ARC: Low level IRQ/Trap/Exception Handling

/*

 * 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: 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

 *  - 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/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]

 */

/*--------------------------------------------------------------

 * Save caller saved registers (scratch registers) ( r0 - r12 )

 * Registers are pushed / popped in the order defined in struct ptregs

 * in asm/ptrace.h

 *-------------------------------------------------------------*/

.macro  SAVE_CALLER_SAVED

	st.a    r0, [sp, -4]

	st.a    r1, [sp, -4]

	st.a    r2, [sp, -4]

	st.a    r3, [sp, -4]

	st.a    r4, [sp, -4]

	st.a    r5, [sp, -4]

	st.a    r6, [sp, -4]

	st.a    r7, [sp, -4]

	st.a    r8, [sp, -4]

	st.a    r9, [sp, -4]

	st.a    r10, [sp, -4]

	st.a    r11, [sp, -4]

	st.a    r12, [sp, -4]

.endm

/*--------------------------------------------------------------

 * Restore caller saved registers (scratch registers)

 *-------------------------------------------------------------*/

.macro RESTORE_CALLER_SAVED

	ld.ab   r12, [sp, 4]

	ld.ab   r11, [sp, 4]

	ld.ab   r10, [sp, 4]

	ld.ab   r9, [sp, 4]

	ld.ab   r8, [sp, 4]

	ld.ab   r7, [sp, 4]

	ld.ab   r6, [sp, 4]

	ld.ab   r5, [sp, 4]

	ld.ab   r4, [sp, 4]

	ld.ab   r3, [sp, 4]

	ld.ab   r2, [sp, 4]

	ld.ab   r1, [sp, 4]

	ld.ab   r0, [sp, 4]

.endm

/*--------------------------------------------------------------

 * Save callee saved registers (non scratch registers) ( r13 - r25 )

 *  on kernel stack.

 * User mode callee regs need to be saved in case of

 *    -fork and friends for replicating from parent to child

 *    -before going into do_signal( ) for ptrace/core-dump

 * Special case handling is required for r25 in case it is used by kernel

 *  for caching task ptr. Low level exception/ISR save user mode r25

 *  into task->thread.user_r25. So it needs to be retrieved from there and

 *  saved into kernel stack with rest of callee reg-file

 *-------------------------------------------------------------*/

.macro SAVE_CALLEE_SAVED_USER

	st.a    r13, [sp, -4]

	st.a    r14, [sp, -4]

	st.a    r15, [sp, -4]

	st.a    r16, [sp, -4]

	st.a    r17, [sp, -4]

	st.a    r18, [sp, -4]

	st.a    r19, [sp, -4]

	st.a    r20, [sp, -4]

	st.a    r21, [sp, -4]

	st.a    r22, [sp, -4]

	st.a    r23, [sp, -4]

	st.a    r24, [sp, -4]

	st.a    r25, [sp, -4]

	/* move up by 1 word to "create" callee_regs->"stack_place_holder" */

	sub sp, sp, 4

.endm

/*--------------------------------------------------------------

 * Save callee saved registers (non scratch registers) ( r13 - r25 )

 * kernel mode callee regs needed to be saved in case of context switch

 * If r25 is used for caching task pointer then that need not be saved

 * as it can be re-created from current task global

 *-------------------------------------------------------------*/

.macro SAVE_CALLEE_SAVED_KERNEL

	st.a    r13, [sp, -4]

	st.a    r14, [sp, -4]

	st.a    r15, [sp, -4]

	st.a    r16, [sp, -4]

	st.a    r17, [sp, -4]

	st.a    r18, [sp, -4]

	st.a    r19, [sp, -4]

	st.a    r20, [sp, -4]

	st.a    r21, [sp, -4]

	st.a    r22, [sp, -4]

	st.a    r23, [sp, -4]

	st.a    r24, [sp, -4]

	st.a    r25, [sp, -4]

	sub     sp, sp, 4

.endm

/*--------------------------------------------------------------

 * RESTORE_CALLEE_SAVED_KERNEL:

 * Loads callee (non scratch) Reg File by popping from Kernel mode stack.

 *  This is reverse of SAVE_CALLEE_SAVED,

 *

 * NOTE:

 * Ideally this shd only be called in switch_to for loading

 *  switched-IN task's CALLEE Reg File.

 *  For all other cases RESTORE_CALLEE_SAVED_FAST must be used

 *  which simply pops the stack w/o touching regs.

 *-------------------------------------------------------------*/

.macro RESTORE_CALLEE_SAVED_KERNEL

	add     sp, sp, 4   /* skip "callee_regs->stack_place_holder" */

	ld.ab   r25, [sp, 4]

	ld.ab   r24, [sp, 4]

	ld.ab   r23, [sp, 4]

	ld.ab   r22, [sp, 4]

	ld.ab   r21, [sp, 4]

	ld.ab   r20, [sp, 4]

	ld.ab   r19, [sp, 4]

	ld.ab   r18, [sp, 4]

	ld.ab   r17, [sp, 4]

	ld.ab   r16, [sp, 4]

	ld.ab   r15, [sp, 4]

	ld.ab   r14, [sp, 4]

	ld.ab   r13, [sp, 4]

.endm

/*--------------------------------------------------------------

 * Super FAST Restore callee saved regs by simply re-adjusting SP

 *-------------------------------------------------------------*/

.macro DISCARD_CALLEE_SAVED_USER

	add     sp, sp, 14 * 4

.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)/4   /* one word GUTTER */

