arch/parisc/kernel/syscall.S

   1 /*
   2  * Linux/PA-RISC Project (http://www.parisc-linux.org/)
   3  *
   4  * System call entry code / Linux gateway page
   5  * Copyright (c) Matthew Wilcox 1999 <willy@bofh.ai>
   6  * Licensed under the GNU GPL.
   7  * thanks to Philipp Rumpf, Mike Shaver and various others
   8  * sorry about the wall, puffin..
   9  */
  10
  11 /*
  12 How does the Linux gateway page on PA-RISC work?
  13 ------------------------------------------------
  14 The Linux gateway page on PA-RISC is "special".
  15 It actually has PAGE_GATEWAY bits set (this is linux terminology; in parisc
  16 terminology it's Execute, promote to PL0) in the page map.  So anything
  17 executing on this page executes with kernel level privilege (there's more to it
  18 than that: to have this happen, you also have to use a branch with a ,gate
  19 completer to activate the privilege promotion).  The upshot is that everything
  20 that runs on the gateway page runs at kernel privilege but with the current
  21 user process address space (although you have access to kernel space via %sr2).
  22 For the 0x100 syscall entry, we redo the space registers to point to the kernel
  23 address space (preserving the user address space in %sr3), move to wide mode if
  24 required, save the user registers and branch into the kernel syscall entry
  25 point.  For all the other functions, we execute at kernel privilege but don't
  26 flip address spaces. The basic upshot of this is that these code snippets are
  27 executed atomically (because the kernel can't be pre-empted) and they may
  28 perform architecturally forbidden (to PL3) operations (like setting control
  29 registers).
  30 */
  31
  32
  33 #include <asm/asm-offsets.h>
  34 #include <asm/unistd.h>
  35 #include <asm/errno.h>
  36 #include <asm/page.h>
  37 #include <asm/psw.h>
  38 #include <asm/thread_info.h>
  39 #include <asm/assembly.h>
  40 #include <asm/processor.h>
  41 #include <asm/cache.h>
  42
  43 #include <linux/linkage.h>
  44
  45         /* We fill the empty parts of the gateway page with
  46          * something that will kill the kernel or a
  47          * userspace application.
  48          */
  49 #define KILL_INSN       break   0,0
  50
  51         .level          LEVEL
  52
  53         .text
  54
  55         .import syscall_exit,code
  56         .import syscall_exit_rfi,code
  57
  58         /* Linux gateway page is aliased to virtual page 0 in the kernel
  59          * address space. Since it is a gateway page it cannot be
  60          * dereferenced, so null pointers will still fault. We start
  61          * the actual entry point at 0x100. We put break instructions
  62          * at the beginning of the page to trap null indirect function
  63          * pointers.
  64          */
  65
  66         .align PAGE_SIZE
  67 ENTRY(linux_gateway_page)
  68
  69         /* ADDRESS 0x00 to 0xb0 = 176 bytes / 4 bytes per insn = 44 insns */
  70         .rept 44
  71         KILL_INSN
  72         .endr
  73
  74         /* ADDRESS 0xb0 to 0xb8, lws uses two insns for entry */
  75         /* Light-weight-syscall entry must always be located at 0xb0 */
  76         /* WARNING: Keep this number updated with table size changes */
  77 #define __NR_lws_entries (3)
  78
  79 lws_entry:
  80         gate    lws_start, %r0          /* increase privilege */
  81         depi    3, 31, 2, %r31          /* Ensure we return into user mode. */
  82
  83         /* Fill from 0xb8 to 0xe0 */
  84         .rept 10
  85         KILL_INSN
  86         .endr
  87
  88         /* This function MUST be located at 0xe0 for glibc's threading
  89         mechanism to work. DO NOT MOVE THIS CODE EVER! */
  90 set_thread_pointer:
  91         gate    .+8, %r0                /* increase privilege */
  92         depi    3, 31, 2, %r31          /* Ensure we return into user mode. */
  93         be      0(%sr7,%r31)            /* return to user space */
  94         mtctl   %r26, %cr27             /* move arg0 to the control register */
  95
  96         /* Increase the chance of trapping if random jumps occur to this
  97         address, fill from 0xf0 to 0x100 */
  98         .rept 4
  99         KILL_INSN
 100         .endr
 101
 102 /* This address must remain fixed at 0x100 for glibc's syscalls to work */
 103         .align 256
 104 linux_gateway_entry:
 105         gate    .+8, %r0                        /* become privileged */
 106         mtsp    %r0,%sr4                        /* get kernel space into sr4 */
 107         mtsp    %r0,%sr5                        /* get kernel space into sr5 */
 108         mtsp    %r0,%sr6                        /* get kernel space into sr6 */
 109         mfsp    %sr7,%r1                        /* save user sr7 */
 110         mtsp    %r1,%sr3                        /* and store it in sr3 */
 111
 112 #ifdef CONFIG_64BIT
 113         /* for now we can *always* set the W bit on entry to the syscall
 114          * since we don't support wide userland processes.  We could
 115          * also save the current SM other than in r0 and restore it on
 116          * exit from the syscall, and also use that value to know
 117          * whether to do narrow or wide syscalls. -PB
 118          */
 119         ssm     PSW_SM_W, %r1
 120         extrd,u %r1,PSW_W_BIT,1,%r1
 121         /* sp must be aligned on 4, so deposit the W bit setting into
 122          * the bottom of sp temporarily */
 123         or,ev   %r1,%r30,%r30
 124         b,n     1f
 125         /* The top halves of argument registers must be cleared on syscall
 126          * entry from narrow executable.
