codito Technologies 2004
*/
#ifndef __ASM_ARC_ENTRY_H
#define __ASM_ARC_ENTRY_H
#ifdef __ASSEMBLY__
#include <asm/unistd.h> /* For NR_syscalls defination */
#include <asm/asm-offsets.h>
#include <asm/arcregs.h>
#include <asm/ptrace.h>
#include <asm/processor.h> /* For VMALLOC_START */
#include <asm/thread_info.h> /* For THREAD_SIZE */
/* Note on the LD/ST addr modes with addr reg wback
*
* LD.a same as LD.aw
*
* LD.a reg1, [reg2, x] => Pre Incr
* Eff Addr for load = [reg2 + x]
*
* LD.ab reg1, [reg2, x] => Post Incr
* Eff Addr for load = [reg2]
*/
.macro PUSH reg
st.a \reg, [sp, -4]
.endm
.macro PUSHAX aux
lr r9, [\aux]
PUSH r9
.endm
.macro POP reg
ld.ab \reg, [sp, 4]
.endm
.macro POPAX aux
POP r9
sr r9, [\aux]
.endm
/*--------------------------------------------------------------
* Helpers to save/restore Scratch Regs:
* used by Interrupt/Exception Prologue/Epilogue
*-------------------------------------------------------------*/
.macro SAVE_R0_TO_R12
PUSH r0
PUSH r1
PUSH r2
PUSH r3
PUSH r4
PUSH r5
PUSH r6
PUSH r7
PUSH r8
PUSH r9
PUSH r10
PUSH r11
PUSH r12
.endm
.macro RESTORE_R12_TO_R0
POP r12
POP r11
POP r10
POP r9
POP r8
POP r7
POP r6
POP r5
POP r4
POP r3
POP r2
POP r1
POP r0
.endm
/*--------------------------------------------------------------
* Helpers to save/restore callee-saved regs:
* used by several macros below
*-------------------------------------------------------------*/
.macro SAVE_R13_TO_R24
PUSH r13
PUSH r14
PUSH r15
PUSH r16
PUSH r17
PUSH r18
PUSH r19
PUSH r20
PUSH r21
PUSH r22
PUSH r23
PUSH r24
.endm
.macro RESTORE_R24_TO_R13
POP r24
POP r23
POP r22
POP r21
POP r20
POP r19
POP r18
POP r17
POP r16
POP r15
POP r14
POP r13
.endm
/*--------------------------------------------------------------
* Collect User Mode callee regs as struct callee_regs - needed by
* fork/do_signal/unaligned-access-emulation.
* (By default only scratch regs are saved on entry to kernel)
*
* Special handling for r25 if used for caching Task Pointer.
* It would have been saved in task->thread.user_r25 already, but to keep
* the interface same it is copied into regular r25 placeholder in
* struct callee_regs.
*-------------------------------------------------------------*/
.macro SAVE_CALLEE_SAVED_USER
SAVE_R13_TO_R24
#ifdef CONFIG_ARC_CURR_IN_REG
; Retrieve orig r25 and save it on stack
ld r12, [r25, TASK_THREAD + THREAD_USER_R25]
st.a r12, [sp, -4]
#else
PUSH r25
#endif
.endm
/*--------------------------------------------------------------
* Save kernel Mode callee regs at the time of Contect Switch.
*
* Special handling for r25 if used for caching Task Pointer.
