arch/sparc/cpu/leon3/start.S

   1 /* This is where the SPARC/LEON3 starts
   2  * Copyright (C) 2007,
   3  * Daniel Hellstrom, daniel@gaisler.com
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 #include <config.h>
  25 #include <asm/asmmacro.h>
  26 #include <asm/winmacro.h>
  27 #include <asm/psr.h>
  28 #include <asm/stack.h>
  29 #include <asm/leon.h>
  30 #include <timestamp.h>
  31 #include <version.h>
  32
  33 /* Entry for traps which jump to a programmer-specified trap handler.  */
  34 #define TRAPR(H)  \
  35         wr      %g0, 0xfe0, %psr; \
  36         mov     %g0, %tbr; \
  37         ba      (H); \
  38         mov     %g0, %wim;
  39
  40 #define TRAP(H) \
  41         mov     %psr, %l0; \
  42         ba      (H); \
  43         nop; nop;
  44
  45 #define TRAPI(ilevel) \
  46         mov     ilevel, %l7; \
  47         mov     %psr, %l0; \
  48         b       _irq_entry; \
  49         mov     %wim, %l3
  50
  51 /* Unexcpected trap will halt the processor by forcing it to error state */
  52 #undef BAD_TRAP
  53 #define BAD_TRAP ta 0; nop; nop; nop;
  54
  55 /* Software trap. Treat as BAD_TRAP for the time being... */
  56 #define SOFT_TRAP TRAP(_hwerr)
  57
  58 #define PSR_INIT   0x1FC0       /* Disable traps, set s and ps */
  59 #define WIM_INIT   2
  60
  61 /* All traps low-level code here must end with this macro. */
  62 #define RESTORE_ALL b ret_trap_entry; clr %l6;
  63
  64 #define WRITE_PAUSE nop;nop;nop
  65
  66 WINDOWSIZE = (16 * 4)
  67 ARGPUSHSIZE = (6 * 4)
  68 ARGPUSH = (WINDOWSIZE + 4)
  69 MINFRAME = (WINDOWSIZE + ARGPUSHSIZE + 4)
  70
  71 /* Number of register windows */
  72 #ifndef CONFIG_SYS_SPARC_NWINDOWS
  73 #error Must define number of SPARC register windows, default is 8
  74 #endif
  75
  76 #define STACK_ALIGN     8
  77 #define SA(X)   (((X)+(STACK_ALIGN-1)) & ~(STACK_ALIGN-1))
  78
  79         .section ".start", "ax"
  80         .globl  _start, start, _trap_table
  81         .globl  _irq_entry, nmi_trap
  82         .globl  _reset_reloc
  83
  84 /* at address 0
  85  * Hardware traps
  86  */
  87 start:
  88 _start:
  89 _trap_table:
  90         TRAPR(_hardreset);              ! 00 reset trap
  91         BAD_TRAP;                       ! 01 instruction_access_exception
  92         BAD_TRAP;                       ! 02 illegal_instruction
  93         BAD_TRAP;                       ! 03 priveleged_instruction
  94         BAD_TRAP;                       ! 04 fp_disabled
  95         TRAP(_window_overflow);         ! 05 window_overflow
  96         TRAP(_window_underflow);        ! 06 window_underflow
  97         BAD_TRAP;                       ! 07 Memory Address Not Aligned
  98         BAD_TRAP;                       ! 08 Floating Point Exception
  99         BAD_TRAP;                       ! 09 Data Miss Exception
 100         BAD_TRAP;                       ! 0a Tagged Instruction Ovrflw
 101         BAD_TRAP;                       ! 0b Watchpoint Detected
 102         BAD_TRAP;                       ! 0c
 103         BAD_TRAP;                       ! 0d
 104         BAD_TRAP;                       ! 0e
 105         BAD_TRAP;                       ! 0f
 106         BAD_TRAP;                       ! 10
 107         TRAPI(1);                       ! 11 IRQ level 1
 108         TRAPI(2);                       ! 12 IRQ level 2
 109         TRAPI(3);                       ! 13 IRQ level 3
 110         TRAPI(4);                       ! 14 IRQ level 4
 111         TRAPI(5);                       ! 15 IRQ level 5
 112         TRAPI(6);                       ! 16 IRQ level 6
 113         TRAPI(7);                       ! 17 IRQ level 7
 114         TRAPI(8);                       ! 18 IRQ level 8
 115         TRAPI(9);                       ! 19 IRQ level 9
 116         TRAPI(10);                      ! 1a IRQ level 10
 117         TRAPI(11);                      ! 1b IRQ level 11
 118         TRAPI(12);                      ! 1c IRQ level 12
 119         TRAPI(13);                      ! 1d IRQ level 13
 120         TRAPI(14);                      ! 1e IRQ level 14
 121         TRAP(_nmi_trap);                ! 1f IRQ level 15 /
 122                                         ! NMI (non maskable interrupt)
 123         BAD_TRAP;                       ! 20 r_register_access_error
 124         BAD_TRAP;                       ! 21 instruction access error
 125         BAD_TRAP;                       ! 22
 126         BAD_TRAP;                       ! 23
 127         BAD_TRAP;                       ! 24 co-processor disabled
 128         BAD_TRAP;                       ! 25 uniplemented FLUSH
 129         BAD_TRAP;                       ! 26
 130         BAD_TRAP;                       ! 27
 131         BAD_TRAP;                       ! 28 co-processor exception
 132         BAD_TRAP;                       ! 29 data access error
 133         BAD_TRAP;                       ! 2a division by zero
 134         BAD_TRAP;                       ! 2b data store error