.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

 * 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

	 */

	/* 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	77f

	st.a	sp, [sp, -12]	; Make room for orig_r0 and orig_r8

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

	GET_CURR_TASK_ON_CPU   r9

	/* With current tsk in r9, get it's kernel mode stack base */

	GET_TSK_STACK_BASE  r9, r9

#ifdef PT_REGS_CANARY

	st	0xabcdabcd, [r9, 0]

#endif

	/* 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

77: /* ----- 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

	and \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

	st  \reg, [@ex_saved_reg1]

.endm

.macro EXCPN_PROLOG_RESTORE_REG	reg

	ld  \reg, [@ex_saved_reg1]

.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

	/* Restore r9 used to code the early prologue */

	EXCPN_PROLOG_RESTORE_REG  r9

	/* Save the complete regfile now */

	/* orig_r8 marker:

	 * syscalls   -> 1 to NR_SYSCALLS

	 * Exceptions -> NR_SYSCALLS + 1

	 * Break-point-> NR_SYSCALLS + 2

	 */

	st      \marker, [sp, 8]

	st      r0, [sp, 4]    /* orig_r0, needed only for sys calls */

	SAVE_CALLER_SAVED

	st.a    r26, [sp, -4]   /* gp */

	st.a    fp, [sp, -4]

	st.a    blink, [sp, -4]

	lr	r9, [eret]

	st.a    r9, [sp, -4]

	lr	r9, [erstatus]

	st.a    r9, [sp, -4]

	st.a    lp_count, [sp, -4]

	lr	r9, [lp_end]

	st.a    r9, [sp, -4]

	lr	r9, [lp_start]

	st.a    r9, [sp, -4]

	lr	r9, [erbta]

	st.a    r9, [sp, -4]

#ifdef PT_REGS_CANARY

	mov   r9, 0xdeadbeef

	st    r9, [sp, -4]

#endif

	/* move up by 1 word to "create" pt_regs->"stack_place_holder" */

	sub sp, sp, 4

.endm

/*--------------------------------------------------------------

 * Save scratch regs for exceptions

 *-------------------------------------------------------------*/

.macro SAVE_ALL_SYS

	SAVE_ALL_EXCEPTION  (NR_syscalls + 1)

.endm

/*--------------------------------------------------------------

 * Save scratch regs for sys calls

 *-------------------------------------------------------------*/

.macro SAVE_ALL_TRAP

	SAVE_ALL_EXCEPTION  r8

.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

	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]

	sr	r9, [lp_start]

	ld.ab   r9, [sp, 4]

	sr	r9, [lp_end]

	ld.ab   r9, [sp, 4]

	mov	lp_count, r9

	ld.ab   r9, [sp, 4]

	sr	r9, [erstatus]

	ld.ab   r9, [sp, 4]

	sr	r9, [eret]

	ld.ab   blink, [sp, 4]

	ld.ab   fp, [sp, 4]

	ld.ab   r26, [sp, 4]    /* gp */

	RESTORE_CALLER_SAVED

	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 , saved in int1_saved_reg

	* It will be saved on stack in macro: SAVE_CALLER_SAVED

	*/

	ld  r9, [@int1_saved_reg]

	/* now we are ready to save the remaining context :) */

	st     -1, [sp, 8]    /* orig_r8, -1 for interuppt level one */

	st      0, [sp, 4]    /* orig_r0 , N/A for IRQ */

	SAVE_CALLER_SAVED

	st.a    r26, [sp, -4]   /* gp */

	st.a    fp, [sp, -4]

	st.a    blink, [sp, -4]

	st.a    ilink1, [sp, -4]

	lr	r9, [status32_l1]

	st.a    r9, [sp, -4]

	st.a    lp_count, [sp, -4]

	lr	r9, [lp_end]

	st.a    r9, [sp, -4]

	lr	r9, [lp_start]

	st.a    r9, [sp, -4]

	lr	r9, [bta_l1]

	st.a    r9, [sp, -4]

#ifdef PT_REGS_CANARY

	mov   r9, 0xdeadbee1

	st    r9, [sp, -4]

#endif

	/* move up by 1 word to "create" pt_regs->"stack_place_holder" */

	sub sp, sp, 4

.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

	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]

	sr	r9, [lp_start]

	ld.ab   r9, [sp, 4]

	sr	r9, [lp_end]

	ld.ab   r9, [sp, 4]

	mov	lp_count, r9

	ld.ab   r9, [sp, 4]

	sr	r9, [status32_l1]

	ld.ab   r9, [sp, 4]

	mov	ilink1, r9

	ld.ab   blink, [sp, 4]

	ld.ab   fp, [sp, 4]

	ld.ab   r26, [sp, 4]    /* gp */

	RESTORE_CALLER_SAVED

	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

.macro  GET_CURR_TASK_ON_CPU    reg

	ld  \reg, [@_current_task]

.endm

.macro  SET_CURR_TASK_ON_CPU    tsk, tmp

	st  \tsk, [@_current_task]

.endm

/* ------------------------------------------------------------------

 * Get the ptr to some field of Current Task at @off in task struct

 */

.macro GET_CURR_TASK_FIELD_PTR  off,  reg

	GET_CURR_TASK_ON_CPU  \reg

	add \reg, \reg, \off

.endm

#endif  /* __ASSEMBLY__ */

#endif  /* __ASM_ARC_ENTRY_H */