* Kernel simply skips saving it since it will be loaded with
* incoming task pointer anyways
*-------------------------------------------------------------*/
.macro SAVE_CALLEE_SAVED_KERNEL
SAVE_R13_TO_R24
#ifdef CONFIG_ARC_CURR_IN_REG
sub sp, sp, 4
#else
PUSH r25
#endif
.endm
/*--------------------------------------------------------------
* Opposite of SAVE_CALLEE_SAVED_KERNEL
*-------------------------------------------------------------*/
.macro RESTORE_CALLEE_SAVED_KERNEL
#ifdef CONFIG_ARC_CURR_IN_REG
add sp, sp, 4 /* skip usual r25 placeholder */
#else
POP r25
#endif
RESTORE_R24_TO_R13
.endm
/*--------------------------------------------------------------
* Opposite of SAVE_CALLEE_SAVED_USER
*
* ptrace tracer or unaligned-access fixup might have changed a user mode
* callee reg which is saved back to usual r25 storage location
*-------------------------------------------------------------*/
.macro RESTORE_CALLEE_SAVED_USER
#ifdef CONFIG_ARC_CURR_IN_REG
ld.ab r12, [sp, 4]
st r12, [r25, TASK_THREAD + THREAD_USER_R25]
#else
POP r25
#endif
RESTORE_R24_TO_R13
.endm
/*--------------------------------------------------------------
* Super FAST Restore callee saved regs by simply re-adjusting SP
*-------------------------------------------------------------*/
.macro DISCARD_CALLEE_SAVED_USER
add sp, sp, SZ_CALLEE_REGS
.endm
/*--------------------------------------------------------------
* Restore User mode r25 saved in task_struct->thread.user_r25
*-------------------------------------------------------------*/
.macro RESTORE_USER_R25
ld r25, [r25, TASK_THREAD + THREAD_USER_R25]
.endm
/*-------------------------------------------------------------
* given a tsk struct, get to the base of it's kernel mode stack
* tsk->thread_info is really a PAGE, whose bottom hoists stack
* which grows upwards towards thread_info
*------------------------------------------------------------*/
.macro GET_TSK_STACK_BASE tsk, out
/* Get task->thread_info (this is essentially start of a PAGE) */
ld \out, [\tsk, TASK_THREAD_INFO]
/* Go to end of page where stack begins (grows upwards) */
add2 \out, \out, (THREAD_SIZE)/4
.endm
/*--------------------------------------------------------------
* 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
* Clobbers: r9
*-------------------------------------------------------------*/
.macro SWITCH_TO_KERNEL_STK
/* User Mode when this happened ? Yes: Proceed to switch stack */
bbit1 r9, STATUS_U_BIT, 88f
/* OK we were already in kernel mode when this event happened, thus can
* assume SP is kernel mode SP. _NO_ need to do any stack switching
*/
#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
/* However....
* If Level 2 Interrupts enabled, we may end up with a corner case:
* 1. User Task executing
* 2. L1 IRQ taken, ISR starts (CPU auto-switched to KERNEL mode)
* 3. But before it could switch SP from USER to KERNEL stack
* a L2 IRQ "Interrupts" L1
* Thay way although L2 IRQ happened in Kernel mode, stack is still
* not switched.
* To handle this, we may need to switch stack even if in kernel mode
* provided SP has values in range of USER mode stack ( < 0x7000_0000 )
*/
brlo sp, VMALLOC_START, 88f
/* TODO: vineetg:
* We need to be a bit more cautious here. What if a kernel bug in
* L1 ISR, caused SP to go whaco (some small value which looks like
* USER stk) and then we take L2 ISR.
* Above brlo alone would treat it as a valid L1-L2 sceanrio
* instead of shouting alound
* The only feasible way is to make sure this L2 happened in
* L1 prelogue ONLY i.e. ilink2 is less than a pre-set marker in
* L1 ISR before it switches stack
*/
#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.
*/
b.d 66f
mov r9, sp
88: /*------Intr/Ecxp happened in user mode, "switch" stack ------ */
GET_CURR_TASK_ON_CPU r9
#ifdef CONFIG_ARC_CURR_IN_REG
/* If current task pointer cached in r25, time to
* -safekeep USER r25 in task->thread_struct->user_r25
* -load r25 with current task ptr
*/
st.as r25, [r9, (TASK_THREAD + THREAD_USER_R25)/4]
mov r25, r9
#endif
/* With current tsk in r9, get it's kernel mode stack base */
GET_TSK_STACK_BASE r9, r9
66:
/* Save Pre Intr/Exception User SP on kernel stack */
st.a sp, [r9, -12] ; Make room for orig_r0 and orig_r8
/* 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
/*------------------------------------------------------------
* "FAKE" a rtie to return from CPU Exception context
* This is to re-enable Exceptions within exception
* Look at EV_ProtV to see how this is actually used
*-------------------------------------------------------------*/
.macro FAKE_RET_FROM_EXCPN reg
ld \reg, [sp, PT_status32]
bic \reg, \reg, (STATUS_U_MASK|STATUS_DE_MASK)
bset \reg, \reg, STATUS_L_BIT
sr \reg, [erstatus]
mov \reg, 55f
sr \reg, [eret]
rtie
55:
.endm
/*
* @reg [OUT] &thread_info of "current"
*/
.macro GET_CURR_THR_INFO_FROM_SP reg
bic \reg, sp, (THREAD_SIZE - 1)
.endm
/*
* @reg [OUT] thread_info->flags of "current"
*/
.macro GET_CURR_THR_INFO_FLAGS reg
GET_CURR_THR_INFO_FROM_SP \reg
ld \reg, [\reg, THREAD_INFO_FLAGS]
.endm
/*--------------------------------------------------------------
* For early Exception Prologue, a core reg is temporarily needed to
* code the rest of prolog (stack switching). This is done by stashing
* it to memory (non-SMP case) or SCRATCH0 Aux Reg (SMP).
