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 LINUX_GATEWAY_ADDR
 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
 110 #ifdef CONFIG_64BIT
 111         /* for now we can *always* set the W bit on entry to the syscall
 112          * since we don't support wide userland processes.  We could
 113          * also save the current SM other than in r0 and restore it on
 114          * exit from the syscall, and also use that value to know
 115          * whether to do narrow or wide syscalls. -PB
 116          */
 117         ssm     PSW_SM_W, %r1
 118         extrd,u %r1,PSW_W_BIT,1,%r1
 119         /* sp must be aligned on 4, so deposit the W bit setting into
 120          * the bottom of sp temporarily */
 121         or,ev   %r1,%r30,%r30
 122         b,n     1f
 123         /* The top halves of argument registers must be cleared on syscall
 124          * entry from narrow executable.
 125          */
 126         depdi   0, 31, 32, %r26
 127         depdi   0, 31, 32, %r25
 128         depdi   0, 31, 32, %r24
 129         depdi   0, 31, 32, %r23
 130         depdi   0, 31, 32, %r22
 131         depdi   0, 31, 32, %r21
 132 1:
 133 #endif
 134
 135         /* We use a rsm/ssm pair to prevent sr3 from being clobbered
 136          * by external interrupts.
 137          */
 138         mfsp    %sr7,%r1                        /* save user sr7 */
 139         rsm     PSW_SM_I, %r0                   /* disable interrupts */
 140         mtsp    %r1,%sr3                        /* and store it in sr3 */
 141
 142         mfctl   %cr30,%r1
 143         xor     %r1,%r30,%r30                   /* ye olde xor trick */
 144         xor     %r1,%r30,%r1
 145         xor     %r1,%r30,%r30
 146
 147         ldo     THREAD_SZ_ALGN+FRAME_SIZE(%r30),%r30  /* set up kernel stack */
 148
 149         /* N.B.: It is critical that we don't set sr7 to 0 until r30
 150          *       contains a valid kernel stack pointer. It is also
 151          *       critical that we don't start using the kernel stack
 152          *       until after sr7 has been set to 0.
 153          */
 154
 155         mtsp    %r0,%sr7                        /* get kernel space into sr7 */
 156         ssm     PSW_SM_I, %r0                   /* enable interrupts */
 157         STREGM  %r1,FRAME_SIZE(%r30)            /* save r1 (usp) here for now */
 158         mfctl   %cr30,%r1                       /* get task ptr in %r1 */
 159         LDREG   TI_TASK(%r1),%r1
 160
 161         /* Save some registers for sigcontext and potential task
 162            switch (see entry.S for the details of which ones are
 163            saved/restored).  TASK_PT_PSW is zeroed so we can see whether
 164            a process is on a syscall or not.  For an interrupt the real
 165            PSW value is stored.  This is needed for gdb and sys_ptrace. */
 166         STREG   %r0,  TASK_PT_PSW(%r1)
 167         STREG   %r2,  TASK_PT_GR2(%r1)          /* preserve rp */
 168         STREG   %r19, TASK_PT_GR19(%r1)
 169
 170         LDREGM  -FRAME_SIZE(%r30), %r2          /* get users sp back */
 171 #ifdef CONFIG_64BIT
 172         extrd,u %r2,63,1,%r19                   /* W hidden in bottom bit */
 173 #if 0
 174         xor     %r19,%r2,%r2                    /* clear bottom bit */
 175         depd,z  %r19,1,1,%r19
 176         std     %r19,TASK_PT_PSW(%r1)
 177 #endif
 178 #endif
 179         STREG   %r2,  TASK_PT_GR30(%r1)         /* ... and save it */
 180
 181         STREG   %r20, TASK_PT_GR20(%r1)         /* Syscall number */
 182         STREG   %r21, TASK_PT_GR21(%r1)
 183         STREG   %r22, TASK_PT_GR22(%r1)
 184         STREG   %r23, TASK_PT_GR23(%r1)         /* 4th argument */
 185         STREG   %r24, TASK_PT_GR24(%r1)         /* 3rd argument */
 186         STREG   %r25, TASK_PT_GR25(%r1)         /* 2nd argument */
 187         STREG   %r26, TASK_PT_GR26(%r1)         /* 1st argument */
 188         STREG   %r27, TASK_PT_GR27(%r1)         /* user dp */
