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 #include <asm/dwarf.h>
  47
  48 #if defined(CONFIG_PREEMPT)
  49 #  define preempt_stop()        cli ; TRACE_IRQS_OFF
  50 #else
  51 #  define preempt_stop()
  52 #  define resume_kernel         __restore_all
  53 #endif
  54
  55
  56         .align  2
  57 ENTRY(exception_error)
  58         !
  59         TRACE_IRQS_ON
  60         sti
  61         mov.l   1f, r0
  62         jmp     @r0
  63          nop
  64
  65         .align  2
  66 1:      .long   do_exception_error
  67
  68         .align  2
  69 ret_from_exception:
  70         CFI_STARTPROC simple
  71         CFI_DEF_CFA r14, 0
  72         CFI_REL_OFFSET 17, 64
  73         CFI_REL_OFFSET 15, 60
  74         CFI_REL_OFFSET 14, 56
  75         CFI_REL_OFFSET 13, 52
  76         CFI_REL_OFFSET 12, 48
  77         CFI_REL_OFFSET 11, 44
  78         CFI_REL_OFFSET 10, 40
  79         CFI_REL_OFFSET 9, 36
  80         CFI_REL_OFFSET 8, 32
  81         preempt_stop()
  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         TRACE_IRQS_OFF
  97         mov.l   @(TI_PRE_COUNT,r8), r0  ! current_thread_info->preempt_count
  98         tst     r0, r0
  99         bf      noresched
 100 need_resched:
 101         mov.l   @(TI_FLAGS,r8), r0      ! current_thread_info->flags
 102         tst     #_TIF_NEED_RESCHED, r0  ! need_resched set?
 103         bt      noresched
 104
 105         mov     #OFF_SR, r0
 106         mov.l   @(r0,r15), r0           ! get status register
 107         shlr    r0
 108         and     #(0xf0>>1), r0          ! interrupts off (exception path)?
 109         cmp/eq  #(0xf0>>1), r0
 110         bt      noresched
 111         mov.l   1f, r0
 112         jsr     @r0                     ! call preempt_schedule_irq
 113          nop
 114         bra     need_resched
 115          nop
 116
 117 noresched:
 118         bra     __restore_all
 119          nop
 120
 121         .align 2
 122 1:      .long   preempt_schedule_irq
 123 #endif
 124
 125 ENTRY(resume_userspace)
 126         ! r8: current_thread_info
 127         cli
 128         TRACE_IRQS_OFF
 129         mov.l   @(TI_FLAGS,r8), r0              ! current_thread_info->flags
 130         tst     #(_TIF_WORK_MASK & 0xff), r0
 131         bt/s    __restore_all
 132          tst    #_TIF_NEED_RESCHED, r0
 133
 134         .align  2
 135 work_pending:
 136         ! r0: current_thread_info->flags
 137         ! r8: current_thread_info
 138         ! t:  result of "tst    #_TIF_NEED_RESCHED, r0"
 139         bf/s    work_resched
 140          tst    #(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME), r0
 141 work_notifysig:
 142         bt/s    __restore_all
 143          mov    r15, r4
 144         mov     r12, r5         ! set arg1(save_r0)
 145         mov     r0, r6
 146         sti
 147         mov.l   2f, r1
 148         mov.l   3f, r0
 149         jmp     @r1
 150          lds    r0, pr
 151 work_resched:
 152         mov.l   1f, r1
 153         jsr     @r1                             ! schedule
 154          nop
 155         cli
 156         TRACE_IRQS_OFF
 157         !
 158         mov.l   @(TI_FLAGS,r8), r0              ! current_thread_info->flags
 159         tst     #(_TIF_WORK_MASK & 0xff), r0
 160         bt      __restore_all
 161         bra     work_pending
 162          tst    #_TIF_NEED_RESCHED, r0
 163
 164         .align  2
 165 1:      .long   schedule
 166 2:      .long   do_notify_resume
 167 3:      .long   resume_userspace
 168
 169         .align  2
 170 syscall_exit_work:
 171         ! r0: current_thread_info->flags
 172         ! r8: current_thread_info
 173         tst     #(_TIF_WORK_SYSCALL_MASK & 0xff), r0
 174         bt/s    work_pending
 175          tst    #_TIF_NEED_RESCHED, r0
 176         TRACE_IRQS_ON
 177         sti
 178         mov     r15, r4
 179         mov.l   8f, r0                  ! do_syscall_trace_leave
 180         jsr     @r0
 181          nop
 182         bra     resume_userspace
 183          nop
 184
 185         .align  2
 186 syscall_trace_entry:
 187         !                       Yes it is traced.
 188         mov     r15, r4
 189         mov.l   7f, r11         ! Call do_syscall_trace_enter which notifies
 190         jsr     @r11            ! superior (will chomp R[0-7])
 191          nop
 192         mov.l   r0, @(OFF_R0,r15)       ! Save return value
 193         !                       Reload R0-R4 from kernel stack, where the
 194         !                       parent may have modified them using
 195         !                       ptrace(POKEUSR).  (Note that R0-R2 are
 196         !                       reloaded from the kernel stack by syscall_call
 197         !                       below, so don't need to be reloaded here.)
 198         !                       This allows the parent to rewrite system calls
 199         !                       and args on the fly.
 200         mov.l   @(OFF_R4,r15), r4   ! arg0
 201         mov.l   @(OFF_R5,r15), r5
 202         mov.l   @(OFF_R6,r15), r6
 203         mov.l   @(OFF_R7,r15), r7   ! arg3
 204         mov.l   @(OFF_R3,r15), r3   ! syscall_nr
 205         !
 206         mov.l   2f, r10                 ! Number of syscalls
 207         cmp/hs  r10, r3
 208         bf      syscall_call
 209         mov     #-ENOSYS, r0
 210         bra     syscall_exit
 211          mov.l  r0, @(OFF_R0,r15)       ! Return value
 212
 213 __restore_all:
 214         mov     #OFF_SR, r0
 215         mov.l   @(r0,r15), r0   ! get status register
 216
 217         shlr2   r0
 218         and     #0x3c, r0
 219         cmp/eq  #0x3c, r0
 220         bt      1f
 221         TRACE_IRQS_ON
 222         bra     2f
 223          nop
 224 1:
 225         TRACE_IRQS_OFF
 226 2:
 227         mov.l   3f, r0
 228         jmp     @r0
 229          nop
 230
 231         .align  2
 232 3:      .long   restore_all
 233
 234         .align  2
 235 syscall_badsys:                 ! Bad syscall number
 236         get_current_thread_info r8, r0
 237         mov     #-ENOSYS, r0
 238         bra     resume_userspace
 239          mov.l  r0, @(OFF_R0,r15)       ! Return value
 240
 241 /*
 242  * The main debug trap handler.
 243  *
 244  * r8=TRA (not the trap number!)
 245  *
 246  * Note: This assumes that the trapa value is left in its original
 247  * form (without the shlr2 shift) so the calculation for the jump
 248  * call table offset remains a simple in place mask.
 249  */
 250 debug_trap:
 251         mov     r8, r0
 252         and     #(0xf << 2), r0
 253         mov.l   1f, r8
 254         add     r0, r8
 255         mov.l   @r8, r8
 256         jsr     @r8
 257          nop
 258         bra     __restore_all
 259          nop
 260         CFI_ENDPROC
 261
 262         .align  2
 263 1:      .long   debug_trap_table
 264
 265 /*
 266  * Syscall interface:
 267  *
 268  *      Syscall #: R3
 269  *      Arguments #0 to #3: R4--R7
 270  *      Arguments #4 to #6: R0, R1, R2
 271  *      TRA: See following table.
 272  *
 273  * (TRA>>2)     Purpose
 274  * --------     -------
 275  * 0x00-0x0f    original SH-3/4 syscall ABI (not in general use).
 276  * 0x10-0x1f    general SH-3/4 syscall ABI.
 277  *      0x1f    unified SH-2/3/4 syscall ABI (preferred).
 278  * 0x20-0x2f    original SH-2 syscall ABI.
 279  * 0x30-0x3f    debug traps used by the kernel.
 280  * 0x40-0xff    Not supported by all parts, so left unhandled.
 281  *
 282  * For making system calls, any trap number in the range for the
 283  * given cpu model may be used, but the unified trap number 0x1f is
 284  * preferred for compatibility with all models.