*
* Before saving the full regfile - this reg is restored back, only
* to be saved again on kernel mode stack, as part of ptregs.
*-------------------------------------------------------------*/
.macro EXCPN_PROLOG_FREEUP_REG reg
#ifdef CONFIG_SMP
sr \reg, [ARC_REG_SCRATCH_DATA0]
#else
st \reg, [@ex_saved_reg1]
#endif
.endm
.macro EXCPN_PROLOG_RESTORE_REG reg
#ifdef CONFIG_SMP
lr \reg, [ARC_REG_SCRATCH_DATA0]
#else
ld \reg, [@ex_saved_reg1]
#endif
.endm
/*--------------------------------------------------------------
* Save all registers used by Exceptions (TLB Miss, Prot-V, Mem err etc)
* Requires SP to be already switched to kernel mode Stack
* sp points to the next free element on the stack at exit of this macro.
* Registers are pushed / popped in the order defined in struct ptregs
* in asm/ptrace.h
* Note that syscalls are implemented via TRAP which is also a exception
* from CPU's point of view
*-------------------------------------------------------------*/
.macro SAVE_ALL_EXCEPTION marker
st \marker, [sp, 8] /* orig_r8 */
st r0, [sp, 4] /* orig_r0, needed only for sys calls */
/* Restore r9 used to code the early prologue */
EXCPN_PROLOG_RESTORE_REG r9
SAVE_R0_TO_R12
PUSH gp
PUSH fp
PUSH blink
PUSHAX eret
PUSHAX erstatus
PUSH lp_count
PUSHAX lp_end
PUSHAX lp_start
PUSHAX erbta
.endm
/*--------------------------------------------------------------
* Save scratch regs for exceptions
*-------------------------------------------------------------*/
.macro SAVE_ALL_SYS
SAVE_ALL_EXCEPTION orig_r8_IS_EXCPN
.endm
/*--------------------------------------------------------------
* Save scratch regs for sys calls
*-------------------------------------------------------------*/
.macro SAVE_ALL_TRAP
/*
* Setup pt_regs->orig_r8.
* Encode syscall number (r8) in upper short word of event type (r9)
* N.B. #1: This is already endian safe (see ptrace.h)
* #2: Only r9 can be used as scratch as it is already clobbered
* and it's contents are no longer needed by the latter part
* of exception prologue
*/
lsl r9, r8, 16
or r9, r9, orig_r8_IS_SCALL
SAVE_ALL_EXCEPTION r9
.endm
/*--------------------------------------------------------------
* Restore all registers used by system call or Exceptions
* SP should always be pointing to the next free stack element
* when entering this macro.
*
* NOTE:
*
* It is recommended that lp_count/ilink1/ilink2 not be used as a dest reg
* for memory load operations. If used in that way interrupts are deffered
* by hardware and that is not good.
*-------------------------------------------------------------*/
.macro RESTORE_ALL_SYS
POPAX erbta
POPAX lp_start
POPAX lp_end
POP r9
mov lp_count, r9 ;LD to lp_count is not allowed
POPAX erstatus
POPAX eret
POP blink
POP fp
POP gp
RESTORE_R12_TO_R0
ld sp, [sp] /* restore original sp */
/* orig_r0 and orig_r8 skipped automatically */
.endm
/*--------------------------------------------------------------
* Save all registers used by interrupt handlers.
