root/arch/nios2/kernel/entry.S

   1 /*
   2  * linux/arch/nios2/kernel/entry.S
   3  *
   4  * Copyright (C) 2013-2014  Altera Corporation
   5  * Copyright (C) 2009, Wind River Systems Inc
   6  *
   7  * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
   8  *
   9  *  Copyright (C) 1999-2002, Greg Ungerer (gerg@snapgear.com)
  10  *  Copyright (C) 1998  D. Jeff Dionne <jeff@lineo.ca>,
  11  *                      Kenneth Albanowski <kjahds@kjahds.com>,
  12  *  Copyright (C) 2000  Lineo Inc. (www.lineo.com)
  13  *  Copyright (C) 2004  Microtronix Datacom Ltd.
  14  *
  15  * This file is subject to the terms and conditions of the GNU General Public
  16  * License.  See the file "COPYING" in the main directory of this archive
  17  * for more details.
  18  *
  19  * Linux/m68k support by Hamish Macdonald
  20  *
  21  * 68060 fixes by Jesper Skov
  22  * ColdFire support by Greg Ungerer (gerg@snapgear.com)
  23  * 5307 fixes by David W. Miller
  24  * linux 2.4 support David McCullough <davidm@snapgear.com>
  25  */
  26 
  27 #include <linux/sys.h>
  28 #include <linux/linkage.h>
  29 #include <asm/asm-offsets.h>
  30 #include <asm/asm-macros.h>
  31 #include <asm/thread_info.h>
  32 #include <asm/errno.h>
  33 #include <asm/setup.h>
  34 #include <asm/entry.h>
  35 #include <asm/unistd.h>
  36 #include <asm/processor.h>
  37 
  38 .macro GET_THREAD_INFO reg
  39 .if THREAD_SIZE & 0xffff0000
  40         andhi   \reg, sp, %hi(~(THREAD_SIZE-1))
  41 .else
  42         addi    \reg, r0, %lo(~(THREAD_SIZE-1))
  43         and     \reg, \reg, sp
  44 .endif
  45 .endm
  46 
  47 .macro  kuser_cmpxchg_check
  48         /*
  49          * Make sure our user space atomic helper is restarted if it was
  50          * interrupted in a critical region.
  51          * ea-4 = address of interrupted insn (ea must be preserved).
  52          * sp = saved regs.
  53          * cmpxchg_ldw = first critical insn, cmpxchg_stw = last critical insn.
  54          * If ea <= cmpxchg_stw and ea > cmpxchg_ldw then saved EA is set to
  55          * cmpxchg_ldw + 4.
  56         */
  57         /* et = cmpxchg_stw + 4 */
  58         movui   et, (KUSER_BASE + 4 + (cmpxchg_stw - __kuser_helper_start))
  59         bgtu    ea, et, 1f
  60 
  61         subi    et, et, (cmpxchg_stw - cmpxchg_ldw) /* et = cmpxchg_ldw + 4 */
  62         bltu    ea, et, 1f
  63         stw     et, PT_EA(sp)   /* fix up EA */
  64         mov     ea, et
  65 1:
  66 .endm
  67 
  68 .section .rodata
  69 .align 4
  70 exception_table:
  71         .word unhandled_exception       /* 0 - Reset */
  72         .word unhandled_exception       /* 1 - Processor-only Reset */
  73         .word external_interrupt        /* 2 - Interrupt */
  74         .word handle_trap               /* 3 - Trap Instruction */
  75 
  76         .word instruction_trap          /* 4 - Unimplemented instruction */
  77         .word handle_illegal            /* 5 - Illegal instruction */
  78         .word handle_unaligned          /* 6 - Misaligned data access */
  79         .word handle_unaligned          /* 7 - Misaligned destination address */
  80 
  81         .word handle_diverror           /* 8 - Division error */
  82         .word protection_exception_ba   /* 9 - Supervisor-only instr. address */
  83         .word protection_exception_instr /* 10 - Supervisor only instruction */
  84         .word protection_exception_ba   /* 11 - Supervisor only data address */
  85 
  86         .word unhandled_exception       /* 12 - Double TLB miss (data) */
  87         .word protection_exception_pte  /* 13 - TLB permission violation (x) */
  88         .word protection_exception_pte  /* 14 - TLB permission violation (r) */
  89         .word protection_exception_pte  /* 15 - TLB permission violation (w) */
  90 
  91         .word unhandled_exception       /* 16 - MPU region violation */
  92 
  93 trap_table:
  94         .word   handle_system_call      /* 0  */
  95         .word   handle_trap_1           /* 1  */
  96         .word   handle_trap_2           /* 2  */
  97         .word   handle_trap_3           /* 3  */
  98         .word   handle_trap_reserved    /* 4  */
  99         .word   handle_trap_reserved    /* 5  */
 100         .word   handle_trap_reserved    /* 6  */