 127          */
 128         depdi   0, 31, 32, %r26
 129         depdi   0, 31, 32, %r25
 130         depdi   0, 31, 32, %r24
 131         depdi   0, 31, 32, %r23
 132         depdi   0, 31, 32, %r22
 133         depdi   0, 31, 32, %r21
 134 1:
 135 #endif
 136         mfctl   %cr30,%r1
 137         xor     %r1,%r30,%r30                   /* ye olde xor trick */
 138         xor     %r1,%r30,%r1
 139         xor     %r1,%r30,%r30
 140
 141         ldo     THREAD_SZ_ALGN+FRAME_SIZE(%r30),%r30  /* set up kernel stack */
 142
 143         /* N.B.: It is critical that we don't set sr7 to 0 until r30
 144          *       contains a valid kernel stack pointer. It is also
 145          *       critical that we don't start using the kernel stack
 146          *       until after sr7 has been set to 0.
 147          */
 148
 149         mtsp    %r0,%sr7                        /* get kernel space into sr7 */
 150         STREGM  %r1,FRAME_SIZE(%r30)            /* save r1 (usp) here for now */
 151         mfctl   %cr30,%r1                       /* get task ptr in %r1 */
 152         LDREG   TI_TASK(%r1),%r1
 153
 154         /* Save some registers for sigcontext and potential task
 155            switch (see entry.S for the details of which ones are
 156            saved/restored).  TASK_PT_PSW is zeroed so we can see whether
 157            a process is on a syscall or not.  For an interrupt the real
 158            PSW value is stored.  This is needed for gdb and sys_ptrace. */
 159         STREG   %r0,  TASK_PT_PSW(%r1)
 160         STREG   %r2,  TASK_PT_GR2(%r1)          /* preserve rp */
 161         STREG   %r19, TASK_PT_GR19(%r1)
 162
 163         LDREGM  -FRAME_SIZE(%r30), %r2          /* get users sp back */
 164 #ifdef CONFIG_64BIT
 165         extrd,u %r2,63,1,%r19                   /* W hidden in bottom bit */
 166 #if 0
 167         xor     %r19,%r2,%r2                    /* clear bottom bit */
 168         depd,z  %r19,1,1,%r19
 169         std     %r19,TASK_PT_PSW(%r1)
 170 #endif
 171 #endif
 172         STREG   %r2,  TASK_PT_GR30(%r1)         /* ... and save it */
 173
 174         STREG   %r20, TASK_PT_GR20(%r1)         /* Syscall number */
 175         STREG   %r21, TASK_PT_GR21(%r1)
 176         STREG   %r22, TASK_PT_GR22(%r1)
 177         STREG   %r23, TASK_PT_GR23(%r1)         /* 4th argument */
 178         STREG   %r24, TASK_PT_GR24(%r1)         /* 3rd argument */
 179         STREG   %r25, TASK_PT_GR25(%r1)         /* 2nd argument */
 180         STREG   %r26, TASK_PT_GR26(%r1)         /* 1st argument */
 181         STREG   %r27, TASK_PT_GR27(%r1)         /* user dp */
 182         STREG   %r28, TASK_PT_GR28(%r1)         /* return value 0 */
 183         STREG   %r0, TASK_PT_ORIG_R28(%r1)      /* don't prohibit restarts */
 184         STREG   %r29, TASK_PT_GR29(%r1)         /* return value 1 */
 185         STREG   %r31, TASK_PT_GR31(%r1)         /* preserve syscall return ptr */
 186
 187         ldo     TASK_PT_FR0(%r1), %r27          /* save fpregs from the kernel */
 188         save_fp %r27                            /* or potential task switch  */
 189
 190         mfctl   %cr11, %r27                     /* i.e. SAR */
 191         STREG   %r27, TASK_PT_SAR(%r1)
 192
 193         loadgp
 194
 195 #ifdef CONFIG_64BIT
 196         ldo     -16(%r30),%r29                  /* Reference param save area */
 197         copy    %r19,%r2                        /* W bit back to r2 */
 198 #else
 199         /* no need to save these on stack in wide mode because the first 8
 200          * args are passed in registers */
 201         stw     %r22, -52(%r30)                 /* 5th argument */
 202         stw     %r21, -56(%r30)                 /* 6th argument */
 203 #endif
 204
 205         /* Are we being ptraced? */
 206         mfctl   %cr30, %r1
 207         LDREG   TI_FLAGS(%r1),%r1
 208         ldi     _TIF_SYSCALL_TRACE_MASK, %r19
 209         and,COND(=) %r1, %r19, %r0
 210         b,n     .Ltracesys
 211
 212         /* Note!  We cannot use the syscall table that is mapped
 213         nearby since the gateway page is mapped execute-only. */
 214
 215 #ifdef CONFIG_64BIT
 216         ldil    L%sys_call_table, %r1
 217         or,=    %r2,%r2,%r2
 218         addil   L%(sys_call_table64-sys_call_table), %r1
 219         ldo     R%sys_call_table(%r1), %r19
 220         or,=    %r2,%r2,%r2
 221         ldo     R%sys_call_table64(%r1), %r19
 222 #else
 223         ldil    L%sys_call_table, %r1
 224         ldo     R%sys_call_table(%r1), %r19
 225 #endif
 226         comiclr,>>      __NR_Linux_syscalls, %r20, %r0
 227         b,n     .Lsyscall_nosys
 228
 229         LDREGX  %r20(%r19), %r19
 230
 231         /* If this is a sys_rt_sigreturn call, and the signal was received
 232          * when not in_syscall, then we want to return via syscall_exit_rfi,
 233          * not syscall_exit.  Signal no. in r20, in_syscall in r25 (see
 234          * trampoline code in signal.c).