*-------------------------------------------------------------*/
.macro SAVE_ALL_INT1
/* restore original r9 to be saved as part of reg-file */
#ifdef CONFIG_SMP
lr r9, [ARC_REG_SCRATCH_DATA0]
#else
ld r9, [@int1_saved_reg]
#endif
/* now we are ready to save the remaining context :) */
st orig_r8_IS_IRQ1, [sp, 8] /* Event Type */
st 0, [sp, 4] /* orig_r0 , N/A for IRQ */
SAVE_R0_TO_R12
PUSH gp
PUSH fp
PUSH blink
PUSH ilink1
PUSHAX status32_l1
PUSH lp_count
PUSHAX lp_end
PUSHAX lp_start
PUSHAX bta_l1
.endm
.macro SAVE_ALL_INT2
/* TODO-vineetg: SMP we can't use global nor can we use
* SCRATCH0 as we do for int1 because while int1 is using
* it, int2 can come
*/
/* retsore original r9 , saved in sys_saved_r9 */
ld r9, [@int2_saved_reg]
/* now we are ready to save the remaining context :) */
st orig_r8_IS_IRQ2, [sp, 8] /* Event Type */
st 0, [sp, 4] /* orig_r0 , N/A for IRQ */
SAVE_R0_TO_R12
PUSH gp
PUSH fp
PUSH blink
PUSH ilink2
PUSHAX status32_l2
PUSH lp_count
PUSHAX lp_end
PUSHAX lp_start
PUSHAX bta_l2
.endm
/*--------------------------------------------------------------
* Restore all registers used by interrupt handlers.
*
* NOTE:
*
* It is recommended that lp_count/ilink1/ilink2 not be used as a dest reg
* for memory load operations. If used in that way interrupts are deffered
* by hardware and that is not good.
*-------------------------------------------------------------*/
.macro RESTORE_ALL_INT1
POPAX bta_l1
POPAX lp_start
POPAX lp_end
POP r9
mov lp_count, r9 ;LD to lp_count is not allowed
POPAX status32_l1
POP ilink1
POP blink
POP fp
POP gp
RESTORE_R12_TO_R0
ld sp, [sp] /* restore original sp */
/* orig_r0 and orig_r8 skipped automatically */
.endm
.macro RESTORE_ALL_INT2
POPAX bta_l2
POPAX lp_start
POPAX lp_end
POP r9
mov lp_count, r9 ;LD to lp_count is not allowed
POPAX status32_l2
POP ilink2
POP blink
POP fp
POP gp
RESTORE_R12_TO_R0
ld sp, [sp] /* restore original sp */
/* orig_r0 and orig_r8 skipped automatically */
.endm
/* Get CPU-ID of this core */
.macro GET_CPU_ID reg
lr \reg, [identity]
lsr \reg, \reg, 8
bmsk \reg, \reg, 7
.endm
#ifdef CONFIG_SMP
/*-------------------------------------------------
* Retrieve the current running task on this CPU
* 1. Determine curr CPU id.
* 2. Use it to index into _current_task[ ]
*/
.macro GET_CURR_TASK_ON_CPU reg
GET_CPU_ID \reg
ld.as \reg, [@_current_task, \reg]
.endm
/*-------------------------------------------------
* Save a new task as the "current" task on this CPU
* 1. Determine curr CPU id.
* 2. Use it to index into _current_task[ ]
*
* Coded differently than GET_CURR_TASK_ON_CPU (which uses LD.AS)
* because ST r0, [r1, offset] can ONLY have s9 @offset
* while LD can take s9 (4 byte insn) or LIMM (8 byte insn)
*/
.macro SET_CURR_TASK_ON_CPU tsk, tmp
GET_CPU_ID \tmp
add2 \tmp, @_current_task, \tmp
st \tsk, [\tmp]
#ifdef CONFIG_ARC_CURR_IN_REG
mov r25, \tsk
#endif
.endm
#else /* Uniprocessor implementation of macros */
.macro GET_CURR_TASK_ON_CPU reg
ld \reg, [@_current_task]
.endm
.macro SET_CURR_TASK_ON_CPU tsk, tmp
st \tsk, [@_current_task]
#ifdef CONFIG_ARC_CURR_IN_REG
mov r25, \tsk
#endif
.endm
#endif /* SMP / UNI */
/* ------------------------------------------------------------------
* Get the ptr to some field of Current Task at @off in task struct
* -Uses r25 for Current task ptr if that is enabled
*/
#ifdef CONFIG_ARC_CURR_IN_REG
.macro GET_CURR_TASK_FIELD_PTR off, reg
add \reg, r25, \off
.endm
#else
.macro GET_CURR_TASK_FIELD_PTR off, reg
GET_CURR_TASK_ON_CPU \reg
add \reg, \reg, \off
.endm
#endif /* CONFIG_ARC_CURR_IN_REG */
#endif /* __ASSEMBLY__ */
#endif /* __ASM_ARC_ENTRY_H */
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