arch/arc/include/asm/entry-compact.h

   1 /*
   2  * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
   3  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Vineetg: March 2009 (Supporting 2 levels of Interrupts)
  10  *  Stack switching code can no longer reliably rely on the fact that
  11  *  if we are NOT in user mode, stack is switched to kernel mode.
  12  *  e.g. L2 IRQ interrupted a L1 ISR which had not yet completed
  13  *  it's prologue including stack switching from user mode
  14  *
  15  * Vineetg: Aug 28th 2008: Bug #94984
  16  *  -Zero Overhead Loop Context shd be cleared when entering IRQ/EXcp/Trap
  17  *   Normally CPU does this automatically, however when doing FAKE rtie,
  18  *   we also need to explicitly do this. The problem in macros
  19  *   FAKE_RET_FROM_EXCPN and FAKE_RET_FROM_EXCPN_LOCK_IRQ was that this bit
  20  *   was being "CLEARED" rather then "SET". Actually "SET" clears ZOL context
  21  *
  22  * Vineetg: May 5th 2008
  23  *  -Modified CALLEE_REG save/restore macros to handle the fact that
  24  *      r25 contains the kernel current task ptr
  25  *  - Defined Stack Switching Macro to be reused in all intr/excp hdlrs
  26  *  - Shaved off 11 instructions from RESTORE_ALL_INT1 by using the
  27  *      address Write back load ld.ab instead of seperate ld/add instn
  28  *
  29  * Amit Bhor, Sameer Dhavale: Codito Technologies 2004
  30  */
  31
  32 #ifndef __ASM_ARC_ENTRY_COMPACT_H
  33 #define __ASM_ARC_ENTRY_COMPACT_H
  34
  35 #include <asm/asm-offsets.h>
  36 #include <asm/irqflags-compact.h>
  37 #include <asm/thread_info.h>    /* For THREAD_SIZE */
  38
  39 #ifdef CONFIG_ARC_PLAT_EZNPS
  40 #include <plat/ctop.h>
  41 #endif
  42
  43 /*--------------------------------------------------------------
  44  * Switch to Kernel Mode stack if SP points to User Mode stack
  45  *
  46  * Entry   : r9 contains pre-IRQ/exception/trap status32
  47  * Exit    : SP set to K mode stack
  48  *           SP at the time of entry (K/U) saved @ pt_regs->sp
  49  * Clobbers: r9
  50  *-------------------------------------------------------------*/
  51
  52 .macro SWITCH_TO_KERNEL_STK
  53
  54         /* User Mode when this happened ? Yes: Proceed to switch stack */
  55         bbit1   r9, STATUS_U_BIT, 88f
  56
  57         /* OK we were already in kernel mode when this event happened, thus can
  58          * assume SP is kernel mode SP. _NO_ need to do any stack switching
  59          */
  60
  61 #ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
  62         /* However....
  63          * If Level 2 Interrupts enabled, we may end up with a corner case:
  64          * 1. User Task executing
  65          * 2. L1 IRQ taken, ISR starts (CPU auto-switched to KERNEL mode)
  66          * 3. But before it could switch SP from USER to KERNEL stack
  67          *      a L2 IRQ "Interrupts" L1
  68          * Thay way although L2 IRQ happened in Kernel mode, stack is still
  69          * not switched.
  70          * To handle this, we may need to switch stack even if in kernel mode
  71          * provided SP has values in range of USER mode stack ( < 0x7000_0000 )
  72          */
  73         brlo sp, VMALLOC_START, 88f
  74
  75         /* TODO: vineetg:
  76          * We need to be a bit more cautious here. What if a kernel bug in
  77          * L1 ISR, caused SP to go whaco (some small value which looks like
  78          * USER stk) and then we take L2 ISR.