 189         STREG   %r28, TASK_PT_GR28(%r1)         /* return value 0 */
 190         STREG   %r0, TASK_PT_ORIG_R28(%r1)      /* don't prohibit restarts */
 191         STREG   %r29, TASK_PT_GR29(%r1)         /* return value 1 */
 192         STREG   %r31, TASK_PT_GR31(%r1)         /* preserve syscall return ptr */
 193
 194         ldo     TASK_PT_FR0(%r1), %r27          /* save fpregs from the kernel */
 195         save_fp %r27                            /* or potential task switch  */
 196
 197         mfctl   %cr11, %r27                     /* i.e. SAR */
 198         STREG   %r27, TASK_PT_SAR(%r1)
 199
 200         loadgp
 201
 202 #ifdef CONFIG_64BIT
 203         ldo     -16(%r30),%r29                  /* Reference param save area */
 204         copy    %r19,%r2                        /* W bit back to r2 */
 205 #else
 206         /* no need to save these on stack in wide mode because the first 8
 207          * args are passed in registers */
 208         stw     %r22, -52(%r30)                 /* 5th argument */
 209         stw     %r21, -56(%r30)                 /* 6th argument */
 210 #endif
 211
 212         /* Are we being ptraced? */
 213         mfctl   %cr30, %r1
 214         LDREG   TI_FLAGS(%r1),%r1
 215         ldi     _TIF_SYSCALL_TRACE_MASK, %r19
 216         and,COND(=) %r1, %r19, %r0
 217         b,n     .Ltracesys
 218
 219         /* Note!  We cannot use the syscall table that is mapped
 220         nearby since the gateway page is mapped execute-only. */
 221
 222 #ifdef CONFIG_64BIT
 223         ldil    L%sys_call_table, %r1
 224         or,=    %r2,%r2,%r2
 225         addil   L%(sys_call_table64-sys_call_table), %r1
 226         ldo     R%sys_call_table(%r1), %r19
 227         or,=    %r2,%r2,%r2
 228         ldo     R%sys_call_table64(%r1), %r19
 229 #else
 230         ldil    L%sys_call_table, %r1
 231         ldo     R%sys_call_table(%r1), %r19
 232 #endif
 233         comiclr,>>      __NR_Linux_syscalls, %r20, %r0
 234         b,n     .Lsyscall_nosys
 235
 236         LDREGX  %r20(%r19), %r19
 237
 238         /* If this is a sys_rt_sigreturn call, and the signal was received
 239          * when not in_syscall, then we want to return via syscall_exit_rfi,
 240          * not syscall_exit.  Signal no. in r20, in_syscall in r25 (see
 241          * trampoline code in signal.c).
 242          */
 243         ldi     __NR_rt_sigreturn,%r2
 244         comb,=  %r2,%r20,.Lrt_sigreturn
 245 .Lin_syscall:
 246         ldil    L%syscall_exit,%r2
 247         be      0(%sr7,%r19)
 248         ldo     R%syscall_exit(%r2),%r2
 249 .Lrt_sigreturn:
 250         comib,<> 0,%r25,.Lin_syscall
 251         ldil    L%syscall_exit_rfi,%r2
 252         be      0(%sr7,%r19)
 253         ldo     R%syscall_exit_rfi(%r2),%r2
 254
 255         /* Note!  Because we are not running where we were linked, any
 256         calls to functions external to this file must be indirect.  To
 257         be safe, we apply the opposite rule to functions within this
 258         file, with local labels given to them to ensure correctness. */
 259
 260 .Lsyscall_nosys:
 261 syscall_nosys:
 262         ldil    L%syscall_exit,%r1
 263         be      R%syscall_exit(%sr7,%r1)
 264         ldo     -ENOSYS(%r0),%r28                  /* set errno */
 265
 266
 267 /* Warning! This trace code is a virtual duplicate of the code above so be
 268  * sure to maintain both! */
 269 .Ltracesys:
 270 tracesys:
 271         /* Need to save more registers so the debugger can see where we
 272          * are.  This saves only the lower 8 bits of PSW, so that the C
 273          * bit is still clear on syscalls, and the D bit is set if this
 274          * full register save path has been executed.  We check the D
 275          * bit on syscall_return_rfi to determine which registers to
 276          * restore.  An interrupt results in a full PSW saved with the
 277          * C bit set, a non-straced syscall entry results in C and D clear
 278          * in the saved PSW.