 235          */
 236         ldi     __NR_rt_sigreturn,%r2
 237         comb,=  %r2,%r20,.Lrt_sigreturn
 238 .Lin_syscall:
 239         ldil    L%syscall_exit,%r2
 240         be      0(%sr7,%r19)
 241         ldo     R%syscall_exit(%r2),%r2
 242 .Lrt_sigreturn:
 243         comib,<> 0,%r25,.Lin_syscall
 244         ldil    L%syscall_exit_rfi,%r2
 245         be      0(%sr7,%r19)
 246         ldo     R%syscall_exit_rfi(%r2),%r2
 247
 248         /* Note!  Because we are not running where we were linked, any
 249         calls to functions external to this file must be indirect.  To
 250         be safe, we apply the opposite rule to functions within this
 251         file, with local labels given to them to ensure correctness. */
 252
 253 .Lsyscall_nosys:
 254 syscall_nosys:
 255         ldil    L%syscall_exit,%r1
 256         be      R%syscall_exit(%sr7,%r1)
 257         ldo     -ENOSYS(%r0),%r28                  /* set errno */
 258
 259
 260 /* Warning! This trace code is a virtual duplicate of the code above so be
 261  * sure to maintain both! */
 262 .Ltracesys:
 263 tracesys:
 264         /* Need to save more registers so the debugger can see where we
 265          * are.  This saves only the lower 8 bits of PSW, so that the C
 266          * bit is still clear on syscalls, and the D bit is set if this
 267          * full register save path has been executed.  We check the D
 268          * bit on syscall_return_rfi to determine which registers to
 269          * restore.  An interrupt results in a full PSW saved with the
 270          * C bit set, a non-straced syscall entry results in C and D clear
 271          * in the saved PSW.
 272          */
 273         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 274         LDREG   TI_TASK(%r1), %r1
 275         ssm     0,%r2
 276         STREG   %r2,TASK_PT_PSW(%r1)            /* Lower 8 bits only!! */
 277         mfsp    %sr0,%r2
 278         STREG   %r2,TASK_PT_SR0(%r1)
 279         mfsp    %sr1,%r2
 280         STREG   %r2,TASK_PT_SR1(%r1)
 281         mfsp    %sr2,%r2
 282         STREG   %r2,TASK_PT_SR2(%r1)
 283         mfsp    %sr3,%r2
 284         STREG   %r2,TASK_PT_SR3(%r1)
 285         STREG   %r2,TASK_PT_SR4(%r1)
 286         STREG   %r2,TASK_PT_SR5(%r1)
 287         STREG   %r2,TASK_PT_SR6(%r1)
 288         STREG   %r2,TASK_PT_SR7(%r1)
 289         STREG   %r2,TASK_PT_IASQ0(%r1)
 290         STREG   %r2,TASK_PT_IASQ1(%r1)
 291         LDREG   TASK_PT_GR31(%r1),%r2
 292         STREG   %r2,TASK_PT_IAOQ0(%r1)
 293         ldo     4(%r2),%r2
 294         STREG   %r2,TASK_PT_IAOQ1(%r1)
 295         ldo     TASK_REGS(%r1),%r2
 296         /* reg_save %r2 */
 297         STREG   %r3,PT_GR3(%r2)
 298         STREG   %r4,PT_GR4(%r2)
 299         STREG   %r5,PT_GR5(%r2)
 300         STREG   %r6,PT_GR6(%r2)
 301         STREG   %r7,PT_GR7(%r2)
 302         STREG   %r8,PT_GR8(%r2)
 303         STREG   %r9,PT_GR9(%r2)
 304         STREG   %r10,PT_GR10(%r2)
 305         STREG   %r11,PT_GR11(%r2)
 306         STREG   %r12,PT_GR12(%r2)
 307         STREG   %r13,PT_GR13(%r2)
 308         STREG   %r14,PT_GR14(%r2)
 309         STREG   %r15,PT_GR15(%r2)
 310         STREG   %r16,PT_GR16(%r2)
 311         STREG   %r17,PT_GR17(%r2)
 312         STREG   %r18,PT_GR18(%r2)
 313         /* Finished saving things for the debugger */
 314
 315         copy    %r2,%r26
 316         ldil    L%do_syscall_trace_enter,%r1
 317         ldil    L%tracesys_next,%r2
 318         be      R%do_syscall_trace_enter(%sr7,%r1)
 319         ldo     R%tracesys_next(%r2),%r2
 320
 321 tracesys_next:
 322         /* do_syscall_trace_enter either returned the syscallno, or -1L,
 323          *  so we skip restoring the PT_GR20 below, since we pulled it from
 324          *  task->thread.regs.gr[20] above.
 325          */
 326         copy    %ret0,%r20
 327         ldil    L%sys_call_table,%r1
 328         ldo     R%sys_call_table(%r1), %r19
 329
 330         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 331         LDREG   TI_TASK(%r1), %r1
 332         LDREG   TASK_PT_GR26(%r1), %r26         /* Restore the users args */
 333         LDREG   TASK_PT_GR25(%r1), %r25
 334         LDREG   TASK_PT_GR24(%r1), %r24
 335         LDREG   TASK_PT_GR23(%r1), %r23
 336         LDREG   TASK_PT_GR22(%r1), %r22
 337         LDREG   TASK_PT_GR21(%r1), %r21
 338 #ifdef CONFIG_64BIT
 339         ldo     -16(%r30),%r29                  /* Reference param save area */
 340 #else
 341         stw     %r22, -52(%r30)                 /* 5th argument */
 342         stw     %r21, -56(%r30)                 /* 6th argument */
 343 #endif
 344
 345         comiclr,>>=     __NR_Linux_syscalls, %r20, %r0
 346         b,n     .Lsyscall_nosys
 347
 348         LDREGX  %r20(%r19), %r19
 349
 350         /* If this is a sys_rt_sigreturn call, and the signal was received
 351          * when not in_syscall, then we want to return via syscall_exit_rfi,
 352          * not syscall_exit.  Signal no. in r20, in_syscall in r25 (see
 353          * trampoline code in signal.c).
 354          */
 355         ldi     __NR_rt_sigreturn,%r2
 356         comb,=  %r2,%r20,.Ltrace_rt_sigreturn
 357 .Ltrace_in_syscall:
 358         ldil    L%tracesys_exit,%r2
 359         be      0(%sr7,%r19)
 360         ldo     R%tracesys_exit(%r2),%r2
 361
 362         /* Do *not* call this function on the gateway page, because it
 363         makes a direct call to syscall_trace. */
 364
 365 tracesys_exit:
 366         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 367         LDREG   TI_TASK(%r1), %r1
 368 #ifdef CONFIG_64BIT
 369         ldo     -16(%r30),%r29                  /* Reference param save area */
 370 #endif
 371         ldo     TASK_REGS(%r1),%r26
 372         BL      do_syscall_trace_exit,%r2
 373         STREG   %r28,TASK_PT_GR28(%r1)          /* save return value now */
 374         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 375         LDREG   TI_TASK(%r1), %r1
 376         LDREG   TASK_PT_GR28(%r1), %r28         /* Restore return val. */
 377
 378         ldil    L%syscall_exit,%r1
 379         be,n    R%syscall_exit(%sr7,%r1)
 380
 381 .Ltrace_rt_sigreturn:
 382         comib,<> 0,%r25,.Ltrace_in_syscall
 383         ldil    L%tracesys_sigexit,%r2
 384         be      0(%sr7,%r19)
 385         ldo     R%tracesys_sigexit(%r2),%r2
 386
 387 tracesys_sigexit:
 388         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 389         LDREG   TI_TASK(%r1), %r1
 390 #ifdef CONFIG_64BIT
 391         ldo     -16(%r30),%r29                  /* Reference param save area */
 392 #endif
 393         BL      do_syscall_trace_exit,%r2
 394         ldo     TASK_REGS(%r1),%r26
 395
 396         ldil    L%syscall_exit_rfi,%r1
 397         be,n    R%syscall_exit_rfi(%sr7,%r1)
 398
 399
 400         /*********************************************************
 401                 32/64-bit Light-Weight-Syscall ABI
 402
 403                 * - Indicates a hint for userspace inline asm
 404                 implementations.
 405
 406                 Syscall number (caller-saves)
 407                 - %r20
 408                 * In asm clobber.
 409
 410                 Argument registers (caller-saves)
 411                 - %r26, %r25, %r24, %r23, %r22
 412                 * In asm input.
 413
 414                 Return registers (caller-saves)
 415                 - %r28 (return), %r21 (errno)
 416                 * In asm output.
 417
 418                 Caller-saves registers
 419                 - %r1, %r27, %r29
 420                 - %r2 (return pointer)
 421                 - %r31 (ble link register)
 422                 * In asm clobber.
 423
 424                 Callee-saves registers
 425                 - %r3-%r18
 426                 - %r30 (stack pointer)
 427                 * Not in asm clobber.
 428
 429                 If userspace is 32-bit:
 430                 Callee-saves registers
 431                 - %r19 (32-bit PIC register)
 432
 433                 Differences from 32-bit calling convention:
 434                 - Syscall number in %r20
 435                 - Additional argument register %r22 (arg4)
 436                 - Callee-saves %r19.
 437
 438                 If userspace is 64-bit:
 439                 Callee-saves registers
 440                 - %r27 (64-bit PIC register)
 441
 442                 Differences from 64-bit calling convention:
 443                 - Syscall number in %r20
 444                 - Additional argument register %r22 (arg4)
 445                 - Callee-saves %r27.
 446
 447                 Error codes returned by entry path:
 448
 449                 ENOSYS - r20 was an invalid LWS number.
 450
 451         *********************************************************/
 452 lws_start:
 453
 454 #ifdef CONFIG_64BIT
 455         /* FIXME: If we are a 64-bit kernel just
 456          *        turn this on unconditionally.
 457          */
 458         ssm     PSW_SM_W, %r1
 459         extrd,u %r1,PSW_W_BIT,1,%r1
 460         /* sp must be aligned on 4, so deposit the W bit setting into
 461          * the bottom of sp temporarily */
 462         or,ev   %r1,%r30,%r30
 463
 464         /* Clip LWS number to a 32-bit value always */
 465         depdi   0, 31, 32, %r20
 466 #endif
 467
 468         /* Is the lws entry number valid? */
 469         comiclr,>>      __NR_lws_entries, %r20, %r0
 470         b,n     lws_exit_nosys
 471
 472         /* WARNING: Trashing sr2 and sr3 */
 473         mfsp    %sr7,%r1                        /* get userspace into sr3 */
 474         mtsp    %r1,%sr3
 475         mtsp    %r0,%sr2                        /* get kernel space into sr2 */
 476
 477         /* Load table start */
 478         ldil    L%lws_table, %r1
 479         ldo     R%lws_table(%r1), %r28  /* Scratch use of r28 */
 480         LDREGX  %r20(%sr2,r28), %r21    /* Scratch use of r21 */
 481
 482         /* Jump to lws, lws table pointers already relocated */
 483         be,n    0(%sr2,%r21)
 484
 485 lws_exit_nosys:
 486         ldo     -ENOSYS(%r0),%r21                  /* set errno */
 487         /* Fall through: Return to userspace */
 488
 489 lws_exit:
 490 #ifdef CONFIG_64BIT
 491         /* decide whether to reset the wide mode bit
 492          *
 493          * For a syscall, the W bit is stored in the lowest bit
 494          * of sp.  Extract it and reset W if it is zero */
 495         extrd,u,*<>     %r30,63,1,%r1
 496         rsm     PSW_SM_W, %r0
 497         /* now reset the lowest bit of sp if it was set */
 498         xor     %r30,%r1,%r30
 499 #endif
 500         be,n    0(%sr7, %r31)
 501
 502
 503
 504         /***************************************************
 505                 Implementing 32bit CAS as an atomic operation:
 506
 507                 %r26 - Address to examine
 508                 %r25 - Old value to check (old)
 509                 %r24 - New value to set (new)
 510                 %r28 - Return prev through this register.
 511                 %r21 - Kernel error code
 512
 513                 If debugging is DISabled:
 514
 515                 %r21 has the following meanings:
 516
 517                 EAGAIN - CAS is busy, ldcw failed, try again.
 518                 EFAULT - Read or write failed.
 519
 520                 If debugging is enabled:
 521
 522                 EDEADLOCK - CAS called recursively.
 523                 EAGAIN && r28 == 1 - CAS is busy. Lock contended.
 524                 EAGAIN && r28 == 2 - CAS is busy. ldcw failed.
 525                 EFAULT - Read or write failed.
 526
 527                 Scratch: r20, r28, r1
 528
 529         ****************************************************/
 530
 531         /* Do not enable LWS debugging */
 532 #define ENABLE_LWS_DEBUG 0
 533
 534         /* ELF64 Process entry path */
 535 lws_compare_and_swap64:
 536 #ifdef CONFIG_64BIT
 537         b,n     lws_compare_and_swap
 538 #else
 539         /* If we are not a 64-bit kernel, then we don't
 540          * have 64-bit input registers, and calling
 541          * the 64-bit LWS CAS returns ENOSYS.
 542          */
 543         b,n     lws_exit_nosys
 544 #endif
 545
 546         /* ELF32 Process entry path */
 547 lws_compare_and_swap32:
 548 #ifdef CONFIG_64BIT
 549         /* Clip all the input registers */
 550         depdi   0, 31, 32, %r26
 551         depdi   0, 31, 32, %r25
 552         depdi   0, 31, 32, %r24
 553 #endif
 554
 555 lws_compare_and_swap:
 556         /* Load start of lock table */
 557         ldil    L%lws_lock_start, %r20
 558         ldo     R%lws_lock_start(%r20), %r28
 559
 560         /* Extract four bits from r26 and hash lock (Bits 4-7) */
 561         extru  %r26, 27, 4, %r20
 562
 563         /* Find lock to use, the hash is either one of 0 to
 564            15, multiplied by 16 (keep it 16-byte aligned)
 565            and add to the lock table offset. */
 566         shlw    %r20, 4, %r20
 567         add     %r20, %r28, %r20
 568
 569 # if ENABLE_LWS_DEBUG
 570         /*
 571                 DEBUG, check for deadlock!
 572                 If the thread register values are the same
 573                 then we were the one that locked it last and
 574                 this is a recurisve call that will deadlock.
 575                 We *must* giveup this call and fail.
 576         */
 577         ldw     4(%sr2,%r20), %r28                      /* Load thread register */
 578         /* WARNING: If cr27 cycles to the same value we have problems */
 579         mfctl   %cr27, %r21                             /* Get current thread register */
 580         cmpb,<>,n       %r21, %r28, cas_lock            /* Called recursive? */
 581         b       lws_exit                                /* Return error! */
 582         ldo     -EDEADLOCK(%r0), %r21
 583 cas_lock:
 584         cmpb,=,n        %r0, %r28, cas_nocontend        /* Is nobody using it? */
 585         ldo     1(%r0), %r28                            /* 1st case */
 586         b       lws_exit                                /* Contended... */
 587         ldo     -EAGAIN(%r0), %r21                      /* Spin in userspace */
 588 cas_nocontend:
 589 # endif
 590 /* ENABLE_LWS_DEBUG */
 591
 592         rsm     PSW_SM_I, %r0                           /* Disable interrupts */
 593         /* COW breaks can cause contention on UP systems */
 594         LDCW    0(%sr2,%r20), %r28                      /* Try to acquire the lock */
 595         cmpb,<>,n       %r0, %r28, cas_action           /* Did we get it? */
 596 cas_wouldblock:
 597         ldo     2(%r0), %r28                            /* 2nd case */
 598         ssm     PSW_SM_I, %r0
 599         b       lws_exit                                /* Contended... */
 600         ldo     -EAGAIN(%r0), %r21                      /* Spin in userspace */
 601
 602         /*
 603                 prev = *addr;
 604                 if ( prev == old )
 605                   *addr = new;
 606                 return prev;
 607         */
 608
 609         /* NOTES:
 610                 This all works becuse intr_do_signal
 611                 and schedule both check the return iasq
 612                 and see that we are on the kernel page
 613                 so this process is never scheduled off
 614                 or is ever sent any signal of any sort,
 615                 thus it is wholly atomic from usrspaces
 616                 perspective
 617         */
 618 cas_action:
 619 #if defined CONFIG_SMP && ENABLE_LWS_DEBUG
 620         /* DEBUG */
 621         mfctl   %cr27, %r1
 622         stw     %r1, 4(%sr2,%r20)
 623 #endif
 624         /* The load and store could fail */
 625 1:      ldw,ma  0(%sr3,%r26), %r28
 626         sub,<>  %r28, %r25, %r0
 627 2:      stw,ma  %r24, 0(%sr3,%r26)
 628         /* Free lock */
 629         stw,ma  %r20, 0(%sr2,%r20)
 630 #if ENABLE_LWS_DEBUG
 631         /* Clear thread register indicator */
 632         stw     %r0, 4(%sr2,%r20)
 633 #endif
 634         /* Enable interrupts */
 635         ssm     PSW_SM_I, %r0
 636         /* Return to userspace, set no error */
 637         b       lws_exit
 638         copy    %r0, %r21
 639
 640 3:
 641         /* Error occurred on load or store */
 642         /* Free lock */
 643         stw     %r20, 0(%sr2,%r20)
 644 #if ENABLE_LWS_DEBUG
 645         stw     %r0, 4(%sr2,%r20)
 646 #endif
 647         ssm     PSW_SM_I, %r0
 648         b       lws_exit
 649         ldo     -EFAULT(%r0),%r21       /* set errno */
 650         nop
 651         nop
 652         nop
 653         nop
 654
 655         /* Two exception table entries, one for the load,
 656            the other for the store. Either return -EFAULT.
 657            Each of the entries must be relocated. */
 658         ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 3b-linux_gateway_page)
 659         ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 3b-linux_gateway_page)
 660
 661
 662         /***************************************************
 663                 New CAS implementation which uses pointers and variable size
 664                 information. The value pointed by old and new MUST NOT change
 665                 while performing CAS. The lock only protect the value at %r26.
 666
 667                 %r26 - Address to examine
 668                 %r25 - Pointer to the value to check (old)
 669                 %r24 - Pointer to the value to set (new)
 670                 %r23 - Size of the variable (0/1/2/3 for 8/16/32/64 bit)
 671                 %r28 - Return non-zero on failure
 672                 %r21 - Kernel error code
 673
 674                 %r21 has the following meanings:
 675
 676                 EAGAIN - CAS is busy, ldcw failed, try again.
 677                 EFAULT - Read or write failed.
 678
 679                 Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only)
 680
 681         ****************************************************/
 682
 683         /* ELF32 Process entry path */
 684 lws_compare_and_swap_2:
 685 #ifdef CONFIG_64BIT
 686         /* Clip the input registers */
 687         depdi   0, 31, 32, %r26
 688         depdi   0, 31, 32, %r25
 689         depdi   0, 31, 32, %r24
 690         depdi   0, 31, 32, %r23
 691 #endif
 692
 693         /* Check the validity of the size pointer */
 694         subi,>>= 4, %r23, %r0
 695         b,n     lws_exit_nosys
 696
 697         /* Jump to the functions which will load the old and new values into
 698            registers depending on the their size */
 699         shlw    %r23, 2, %r29
 700         blr     %r29, %r0
 701         nop
 702
 703         /* 8bit load */
 704 4:      ldb     0(%sr3,%r25), %r25
 705         b       cas2_lock_start
 706 5:      ldb     0(%sr3,%r24), %r24
 707         nop
 708         nop
 709         nop
 710         nop
 711         nop
 712
 713         /* 16bit load */
 714 6:      ldh     0(%sr3,%r25), %r25
 715         b       cas2_lock_start
 716 7:      ldh     0(%sr3,%r24), %r24
 717         nop
 718         nop
 719         nop
 720         nop
 721         nop
 722
 723         /* 32bit load */
 724 8:      ldw     0(%sr3,%r25), %r25
 725         b       cas2_lock_start
 726 9:      ldw     0(%sr3,%r24), %r24
 727         nop
 728         nop
 729         nop
 730         nop
 731         nop
 732
 733         /* 64bit load */
 734 #ifdef CONFIG_64BIT
 735 10:     ldd     0(%sr3,%r25), %r25
 736 11:     ldd     0(%sr3,%r24), %r24
 737 #else
 738         /* Load new value into r22/r23 - high/low */
 739 10:     ldw     0(%sr3,%r25), %r22
 740 11:     ldw     4(%sr3,%r25), %r23
 741         /* Load new value into fr4 for atomic store later */
 742 12:     flddx   0(%sr3,%r24), %fr4
 743 #endif
 744
 745 cas2_lock_start:
 746         /* Load start of lock table */
 747         ldil    L%lws_lock_start, %r20
 748         ldo     R%lws_lock_start(%r20), %r28
 749
 750         /* Extract four bits from r26 and hash lock (Bits 4-7) */
 751         extru  %r26, 27, 4, %r20
 752
 753         /* Find lock to use, the hash is either one of 0 to
 754            15, multiplied by 16 (keep it 16-byte aligned)
 755            and add to the lock table offset. */
 756         shlw    %r20, 4, %r20
 757         add     %r20, %r28, %r20
 758
 759         rsm     PSW_SM_I, %r0                   /* Disable interrupts */
 760         /* COW breaks can cause contention on UP systems */
 761         LDCW    0(%sr2,%r20), %r28              /* Try to acquire the lock */
 762         cmpb,<>,n       %r0, %r28, cas2_action  /* Did we get it? */
 763 cas2_wouldblock:
 764         ldo     2(%r0), %r28                    /* 2nd case */
 765         ssm     PSW_SM_I, %r0
 766         b       lws_exit                        /* Contended... */
 767         ldo     -EAGAIN(%r0), %r21              /* Spin in userspace */
 768
 769         /*
 770                 prev = *addr;
 771                 if ( prev == old )
 772                   *addr = new;
 773                 return prev;
 774         */
 775
 776         /* NOTES:
 777                 This all works becuse intr_do_signal
 778                 and schedule both check the return iasq
 779                 and see that we are on the kernel page
 780                 so this process is never scheduled off
 781                 or is ever sent any signal of any sort,
 782                 thus it is wholly atomic from usrspaces
 783                 perspective
 784         */
 785 cas2_action:
 786         /* Jump to the correct function */
 787         blr     %r29, %r0
 788         /* Set %r28 as non-zero for now */
 789         ldo     1(%r0),%r28
 790
 791         /* 8bit CAS */
 792 13:     ldb,ma  0(%sr3,%r26), %r29
 793         sub,=   %r29, %r25, %r0
 794         b,n     cas2_end
 795 14:     stb,ma  %r24, 0(%sr3,%r26)
 796         b       cas2_end
 797         copy    %r0, %r28
 798         nop
 799         nop
 800
 801         /* 16bit CAS */
 802 15:     ldh,ma  0(%sr3,%r26), %r29
 803         sub,=   %r29, %r25, %r0
 804         b,n     cas2_end
 805 16:     sth,ma  %r24, 0(%sr3,%r26)
 806         b       cas2_end
 807         copy    %r0, %r28
 808         nop
 809         nop
 810
 811         /* 32bit CAS */
 812 17:     ldw,ma  0(%sr3,%r26), %r29
 813         sub,=   %r29, %r25, %r0
 814         b,n     cas2_end
 815 18:     stw,ma  %r24, 0(%sr3,%r26)
 816         b       cas2_end
 817         copy    %r0, %r28
 818         nop
 819         nop
 820
 821         /* 64bit CAS */
 822 #ifdef CONFIG_64BIT
 823 19:     ldd,ma  0(%sr3,%r26), %r29
 824         sub,*=  %r29, %r25, %r0
 825         b,n     cas2_end
 826 20:     std,ma  %r24, 0(%sr3,%r26)
 827         copy    %r0, %r28
 828 #else
 829         /* Compare first word */
 830 19:     ldw,ma  0(%sr3,%r26), %r29
 831         sub,=   %r29, %r22, %r0
 832         b,n     cas2_end
 833         /* Compare second word */
 834 20:     ldw,ma  4(%sr3,%r26), %r29
 835         sub,=   %r29, %r23, %r0
 836         b,n     cas2_end
 837         /* Perform the store */
 838 21:     fstdx   %fr4, 0(%sr3,%r26)
 839         copy    %r0, %r28
 840 #endif
 841
 842 cas2_end:
 843         /* Free lock */
 844         stw,ma  %r20, 0(%sr2,%r20)
 845         /* Enable interrupts */
 846         ssm     PSW_SM_I, %r0
 847         /* Return to userspace, set no error */
 848         b       lws_exit
 849         copy    %r0, %r21
 850
 851 22:
 852         /* Error occurred on load or store */
 853         /* Free lock */
 854         stw     %r20, 0(%sr2,%r20)
 855         ssm     PSW_SM_I, %r0
 856         ldo     1(%r0),%r28
 857         b       lws_exit
 858         ldo     -EFAULT(%r0),%r21       /* set errno */
 859         nop
 860         nop
 861         nop
 862
 863         /* Exception table entries, for the load and store, return EFAULT.
 864            Each of the entries must be relocated. */
 865         ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 22b-linux_gateway_page)
 866         ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 22b-linux_gateway_page)
 867         ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 22b-linux_gateway_page)
 868         ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 22b-linux_gateway_page)
 869         ASM_EXCEPTIONTABLE_ENTRY(8b-linux_gateway_page, 22b-linux_gateway_page)
 870         ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 22b-linux_gateway_page)
 871         ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 22b-linux_gateway_page)
 872         ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 22b-linux_gateway_page)
 873         ASM_EXCEPTIONTABLE_ENTRY(13b-linux_gateway_page, 22b-linux_gateway_page)
 874         ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 22b-linux_gateway_page)
 875         ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 22b-linux_gateway_page)
 876         ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 22b-linux_gateway_page)
 877         ASM_EXCEPTIONTABLE_ENTRY(17b-linux_gateway_page, 22b-linux_gateway_page)
 878         ASM_EXCEPTIONTABLE_ENTRY(18b-linux_gateway_page, 22b-linux_gateway_page)
 879         ASM_EXCEPTIONTABLE_ENTRY(19b-linux_gateway_page, 22b-linux_gateway_page)
 880         ASM_EXCEPTIONTABLE_ENTRY(20b-linux_gateway_page, 22b-linux_gateway_page)
 881 #ifndef CONFIG_64BIT
 882         ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 22b-linux_gateway_page)
 883         ASM_EXCEPTIONTABLE_ENTRY(21b-linux_gateway_page, 22b-linux_gateway_page)
 884 #endif
 885
 886         /* Make sure nothing else is placed on this page */
 887         .align PAGE_SIZE
 888 END(linux_gateway_page)
 889 ENTRY(end_linux_gateway_page)
 890
 891         /* Relocate symbols assuming linux_gateway_page is mapped
 892            to virtual address 0x0 */
 893
 894 #define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page)
 895
 896         .section .rodata,"a"
 897
 898         .align 8
 899         /* Light-weight-syscall table */
 900         /* Start of lws table. */
 901 ENTRY(lws_table)
 902         LWS_ENTRY(compare_and_swap32)           /* 0 - ELF32 Atomic 32bit CAS */
 903         LWS_ENTRY(compare_and_swap64)           /* 1 - ELF64 Atomic 32bit CAS */
 904         LWS_ENTRY(compare_and_swap_2)           /* 2 - ELF32 Atomic 64bit CAS */
 905 END(lws_table)
 906         /* End of lws table */
 907
 908         .align 8
 909 ENTRY(sys_call_table)
 910 #include "syscall_table.S"
 911 END(sys_call_table)
 912
 913 #ifdef CONFIG_64BIT
 914         .align 8
 915 ENTRY(sys_call_table64)
 916 #define SYSCALL_TABLE_64BIT
 917 #include "syscall_table.S"
 918 END(sys_call_table64)
 919 #endif
 920
 921         /*
 922                 All light-weight-syscall atomic operations
 923                 will use this set of locks
 924
 925                 NOTE: The lws_lock_start symbol must be
 926                 at least 16-byte aligned for safe use
 927                 with ldcw.
 928         */
 929         .section .data
 930         .align  L1_CACHE_BYTES
 931 ENTRY(lws_lock_start)
 932         /* lws locks */
 933         .rept 16
 934         /* Keep locks aligned at 16-bytes */
 935         .word 1
 936         .word 0
 937         .word 0
 938         .word 0
 939         .endr
 940 END(lws_lock_start)
 941         .previous
 942
 943 .end
 944
 945