 101         .word   handle_trap_reserved    /* 7  */
 102         .word   handle_trap_reserved    /* 8  */
 103         .word   handle_trap_reserved    /* 9  */
 104         .word   handle_trap_reserved    /* 10 */
 105         .word   handle_trap_reserved    /* 11 */
 106         .word   handle_trap_reserved    /* 12 */
 107         .word   handle_trap_reserved    /* 13 */
 108         .word   handle_trap_reserved    /* 14 */
 109         .word   handle_trap_reserved    /* 15 */
 110         .word   handle_trap_reserved    /* 16 */
 111         .word   handle_trap_reserved    /* 17 */
 112         .word   handle_trap_reserved    /* 18 */
 113         .word   handle_trap_reserved    /* 19 */
 114         .word   handle_trap_reserved    /* 20 */
 115         .word   handle_trap_reserved    /* 21 */
 116         .word   handle_trap_reserved    /* 22 */
 117         .word   handle_trap_reserved    /* 23 */
 118         .word   handle_trap_reserved    /* 24 */
 119         .word   handle_trap_reserved    /* 25 */
 120         .word   handle_trap_reserved    /* 26 */
 121         .word   handle_trap_reserved    /* 27 */
 122         .word   handle_trap_reserved    /* 28 */
 123         .word   handle_trap_reserved    /* 29 */
 124 #ifdef CONFIG_KGDB
 125         .word   handle_kgdb_breakpoint  /* 30 KGDB breakpoint */
 126 #else
 127         .word   instruction_trap                /* 30 */
 128 #endif
 129         .word   handle_breakpoint       /* 31 */
 130 
 131 .text
 132 .set noat
 133 .set nobreak
 134 
 135 ENTRY(inthandler)
 136         SAVE_ALL
 137 
 138         kuser_cmpxchg_check
 139 
 140         /* Clear EH bit before we get a new excpetion in the kernel
 141          * and after we have saved it to the exception frame. This is done
 142          * whether it's trap, tlb-miss or interrupt. If we don't do this
 143          * estatus is not updated the next exception.
 144          */
 145         rdctl   r24, status
 146         movi    r9, %lo(~STATUS_EH)
 147         and     r24, r24, r9
 148         wrctl   status, r24
 149 
 150         /* Read cause and vector and branch to the associated handler */
 151         mov     r4, sp
 152         rdctl   r5, exception
 153         movia   r9, exception_table
 154         add     r24, r9, r5
 155         ldw     r24, 0(r24)
 156         jmp     r24
 157 
 158 
 159 /***********************************************************************
 160  * Handle traps
 161  ***********************************************************************
 162  */
 163 ENTRY(handle_trap)
 164         ldwio   r24, -4(ea)     /* instruction that caused the exception */
 165         srli    r24, r24, 4
 166         andi    r24, r24, 0x7c
 167         movia   r9,trap_table
 168         add     r24, r24, r9
 169         ldw     r24, 0(r24)
 170         jmp     r24
 171 
 172 
 173 /***********************************************************************
 174  * Handle system calls
 175  ***********************************************************************
 176  */
 177 ENTRY(handle_system_call)
 178         /* Enable interrupts */
 179         rdctl   r10, status
 180         ori     r10, r10, STATUS_PIE
 181         wrctl   status, r10
 182 
 183         /* Reload registers destroyed by common code. */
 184         ldw     r4, PT_R4(sp)
 185         ldw     r5, PT_R5(sp)
 186 
 187 local_restart:
 188         /* Check that the requested system call is within limits */
 189         movui   r1, __NR_syscalls
 190         bgeu    r2, r1, ret_invsyscall
 191         slli    r1, r2, 2
 192         movhi   r11, %hiadj(sys_call_table)
 193         add     r1, r1, r11
 194         ldw     r1, %lo(sys_call_table)(r1)
 195         beq     r1, r0, ret_invsyscall
 196 
 197         /* Check if we are being traced */
 198         GET_THREAD_INFO r11
 199         ldw     r11,TI_FLAGS(r11)
 200         BTBNZ   r11,r11,TIF_SYSCALL_TRACE,traced_system_call
 201 
 202         /* Execute the system call */
 203         callr   r1
 204 
 205         /* If the syscall returns a negative result:
 206          *   Set r7 to 1 to indicate error,
 207          *   Negate r2 to get a positive error code
 208          * If the syscall returns zero or a positive value:
 209          *   Set r7 to 0.