 279          */
 280         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 281         LDREG   TI_TASK(%r1), %r1
 282         ssm     0,%r2
 283         STREG   %r2,TASK_PT_PSW(%r1)            /* Lower 8 bits only!! */
 284         mfsp    %sr0,%r2
 285         STREG   %r2,TASK_PT_SR0(%r1)
 286         mfsp    %sr1,%r2
 287         STREG   %r2,TASK_PT_SR1(%r1)
 288         mfsp    %sr2,%r2
 289         STREG   %r2,TASK_PT_SR2(%r1)
 290         mfsp    %sr3,%r2
 291         STREG   %r2,TASK_PT_SR3(%r1)
 292         STREG   %r2,TASK_PT_SR4(%r1)
 293         STREG   %r2,TASK_PT_SR5(%r1)
 294         STREG   %r2,TASK_PT_SR6(%r1)
 295         STREG   %r2,TASK_PT_SR7(%r1)
 296         STREG   %r2,TASK_PT_IASQ0(%r1)
 297         STREG   %r2,TASK_PT_IASQ1(%r1)
 298         LDREG   TASK_PT_GR31(%r1),%r2
 299         STREG   %r2,TASK_PT_IAOQ0(%r1)
 300         ldo     4(%r2),%r2
 301         STREG   %r2,TASK_PT_IAOQ1(%r1)
 302         ldo     TASK_REGS(%r1),%r2
 303         /* reg_save %r2 */
 304         STREG   %r3,PT_GR3(%r2)
 305         STREG   %r4,PT_GR4(%r2)
 306         STREG   %r5,PT_GR5(%r2)
 307         STREG   %r6,PT_GR6(%r2)
 308         STREG   %r7,PT_GR7(%r2)
 309         STREG   %r8,PT_GR8(%r2)
 310         STREG   %r9,PT_GR9(%r2)
 311         STREG   %r10,PT_GR10(%r2)
 312         STREG   %r11,PT_GR11(%r2)
 313         STREG   %r12,PT_GR12(%r2)
 314         STREG   %r13,PT_GR13(%r2)
 315         STREG   %r14,PT_GR14(%r2)
 316         STREG   %r15,PT_GR15(%r2)
 317         STREG   %r16,PT_GR16(%r2)
 318         STREG   %r17,PT_GR17(%r2)
 319         STREG   %r18,PT_GR18(%r2)
 320         /* Finished saving things for the debugger */
 321
 322         copy    %r2,%r26
 323         ldil    L%do_syscall_trace_enter,%r1
 324         ldil    L%tracesys_next,%r2
 325         be      R%do_syscall_trace_enter(%sr7,%r1)
 326         ldo     R%tracesys_next(%r2),%r2
 327
 328 tracesys_next:
 329         /* do_syscall_trace_enter either returned the syscallno, or -1L,
 330          *  so we skip restoring the PT_GR20 below, since we pulled it from
 331          *  task->thread.regs.gr[20] above.
 332          */
 333         copy    %ret0,%r20
 334         ldil    L%sys_call_table,%r1
 335         ldo     R%sys_call_table(%r1), %r19
 336
 337         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 338         LDREG   TI_TASK(%r1), %r1
 339         LDREG   TASK_PT_GR28(%r1), %r28         /* Restore return value */
 340         LDREG   TASK_PT_GR26(%r1), %r26         /* Restore the users args */
 341         LDREG   TASK_PT_GR25(%r1), %r25
 342         LDREG   TASK_PT_GR24(%r1), %r24
 343         LDREG   TASK_PT_GR23(%r1), %r23
 344         LDREG   TASK_PT_GR22(%r1), %r22
 345         LDREG   TASK_PT_GR21(%r1), %r21
 346 #ifdef CONFIG_64BIT
 347         ldo     -16(%r30),%r29                  /* Reference param save area */
 348 #else
 349         stw     %r22, -52(%r30)                 /* 5th argument */
 350         stw     %r21, -56(%r30)                 /* 6th argument */
 351 #endif
 352
 353         cmpib,COND(=),n -1,%r20,tracesys_exit /* seccomp may have returned -1 */
 354         comiclr,>>      __NR_Linux_syscalls, %r20, %r0
 355         b,n     .Ltracesys_nosys
 356
 357         LDREGX  %r20(%r19), %r19
 358
 359         /* If this is a sys_rt_sigreturn call, and the signal was received
 360          * when not in_syscall, then we want to return via syscall_exit_rfi,
 361          * not syscall_exit.  Signal no. in r20, in_syscall in r25 (see
 362          * trampoline code in signal.c).
 363          */
 364         ldi     __NR_rt_sigreturn,%r2
 365         comb,=  %r2,%r20,.Ltrace_rt_sigreturn
 366 .Ltrace_in_syscall:
 367         ldil    L%tracesys_exit,%r2
 368         be      0(%sr7,%r19)
 369         ldo     R%tracesys_exit(%r2),%r2
 370
 371 .Ltracesys_nosys:
 372         ldo     -ENOSYS(%r0),%r28               /* set errno */
 373
 374         /* Do *not* call this function on the gateway page, because it
 375         makes a direct call to syscall_trace. */
 376
 377 tracesys_exit:
 378         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 379         LDREG   TI_TASK(%r1), %r1
 380 #ifdef CONFIG_64BIT
 381         ldo     -16(%r30),%r29                  /* Reference param save area */
 382 #endif
 383         ldo     TASK_REGS(%r1),%r26
 384         BL      do_syscall_trace_exit,%r2
 385         STREG   %r28,TASK_PT_GR28(%r1)          /* save return value now */
 386         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 387         LDREG   TI_TASK(%r1), %r1
 388         LDREG   TASK_PT_GR28(%r1), %r28         /* Restore return val. */
 389
 390         ldil    L%syscall_exit,%r1
 391         be,n    R%syscall_exit(%sr7,%r1)
 392
 393 .Ltrace_rt_sigreturn:
 394         comib,<> 0,%r25,.Ltrace_in_syscall
 395         ldil    L%tracesys_sigexit,%r2
 396         be      0(%sr7,%r19)
 397         ldo     R%tracesys_sigexit(%r2),%r2
 398
 399 tracesys_sigexit:
 400         ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
 401         LDREG   TI_TASK(%r1), %r1
 402 #ifdef CONFIG_64BIT
 403         ldo     -16(%r30),%r29                  /* Reference param save area */
 404 #endif
 405         BL      do_syscall_trace_exit,%r2
 406         ldo     TASK_REGS(%r1),%r26
 407
 408         ldil    L%syscall_exit_rfi,%r1
 409         be,n    R%syscall_exit_rfi(%sr7,%r1)
 410
 411
 412         /*********************************************************
 413                 32/64-bit Light-Weight-Syscall ABI
 414
 415                 * - Indicates a hint for userspace inline asm
 416                 implementations.
 417
 418                 Syscall number (caller-saves)
 419                 - %r20
 420                 * In asm clobber.
 421
 422                 Argument registers (caller-saves)
 423                 - %r26, %r25, %r24, %r23, %r22
 424                 * In asm input.
 425
 426                 Return registers (caller-saves)
 427                 - %r28 (return), %r21 (errno)
 428                 * In asm output.
 429
 430                 Caller-saves registers
 431                 - %r1, %r27, %r29
 432                 - %r2 (return pointer)
 433                 - %r31 (ble link register)
 434                 * In asm clobber.
 435
 436                 Callee-saves registers
 437                 - %r3-%r18
 438                 - %r30 (stack pointer)
 439                 * Not in asm clobber.
 440
 441                 If userspace is 32-bit:
 442                 Callee-saves registers
 443                 - %r19 (32-bit PIC register)
 444
 445                 Differences from 32-bit calling convention:
 446                 - Syscall number in %r20
 447                 - Additional argument register %r22 (arg4)
 448                 - Callee-saves %r19.
 449
 450                 If userspace is 64-bit:
 451                 Callee-saves registers
 452                 - %r27 (64-bit PIC register)
 453
 454                 Differences from 64-bit calling convention:
 455                 - Syscall number in %r20
 456                 - Additional argument register %r22 (arg4)
 457                 - Callee-saves %r27.
 458
 459                 Error codes returned by entry path:
 460
 461                 ENOSYS - r20 was an invalid LWS number.
 462
 463         *********************************************************/
 464 lws_start:
 465
 466 #ifdef CONFIG_64BIT
 467         /* FIXME: If we are a 64-bit kernel just
 468          *        turn this on unconditionally.
 469          */
 470         ssm     PSW_SM_W, %r1
 471         extrd,u %r1,PSW_W_BIT,1,%r1
 472         /* sp must be aligned on 4, so deposit the W bit setting into
 473          * the bottom of sp temporarily */
 474         or,ev   %r1,%r30,%r30
 475
 476         /* Clip LWS number to a 32-bit value always */
 477         depdi   0, 31, 32, %r20
 478 #endif
 479
 480         /* Is the lws entry number valid? */
 481         comiclr,>>      __NR_lws_entries, %r20, %r0
 482         b,n     lws_exit_nosys
 483
 484         /* Load table start */
 485         ldil    L%lws_table, %r1
 486         ldo     R%lws_table(%r1), %r28  /* Scratch use of r28 */
 487         LDREGX  %r20(%sr2,r28), %r21    /* Scratch use of r21 */
 488
 489         /* Jump to lws, lws table pointers already relocated */
 490         be,n    0(%sr2,%r21)
 491
 492 lws_exit_nosys:
 493         ldo     -ENOSYS(%r0),%r21                  /* set errno */
 494         /* Fall through: Return to userspace */
 495
 496 lws_exit:
 497 #ifdef CONFIG_64BIT
 498         /* decide whether to reset the wide mode bit
 499          *
 500          * For a syscall, the W bit is stored in the lowest bit
 501          * of sp.  Extract it and reset W if it is zero */
 502         extrd,u,*<>     %r30,63,1,%r1
 503         rsm     PSW_SM_W, %r0
 504         /* now reset the lowest bit of sp if it was set */
 505         xor     %r30,%r1,%r30
 506 #endif
 507         be,n    0(%sr7, %r31)
 508
 509
 510
 511         /***************************************************
 512                 Implementing 32bit CAS as an atomic operation:
 513
 514                 %r26 - Address to examine
 515                 %r25 - Old value to check (old)
 516                 %r24 - New value to set (new)
 517                 %r28 - Return prev through this register.
 518                 %r21 - Kernel error code
 519
 520                 If debugging is DISabled:
 521
 522                 %r21 has the following meanings:
 523
 524                 EAGAIN - CAS is busy, ldcw failed, try again.
 525                 EFAULT - Read or write failed.
 526
 527                 If debugging is enabled:
 528
 529                 EDEADLOCK - CAS called recursively.
 530                 EAGAIN && r28 == 1 - CAS is busy. Lock contended.
 531                 EAGAIN && r28 == 2 - CAS is busy. ldcw failed.
 532                 EFAULT - Read or write failed.
 533
 534                 Scratch: r20, r28, r1
 535
 536         ****************************************************/
 537
 538         /* Do not enable LWS debugging */
 539 #define ENABLE_LWS_DEBUG 0
 540
 541         /* ELF64 Process entry path */
 542 lws_compare_and_swap64:
 543 #ifdef CONFIG_64BIT
 544         b,n     lws_compare_and_swap
 545 #else
 546         /* If we are not a 64-bit kernel, then we don't
 547          * have 64-bit input registers, and calling
 548          * the 64-bit LWS CAS returns ENOSYS.
 549          */
 550         b,n     lws_exit_nosys
 551 #endif
 552
 553         /* ELF32 Process entry path */
 554 lws_compare_and_swap32:
 555 #ifdef CONFIG_64BIT
 556         /* Clip all the input registers */
 557         depdi   0, 31, 32, %r26
 558         depdi   0, 31, 32, %r25
 559         depdi   0, 31, 32, %r24
 560 #endif
 561
 562 lws_compare_and_swap:
 563         /* Load start of lock table */
 564         ldil    L%lws_lock_start, %r20
 565         ldo     R%lws_lock_start(%r20), %r28
 566
 567         /* Extract four bits from r26 and hash lock (Bits 4-7) */
 568         extru  %r26, 27, 4, %r20
 569
 570         /* Find lock to use, the hash is either one of 0 to
 571            15, multiplied by 16 (keep it 16-byte aligned)
 572            and add to the lock table offset. */
 573         shlw    %r20, 4, %r20
 574         add     %r20, %r28, %r20
 575
 576 # if ENABLE_LWS_DEBUG
 577         /*
 578                 DEBUG, check for deadlock!
 579                 If the thread register values are the same
 580                 then we were the one that locked it last and
 581                 this is a recurisve call that will deadlock.
 582                 We *must* giveup this call and fail.
 583         */
 584         ldw     4(%sr2,%r20), %r28                      /* Load thread register */
 585         /* WARNING: If cr27 cycles to the same value we have problems */
 586         mfctl   %cr27, %r21                             /* Get current thread register */
 587         cmpb,<>,n       %r21, %r28, cas_lock            /* Called recursive? */
 588         b       lws_exit                                /* Return error! */
 589         ldo     -EDEADLOCK(%r0), %r21
 590 cas_lock:
 591         cmpb,=,n        %r0, %r28, cas_nocontend        /* Is nobody using it? */
 592         ldo     1(%r0), %r28                            /* 1st case */
 593         b       lws_exit                                /* Contended... */
 594         ldo     -EAGAIN(%r0), %r21                      /* Spin in userspace */
 595 cas_nocontend:
 596 # endif
 597 /* ENABLE_LWS_DEBUG */
 598
 599         rsm     PSW_SM_I, %r0                           /* Disable interrupts */
 600         /* COW breaks can cause contention on UP systems */
 601         LDCW    0(%sr2,%r20), %r28                      /* Try to acquire the lock */
 602         cmpb,<>,n       %r0, %r28, cas_action           /* Did we get it? */
 603 cas_wouldblock:
 604         ldo     2(%r0), %r28                            /* 2nd case */
 605         ssm     PSW_SM_I, %r0
 606         b       lws_exit                                /* Contended... */
 607         ldo     -EAGAIN(%r0), %r21                      /* Spin in userspace */
 608
 609         /*
 610                 prev = *addr;
 611                 if ( prev == old )
 612                   *addr = new;
 613                 return prev;
 614         */
 615
 616         /* NOTES:
 617                 This all works becuse intr_do_signal
 618                 and schedule both check the return iasq
 619                 and see that we are on the kernel page
 620                 so this process is never scheduled off
 621                 or is ever sent any signal of any sort,
 622                 thus it is wholly atomic from usrspaces
 623                 perspective
 624         */
 625 cas_action:
 626 #if defined CONFIG_SMP && ENABLE_LWS_DEBUG
 627         /* DEBUG */
 628         mfctl   %cr27, %r1
 629         stw     %r1, 4(%sr2,%r20)
 630 #endif
 631         /* The load and store could fail */
 632 1:      ldw,ma  0(%r26), %r28
 633         sub,<>  %r28, %r25, %r0
 634 2:      stw,ma  %r24, 0(%r26)
 635         /* Free lock */
 636         stw,ma  %r20, 0(%sr2,%r20)
 637 #if ENABLE_LWS_DEBUG
 638         /* Clear thread register indicator */
 639         stw     %r0, 4(%sr2,%r20)
 640 #endif
 641         /* Enable interrupts */
 642         ssm     PSW_SM_I, %r0
 643         /* Return to userspace, set no error */
 644         b       lws_exit
 645         copy    %r0, %r21
 646
 647 3:
 648         /* Error occurred on load or store */
 649         /* Free lock */
 650         stw     %r20, 0(%sr2,%r20)
 651 #if ENABLE_LWS_DEBUG
 652         stw     %r0, 4(%sr2,%r20)
 653 #endif
 654         ssm     PSW_SM_I, %r0
 655         b       lws_exit
 656         ldo     -EFAULT(%r0),%r21       /* set errno */
 657         nop
 658         nop
 659         nop
 660         nop
 661
 662         /* Two exception table entries, one for the load,
 663            the other for the store. Either return -EFAULT.
 664            Each of the entries must be relocated. */
 665         ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 3b-linux_gateway_page)
 666         ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 3b-linux_gateway_page)
 667
 668
 669         /***************************************************
 670                 New CAS implementation which uses pointers and variable size
 671                 information. The value pointed by old and new MUST NOT change
 672                 while performing CAS. The lock only protect the value at %r26.
 673
 674                 %r26 - Address to examine
 675                 %r25 - Pointer to the value to check (old)
 676                 %r24 - Pointer to the value to set (new)
 677                 %r23 - Size of the variable (0/1/2/3 for 8/16/32/64 bit)
 678                 %r28 - Return non-zero on failure
 679                 %r21 - Kernel error code
 680
 681                 %r21 has the following meanings:
 682
 683                 EAGAIN - CAS is busy, ldcw failed, try again.
 684                 EFAULT - Read or write failed.
 685
 686                 Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only)
 687
 688         ****************************************************/
 689
 690         /* ELF32 Process entry path */
 691 lws_compare_and_swap_2:
 692 #ifdef CONFIG_64BIT
 693         /* Clip the input registers */
 694         depdi   0, 31, 32, %r26
 695         depdi   0, 31, 32, %r25
 696         depdi   0, 31, 32, %r24
 697         depdi   0, 31, 32, %r23
 698 #endif
 699
 700         /* Check the validity of the size pointer */
 701         subi,>>= 4, %r23, %r0
 702         b,n     lws_exit_nosys
 703
 704         /* Jump to the functions which will load the old and new values into
 705            registers depending on the their size */
 706         shlw    %r23, 2, %r29
 707         blr     %r29, %r0
 708         nop
 709
 710         /* 8bit load */
 711 4:      ldb     0(%r25), %r25
 712         b       cas2_lock_start
 713 5:      ldb     0(%r24), %r24
 714         nop
 715         nop
 716         nop
 717         nop
 718         nop
 719
 720         /* 16bit load */
 721 6:      ldh     0(%r25), %r25
 722         b       cas2_lock_start
 723 7:      ldh     0(%r24), %r24
 724         nop
 725         nop
 726         nop
 727         nop
 728         nop
 729
 730         /* 32bit load */
 731 8:      ldw     0(%r25), %r25
 732         b       cas2_lock_start
 733 9:      ldw     0(%r24), %r24
 734         nop
 735         nop
 736         nop
 737         nop
 738         nop
 739
 740         /* 64bit load */
 741 #ifdef CONFIG_64BIT
 742 10:     ldd     0(%r25), %r25
 743 11:     ldd     0(%r24), %r24
 744 #else
 745         /* Load old value into r22/r23 - high/low */
 746 10:     ldw     0(%r25), %r22
 747 11:     ldw     4(%r25), %r23
 748         /* Load new value into fr4 for atomic store later */
 749 12:     flddx   0(%r24), %fr4
 750 #endif
 751
 752 cas2_lock_start:
 753         /* Load start of lock table */
 754         ldil    L%lws_lock_start, %r20
 755         ldo     R%lws_lock_start(%r20), %r28
 756
 757         /* Extract four bits from r26 and hash lock (Bits 4-7) */
 758         extru  %r26, 27, 4, %r20
 759
 760         /* Find lock to use, the hash is either one of 0 to
 761            15, multiplied by 16 (keep it 16-byte aligned)
 762            and add to the lock table offset. */
 763         shlw    %r20, 4, %r20
 764         add     %r20, %r28, %r20
 765
 766         rsm     PSW_SM_I, %r0                   /* Disable interrupts */
 767         /* COW breaks can cause contention on UP systems */
 768         LDCW    0(%sr2,%r20), %r28              /* Try to acquire the lock */
 769         cmpb,<>,n       %r0, %r28, cas2_action  /* Did we get it? */
 770 cas2_wouldblock:
 771         ldo     2(%r0), %r28                    /* 2nd case */
 772         ssm     PSW_SM_I, %r0
 773         b       lws_exit                        /* Contended... */
 774         ldo     -EAGAIN(%r0), %r21              /* Spin in userspace */
 775
 776         /*
 777                 prev = *addr;
 778                 if ( prev == old )
 779                   *addr = new;
 780                 return prev;
 781         */
 782
 783         /* NOTES:
 784                 This all works becuse intr_do_signal
 785                 and schedule both check the return iasq
 786                 and see that we are on the kernel page
 787                 so this process is never scheduled off
 788                 or is ever sent any signal of any sort,
 789                 thus it is wholly atomic from usrspaces
 790                 perspective
 791         */
 792 cas2_action:
 793         /* Jump to the correct function */
 794         blr     %r29, %r0
 795         /* Set %r28 as non-zero for now */
 796         ldo     1(%r0),%r28
 797
 798         /* 8bit CAS */
 799 13:     ldb,ma  0(%r26), %r29
 800         sub,=   %r29, %r25, %r0
 801         b,n     cas2_end
 802 14:     stb,ma  %r24, 0(%r26)
 803         b       cas2_end
 804         copy    %r0, %r28
 805         nop
 806         nop
 807
 808         /* 16bit CAS */
 809 15:     ldh,ma  0(%r26), %r29
 810         sub,=   %r29, %r25, %r0
 811         b,n     cas2_end
 812 16:     sth,ma  %r24, 0(%r26)
 813         b       cas2_end
 814         copy    %r0, %r28
 815         nop
 816         nop
 817
 818         /* 32bit CAS */
 819 17:     ldw,ma  0(%r26), %r29
 820         sub,=   %r29, %r25, %r0
 821         b,n     cas2_end
 822 18:     stw,ma  %r24, 0(%r26)
 823         b       cas2_end
 824         copy    %r0, %r28
 825         nop
 826         nop
 827
 828         /* 64bit CAS */
 829 #ifdef CONFIG_64BIT
 830 19:     ldd,ma  0(%r26), %r29
 831         sub,*=  %r29, %r25, %r0
 832         b,n     cas2_end
 833 20:     std,ma  %r24, 0(%r26)
 834         copy    %r0, %r28
 835 #else
 836         /* Compare first word */
 837 19:     ldw     0(%r26), %r29
 838         sub,=   %r29, %r22, %r0
 839         b,n     cas2_end
 840         /* Compare second word */
 841 20:     ldw     4(%r26), %r29
 842         sub,=   %r29, %r23, %r0
 843         b,n     cas2_end
 844         /* Perform the store */
 845 21:     fstdx   %fr4, 0(%r26)
 846         copy    %r0, %r28
 847 #endif
 848
 849 cas2_end:
 850         /* Free lock */
 851         stw,ma  %r20, 0(%sr2,%r20)
 852         /* Enable interrupts */
 853         ssm     PSW_SM_I, %r0
 854         /* Return to userspace, set no error */
 855         b       lws_exit
 856         copy    %r0, %r21
 857
 858 22:
 859         /* Error occurred on load or store */
 860         /* Free lock */
 861         stw     %r20, 0(%sr2,%r20)
 862         ssm     PSW_SM_I, %r0
 863         ldo     1(%r0),%r28
 864         b       lws_exit
 865         ldo     -EFAULT(%r0),%r21       /* set errno */
 866         nop
 867         nop
 868         nop
 869
 870         /* Exception table entries, for the load and store, return EFAULT.
 871            Each of the entries must be relocated. */
 872         ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 22b-linux_gateway_page)
 873         ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 22b-linux_gateway_page)
 874         ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 22b-linux_gateway_page)
 875         ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 22b-linux_gateway_page)
 876         ASM_EXCEPTIONTABLE_ENTRY(8b-linux_gateway_page, 22b-linux_gateway_page)
 877         ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 22b-linux_gateway_page)
 878         ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 22b-linux_gateway_page)
 879         ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 22b-linux_gateway_page)
 880         ASM_EXCEPTIONTABLE_ENTRY(13b-linux_gateway_page, 22b-linux_gateway_page)
 881         ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 22b-linux_gateway_page)
 882         ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 22b-linux_gateway_page)
 883         ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 22b-linux_gateway_page)
 884         ASM_EXCEPTIONTABLE_ENTRY(17b-linux_gateway_page, 22b-linux_gateway_page)
 885         ASM_EXCEPTIONTABLE_ENTRY(18b-linux_gateway_page, 22b-linux_gateway_page)
 886         ASM_EXCEPTIONTABLE_ENTRY(19b-linux_gateway_page, 22b-linux_gateway_page)
 887         ASM_EXCEPTIONTABLE_ENTRY(20b-linux_gateway_page, 22b-linux_gateway_page)
 888 #ifndef CONFIG_64BIT
 889         ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 22b-linux_gateway_page)
 890         ASM_EXCEPTIONTABLE_ENTRY(21b-linux_gateway_page, 22b-linux_gateway_page)
 891 #endif
 892
 893         /* Make sure nothing else is placed on this page */
 894         .align PAGE_SIZE
 895 END(linux_gateway_page)
 896 ENTRY(end_linux_gateway_page)
 897
 898         /* Relocate symbols assuming linux_gateway_page is mapped
 899            to virtual address 0x0 */
 900
 901 #define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page)
 902
 903         .section .rodata,"a"
 904
 905         .align 8
 906         /* Light-weight-syscall table */
 907         /* Start of lws table. */
 908 ENTRY(lws_table)
 909         LWS_ENTRY(compare_and_swap32)           /* 0 - ELF32 Atomic 32bit CAS */
 910         LWS_ENTRY(compare_and_swap64)           /* 1 - ELF64 Atomic 32bit CAS */
 911         LWS_ENTRY(compare_and_swap_2)           /* 2 - ELF32 Atomic 64bit CAS */
 912 END(lws_table)
 913         /* End of lws table */
 914
 915         .align 8
 916 ENTRY(sys_call_table)
 917         .export sys_call_table,data
 918 #include "syscall_table.S"
 919 END(sys_call_table)
 920
 921 #ifdef CONFIG_64BIT
 922         .align 8
 923 ENTRY(sys_call_table64)
 924 #define SYSCALL_TABLE_64BIT
 925 #include "syscall_table.S"
 926 END(sys_call_table64)
 927 #endif
 928
 929         /*
 930                 All light-weight-syscall atomic operations
 931                 will use this set of locks
 932
 933                 NOTE: The lws_lock_start symbol must be
 934                 at least 16-byte aligned for safe use
 935                 with ldcw.
 936         */
 937         .section .data
 938         .align  L1_CACHE_BYTES
 939 ENTRY(lws_lock_start)
 940         /* lws locks */
 941         .rept 16
 942         /* Keep locks aligned at 16-bytes */
 943         .word 1
 944         .word 0
 945         .word 0
 946         .word 0
 947         .endr
 948 END(lws_lock_start)
 949         .previous
 950
 951 .end
 952
 953