 135         BAD_TRAP;                       ! 2c data access MMU miss
 136         BAD_TRAP;                       ! 2d
 137         BAD_TRAP;                       ! 2e
 138         BAD_TRAP;                       ! 2f
 139         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 30-33
 140         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 34-37
 141         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 38-3b
 142         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 3c-3f
 143         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 40-43
 144         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 44-47
 145         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 48-4b
 146         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 4c-4f
 147         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 50-53
 148         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 54-57
 149         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 58-5b
 150         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 5c-5f
 151
 152         /* implementaion dependent */
 153         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 60-63
 154         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 64-67
 155         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 68-6b
 156         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 6c-6f
 157         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 70-73
 158         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 74-77
 159         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 78-7b
 160         BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 7c-7f
 161
 162         /* Software traps, not handled */
 163         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! 80-83
 164         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! 84-87
 165         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! 88-8b
 166         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! 8c-8f
 167         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! 90-93
 168         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! 94-97
 169         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! 98-9b
 170         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! 9c-9f
 171         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! a0-a3
 172         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! a4-a7
 173         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! a8-ab
 174         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! ac-af
 175         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! b0-b3
 176         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! b4-b7
 177         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! b8-bb
 178         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! bc-bf
 179         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! c0-c3
 180         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! c4-c7
 181         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! c8-cb
 182         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! cc-cf
 183         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! d0-d3
 184         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! d4-d7
 185         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! d8-db
 186         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! dc-df
 187         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! e0-e3
 188         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! e4-e7
 189         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! e8-eb
 190         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! ec-ef
 191         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! f0-f3
 192         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! f4-f7
 193         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! f8-fb
 194         SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;     ! fc-ff
 195 /*
 196  * Version string
 197  */
 198
 199         .data
 200         .extern leon3_snooping_avail
 201         .globl  version_string
 202 version_string:
 203         .ascii U_BOOT_VERSION
 204         .ascii " (", U_BOOT_DATE, " - ", U_BOOT_TIME, ")"
 205         .ascii CONFIG_IDENT_STRING, "\0"
 206
 207         .section        ".text"
 208         .align 4
 209
 210 _hardreset:
 211 1000:
 212         flush
 213
 214         /* Enable I/D-Cache and Snooping */
 215         set     0x0081000f, %g2
 216         sta     %g2, [%g0] 2
 217
 218         mov     %g0, %y
 219         clr     %g1
 220         clr     %g2
 221         clr     %g3
 222         clr     %g4
 223         clr     %g5
 224         clr     %g6
 225         clr     %g7
 226
 227         mov     %asr17, %g3
 228         and     %g3, 0x1f, %g3
 229 clear_window:
 230         mov     %g0, %l0
