arch/parisc/kernel/syscall.S

   1 /*
   2  * Linux/PA-RISC Project (http://www.parisc-linux.org/)
   3  *
   4  * System call entry code Copyright (c) Matthew Wilcox 1999 <willy@bofh.ai>
   5  * Licensed under the GNU GPL.
   6  * thanks to Philipp Rumpf, Mike Shaver and various others
   7  * sorry about the wall, puffin..
   8  */
   9 #include <linux/config.h> /* for CONFIG_SMP */
  10
  11 #include <asm/asm-offsets.h>
  12 #include <asm/unistd.h>
  13 #include <asm/errno.h>
  14 #include <asm/psw.h>
  15 #include <asm/thread_info.h>
  16
  17 #include <asm/assembly.h>
  18 #include <asm/processor.h>
  19
  20         /* We fill the empty parts of the gateway page with
  21          * something that will kill the kernel or a
  22          * userspace application.
  23          */
  24 #define KILL_INSN       break   0,0
  25
  26 #ifdef CONFIG_64BIT
  27         .level          2.0w
  28 #else
  29         .level          1.1
  30 #endif
  31
  32         .text
  33
  34         .import syscall_exit,code
  35         .import syscall_exit_rfi,code
  36         .export linux_gateway_page
  37
  38         /* Linux gateway page is aliased to virtual page 0 in the kernel
  39          * address space. Since it is a gateway page it cannot be
  40          * dereferenced, so null pointers will still fault. We start
  41          * the actual entry point at 0x100. We put break instructions
  42          * at the beginning of the page to trap null indirect function
  43          * pointers.
  44          */
  45
  46         .align ASM_PAGE_SIZE
  47 linux_gateway_page:
  48
  49         /* ADDRESS 0x00 to 0xb0 = 176 bytes / 4 bytes per insn = 44 insns */
  50         .rept 44
  51         KILL_INSN
  52         .endr
  53
  54         /* ADDRESS 0xb0 to 0xb4, lws uses 1 insns for entry */
  55         /* Light-weight-syscall entry must always be located at 0xb0 */
  56         /* WARNING: Keep this number updated with table size changes */
  57 #define __NR_lws_entries (2)
  58
  59 lws_entry:
  60         /* Unconditional branch to lws_start, located on the
  61            same gateway page */
  62         b,n     lws_start
  63
  64         /* Fill from 0xb4 to 0xe0 */
  65         .rept 11
  66         KILL_INSN
  67         .endr
  68
  69         /* This function MUST be located at 0xe0 for glibc's threading
  70         mechanism to work. DO NOT MOVE THIS CODE EVER! */
  71 set_thread_pointer:
  72         gate    .+8, %r0                /* increase privilege */
  73         depi    3, 31, 2, %r31          /* Ensure we return into user mode. */
  74         be      0(%sr7,%r31)            /* return to user space */
  75         mtctl   %r26, %cr27             /* move arg0 to the control register */
  76
  77         /* Increase the chance of trapping if random jumps occur to this
  78         address, fill from 0xf0 to 0x100 */
  79         .rept 4
  80         KILL_INSN
  81         .endr
  82
  83 /* This address must remain fixed at 0x100 for glibc's syscalls to work */
  84         .align 256
  85 linux_gateway_entry:
  86         gate    .+8, %r0                        /* become privileged */
  87         mtsp    %r0,%sr4                        /* get kernel space into sr4 */
  88         mtsp    %r0,%sr5                        /* get kernel space into sr5 */
  89         mtsp    %r0,%sr6                        /* get kernel space into sr6 */
  90         mfsp    %sr7,%r1                        /* save user sr7 */
  91         mtsp    %r1,%sr3                        /* and store it in sr3 */
  92
  93 #ifdef CONFIG_64BIT
  94         /* for now we can *always* set the W bit on entry to the syscall
  95          * since we don't support wide userland processes.  We could
  96          * also save the current SM other than in r0 and restore it on
  97          * exit from the syscall, and also use that value to know
  98          * whether to do narrow or wide syscalls. -PB
  99          */
 100         ssm     PSW_SM_W, %r1
 101         extrd,u %r1,PSW_W_BIT,1,%r1
 102         /* sp must be aligned on 4, so deposit the W bit setting into
 103          * the bottom of sp temporarily */
 104         or,ev   %r1,%r30,%r30
 105         b,n     1f
 106         /* The top halves of argument registers must be cleared on syscall
 107          * entry from narrow executable.
 108          */
 109         depdi   0, 31, 32, %r26
 110         depdi   0, 31, 32, %r25
 111         depdi   0, 31, 32, %r24
 112         depdi   0, 31, 32, %r23
 113         depdi   0, 31, 32, %r22
 114         depdi   0, 31, 32, %r21
 115 1:
 116 #endif
 117         mfctl   %cr30,%r1
 118         xor     %r1,%r30,%r30                   /* ye olde xor trick */
 119         xor     %r1,%r30,%r1
 120         xor     %r1,%r30,%r30
 121
 122         ldo     THREAD_SZ_ALGN+FRAME_SIZE(%r30),%r30  /* set up kernel stack */
 123
 124         /* N.B.: It is critical that we don't set sr7 to 0 until r30
 125          *       contains a valid kernel stack pointer. It is also
 126          *       critical that we don't start using the kernel stack
 127          *       until after sr7 has been set to 0.
 128          */
 129
 130         mtsp    %r0,%sr7                        /* get kernel space into sr7 */
 131         STREGM  %r1,FRAME_SIZE(%r30)            /* save r1 (usp) here for now */
 132         mfctl   %cr30,%r1                       /* get task ptr in %r1 */
 133         LDREG   TI_TASK(%r1),%r1
 134
 135         /* Save some registers for sigcontext and potential task
 136            switch (see entry.S for the details of which ones are
 137            saved/restored).  TASK_PT_PSW is zeroed so we can see whether
 138            a process is on a syscall or not.  For an interrupt the real
 139            PSW value is stored.  This is needed for gdb and sys_ptrace. */
 140         STREG   %r0,  TASK_PT_PSW(%r1)
 141         STREG   %r2,  TASK_PT_GR2(%r1)          /* preserve rp */
 142         STREG   %r19, TASK_PT_GR19(%r1)
 143
 144         LDREGM  -FRAME_SIZE(%r30), %r2          /* get users sp back */
 145 #ifdef CONFIG_64BIT
 146         extrd,u %r2,63,1,%r19                   /* W hidden in bottom bit */
 147 #if 0
 148         xor     %r19,%r2,%r2                    /* clear bottom bit */
 149         depd,z  %r19,1,1,%r19
 150         std     %r19,TASK_PT_PSW(%r1)
 151 #endif
 152 #endif
 153         STREG   %r2,  TASK_PT_GR30(%r1)         /* ... and save it */
 154
 155         STREG   %r20, TASK_PT_GR20(%r1)         /* Syscall number */
 156         STREG   %r21, TASK_PT_GR21(%r1)
 157         STREG   %r22, TASK_PT_GR22(%r1)
 158         STREG   %r23, TASK_PT_GR23(%r1)         /* 4th argument */
 159         STREG   %r24, TASK_PT_GR24(%r1)         /* 3rd argument */
 160         STREG   %r25, TASK_PT_GR25(%r1)         /* 2nd argument */
 161         STREG   %r26, TASK_PT_GR26(%r1)         /* 1st argument */
 162         STREG   %r27, TASK_PT_GR27(%r1)         /* user dp */
 163         STREG   %r28, TASK_PT_GR28(%r1)         /* return value 0 */
 164         STREG   %r28, TASK_PT_ORIG_R28(%r1)     /* return value 0 (saved for signals) */
 165         STREG   %r29, TASK_PT_GR29(%r1)         /* return value 1 */
 166         STREG   %r31, TASK_PT_GR31(%r1)         /* preserve syscall return ptr */
 167
 168         ldo     TASK_PT_FR0(%r1), %r27          /* save fpregs from the kernel */
 169         save_fp %r27                            /* or potential task switch  */
 170
 171         mfctl   %cr11, %r27                     /* i.e. SAR */
 172         STREG   %r27, TASK_PT_SAR(%r1)
 173
 174         loadgp
 175
 176 #ifdef CONFIG_64BIT
 177         ldo     -16(%r30),%r29                  /* Reference param save area */
 178         copy    %r19,%r2                        /* W bit back to r2 */
 179 #else
 180         /* no need to save these on stack in wide mode because the first 8
 181          * args are passed in registers */
 182         stw     %r22, -52(%r30)                 /* 5th argument */
 183         stw     %r21, -56(%r30)                 /* 6th argument */
 184 #endif
 185
 186         /* Are we being ptraced? */
 187         mfctl   %cr30, %r1
 188         LDREG   TI_TASK(%r1),%r1
 189         LDREG   TASK_PTRACE(%r1), %r1
 190         bb,<,n  %r1,31,.Ltracesys
 191
 192         /* Note!  We cannot use the syscall table that is mapped
 193         nearby since the gateway page is mapped execute-only. */
 194
 195 #ifdef CONFIG_64BIT
 196         ldil    L%sys_call_table, %r1
 197         or,=    %r2,%r2,%r2
 198         addil   L%(sys_call_table64-sys_call_table), %r1
 199         ldo     R%sys_call_table(%r1), %r19
 200         or,=    %r2,%r2,%r2
 201         ldo     R%sys_call_table64(%r1), %r19
 202 #else
 203         ldil    L%sys_call_table, %r1
 204         ldo     R%sys_call_table(%r1), %r19
 205 #endif
 206         comiclr,>>=     __NR_Linux_syscalls, %r20, %r0
 207         b,n     .Lsyscall_nosys
 208
 209         LDREGX  %r20(%r19), %r19
 210
 211         /* If this is a sys_rt_sigreturn call, and the signal was received
 212          * when not in_syscall, then we want to return via syscall_exit_rfi,
 213          * not syscall_exit.  Signal no. in r20, in_syscall in r25 (see
 214          * trampoline code in signal.c).
 215          */
 216         ldi     __NR_rt_sigreturn,%r2
 217         comb,=  %r2,%r20,.Lrt_sigreturn
 218 .Lin_syscall:
 219         ldil    L%syscall_exit,%r2
 220         be      0(%sr7,%r19)
 221         ldo     R%syscall_exit(%r2),%r2
 222 .Lrt_sigreturn:
 223         comib,<> 0,%r25,.Lin_syscall
 224         ldil    L%syscall_exit_rfi,%r2
 225         be      0(%sr7,%r19)
 226         ldo     R%syscall_exit_rfi(%r2),%r2
 227
 228         /* Note!  Because we are not running where we were linked, any
 229         calls to functions external to this file must be indirect.  To
 230         be safe, we apply the opposite rule to functions within this
 231         file, with local labels given to them to ensure correctness. */
 232
 233 .Lsyscall_nosys:
 234 syscall_nosys:
 235         ldil    L%syscall_exit,%r1
 236         be      R%syscall_exit(%sr7,%r1)
 237         ldo     -ENOSYS(%r0),%r28                  /* set errno */
 238
 239
 240 /* Warning! This trace code is a virtual duplicate of the code above so be
 241  * sure to maintain both! */
 242 .Ltracesys:
 243 tracesys:
 244         /* Need to save more registers so the debugger can see where we
 245          * are.  This saves only the lower 8 bits of PSW, so that the C
 246          * bit is still clear on syscalls, and the D bit is set if this
 247          * full register save path has been executed.  We check the D
 248          * bit on syscall_return_rfi to determine which registers to
 249          * restore.  An interrupt results in a full PSW saved with the
 250          * C bit set, a non-straced syscall entry results in C and D clear
 251          * in the saved PSW.
 252          */
 253         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 254         LDREG   TI_TASK(%r1), %r1
 255         ssm     0,%r2
 256         STREG   %r2,TASK_PT_PSW(%r1)            /* Lower 8 bits only!! */
 257         mfsp    %sr0,%r2
 258         STREG   %r2,TASK_PT_SR0(%r1)
 259         mfsp    %sr1,%r2
 260         STREG   %r2,TASK_PT_SR1(%r1)
 261         mfsp    %sr2,%r2
 262         STREG   %r2,TASK_PT_SR2(%r1)
 263         mfsp    %sr3,%r2
 264         STREG   %r2,TASK_PT_SR3(%r1)
 265         STREG   %r2,TASK_PT_SR4(%r1)
 266         STREG   %r2,TASK_PT_SR5(%r1)
 267         STREG   %r2,TASK_PT_SR6(%r1)
 268         STREG   %r2,TASK_PT_SR7(%r1)
 269         STREG   %r2,TASK_PT_IASQ0(%r1)
 270         STREG   %r2,TASK_PT_IASQ1(%r1)
 271         LDREG   TASK_PT_GR31(%r1),%r2
 272         STREG   %r2,TASK_PT_IAOQ0(%r1)
 273         ldo     4(%r2),%r2
 274         STREG   %r2,TASK_PT_IAOQ1(%r1)
 275         ldo     TASK_REGS(%r1),%r2
 276         /* reg_save %r2 */
 277         STREG   %r3,PT_GR3(%r2)
 278         STREG   %r4,PT_GR4(%r2)
 279         STREG   %r5,PT_GR5(%r2)
 280         STREG   %r6,PT_GR6(%r2)
 281         STREG   %r7,PT_GR7(%r2)
 282         STREG   %r8,PT_GR8(%r2)
 283         STREG   %r9,PT_GR9(%r2)
 284         STREG   %r10,PT_GR10(%r2)
 285         STREG   %r11,PT_GR11(%r2)
 286         STREG   %r12,PT_GR12(%r2)
 287         STREG   %r13,PT_GR13(%r2)
 288         STREG   %r14,PT_GR14(%r2)
 289         STREG   %r15,PT_GR15(%r2)
 290         STREG   %r16,PT_GR16(%r2)
 291         STREG   %r17,PT_GR17(%r2)
 292         STREG   %r18,PT_GR18(%r2)
 293         /* Finished saving things for the debugger */
 294
 295         ldil    L%syscall_trace,%r1
 296         ldil    L%tracesys_next,%r2
 297         be      R%syscall_trace(%sr7,%r1)
 298         ldo     R%tracesys_next(%r2),%r2
 299
 300 tracesys_next:
 301         ldil    L%sys_call_table,%r1
 302         ldo     R%sys_call_table(%r1), %r19
 303
 304         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 305         LDREG   TI_TASK(%r1), %r1
 306         LDREG   TASK_PT_GR20(%r1), %r20
 307         LDREG   TASK_PT_GR26(%r1), %r26         /* Restore the users args */
 308         LDREG   TASK_PT_GR25(%r1), %r25
 309         LDREG   TASK_PT_GR24(%r1), %r24
 310         LDREG   TASK_PT_GR23(%r1), %r23
 311 #ifdef CONFIG_64BIT
 312         LDREG   TASK_PT_GR22(%r1), %r22
 313         LDREG   TASK_PT_GR21(%r1), %r21
 314         ldo     -16(%r30),%r29                  /* Reference param save area */
 315 #endif
 316
 317         comiclr,>>=     __NR_Linux_syscalls, %r20, %r0
 318         b,n     .Lsyscall_nosys
 319
 320         LDREGX  %r20(%r19), %r19
 321
 322         /* If this is a sys_rt_sigreturn call, and the signal was received
 323          * when not in_syscall, then we want to return via syscall_exit_rfi,
 324          * not syscall_exit.  Signal no. in r20, in_syscall in r25 (see
 325          * trampoline code in signal.c).
 326          */
 327         ldi     __NR_rt_sigreturn,%r2
 328         comb,=  %r2,%r20,.Ltrace_rt_sigreturn
 329 .Ltrace_in_syscall:
 330         ldil    L%tracesys_exit,%r2
 331         be      0(%sr7,%r19)
 332         ldo     R%tracesys_exit(%r2),%r2
 333
 334         /* Do *not* call this function on the gateway page, because it
 335         makes a direct call to syscall_trace. */
 336
 337 tracesys_exit:
 338         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 339         LDREG   TI_TASK(%r1), %r1
 340 #ifdef CONFIG_64BIT
 341         ldo     -16(%r30),%r29                  /* Reference param save area */
 342 #endif
 343         bl      syscall_trace, %r2
 344         STREG   %r28,TASK_PT_GR28(%r1)          /* save return value now */
 345         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 346         LDREG   TI_TASK(%r1), %r1
 347         LDREG   TASK_PT_GR28(%r1), %r28         /* Restore return val. */
 348
 349         ldil    L%syscall_exit,%r1
 350         be,n    R%syscall_exit(%sr7,%r1)
 351
 352 .Ltrace_rt_sigreturn:
 353         comib,<> 0,%r25,.Ltrace_in_syscall
 354         ldil    L%tracesys_sigexit,%r2
 355         be      0(%sr7,%r19)
 356         ldo     R%tracesys_sigexit(%r2),%r2
 357
 358 tracesys_sigexit:
 359         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 360         LDREG   0(%r1), %r1
 361 #ifdef CONFIG_64BIT
 362         ldo     -16(%r30),%r29                  /* Reference param save area */
 363 #endif
 364         bl      syscall_trace, %r2
 365         nop
 366
 367         ldil    L%syscall_exit_rfi,%r1
 368         be,n    R%syscall_exit_rfi(%sr7,%r1)
 369
 370
 371         /*********************************************************
 372                 Light-weight-syscall code
 373
 374                 r20 - lws number
 375                 r26,r25,r24,r23,r22 - Input registers
 376                 r28 - Function return register
 377                 r21 - Error code.
 378
 379                 Scracth: Any of the above that aren't being
 380                 currently used, including r1.
 381
 382                 Return pointer: r31 (Not usable)
 383
 384                 Error codes returned by entry path:
 385
 386                 ENOSYS - r20 was an invalid LWS number.
 387
 388         *********************************************************/
 389 lws_start:
 390         /* Gate and ensure we return to userspace */
 391         gate    .+8, %r0
 392         depi    3, 31, 2, %r31  /* Ensure we return to userspace */
 393
 394 #ifdef CONFIG_64BIT
 395         /* FIXME: If we are a 64-bit kernel just
 396          *        turn this on unconditionally.
 397          */
 398         ssm     PSW_SM_W, %r1
 399         extrd,u %r1,PSW_W_BIT,1,%r1
 400         /* sp must be aligned on 4, so deposit the W bit setting into
 401          * the bottom of sp temporarily */
 402         or,ev   %r1,%r30,%r30
 403
 404         /* Clip LWS number to a 32-bit value always */
 405         depdi   0, 31, 32, %r20
 406 #endif
 407
 408         /* Is the lws entry number valid? */
 409         comiclr,>>=     __NR_lws_entries, %r20, %r0
 410         b,n     lws_exit_nosys
 411
 412         /* WARNING: Trashing sr2 and sr3 */
 413         mfsp    %sr7,%r1                        /* get userspace into sr3 */
 414         mtsp    %r1,%sr3
 415         mtsp    %r0,%sr2                        /* get kernel space into sr2 */
 416
 417         /* Load table start */
 418         ldil    L%lws_table, %r1
 419         ldo     R%lws_table(%r1), %r28  /* Scratch use of r28 */
 420         LDREGX  %r20(%sr2,r28), %r21    /* Scratch use of r21 */
 421
 422         /* Jump to lws, lws table pointers already relocated */
 423         be,n    0(%sr2,%r21)
 424
 425 lws_exit_nosys:
 426         ldo     -ENOSYS(%r0),%r21                  /* set errno */
 427         /* Fall through: Return to userspace */
 428
 429 lws_exit:
 430 #ifdef CONFIG_64BIT
 431         /* decide whether to reset the wide mode bit
 432          *
 433          * For a syscall, the W bit is stored in the lowest bit
 434          * of sp.  Extract it and reset W if it is zero */
 435         extrd,u,*<>     %r30,63,1,%r1
 436         rsm     PSW_SM_W, %r0
 437         /* now reset the lowest bit of sp if it was set */
 438         xor     %r30,%r1,%r30
 439 #endif
 440         be,n    0(%sr3, %r31)
 441
 442
 443
 444         /***************************************************
 445                 Implementing CAS as an atomic operation:
 446
 447                 %r26 - Address to examine
 448                 %r25 - Old value to check (old)
 449                 %r24 - New value to set (new)
 450                 %r28 - Return prev through this register.
 451                 %r21 - Kernel error code
 452
 453                 If debugging is DISabled:
 454
 455                 %r21 has the following meanings:
 456
 457                 EAGAIN - CAS is busy, ldcw failed, try again.
 458                 EFAULT - Read or write failed.
 459
 460                 If debugging is enabled:
 461
 462                 EDEADLOCK - CAS called recursively.
 463                 EAGAIN && r28 == 1 - CAS is busy. Lock contended.
 464                 EAGAIN && r28 == 2 - CAS is busy. ldcw failed.
 465                 EFAULT - Read or write failed.
 466
 467                 Scratch: r20, r28, r1
 468
 469         ****************************************************/
 470
 471         /* Do not enable LWS debugging */
 472 #define ENABLE_LWS_DEBUG 0
 473
 474         /* ELF64 Process entry path */
 475 lws_compare_and_swap64:
 476 #ifdef CONFIG_64BIT
 477         b,n     lws_compare_and_swap
 478 #else
 479         /* If we are not a 64-bit kernel, then we don't
 480          * implement having 64-bit input registers
 481          */
 482         b,n     lws_exit_nosys
 483 #endif
 484
 485         /* ELF32 Process entry path */
 486 lws_compare_and_swap32:
 487 #ifdef CONFIG_64BIT
 488         /* Clip all the input registers */
 489         depdi   0, 31, 32, %r26
 490         depdi   0, 31, 32, %r25
 491         depdi   0, 31, 32, %r24
 492 #endif
 493
 494 lws_compare_and_swap:
 495 #ifdef CONFIG_SMP
 496         /* Load start of lock table */
 497         ldil    L%lws_lock_start, %r20
 498         ldo     R%lws_lock_start(%r20), %r28
 499
 500         /* Extract four bits from r26 and hash lock (Bits 4-7) */
 501         extru  %r26, 27, 4, %r20
 502
 503         /* Find lock to use, the hash is either one of 0 to
 504            15, multiplied by 16 (keep it 16-byte aligned)
 505            and add to the lock table offset. */
 506         shlw    %r20, 4, %r20
 507         add     %r20, %r28, %r20
 508
 509 # ifdef ENABLE_LWS_DEBUG
 510         /*
 511                 DEBUG, check for deadlock!
 512                 If the thread register values are the same
 513                 then we were the one that locked it last and
 514                 this is a recurisve call that will deadlock.
 515                 We *must* giveup this call and fail.
 516         */
 517         ldw     4(%sr2,%r20), %r28                      /* Load thread register */
 518         /* WARNING: If cr27 cycles to the same value we have problems */
 519         mfctl   %cr27, %r21                             /* Get current thread register */
 520         cmpb,<>,n       %r21, %r28, cas_lock            /* Called recursive? */
 521         b       lws_exit                                /* Return error! */
 522         ldo     -EDEADLOCK(%r0), %r21
 523 cas_lock:
 524         cmpb,=,n        %r0, %r28, cas_nocontend        /* Is nobody using it? */
 525         ldo     1(%r0), %r28                            /* 1st case */
 526         b       lws_exit                                /* Contended... */
 527         ldo     -EAGAIN(%r0), %r21                      /* Spin in userspace */
 528 cas_nocontend:
 529 # endif
 530 /* ENABLE_LWS_DEBUG */
 531
 532         LDCW    0(%sr2,%r20), %r28                      /* Try to acquire the lock */
 533         cmpb,<>,n       %r0, %r28, cas_action           /* Did we get it? */
 534 cas_wouldblock:
 535         ldo     2(%r0), %r28                            /* 2nd case */
 536         b       lws_exit                                /* Contended... */
 537         ldo     -EAGAIN(%r0), %r21                      /* Spin in userspace */
 538 #endif
 539 /* CONFIG_SMP */
 540
 541         /*
 542                 prev = *addr;
 543                 if ( prev == old )
 544                   *addr = new;
 545                 return prev;
 546         */
 547
 548         /* NOTES:
 549                 This all works becuse intr_do_signal
 550                 and schedule both check the return iasq
 551                 and see that we are on the kernel page
 552                 so this process is never scheduled off
 553                 or is ever sent any signal of any sort,
 554                 thus it is wholly atomic from usrspaces
 555                 perspective
 556         */
 557 cas_action:
 558 #if defined CONFIG_SMP && defined ENABLE_LWS_DEBUG
 559         /* DEBUG */
 560         mfctl   %cr27, %r1
 561         stw     %r1, 4(%sr2,%r20)
 562 #endif
 563         /* The load and store could fail */
 564 1:      ldw     0(%sr3,%r26), %r28
 565         sub,<>  %r28, %r25, %r0
 566 2:      stw     %r24, 0(%sr3,%r26)
 567 #ifdef CONFIG_SMP
 568         /* Free lock */
 569         stw     %r20, 0(%sr2,%r20)
 570 # ifdef ENABLE_LWS_DEBUG
 571         /* Clear thread register indicator */
 572         stw     %r0, 4(%sr2,%r20)
 573 # endif
 574 #endif
 575         /* Return to userspace, set no error */
 576         b       lws_exit
 577         copy    %r0, %r21
 578
 579 3:
 580         /* Error occured on load or store */
 581 #ifdef CONFIG_SMP
 582         /* Free lock */
 583         stw     %r20, 0(%sr2,%r20)
 584 # ifdef ENABLE_LWS_DEBUG
 585         stw     %r0, 4(%sr2,%r20)
 586 # endif
 587 #endif
 588         b       lws_exit
 589         ldo     -EFAULT(%r0),%r21       /* set errno */
 590         nop
 591         nop
 592         nop
 593         nop
 594
 595         /* Two exception table entries, one for the load,
 596            the other for the store. Either return -EFAULT.
 597            Each of the entries must be relocated. */
 598         .section __ex_table,"aw"
 599 #ifdef CONFIG_64BIT
 600         /* Pad the address calculation */
 601         .word   0,(2b - linux_gateway_page)
 602         .word   0,(3b - linux_gateway_page)
 603 #else
 604         .word   (2b - linux_gateway_page)
 605         .word   (3b - linux_gateway_page)
 606 #endif
 607         .previous
 608
 609         .section __ex_table,"aw"
 610 #ifdef CONFIG_64BIT
 611         /* Pad the address calculation */
 612         .word   0,(1b - linux_gateway_page)
 613         .word   0,(3b - linux_gateway_page)
 614 #else
 615         .word   (1b - linux_gateway_page)
 616         .word   (3b - linux_gateway_page)
 617 #endif
 618         .previous
 619
 620 end_compare_and_swap:
 621
 622         /* Make sure nothing else is placed on this page */
 623         .align ASM_PAGE_SIZE
 624         .export end_linux_gateway_page
 625 end_linux_gateway_page:
 626
 627         /* Relocate symbols assuming linux_gateway_page is mapped
 628            to virtual address 0x0 */
 629 #ifdef CONFIG_64BIT
 630         /* FIXME: The code will always be on the gateay page
 631                   and thus it will be on the first 4k, the
 632                   assembler seems to think that the final
 633                   subtraction result is only a word in
 634                   length, so we pad the value.
 635         */
 636 #define LWS_ENTRY(_name_) .word 0,(lws_##_name_ - linux_gateway_page)
 637 #else
 638 #define LWS_ENTRY(_name_) .word  (lws_##_name_ - linux_gateway_page)
 639 #endif
 640
 641         .section .rodata,"a"
 642
 643         .align ASM_PAGE_SIZE
 644         /* Light-weight-syscall table */
 645         /* Start of lws table. */
 646         .export lws_table
 647 .Llws_table:
 648 lws_table:
 649         LWS_ENTRY(compare_and_swap32)   /* 0 - ELF32 Atomic compare and swap */
 650         LWS_ENTRY(compare_and_swap64)   /* 1 - ELF64 Atomic compare and swap */
 651         /* End of lws table */
 652
 653         .align ASM_PAGE_SIZE
 654         .export sys_call_table
 655 .Lsys_call_table:
 656 sys_call_table:
 657 #include "syscall_table.S"
 658
 659 #ifdef CONFIG_64BIT
 660         .align ASM_PAGE_SIZE
 661         .export sys_call_table64
 662 .Lsys_call_table64:
 663 sys_call_table64:
 664 #define SYSCALL_TABLE_64BIT
 665 #include "syscall_table.S"
 666 #endif
 667
 668 #ifdef CONFIG_SMP
 669         /*
 670                 All light-weight-syscall atomic operations
 671                 will use this set of locks
 672         */
 673         .section .data
 674         .align 4096
 675         .export lws_lock_start
 676 .Llws_lock_start:
 677 lws_lock_start:
 678         /* lws locks */
 679         .align 16
 680         .rept 16
 681         /* Keep locks aligned at 16-bytes */
 682         .word 1
 683         .word 0
 684         .word 0
 685         .word 0
 686         .endr
 687         .previous
 688 #endif
 689 /* CONFIG_SMP for lws_lock_start */
 690
 691 .end
 692
 693