  79          * Above brlo alone would treat it as a valid L1-L2 scenario
  80          * instead of shouting around
  81          * The only feasible way is to make sure this L2 happened in
  82          * L1 prelogue ONLY i.e. ilink2 is less than a pre-set marker in
  83          * L1 ISR before it switches stack
  84          */
  85
  86 #endif
  87
  88     /*------Intr/Ecxp happened in kernel mode, SP already setup ------ */
  89         /* save it nevertheless @ pt_regs->sp for uniformity */
  90
  91         b.d     66f
  92         st      sp, [sp, PT_sp - SZ_PT_REGS]
  93
  94 88: /*------Intr/Ecxp happened in user mode, "switch" stack ------ */
  95
  96         GET_CURR_TASK_ON_CPU   r9
  97
  98         /* With current tsk in r9, get it's kernel mode stack base */
  99         GET_TSK_STACK_BASE  r9, r9
 100
 101         /* save U mode SP @ pt_regs->sp */
 102         st      sp, [r9, PT_sp - SZ_PT_REGS]
 103
 104         /* final SP switch */
 105         mov     sp, r9
 106 66:
 107 .endm
 108
 109 /*------------------------------------------------------------
 110  * "FAKE" a rtie to return from CPU Exception context
 111  * This is to re-enable Exceptions within exception
 112  * Look at EV_ProtV to see how this is actually used
 113  *-------------------------------------------------------------*/
 114
 115 .macro FAKE_RET_FROM_EXCPN
 116
 117         lr      r9, [status32]
 118         bclr    r9, r9, STATUS_AE_BIT
 119         or      r9, r9, (STATUS_E1_MASK|STATUS_E2_MASK)
 120         sr      r9, [erstatus]
 121         mov     r9, 55f
 122         sr      r9, [eret]
 123         rtie
 124 55:
 125 .endm
 126
 127 /*--------------------------------------------------------------
 128  * For early Exception/ISR Prologue, a core reg is temporarily needed to
 129  * code the rest of prolog (stack switching). This is done by stashing
 130  * it to memory (non-SMP case) or SCRATCH0 Aux Reg (SMP).
 131  *
 132  * Before saving the full regfile - this reg is restored back, only
 133  * to be saved again on kernel mode stack, as part of pt_regs.
 134  *-------------------------------------------------------------*/
 135 .macro PROLOG_FREEUP_REG        reg, mem
 136 #ifdef CONFIG_SMP
 137         sr  \reg, [ARC_REG_SCRATCH_DATA0]
 138 #else
 139         st  \reg, [\mem]
 140 #endif
 141 .endm
 142
 143 .macro PROLOG_RESTORE_REG       reg, mem
 144 #ifdef CONFIG_SMP
 145         lr  \reg, [ARC_REG_SCRATCH_DATA0]
 146 #else
 147         ld  \reg, [\mem]
 148 #endif
 149 .endm
 150
 151 /*--------------------------------------------------------------
 152  * Exception Entry prologue
 153  * -Switches stack to K mode (if not already)
 154  * -Saves the register file
 155  *
 156  * After this it is safe to call the "C" handlers
 157  *-------------------------------------------------------------*/
 158 .macro EXCEPTION_PROLOGUE
 159
 160         /* Need at least 1 reg to code the early exception prologue */
 161         PROLOG_FREEUP_REG r9, @ex_saved_reg1
 162
 163         /* U/K mode at time of exception (stack not switched if already K) */
 164         lr  r9, [erstatus]
 165
 166         /* ARC700 doesn't provide auto-stack switching */
 167         SWITCH_TO_KERNEL_STK
 168
 169 #ifdef CONFIG_ARC_CURR_IN_REG
 170         /* Treat r25 as scratch reg (save on stack) and load with "current" */
 171         PUSH    r25
 172         GET_CURR_TASK_ON_CPU   r25
 173 #else
 174         sub     sp, sp, 4
 175 #endif
 176
 177         st.a    r0, [sp, -8]    /* orig_r0 needed for syscall (skip ECR slot) */
 178         sub     sp, sp, 4       /* skip pt_regs->sp, already saved above */
 179
 180         /* Restore r9 used to code the early prologue */
 181         PROLOG_RESTORE_REG  r9, @ex_saved_reg1
 182
 183         /* now we are ready to save the regfile */
 184         SAVE_R0_TO_R12
 185         PUSH    gp
 186         PUSH    fp
 187         PUSH    blink
 188         PUSHAX  eret
 189         PUSHAX  erstatus
 190         PUSH    lp_count
 191         PUSHAX  lp_end
 192         PUSHAX  lp_start
 193         PUSHAX  erbta
 194
 195         lr      r9, [ecr]
 196         st      r9, [sp, PT_event]    /* EV_Trap expects r9 to have ECR */
 197 .endm
 198
 199 /*--------------------------------------------------------------
 200  * Restore all registers used by system call or Exceptions
 201  * SP should always be pointing to the next free stack element
 202  * when entering this macro.