 231         mov     %g0, %l1
 232         mov     %g0, %l2
 233         mov     %g0, %l3
 234         mov     %g0, %l4
 235         mov     %g0, %l5
 236         mov     %g0, %l6
 237         mov     %g0, %l7
 238         mov     %g0, %o0
 239         mov     %g0, %o1
 240         mov     %g0, %o2
 241         mov     %g0, %o3
 242         mov     %g0, %o4
 243         mov     %g0, %o5
 244         mov     %g0, %o6
 245         mov     %g0, %o7
 246         subcc   %g3, 1, %g3
 247         bge     clear_window
 248         save
 249
 250 wininit:
 251         set     WIM_INIT, %g3
 252         mov     %g3, %wim
 253
 254 stackp:
 255         set     CONFIG_SYS_INIT_SP_OFFSET, %fp
 256         andn    %fp, 0x0f, %fp
 257         sub     %fp, 64, %sp
 258
 259 cpu_init_unreloc:
 260         call    cpu_init_f
 261         nop
 262
 263 /* un relocated start address of monitor */
 264 #define TEXT_START _text
 265
 266 /* un relocated end address of monitor */
 267 #define DATA_END __init_end
 268
 269 reloc:
 270         set     TEXT_START,%g2
 271         set     DATA_END,%g3
 272         set     CONFIG_SYS_RELOC_MONITOR_BASE,%g4
 273 reloc_loop:
 274         ldd     [%g2],%l0
 275         ldd     [%g2+8],%l2
 276         std     %l0,[%g4]
 277         std     %l2,[%g4+8]
 278         inc     16,%g2
 279         subcc   %g3,%g2,%g0
 280         bne     reloc_loop
 281         inc     16,%g4
 282
 283         clr     %l0
 284         clr     %l1
 285         clr     %l2
 286         clr     %l3
 287         clr     %g2
 288
 289 /* register g4 contain address to start
 290  * This means that BSS must be directly after data and code segments
 291  *
 292  * g3 is length of bss = (__bss_end-__bss_start)
 293  *
 294  */
 295
 296 clr_bss:
 297 /* clear bss area (the relocated) */
 298         set     __bss_start,%g2
 299         set     __bss_end,%g3
 300         sub     %g3,%g2,%g3
 301         add     %g3,%g4,%g3
 302         clr     %g1     /* std %g0 uses g0 and g1 */
 303 /* clearing 16byte a time ==> linker script need to align to 16 byte offset */
 304 clr_bss_16:
 305         std     %g0,[%g4]
 306         std     %g0,[%g4+8]
 307         inc     16,%g4
 308         cmp     %g3,%g4
 309         bne     clr_bss_16
 310         nop
 311
 312 /* add offsets to GOT table */
 313 fixup_got:
 314         set     __got_start,%g4
 315         set     __got_end,%g3
 316 /*
 317  * new got offset = (old GOT-PTR (read with ld) -
 318  *   CONFIG_SYS_RELOC_MONITOR_BASE(from define) ) +
 319  *   Destination Address (from define)
 320  */
 321         set     CONFIG_SYS_RELOC_MONITOR_BASE,%g2
 322         set     TEXT_START, %g1
 323         add     %g4,%g2,%g4
 324         sub     %g4,%g1,%g4
 325         add     %g3,%g2,%g3
 326         sub     %g3,%g1,%g3
 327         sub     %g2,%g1,%g2     ! prepare register with (new base address) -
 328                                 !  (old base address)
 329 got_loop:
 330         ld      [%g4],%l0       ! load old GOT-PTR
 331         add     %l0,%g2,%l0     ! increase with (new base address) -
 332                                 !  (old base)
 333         st      %l0,[%g4]
 334         inc     4,%g4
 335         cmp     %g3,%g4
 336         bne     got_loop
 337         nop
 338
 339 prom_relocate:
 340         set     __prom_start, %g2
 341         set     __prom_end, %g3
 342         set     CONFIG_SYS_PROM_OFFSET, %g4
 343
 344 prom_relocate_loop:
 345         ldd     [%g2],%l0
 346         ldd     [%g2+8],%l2
 347         std     %l0,[%g4]
 348         std     %l2,[%g4+8]
 349         inc     16,%g2
 350         subcc   %g3,%g2,%g0
 351         bne     prom_relocate_loop
 352         inc     16,%g4
 353
 354 /* Trap table has been moved, lets tell CPU about
 355  * the new trap table address
 356  */
 357
 358         set     CONFIG_SYS_RELOC_MONITOR_BASE, %g2
 359         wr      %g0, %g2, %tbr
 360         nop
 361         nop
 362         nop
 363
 364 /* If CACHE snooping is available in hardware the
 365  * variable leon3_snooping_avail will be set to
 366  * 0x800000 else 0.
 367  */
 368 snoop_detect:
 369         sethi   %hi(0x00800000), %o0
 370         lda     [%g0] 2, %o1
 371         and     %o0, %o1, %o0
 372         sethi   %hi(leon3_snooping_avail+CONFIG_SYS_RELOC_MONITOR_BASE-CONFIG_SYS_TEXT_BASE), %o1
 373         st      %o0, [%lo(leon3_snooping_avail+CONFIG_SYS_RELOC_MONITOR_BASE-CONFIG_SYS_TEXT_BASE)+%o1]
 374
 375 /*      call    relocate*/
 376         nop
 377 /* Call relocated init functions */
 378 jump:
 379         set     cpu_init_f2,%o1
 380         set     CONFIG_SYS_RELOC_MONITOR_BASE,%o2
 381         add     %o1,%o2,%o1
 382         sub     %o1,%g1,%o1
 383         call    %o1
 384         clr     %o0
 385
 386         set     board_init_f,%o1
 387         set     CONFIG_SYS_RELOC_MONITOR_BASE,%o2
 388         add     %o1,%o2,%o1
 389         sub     %o1,%g1,%o1
 390         call    %o1
 391         clr     %o0
 392
 393 dead:   ta 0                            ! if call returns...
 394         nop
 395
 396 /* Interrupt handler caller,
 397  * reg L7: interrupt number
 398  * reg L0: psr after interrupt
 399  * reg L1: PC
 400  * reg L2: next PC
 401  * reg L3: wim
 402  */
 403 _irq_entry:
 404         SAVE_ALL
 405
 406         or      %l0, PSR_PIL, %g2
 407         wr      %g2, 0x0, %psr
 408         WRITE_PAUSE
 409         wr      %g2, PSR_ET, %psr
 410         WRITE_PAUSE
 411         mov     %l7, %o0                ! irq level
 412         set     handler_irq, %o1
 413         set     (CONFIG_SYS_RELOC_MONITOR_BASE-CONFIG_SYS_TEXT_BASE), %o2
 414         add     %o1, %o2, %o1
 415         call    %o1
 416         add     %sp, SF_REGS_SZ, %o1    ! pt_regs ptr
 417         or      %l0, PSR_PIL, %g2       ! restore PIL after handler_irq
 418         wr      %g2, PSR_ET, %psr       ! keep ET up
 419         WRITE_PAUSE
 420
 421         RESTORE_ALL
 422
 423 !Window overflow trap handler.
 424         .global _window_overflow
 425
 426 _window_overflow:
 427
 428         mov     %wim, %l3               ! Calculate next WIM
 429         mov     %g1, %l7
 430         srl     %l3, 1, %g1
 431         sll     %l3, (CONFIG_SYS_SPARC_NWINDOWS-1) , %l4
 432         or      %l4, %g1, %g1
 433
 434         save                            ! Get into window to be saved.
 435         mov     %g1, %wim
 436         nop;
 437         nop;
 438         nop
 439         st      %l0, [%sp + 0];
 440         st      %l1, [%sp + 4];
 441         st      %l2, [%sp + 8];
 442         st      %l3, [%sp + 12];
 443         st      %l4, [%sp + 16];
 444         st      %l5, [%sp + 20];
 445         st      %l6, [%sp + 24];
 446         st      %l7, [%sp + 28];
 447         st      %i0, [%sp + 32];
 448         st      %i1, [%sp + 36];
 449         st      %i2, [%sp + 40];
 450         st      %i3, [%sp + 44];
 451         st      %i4, [%sp + 48];
 452         st      %i5, [%sp + 52];
 453         st      %i6, [%sp + 56];
 454         st      %i7, [%sp + 60];
 455         restore                         ! Go back to trap window.
 456         mov     %l7, %g1
 457         jmp     %l1                     ! Re-execute save.
 458         rett    %l2
 459
 460 /* Window underflow trap handler.  */
 461
 462         .global  _window_underflow
 463
 464 _window_underflow:
 465
 466         mov  %wim, %l3                  ! Calculate next WIM
 467         sll  %l3, 1, %l4
 468         srl  %l3, (CONFIG_SYS_SPARC_NWINDOWS-1), %l5
 469         or   %l5, %l4, %l5
 470         mov  %l5, %wim
 471         nop; nop; nop
 472         restore                         ! Two restores to get into the
 473         restore                         ! window to restore
 474         ld      [%sp + 0], %l0;         ! Restore window from the stack
 475         ld      [%sp + 4], %l1;
 476         ld      [%sp + 8], %l2;
 477         ld      [%sp + 12], %l3;
 478         ld      [%sp + 16], %l4;
 479         ld      [%sp + 20], %l5;
 480         ld      [%sp + 24], %l6;
 481         ld      [%sp + 28], %l7;
 482         ld      [%sp + 32], %i0;
 483         ld      [%sp + 36], %i1;
 484         ld      [%sp + 40], %i2;
 485         ld      [%sp + 44], %i3;
 486         ld      [%sp + 48], %i4;
 487         ld      [%sp + 52], %i5;
 488         ld      [%sp + 56], %i6;
 489         ld      [%sp + 60], %i7;
 490         save                            ! Get back to the trap window.
 491         save
 492         jmp     %l1                     ! Re-execute restore.
 493         rett    %l2
 494
 495         retl
 496
 497 _nmi_trap:
 498         nop
 499         jmp %l1
 500         rett %l2
 501
 502 _hwerr:
 503         ta 0
 504         nop
 505         nop
 506         b _hwerr                        ! loop infinite
 507         nop
 508
 509 /* Registers to not touch at all. */
 510 #define t_psr      l0 /* Set by caller */
 511 #define t_pc       l1 /* Set by caller */
 512 #define t_npc      l2 /* Set by caller */
 513 #define t_wim      l3 /* Set by caller */
 514 #define t_twinmask l4 /* Set at beginning of this entry routine. */
 515 #define t_kstack   l5 /* Set right before pt_regs frame is built */
 516 #define t_retpc    l6 /* If you change this, change winmacro.h header file */
 517 #define t_systable l7 /* Never touch this, could be the syscall table ptr. */
 518 #define curptr     g6 /* Set after pt_regs frame is built */
 519
 520 trap_setup:
 521 /* build a pt_regs trap frame. */
 522         sub     %fp, (SF_REGS_SZ + PT_REGS_SZ), %t_kstack
 523         PT_STORE_ALL(t_kstack, t_psr, t_pc, t_npc, g2)
 524
 525         /* See if we are in the trap window. */
 526         mov     1, %t_twinmask
 527         sll     %t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)
 528         andcc   %t_twinmask, %t_wim, %g0
 529         beq     1f              ! in trap window, clean up
 530         nop
 531
 532         /*-------------------------------------------------
 533          * Spill , adjust %wim and go.
 534          */
 535         srl     %t_wim, 0x1, %g2                ! begin computation of new %wim
 536
 537         set     (CONFIG_SYS_SPARC_NWINDOWS-1), %g3      !NWINDOWS-1
 538
 539         sll     %t_wim, %g3, %t_wim     ! NWINDOWS-1
 540         or      %t_wim, %g2, %g2
 541         and     %g2, 0xff, %g2
 542
 543         save    %g0, %g0, %g0           ! get in window to be saved
 544
 545         /* Set new %wim value */
 546         wr      %g2, 0x0, %wim
 547
 548         /* Save the kernel window onto the corresponding stack. */
 549         RW_STORE(sp)
 550
 551         restore %g0, %g0, %g0
 552         /*-------------------------------------------------*/
 553
 554 1:
 555         /* Trap from kernel with a window available.
 556          * Just do it...
 557          */
 558         jmpl    %t_retpc + 0x8, %g0     ! return to caller
 559          mov    %t_kstack, %sp          ! jump onto new stack
 560
 561 #define twin_tmp1 l4
 562 #define glob_tmp  g4
 563 #define curptr    g6
 564 ret_trap_entry:
 565         wr      %t_psr, 0x0, %psr       ! enable nesting again, clear ET
 566
 567         /* Will the rett land us in the invalid window? */
 568         mov     2, %g1
 569         sll     %g1, %t_psr, %g1
 570
 571         set     CONFIG_SYS_SPARC_NWINDOWS, %g2  !NWINDOWS
 572
 573         srl     %g1, %g2, %g2
 574         or      %g1, %g2, %g1
 575         rd      %wim, %g2
 576         andcc   %g2, %g1, %g0
 577         be      1f              ! Nope, just return from the trap
 578          sll    %g2, 0x1, %g1
 579
 580         /* We have to grab a window before returning. */
 581         set     (CONFIG_SYS_SPARC_NWINDOWS-1), %g3      !NWINDOWS-1
 582
 583         srl     %g2, %g3,  %g2
 584         or      %g1, %g2, %g1
 585         and     %g1, 0xff, %g1
 586
 587         wr      %g1, 0x0, %wim
 588
 589         /* Grrr, make sure we load from the right %sp... */
 590         PT_LOAD_ALL(sp, t_psr, t_pc, t_npc, g1)
 591
 592         restore %g0, %g0, %g0
 593         RW_LOAD(sp)
 594         b       2f
 595         save    %g0, %g0, %g0
 596
 597         /* Reload the entire frame in case this is from a
 598          * kernel system call or whatever...
 599          */
 600 1:
 601         PT_LOAD_ALL(sp, t_psr, t_pc, t_npc, g1)
 602 2:
 603         wr      %t_psr, 0x0, %psr
 604         nop;
 605         nop;
 606         nop
 607
 608         jmp     %t_pc
 609         rett    %t_npc
 610
 611 /* This is called from relocated C-code.
 612  * It resets the system by jumping to _start
 613  */
 614 _reset_reloc:
 615         set     start, %l0
 616         call    %l0
 617         nop