 210          * The sigreturn system calls will skip the code below by
 211          * adding to register ra. To avoid destroying registers
 212          */
 213 translate_rc_and_ret:
 214         movi    r1, 0
 215         bge     r2, zero, 3f
 216         sub     r2, zero, r2
 217         movi    r1, 1
 218 3:
 219         stw     r2, PT_R2(sp)
 220         stw     r1, PT_R7(sp)
 221 end_translate_rc_and_ret:
 222 
 223 ret_from_exception:
 224         ldw     r1, PT_ESTATUS(sp)
 225         /* if so, skip resched, signals */
 226         TSTBNZ  r1, r1, ESTATUS_EU, Luser_return
 227 
 228 restore_all:
 229         rdctl   r10, status                     /* disable intrs */
 230         andi    r10, r10, %lo(~STATUS_PIE)
 231         wrctl   status, r10
 232         RESTORE_ALL
 233         eret
 234 
 235         /* If the syscall number was invalid return ENOSYS */
 236 ret_invsyscall:
 237         movi    r2, -ENOSYS
 238         br      translate_rc_and_ret
 239 
 240         /* This implements the same as above, except it calls
 241          * do_syscall_trace_enter and do_syscall_trace_exit before and after the
 242          * syscall in order for utilities like strace and gdb to work.
 243          */
 244 traced_system_call:
 245         SAVE_SWITCH_STACK
 246         call    do_syscall_trace_enter
 247         RESTORE_SWITCH_STACK
 248 
 249         /* Create system call register arguments. The 5th and 6th
 250            arguments on stack are already in place at the beginning
 251            of pt_regs. */
 252         ldw     r2, PT_R2(sp)
 253         ldw     r4, PT_R4(sp)
 254         ldw     r5, PT_R5(sp)
 255         ldw     r6, PT_R6(sp)
 256         ldw     r7, PT_R7(sp)
 257 
 258         /* Fetch the syscall function, we don't need to check the boundaries
 259          * since this is already done.
 260          */
 261         slli    r1, r2, 2
 262         movhi   r11,%hiadj(sys_call_table)
 263         add     r1, r1, r11
 264         ldw     r1, %lo(sys_call_table)(r1)
 265 
 266         callr   r1
 267 
 268         /* If the syscall returns a negative result:
 269          *   Set r7 to 1 to indicate error,
 270          *   Negate r2 to get a positive error code
 271          * If the syscall returns zero or a positive value:
 272          *   Set r7 to 0.
 273          * The sigreturn system calls will skip the code below by
 274          * adding to register ra. To avoid destroying registers
 275          */
 276 translate_rc_and_ret2:
 277         movi    r1, 0
 278         bge     r2, zero, 4f
 279         sub     r2, zero, r2
 280         movi    r1, 1
 281 4:
 282         stw     r2, PT_R2(sp)
 283         stw     r1, PT_R7(sp)
 284 end_translate_rc_and_ret2:
 285         SAVE_SWITCH_STACK
 286         call    do_syscall_trace_exit
 287         RESTORE_SWITCH_STACK
 288         br      ret_from_exception
 289 
 290 Luser_return:
 291         GET_THREAD_INFO r11                     /* get thread_info pointer */
 292         ldw     r10, TI_FLAGS(r11)              /* get thread_info->flags */
 293         ANDI32  r11, r10, _TIF_WORK_MASK
 294         beq     r11, r0, restore_all            /* Nothing to do */
 295         BTBZ    r1, r10, TIF_NEED_RESCHED, Lsignal_return
 296 
 297         /* Reschedule work */
 298         call    schedule
 299         br      ret_from_exception
 300 
 301 Lsignal_return:
 302         ANDI32  r1, r10, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME
 303         beq     r1, r0, restore_all
 304         mov     r4, sp                  /* pt_regs */
 305         SAVE_SWITCH_STACK
 306         call    do_notify_resume
 307         beq     r2, r0, no_work_pending
 308         RESTORE_SWITCH_STACK
 309         /* prepare restart syscall here without leaving kernel */
 310         ldw     r2, PT_R2(sp)   /* reload syscall number in r2 */
 311         ldw     r4, PT_R4(sp)   /* reload syscall arguments r4-r9 */
 312         ldw     r5, PT_R5(sp)
 313         ldw     r6, PT_R6(sp)
 314         ldw     r7, PT_R7(sp)
 315         ldw     r8, PT_R8(sp)
 316         ldw     r9, PT_R9(sp)
 317         br      local_restart   /* restart syscall */
 318 
 319 no_work_pending:
 320         RESTORE_SWITCH_STACK
 321         br      ret_from_exception
 322 
 323 /***********************************************************************
 324  * Handle external interrupts.
