arch/sh/kernel/entry-common.S

   1 /*
   2  *  Copyright (C) 1999, 2000, 2002  Niibe Yutaka
   3  *  Copyright (C) 2003 - 2008  Paul Mundt
   4  *
   5  * This file is subject to the terms and conditions of the GNU General Public
   6  * License.  See the file "COPYING" in the main directory of this archive
   7  * for more details.
   8  *
   9  */
  10
  11 ! NOTE:
  12 ! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
  13 ! to be jumped is too far, but it causes illegal slot exception.
  14
  15 /*
  16  * entry.S contains the system-call and fault low-level handling routines.
  17  * This also contains the timer-interrupt handler, as well as all interrupts
  18  * and faults that can result in a task-switch.
  19  *
  20  * NOTE: This code handles signal-recognition, which happens every time
  21  * after a timer-interrupt and after each system call.
  22  *
  23  * NOTE: This code uses a convention that instructions in the delay slot
  24  * of a transfer-control instruction are indented by an extra space, thus:
  25  *
  26  *    jmp       @k0         ! control-transfer instruction
  27  *     ldc      k1, ssr     ! delay slot
  28  *
  29  * Stack layout in 'ret_from_syscall':
  30  *      ptrace needs to have all regs on the stack.
  31  *      if the order here is changed, it needs to be
  32  *      updated in ptrace.c and ptrace.h
  33  *
  34  *      r0
  35  *      ...
  36  *      r15 = stack pointer
  37  *      spc
  38  *      pr
  39  *      ssr
  40  *      gbr
  41  *      mach
  42  *      macl
  43  *      syscall #
  44  *
  45  */
  46
  47 #if defined(CONFIG_PREEMPT)
  48 #  define preempt_stop()        cli
  49 #else
  50 #  define preempt_stop()
  51 #  define resume_kernel         __restore_all
  52 #endif
  53
  54
  55         .align  2
  56 ENTRY(exception_error)
  57         !
  58 #ifdef CONFIG_TRACE_IRQFLAGS
  59         mov.l   2f, r0
  60         jsr     @r0
  61          nop
  62 #endif
  63         sti
  64         mov.l   1f, r0
  65         jmp     @r0
  66          nop
  67
  68         .align  2
  69 1:      .long   do_exception_error
  70 #ifdef CONFIG_TRACE_IRQFLAGS
  71 2:      .long   trace_hardirqs_on
  72 #endif
  73
  74         .align  2
  75 ret_from_exception:
  76         preempt_stop()
  77 #ifdef CONFIG_TRACE_IRQFLAGS
  78         mov.l   4f, r0
  79         jsr     @r0
  80          nop
  81 #endif
  82 ENTRY(ret_from_irq)
  83         !
  84         mov     #OFF_SR, r0
  85         mov.l   @(r0,r15), r0   ! get status register
  86         shll    r0
  87         shll    r0              ! kernel space?
  88         get_current_thread_info r8, r0
  89         bt      resume_kernel   ! Yes, it's from kernel, go back soon
  90
  91 #ifdef CONFIG_PREEMPT
  92         bra     resume_userspace
  93          nop
  94 ENTRY(resume_kernel)
  95         cli
  96         mov.l   @(TI_PRE_COUNT,r8), r0  ! current_thread_info->preempt_count
  97         tst     r0, r0
  98         bf      noresched
  99 need_resched:
 100         mov.l   @(TI_FLAGS,r8), r0      ! current_thread_info->flags
 101         tst     #_TIF_NEED_RESCHED, r0  ! need_resched set?
 102         bt      noresched
 103
 104         mov     #OFF_SR, r0
 105         mov.l   @(r0,r15), r0           ! get status register
 106         and     #0xf0, r0               ! interrupts off (exception path)?
 107         cmp/eq  #0xf0, r0
 108         bt      noresched
 109         mov.l   3f, r0
 110         jsr     @r0                     ! call preempt_schedule_irq
 111          nop
 112         bra     need_resched
 113          nop
 114
 115 noresched:
 116         bra     __restore_all
 117          nop
 118
 119         .align 2
 120 1:      .long   PREEMPT_ACTIVE
 121 2:      .long   schedule
 122 3:      .long   preempt_schedule_irq
 123 #endif
 124
 125 ENTRY(resume_userspace)
 126         ! r8: current_thread_info
 127         cli
 128 #ifdef CONFIG_TRACE_IRQFLAGS
 129         mov.l   5f, r0
 130         jsr     @r0
 131          nop
 132 #endif
 133         mov.l   @(TI_FLAGS,r8), r0              ! current_thread_info->flags
 134         tst     #_TIF_WORK_MASK, r0
 135         bt/s    __restore_all
 136          tst    #_TIF_NEED_RESCHED, r0
 137
 138         .align  2
 139 work_pending:
 140         ! r0: current_thread_info->flags
 141         ! r8: current_thread_info
 142         ! t:  result of "tst    #_TIF_NEED_RESCHED, r0"
 143         bf/s    work_resched
 144          tst    #(_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK), r0
 145 work_notifysig:
 146         bt/s    __restore_all
 147          mov    r15, r4
 148         mov     r12, r5         ! set arg1(save_r0)
 149         mov     r0, r6
 150         mov.l   2f, r1
 151         mov.l   3f, r0
 152         jmp     @r1
 153          lds    r0, pr
 154 work_resched:
 155         mov.l   1f, r1
 156         jsr     @r1                             ! schedule
 157          nop
 158         cli
 159 #ifdef CONFIG_TRACE_IRQFLAGS
 160         mov.l   5f, r0
 161         jsr     @r0
 162          nop
 163 #endif
 164         !
 165         mov.l   @(TI_FLAGS,r8), r0              ! current_thread_info->flags
 166         tst     #_TIF_WORK_MASK, r0
 167         bt      __restore_all
 168         bra     work_pending
 169          tst    #_TIF_NEED_RESCHED, r0
 170
 171         .align  2
 172 1:      .long   schedule
 173 2:      .long   do_notify_resume
 174 3:      .long   resume_userspace
 175 #ifdef CONFIG_TRACE_IRQFLAGS
 176 4:      .long   trace_hardirqs_on
 177 5:      .long   trace_hardirqs_off
 178 #endif
 179
 180         .align  2
 181 syscall_exit_work:
 182         ! r0: current_thread_info->flags
 183         ! r8: current_thread_info
 184         tst     #_TIF_WORK_SYSCALL_MASK, r0
 185         bt/s    work_pending
 186          tst    #_TIF_NEED_RESCHED, r0
 187 #ifdef CONFIG_TRACE_IRQFLAGS
 188         mov.l   5f, r0
 189         jsr     @r0
 190          nop
 191 #endif
 192         sti
 193         mov     r15, r4
 194         mov.l   8f, r0                  ! do_syscall_trace_leave
 195         jsr     @r0
 196          nop
 197         bra     resume_userspace
 198          nop
 199
 200         .align  2
 201 syscall_trace_entry:
 202         !                       Yes it is traced.
 203         mov     r15, r4
 204         mov.l   7f, r11         ! Call do_syscall_trace_enter which notifies
 205         jsr     @r11            ! superior (will chomp R[0-7])
 206          nop
 207         mov.l   r0, @(OFF_R0,r15)       ! Save return value
 208         !                       Reload R0-R4 from kernel stack, where the
 209         !                       parent may have modified them using
 210         !                       ptrace(POKEUSR).  (Note that R0-R2 are
 211         !                       used by the system call handler directly
 212         !                       from the kernel stack anyway, so don't need
 213         !                       to be reloaded here.)  This allows the parent
 214         !                       to rewrite system calls and args on the fly.
 215         mov.l   @(OFF_R4,r15), r4   ! arg0
 216         mov.l   @(OFF_R5,r15), r5
 217         mov.l   @(OFF_R6,r15), r6
 218         mov.l   @(OFF_R7,r15), r7   ! arg3
 219         mov.l   @(OFF_R3,r15), r3   ! syscall_nr
 220         !
 221         mov.l   2f, r10                 ! Number of syscalls
 222         cmp/hs  r10, r3
 223         bf      syscall_call
 224         mov     #-ENOSYS, r0
 225         bra     syscall_exit
 226          mov.l  r0, @(OFF_R0,r15)       ! Return value
 227
 228 __restore_all:
 229         mov.l   1f, r0
 230         jmp     @r0
 231          nop
 232
 233         .align  2
 234 1:      .long   restore_all
 235
 236         .align  2
 237 syscall_badsys:                 ! Bad syscall number
 238         get_current_thread_info r8, r0
 239         mov     #-ENOSYS, r0
 240         bra     resume_userspace
 241          mov.l  r0, @(OFF_R0,r15)       ! Return value
 242
 243 /*
 244  * The main debug trap handler.
 245  *
 246  * r8=TRA (not the trap number!)
 247  *
 248  * Note: This assumes that the trapa value is left in its original
 249  * form (without the shlr2 shift) so the calculation for the jump
 250  * call table offset remains a simple in place mask.
 251  */
 252 debug_trap:
 253         mov     r8, r0
 254         and     #(0xf << 2), r0
 255         mov.l   1f, r8
 256         add     r0, r8
 257         mov.l   @r8, r8
 258         jsr     @r8
 259          nop
 260         bra     __restore_all
 261          nop
 262
 263         .align  2
 264 1:      .long   debug_trap_table
 265
 266 /*
 267  * Syscall interface:
 268  *
 269  *      Syscall #: R3
 270  *      Arguments #0 to #3: R4--R7
 271  *      Arguments #4 to #6: R0, R1, R2
 272  *      TRA: (number of arguments + ABI revision) x 4
 273  *
 274  * This code also handles delegating other traps to the BIOS/gdb stub
 275  * according to:
 276  *
 277  * Trap number
 278  * (TRA>>2)     Purpose
 279  * --------     -------
 280  * 0x00-0x0f    original SH-3/4 syscall ABI (not in general use).
 281  * 0x10-0x1f    general SH-3/4 syscall ABI.
 282  * 0x20-0x2f    syscall ABI for SH-2 parts.
 283  * 0x30-0x3f    debug traps used by the kernel.
 284  * 0x40-0xff    Not supported by all parts, so left unhandled.
 285  *
 286  * Note: When we're first called, the TRA value must be shifted
 287  * right 2 bits in order to get the value that was used as the "trapa"
 288  * argument.
 289  */
 290
 291         .align  2
 292         .globl  ret_from_fork
 293 ret_from_fork:
 294         mov.l   1f, r8
 295         jsr     @r8
 296          mov    r0, r4
 297         bra     syscall_exit
 298          nop
 299         .align  2
 300 1:      .long   schedule_tail
 301
 302 /*
 303  * The poorly named main trapa decode and dispatch routine, for
 304  * system calls and debug traps through their respective jump tables.
 305  */
 306 ENTRY(system_call)
 307 #if !defined(CONFIG_CPU_SH2)
 308         mov.l   1f, r9
 309         mov.l   @r9, r8         ! Read from TRA (Trap Address) Register
 310 #endif
 311
 312         mov     #OFF_TRA, r10
 313         add     r15, r10
 314         mov.l   r8, @r10                ! set TRA value to tra
 315
 316         /*
 317          * Check the trap type
 318          */
 319         mov     #((0x20 << 2) - 1), r9
 320         cmp/hi  r9, r8
 321         bt/s    debug_trap              ! it's a debug trap..
 322          nop
 323
 324 #ifdef CONFIG_TRACE_IRQFLAGS
 325         mov.l   5f, r10
 326         jsr     @r10
 327          nop
 328 #endif
 329         sti
 330
 331         !
 332         get_current_thread_info r8, r10
 333         mov.l   @(TI_FLAGS,r8), r8
 334         mov     #_TIF_WORK_SYSCALL_MASK, r10
 335         tst     r10, r8
 336         bf      syscall_trace_entry
 337         !
 338         mov.l   2f, r8                  ! Number of syscalls
 339         cmp/hs  r8, r3
 340         bt      syscall_badsys
 341         !
 342 syscall_call:
 343         shll2   r3              ! x4
 344         mov.l   3f, r8          ! Load the address of sys_call_table
 345         add     r8, r3
 346         mov.l   @r3, r8
 347         jsr     @r8             ! jump to specific syscall handler
 348          nop
 349         mov.l   @(OFF_R0,r15), r12              ! save r0
 350         mov.l   r0, @(OFF_R0,r15)               ! save the return value
 351         !
 352 syscall_exit:
 353         cli
 354 #ifdef CONFIG_TRACE_IRQFLAGS
 355         mov.l   6f, r0
 356         jsr     @r0
 357          nop
 358 #endif
 359         !
 360         get_current_thread_info r8, r0
 361         mov.l   @(TI_FLAGS,r8), r0              ! current_thread_info->flags
 362         tst     #_TIF_ALLWORK_MASK, r0
 363         bf      syscall_exit_work
 364         bra     __restore_all
 365          nop
 366         .align  2
 367 #if !defined(CONFIG_CPU_SH2)
 368 1:      .long   TRA
 369 #endif
 370 2:      .long   NR_syscalls
 371 3:      .long   sys_call_table
 372 #ifdef CONFIG_TRACE_IRQFLAGS
 373 5:      .long   trace_hardirqs_on
 374 6:      .long   trace_hardirqs_off
 375 #endif
 376 7:      .long   do_syscall_trace_enter
 377 8:      .long   do_syscall_trace_leave