 285  *
 286  * The low bits of the trap number were once documented as matching
 287  * the number of arguments, but they were never actually used as such
 288  * by the kernel. SH-2 originally used its own separate trap range
 289  * because several hardware exceptions fell in the range used for the
 290  * SH-3/4 syscall ABI.
 291  *
 292  * This code also handles delegating other traps to the BIOS/gdb stub.
 293  *
 294  * Note: When we're first called, the TRA value must be shifted
 295  * right 2 bits in order to get the value that was used as the "trapa"
 296  * argument.
 297  */
 298
 299         .align  2
 300         .globl  ret_from_fork
 301 ret_from_fork:
 302         mov.l   1f, r8
 303         jsr     @r8
 304          mov    r0, r4
 305         bra     syscall_exit
 306          nop
 307
 308         .align  2
 309         .globl  ret_from_kernel_thread
 310 ret_from_kernel_thread:
 311         mov.l   1f, r8
 312         jsr     @r8
 313          mov    r0, r4
 314         mov.l   @(OFF_R5,r15), r5   ! fn
 315         jsr     @r5
 316          mov.l  @(OFF_R4,r15), r4   ! arg
 317         bra     syscall_exit
 318          nop
 319
 320         .align  2
 321 1:      .long   schedule_tail
 322
 323 /*
 324  * The poorly named main trapa decode and dispatch routine, for
 325  * system calls and debug traps through their respective jump tables.
 326  */
 327 ENTRY(system_call)
 328         setup_frame_reg
 329 #if !defined(CONFIG_CPU_SH2)
 330         mov.l   1f, r9
 331         mov.l   @r9, r8         ! Read from TRA (Trap Address) Register
 332 #endif
 333
 334         mov     #OFF_TRA, r10
 335         add     r15, r10
 336         mov.l   r8, @r10                ! set TRA value to tra
 337
 338         /*
 339          * Check the trap type
 340          */
 341         mov     #((0x20 << 2) - 1), r9
 342         cmp/hi  r9, r8
 343         bt/s    debug_trap              ! it's a debug trap..
 344          nop
 345
 346         TRACE_IRQS_ON
 347         sti
 348
 349         !
 350         get_current_thread_info r8, r10
 351         mov.l   @(TI_FLAGS,r8), r8
 352         mov     #(_TIF_WORK_SYSCALL_MASK & 0xff), r10
 353         mov     #(_TIF_WORK_SYSCALL_MASK >> 8), r9
 354         tst     r10, r8
 355         shll8   r9
 356         bf      syscall_trace_entry
 357         tst     r9, r8
 358         bf      syscall_trace_entry
 359         !
 360         mov.l   2f, r8                  ! Number of syscalls
 361         cmp/hs  r8, r3
 362         bt      syscall_badsys
 363         !
 364 syscall_call:
 365         shll2   r3              ! x4
 366         mov.l   3f, r8          ! Load the address of sys_call_table
 367         add     r8, r3
 368         mov.l   @r3, r8
 369         mov.l   @(OFF_R2,r15), r2
 370         mov.l   @(OFF_R1,r15), r1
 371         mov.l   @(OFF_R0,r15), r0
 372         mov.l   r2, @-r15
 373         mov.l   r1, @-r15
 374         mov.l   r0, @-r15
 375         jsr     @r8             ! jump to specific syscall handler
 376          nop
 377         add     #12, r15
 378         mov.l   @(OFF_R0,r15), r12              ! save r0
 379         mov.l   r0, @(OFF_R0,r15)               ! save the return value
 380         !
 381 syscall_exit:
 382         cli
 383         TRACE_IRQS_OFF
 384         !
 385         get_current_thread_info r8, r0
 386         mov.l   @(TI_FLAGS,r8), r0              ! current_thread_info->flags
 387         tst     #(_TIF_ALLWORK_MASK & 0xff), r0
 388         mov     #(_TIF_ALLWORK_MASK >> 8), r1
 389         bf      syscall_exit_work
 390         shlr8   r0
 391         tst     r0, r1
 392         bf      syscall_exit_work
 393         bra     __restore_all
 394          nop
 395         .align  2
 396 #if !defined(CONFIG_CPU_SH2)
 397 1:      .long   TRA
 398 #endif
 399 2:      .long   NR_syscalls
 400 3:      .long   sys_call_table
 401 7:      .long   do_syscall_trace_enter
 402 8:      .long   do_syscall_trace_leave