 325  ***********************************************************************
 326  */
 327 /*
 328  * This is the generic interrupt handler (for all hardware interrupt
 329  * sources). It figures out the vector number and calls the appropriate
 330  * interrupt service routine directly.
 331  */
 332 external_interrupt:
 333         rdctl   r12, ipending
 334         rdctl   r9, ienable
 335         and     r12, r12, r9
 336         /* skip if no interrupt is pending */
 337         beq     r12, r0, ret_from_interrupt
 338 
 339         movi    r24, -1
 340         stw     r24, PT_ORIG_R2(sp)
 341 
 342         /*
 343          * Process an external hardware interrupt.
 344          */
 345 
 346         addi    ea, ea, -4      /* re-issue the interrupted instruction */
 347         stw     ea, PT_EA(sp)
 348 2:      movi    r4, %lo(-1)     /* Start from bit position 0,
 349                                         highest priority */
 350                                 /* This is the IRQ # for handler call */
 351 1:      andi    r10, r12, 1     /* Isolate bit we are interested in */
 352         srli    r12, r12, 1     /* shift count is costly without hardware
 353                                         multiplier */
 354         addi    r4, r4, 1
 355         beq     r10, r0, 1b
 356         mov     r5, sp          /* Setup pt_regs pointer for handler call */
 357         call    do_IRQ
 358         rdctl   r12, ipending   /* check again if irq still pending */
 359         rdctl   r9, ienable     /* Isolate possible interrupts */
 360         and     r12, r12, r9
 361         bne     r12, r0, 2b
 362         /* br   ret_from_interrupt */ /* fall through to ret_from_interrupt */
 363 
 364 ENTRY(ret_from_interrupt)
 365         ldw     r1, PT_ESTATUS(sp)      /* check if returning to kernel */
 366         TSTBNZ  r1, r1, ESTATUS_EU, Luser_return
 367 
 368 #ifdef CONFIG_PREEMPT
 369         GET_THREAD_INFO r1
 370         ldw     r4, TI_PREEMPT_COUNT(r1)
 371         bne     r4, r0, restore_all
 372         ldw     r4, TI_FLAGS(r1)                /* ? Need resched set */
 373         BTBZ    r10, r4, TIF_NEED_RESCHED, restore_all
 374         ldw     r4, PT_ESTATUS(sp)      /* ? Interrupts off */
 375         andi    r10, r4, ESTATUS_EPIE
 376         beq     r10, r0, restore_all
 377         call    preempt_schedule_irq
 378 #endif
 379         br      restore_all
 380 
 381 /***********************************************************************
 382  * A few syscall wrappers
 383  ***********************************************************************
 384  */
 385 /*
 386  * int clone(unsigned long clone_flags, unsigned long newsp,
 387  *              int __user * parent_tidptr, int __user * child_tidptr,
 388  *              int tls_val)
 389  */
 390 ENTRY(sys_clone)
 391         SAVE_SWITCH_STACK
 392         addi    sp, sp, -4
 393         stw     r7, 0(sp)       /* Pass 5th arg thru stack */
 394         mov     r7, r6          /* 4th arg is 3rd of clone() */
 395         mov     r6, zero        /* 3rd arg always 0 */
 396         call    do_fork
 397         addi    sp, sp, 4
 398         RESTORE_SWITCH_STACK
 399         ret
 400 
 401 ENTRY(sys_rt_sigreturn)
 402         SAVE_SWITCH_STACK
 403         mov     r4, sp
 404         call    do_rt_sigreturn
 405         RESTORE_SWITCH_STACK
 406         addi    ra, ra, (end_translate_rc_and_ret - translate_rc_and_ret)
 407         ret
 408 
 409 /***********************************************************************
 410  * A few other wrappers and stubs
 411  ***********************************************************************
 412  */
 413 protection_exception_pte:
 414         rdctl   r6, pteaddr
 415         slli    r6, r6, 10
 416         call    do_page_fault
 417         br      ret_from_exception
 418 
 419 protection_exception_ba:
 420         rdctl   r6, badaddr
 421         call    do_page_fault
 422         br      ret_from_exception
 423 
 424 protection_exception_instr:
 425         call    handle_supervisor_instr
 426         br      ret_from_exception
 427 
 428 handle_breakpoint:
 429         call    breakpoint_c
 430         br      ret_from_exception
 431 
 432 #ifdef CONFIG_NIOS2_ALIGNMENT_TRAP
 433 handle_unaligned:
 434         SAVE_SWITCH_STACK
 435         call    handle_unaligned_c
 436         RESTORE_SWITCH_STACK
 437         br      ret_from_exception
 438 #else
 439 handle_unaligned:
 440         call    handle_unaligned_c
 441         br      ret_from_exception
 442 #endif
 443 
 444 handle_illegal:
 445         call    handle_illegal_c
 446         br      ret_from_exception
 447 
 448 handle_diverror:
 449         call    handle_diverror_c
 450         br      ret_from_exception
 451 
 452 #ifdef CONFIG_KGDB
 453 handle_kgdb_breakpoint:
 454         call    kgdb_breakpoint_c
 455         br      ret_from_exception
 456 #endif
 457 
 458 handle_trap_1:
 459         call    handle_trap_1_c
 460         br      ret_from_exception
 461 
 462 handle_trap_2:
 463         call    handle_trap_2_c
 464         br      ret_from_exception
 465 
 466 handle_trap_3:
 467 handle_trap_reserved:
 468         call    handle_trap_3_c
 469         br      ret_from_exception
 470 
 471 /*
 472  * Beware - when entering resume, prev (the current task) is
 473  * in r4, next (the new task) is in r5, don't change these
 474  * registers.