 203  *
 204  * NOTE:
 205  *
 206  * It is recommended that lp_count/ilink1/ilink2 not be used as a dest reg
 207  * for memory load operations. If used in that way interrupts are deffered
 208  * by hardware and that is not good.
 209  *-------------------------------------------------------------*/
 210 .macro EXCEPTION_EPILOGUE
 211         POPAX   erbta
 212         POPAX   lp_start
 213         POPAX   lp_end
 214
 215         POP     r9
 216         mov     lp_count, r9    ;LD to lp_count is not allowed
 217
 218         POPAX   erstatus
 219         POPAX   eret
 220         POP     blink
 221         POP     fp
 222         POP     gp
 223         RESTORE_R12_TO_R0
 224
 225         ld  sp, [sp] /* restore original sp */
 226         /* orig_r0, ECR, user_r25 skipped automatically */
 227 .endm
 228
 229 /* Dummy ECR values for Interrupts */
 230 #define event_IRQ1              0x0031abcd
 231 #define event_IRQ2              0x0032abcd
 232
 233 .macro INTERRUPT_PROLOGUE  LVL
 234
 235         /* free up r9 as scratchpad */
 236         PROLOG_FREEUP_REG r9, @int\LVL\()_saved_reg
 237
 238         /* Which mode (user/kernel) was the system in when intr occurred */
 239         lr  r9, [status32_l\LVL\()]
 240
 241         SWITCH_TO_KERNEL_STK
 242
 243 #ifdef CONFIG_ARC_CURR_IN_REG
 244         /* Treat r25 as scratch reg (save on stack) and load with "current" */
 245         PUSH    r25
 246         GET_CURR_TASK_ON_CPU   r25
 247 #else
 248         sub     sp, sp, 4
 249 #endif
 250
 251         PUSH    0x003\LVL\()abcd    /* Dummy ECR */
 252         sub     sp, sp, 8           /* skip orig_r0 (not needed)
 253                                        skip pt_regs->sp, already saved above */
 254
 255         /* Restore r9 used to code the early prologue */
 256         PROLOG_RESTORE_REG  r9, @int\LVL\()_saved_reg
 257
 258         SAVE_R0_TO_R12
 259         PUSH    gp
 260         PUSH    fp
 261         PUSH    blink
 262         PUSH    ilink\LVL\()
 263         PUSHAX  status32_l\LVL\()
 264         PUSH    lp_count
 265         PUSHAX  lp_end
 266         PUSHAX  lp_start
 267         PUSHAX  bta_l\LVL\()
 268 .endm
 269
 270 /*--------------------------------------------------------------
 271  * Restore all registers used by interrupt handlers.
 272  *
 273  * NOTE:
 274  *
 275  * It is recommended that lp_count/ilink1/ilink2 not be used as a dest reg
 276  * for memory load operations. If used in that way interrupts are deffered
 277  * by hardware and that is not good.
 278  *-------------------------------------------------------------*/
 279 .macro INTERRUPT_EPILOGUE  LVL
 280         POPAX   bta_l\LVL\()
 281         POPAX   lp_start
 282         POPAX   lp_end
 283
 284         POP     r9
 285         mov     lp_count, r9    ;LD to lp_count is not allowed
 286
 287         POPAX   status32_l\LVL\()
 288         POP     ilink\LVL\()
 289         POP     blink
 290         POP     fp
 291         POP     gp
 292         RESTORE_R12_TO_R0
 293
 294         ld  sp, [sp] /* restore original sp */
 295         /* orig_r0, ECR, user_r25 skipped automatically */
 296 .endm
 297
 298 /* Get thread_info of "current" tsk */
 299 .macro GET_CURR_THR_INFO_FROM_SP  reg
 300         bic \reg, sp, (THREAD_SIZE - 1)
 301 .endm
 302
 303 #ifndef CONFIG_ARC_PLAT_EZNPS
 304 /* Get CPU-ID of this core */
 305 .macro  GET_CPU_ID  reg
 306         lr  \reg, [identity]
 307         lsr \reg, \reg, 8
 308         bmsk \reg, \reg, 7
 309 .endm
 310 #endif
 311
 312 #endif  /* __ASM_ARC_ENTRY_COMPACT_H */