 475  */
 476 ENTRY(resume)
 477 
 478         rdctl   r7, status                      /* save thread status reg */
 479         stw     r7, TASK_THREAD + THREAD_KPSR(r4)
 480 
 481         andi    r7, r7, %lo(~STATUS_PIE)        /* disable interrupts */
 482         wrctl   status, r7
 483 
 484         SAVE_SWITCH_STACK
 485         stw     sp, TASK_THREAD + THREAD_KSP(r4)/* save kernel stack pointer */
 486         ldw     sp, TASK_THREAD + THREAD_KSP(r5)/* restore new thread stack */
 487         movia   r24, _current_thread            /* save thread */
 488         GET_THREAD_INFO r1
 489         stw     r1, 0(r24)
 490         RESTORE_SWITCH_STACK
 491 
 492         ldw     r7, TASK_THREAD + THREAD_KPSR(r5)/* restore thread status reg */
 493         wrctl   status, r7
 494         ret
 495 
 496 ENTRY(ret_from_fork)
 497         call    schedule_tail
 498         br      ret_from_exception
 499 
 500 ENTRY(ret_from_kernel_thread)
 501         call    schedule_tail
 502         mov     r4,r17  /* arg */
 503         callr   r16     /* function */
 504         br      ret_from_exception
 505 
 506 /*
 507  * Kernel user helpers.
 508  *
 509  * Each segment is 64-byte aligned and will be mapped to the <User space>.
 510  * New segments (if ever needed) must be added after the existing ones.
 511  * This mechanism should be used only for things that are really small and
 512  * justified, and not be abused freely.
 513  *
 514  */
 515 
 516  /* Filling pads with undefined instructions. */
 517 .macro  kuser_pad sym size
 518         .if     ((. - \sym) & 3)
 519         .rept   (4 - (. - \sym) & 3)
 520         .byte   0
 521         .endr
 522         .endif
 523         .rept   ((\size - (. - \sym)) / 4)
 524         .word   0xdeadbeef
 525         .endr
 526 .endm
 527 
 528         .align  6
 529         .globl  __kuser_helper_start
 530 __kuser_helper_start:
 531 
 532 __kuser_helper_version:                         /* @ 0x1000 */
 533         .word   ((__kuser_helper_end - __kuser_helper_start) >> 6)
 534 
 535 __kuser_cmpxchg:                                /* @ 0x1004 */
 536         /*
 537          * r4 pointer to exchange variable
 538          * r5 old value
 539          * r6 new value
 540          */
 541 cmpxchg_ldw:
 542         ldw     r2, 0(r4)                       /* load current value */
 543         sub     r2, r2, r5                      /* compare with old value */
 544         bne     r2, zero, cmpxchg_ret
 545 
 546         /* We had a match, store the new value */
 547 cmpxchg_stw:
 548         stw     r6, 0(r4)
 549 cmpxchg_ret:
 550         ret
 551 
 552         kuser_pad __kuser_cmpxchg, 64
 553 
 554         .globl  __kuser_sigtramp
 555 __kuser_sigtramp:
 556         movi    r2, __NR_rt_sigreturn
 557         trap
 558 
 559         kuser_pad __kuser_sigtramp, 64
 560 
 561         .globl  __kuser_helper_end
 562 __kuser_helper_end: