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/* 12How does the Linux gateway page on PA-RISC work? 13------------------------------------------------ 14The Linux gateway page on PA-RISC is "special". 15It actually has PAGE_GATEWAY bits set (this is linux terminology; in parisc 16terminology it's Execute, promote to PL0) in the page map. So anything 17executing on this page executes with kernel level privilege (there's more to it 18than that: to have this happen, you also have to use a branch with a ,gate 19completer to activate the privilege promotion). The upshot is that everything 20that runs on the gateway page runs at kernel privilege but with the current 21user process address space (although you have access to kernel space via %sr2). 22For the 0x100 syscall entry, we redo the space registers to point to the kernel 23address space (preserving the user address space in %sr3), move to wide mode if 24required, save the user registers and branch into the kernel syscall entry 25point. For all the other functions, we execute at kernel privilege but don't 26flip address spaces. The basic upshot of this is that these code snippets are 27executed atomically (because the kernel can't be pre-empted) and they may 28perform architecturally forbidden (to PL3) operations (like setting control 29registers). 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 67ENTRY(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 79lws_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! */ 90set_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 104linux_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 1341: 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: 254syscall_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: 263tracesys: 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 321tracesys_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_GR28(%r1), %r28 /* Restore return value */ 333 LDREG TASK_PT_GR26(%r1), %r26 /* Restore the users args */ 334 LDREG TASK_PT_GR25(%r1), %r25 335 LDREG TASK_PT_GR24(%r1), %r24 336 LDREG TASK_PT_GR23(%r1), %r23 337 LDREG TASK_PT_GR22(%r1), %r22 338 LDREG TASK_PT_GR21(%r1), %r21 339#ifdef CONFIG_64BIT 340 ldo -16(%r30),%r29 /* Reference param save area */ 341#else 342 stw %r22, -52(%r30) /* 5th argument */ 343 stw %r21, -56(%r30) /* 6th argument */ 344#endif 345 346 cmpib,COND(=),n -1,%r20,tracesys_exit /* seccomp may have returned -1 */ 347 comiclr,>> __NR_Linux_syscalls, %r20, %r0 348 b,n .Ltracesys_nosys 349 350 LDREGX %r20(%r19), %r19 351 352 /* If this is a sys_rt_sigreturn call, and the signal was received 353 * when not in_syscall, then we want to return via syscall_exit_rfi, 354 * not syscall_exit. Signal no. in r20, in_syscall in r25 (see 355 * trampoline code in signal.c). 356 */ 357 ldi __NR_rt_sigreturn,%r2 358 comb,= %r2,%r20,.Ltrace_rt_sigreturn 359.Ltrace_in_syscall: 360 ldil L%tracesys_exit,%r2 361 be 0(%sr7,%r19) 362 ldo R%tracesys_exit(%r2),%r2 363 364.Ltracesys_nosys: 365 ldo -ENOSYS(%r0),%r28 /* set errno */ 366 367 /* Do *not* call this function on the gateway page, because it 368 makes a direct call to syscall_trace. */ 369 370tracesys_exit: 371 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */ 372 LDREG TI_TASK(%r1), %r1 373#ifdef CONFIG_64BIT 374 ldo -16(%r30),%r29 /* Reference param save area */ 375#endif 376 ldo TASK_REGS(%r1),%r26 377 BL do_syscall_trace_exit,%r2 378 STREG %r28,TASK_PT_GR28(%r1) /* save return value now */ 379 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */ 380 LDREG TI_TASK(%r1), %r1 381 LDREG TASK_PT_GR28(%r1), %r28 /* Restore return val. */ 382 383 ldil L%syscall_exit,%r1 384 be,n R%syscall_exit(%sr7,%r1) 385 386.Ltrace_rt_sigreturn: 387 comib,<> 0,%r25,.Ltrace_in_syscall 388 ldil L%tracesys_sigexit,%r2 389 be 0(%sr7,%r19) 390 ldo R%tracesys_sigexit(%r2),%r2 391 392tracesys_sigexit: 393 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */ 394 LDREG TI_TASK(%r1), %r1 395#ifdef CONFIG_64BIT 396 ldo -16(%r30),%r29 /* Reference param save area */ 397#endif 398 BL do_syscall_trace_exit,%r2 399 ldo TASK_REGS(%r1),%r26 400 401 ldil L%syscall_exit_rfi,%r1 402 be,n R%syscall_exit_rfi(%sr7,%r1) 403 404 405 /********************************************************* 406 32/64-bit Light-Weight-Syscall ABI 407 408 * - Indicates a hint for userspace inline asm 409 implementations. 410 411 Syscall number (caller-saves) 412 - %r20 413 * In asm clobber. 414 415 Argument registers (caller-saves) 416 - %r26, %r25, %r24, %r23, %r22 417 * In asm input. 418 419 Return registers (caller-saves) 420 - %r28 (return), %r21 (errno) 421 * In asm output. 422 423 Caller-saves registers 424 - %r1, %r27, %r29 425 - %r2 (return pointer) 426 - %r31 (ble link register) 427 * In asm clobber. 428 429 Callee-saves registers 430 - %r3-%r18 431 - %r30 (stack pointer) 432 * Not in asm clobber. 433 434 If userspace is 32-bit: 435 Callee-saves registers 436 - %r19 (32-bit PIC register) 437 438 Differences from 32-bit calling convention: 439 - Syscall number in %r20 440 - Additional argument register %r22 (arg4) 441 - Callee-saves %r19. 442 443 If userspace is 64-bit: 444 Callee-saves registers 445 - %r27 (64-bit PIC register) 446 447 Differences from 64-bit calling convention: 448 - Syscall number in %r20 449 - Additional argument register %r22 (arg4) 450 - Callee-saves %r27. 451 452 Error codes returned by entry path: 453 454 ENOSYS - r20 was an invalid LWS number. 455 456 *********************************************************/ 457lws_start: 458 459#ifdef CONFIG_64BIT 460 /* FIXME: If we are a 64-bit kernel just 461 * turn this on unconditionally. 462 */ 463 ssm PSW_SM_W, %r1 464 extrd,u %r1,PSW_W_BIT,1,%r1 465 /* sp must be aligned on 4, so deposit the W bit setting into 466 * the bottom of sp temporarily */ 467 or,ev %r1,%r30,%r30 468 469 /* Clip LWS number to a 32-bit value always */ 470 depdi 0, 31, 32, %r20 471#endif 472 473 /* Is the lws entry number valid? */ 474 comiclr,>> __NR_lws_entries, %r20, %r0 475 b,n lws_exit_nosys 476 477 /* WARNING: Trashing sr2 and sr3 */ 478 mfsp %sr7,%r1 /* get userspace into sr3 */ 479 mtsp %r1,%sr3 480 mtsp %r0,%sr2 /* get kernel space into sr2 */ 481 482 /* Load table start */ 483 ldil L%lws_table, %r1 484 ldo R%lws_table(%r1), %r28 /* Scratch use of r28 */ 485 LDREGX %r20(%sr2,r28), %r21 /* Scratch use of r21 */ 486 487 /* Jump to lws, lws table pointers already relocated */ 488 be,n 0(%sr2,%r21) 489 490lws_exit_nosys: 491 ldo -ENOSYS(%r0),%r21 /* set errno */ 492 /* Fall through: Return to userspace */ 493 494lws_exit: 495#ifdef CONFIG_64BIT 496 /* decide whether to reset the wide mode bit 497 * 498 * For a syscall, the W bit is stored in the lowest bit 499 * of sp. Extract it and reset W if it is zero */ 500 extrd,u,*<> %r30,63,1,%r1 501 rsm PSW_SM_W, %r0 502 /* now reset the lowest bit of sp if it was set */ 503 xor %r30,%r1,%r30 504#endif 505 be,n 0(%sr7, %r31) 506 507 508 509 /*************************************************** 510 Implementing 32bit CAS as an atomic operation: 511 512 %r26 - Address to examine 513 %r25 - Old value to check (old) 514 %r24 - New value to set (new) 515 %r28 - Return prev through this register. 516 %r21 - Kernel error code 517 518 If debugging is DISabled: 519 520 %r21 has the following meanings: 521 522 EAGAIN - CAS is busy, ldcw failed, try again. 523 EFAULT - Read or write failed. 524 525 If debugging is enabled: 526 527 EDEADLOCK - CAS called recursively. 528 EAGAIN && r28 == 1 - CAS is busy. Lock contended. 529 EAGAIN && r28 == 2 - CAS is busy. ldcw failed. 530 EFAULT - Read or write failed. 531 532 Scratch: r20, r28, r1 533 534 ****************************************************/ 535 536 /* Do not enable LWS debugging */ 537#define ENABLE_LWS_DEBUG 0 538 539 /* ELF64 Process entry path */ 540lws_compare_and_swap64: 541#ifdef CONFIG_64BIT 542 b,n lws_compare_and_swap 543#else 544 /* If we are not a 64-bit kernel, then we don't 545 * have 64-bit input registers, and calling 546 * the 64-bit LWS CAS returns ENOSYS. 547 */ 548 b,n lws_exit_nosys 549#endif 550 551 /* ELF32 Process entry path */ 552lws_compare_and_swap32: 553#ifdef CONFIG_64BIT 554 /* Clip all the input registers */ 555 depdi 0, 31, 32, %r26 556 depdi 0, 31, 32, %r25 557 depdi 0, 31, 32, %r24 558#endif 559 560lws_compare_and_swap: 561 /* Load start of lock table */ 562 ldil L%lws_lock_start, %r20 563 ldo R%lws_lock_start(%r20), %r28 564 565 /* Extract four bits from r26 and hash lock (Bits 4-7) */ 566 extru %r26, 27, 4, %r20 567 568 /* Find lock to use, the hash is either one of 0 to 569 15, multiplied by 16 (keep it 16-byte aligned) 570 and add to the lock table offset. */ 571 shlw %r20, 4, %r20 572 add %r20, %r28, %r20 573 574# if ENABLE_LWS_DEBUG 575 /* 576 DEBUG, check for deadlock! 577 If the thread register values are the same 578 then we were the one that locked it last and 579 this is a recurisve call that will deadlock. 580 We *must* giveup this call and fail. 581 */ 582 ldw 4(%sr2,%r20), %r28 /* Load thread register */ 583 /* WARNING: If cr27 cycles to the same value we have problems */ 584 mfctl %cr27, %r21 /* Get current thread register */ 585 cmpb,<>,n %r21, %r28, cas_lock /* Called recursive? */ 586 b lws_exit /* Return error! */ 587 ldo -EDEADLOCK(%r0), %r21 588cas_lock: 589 cmpb,=,n %r0, %r28, cas_nocontend /* Is nobody using it? */ 590 ldo 1(%r0), %r28 /* 1st case */ 591 b lws_exit /* Contended... */ 592 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ 593cas_nocontend: 594# endif 595/* ENABLE_LWS_DEBUG */ 596 597 rsm PSW_SM_I, %r0 /* Disable interrupts */ 598 /* COW breaks can cause contention on UP systems */ 599 LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */ 600 cmpb,<>,n %r0, %r28, cas_action /* Did we get it? */ 601cas_wouldblock: 602 ldo 2(%r0), %r28 /* 2nd case */ 603 ssm PSW_SM_I, %r0 604 b lws_exit /* Contended... */ 605 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ 606 607 /* 608 prev = *addr; 609 if ( prev == old ) 610 *addr = new; 611 return prev; 612 */ 613 614 /* NOTES: 615 This all works becuse intr_do_signal 616 and schedule both check the return iasq 617 and see that we are on the kernel page 618 so this process is never scheduled off 619 or is ever sent any signal of any sort, 620 thus it is wholly atomic from usrspaces 621 perspective 622 */ 623cas_action: 624#if defined CONFIG_SMP && ENABLE_LWS_DEBUG 625 /* DEBUG */ 626 mfctl %cr27, %r1 627 stw %r1, 4(%sr2,%r20) 628#endif 629 /* The load and store could fail */ 6301: ldw,ma 0(%sr3,%r26), %r28 631 sub,<> %r28, %r25, %r0 6322: stw,ma %r24, 0(%sr3,%r26) 633 /* Free lock */ 634 stw,ma %r20, 0(%sr2,%r20) 635#if ENABLE_LWS_DEBUG 636 /* Clear thread register indicator */ 637 stw %r0, 4(%sr2,%r20) 638#endif 639 /* Enable interrupts */ 640 ssm PSW_SM_I, %r0 641 /* Return to userspace, set no error */ 642 b lws_exit 643 copy %r0, %r21 644 6453: 646 /* Error occurred on load or store */ 647 /* Free lock */ 648 stw %r20, 0(%sr2,%r20) 649#if ENABLE_LWS_DEBUG 650 stw %r0, 4(%sr2,%r20) 651#endif 652 ssm PSW_SM_I, %r0 653 b lws_exit 654 ldo -EFAULT(%r0),%r21 /* set errno */ 655 nop 656 nop 657 nop 658 nop 659 660 /* Two exception table entries, one for the load, 661 the other for the store. Either return -EFAULT. 662 Each of the entries must be relocated. */ 663 ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 3b-linux_gateway_page) 664 ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 3b-linux_gateway_page) 665 666 667 /*************************************************** 668 New CAS implementation which uses pointers and variable size 669 information. The value pointed by old and new MUST NOT change 670 while performing CAS. The lock only protect the value at %r26. 671 672 %r26 - Address to examine 673 %r25 - Pointer to the value to check (old) 674 %r24 - Pointer to the value to set (new) 675 %r23 - Size of the variable (0/1/2/3 for 8/16/32/64 bit) 676 %r28 - Return non-zero on failure 677 %r21 - Kernel error code 678 679 %r21 has the following meanings: 680 681 EAGAIN - CAS is busy, ldcw failed, try again. 682 EFAULT - Read or write failed. 683 684 Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only) 685 686 ****************************************************/ 687 688 /* ELF32 Process entry path */ 689lws_compare_and_swap_2: 690#ifdef CONFIG_64BIT 691 /* Clip the input registers */ 692 depdi 0, 31, 32, %r26 693 depdi 0, 31, 32, %r25 694 depdi 0, 31, 32, %r24 695 depdi 0, 31, 32, %r23 696#endif 697 698 /* Check the validity of the size pointer */ 699 subi,>>= 4, %r23, %r0 700 b,n lws_exit_nosys 701 702 /* Jump to the functions which will load the old and new values into 703 registers depending on the their size */ 704 shlw %r23, 2, %r29 705 blr %r29, %r0 706 nop 707 708 /* 8bit load */ 7094: ldb 0(%sr3,%r25), %r25 710 b cas2_lock_start 7115: ldb 0(%sr3,%r24), %r24 712 nop 713 nop 714 nop 715 nop 716 nop 717 718 /* 16bit load */ 7196: ldh 0(%sr3,%r25), %r25 720 b cas2_lock_start 7217: ldh 0(%sr3,%r24), %r24 722 nop 723 nop 724 nop 725 nop 726 nop 727 728 /* 32bit load */ 7298: ldw 0(%sr3,%r25), %r25 730 b cas2_lock_start 7319: ldw 0(%sr3,%r24), %r24 732 nop 733 nop 734 nop 735 nop 736 nop 737 738 /* 64bit load */ 739#ifdef CONFIG_64BIT 74010: ldd 0(%sr3,%r25), %r25 74111: ldd 0(%sr3,%r24), %r24 742#else 743 /* Load new value into r22/r23 - high/low */ 74410: ldw 0(%sr3,%r25), %r22 74511: ldw 4(%sr3,%r25), %r23 746 /* Load new value into fr4 for atomic store later */ 74712: flddx 0(%sr3,%r24), %fr4 748#endif 749 750cas2_lock_start: 751 /* Load start of lock table */ 752 ldil L%lws_lock_start, %r20 753 ldo R%lws_lock_start(%r20), %r28 754 755 /* Extract four bits from r26 and hash lock (Bits 4-7) */ 756 extru %r26, 27, 4, %r20 757 758 /* Find lock to use, the hash is either one of 0 to 759 15, multiplied by 16 (keep it 16-byte aligned) 760 and add to the lock table offset. */ 761 shlw %r20, 4, %r20 762 add %r20, %r28, %r20 763 764 rsm PSW_SM_I, %r0 /* Disable interrupts */ 765 /* COW breaks can cause contention on UP systems */ 766 LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */ 767 cmpb,<>,n %r0, %r28, cas2_action /* Did we get it? */ 768cas2_wouldblock: 769 ldo 2(%r0), %r28 /* 2nd case */ 770 ssm PSW_SM_I, %r0 771 b lws_exit /* Contended... */ 772 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */ 773 774 /* 775 prev = *addr; 776 if ( prev == old ) 777 *addr = new; 778 return prev; 779 */ 780 781 /* NOTES: 782 This all works becuse intr_do_signal 783 and schedule both check the return iasq 784 and see that we are on the kernel page 785 so this process is never scheduled off 786 or is ever sent any signal of any sort, 787 thus it is wholly atomic from usrspaces 788 perspective 789 */ 790cas2_action: 791 /* Jump to the correct function */ 792 blr %r29, %r0 793 /* Set %r28 as non-zero for now */ 794 ldo 1(%r0),%r28 795 796 /* 8bit CAS */ 79713: ldb,ma 0(%sr3,%r26), %r29 798 sub,= %r29, %r25, %r0 799 b,n cas2_end 80014: stb,ma %r24, 0(%sr3,%r26) 801 b cas2_end 802 copy %r0, %r28 803 nop 804 nop 805 806 /* 16bit CAS */ 80715: ldh,ma 0(%sr3,%r26), %r29 808 sub,= %r29, %r25, %r0 809 b,n cas2_end 81016: sth,ma %r24, 0(%sr3,%r26) 811 b cas2_end 812 copy %r0, %r28 813 nop 814 nop 815 816 /* 32bit CAS */ 81717: ldw,ma 0(%sr3,%r26), %r29 818 sub,= %r29, %r25, %r0 819 b,n cas2_end 82018: stw,ma %r24, 0(%sr3,%r26) 821 b cas2_end 822 copy %r0, %r28 823 nop 824 nop 825 826 /* 64bit CAS */ 827#ifdef CONFIG_64BIT 82819: ldd,ma 0(%sr3,%r26), %r29 829 sub,*= %r29, %r25, %r0 830 b,n cas2_end 83120: std,ma %r24, 0(%sr3,%r26) 832 copy %r0, %r28 833#else 834 /* Compare first word */ 83519: ldw,ma 0(%sr3,%r26), %r29 836 sub,= %r29, %r22, %r0 837 b,n cas2_end 838 /* Compare second word */ 83920: ldw,ma 4(%sr3,%r26), %r29 840 sub,= %r29, %r23, %r0 841 b,n cas2_end 842 /* Perform the store */ 84321: fstdx %fr4, 0(%sr3,%r26) 844 copy %r0, %r28 845#endif 846 847cas2_end: 848 /* Free lock */ 849 stw,ma %r20, 0(%sr2,%r20) 850 /* Enable interrupts */ 851 ssm PSW_SM_I, %r0 852 /* Return to userspace, set no error */ 853 b lws_exit 854 copy %r0, %r21 855 85622: 857 /* Error occurred on load or store */ 858 /* Free lock */ 859 stw %r20, 0(%sr2,%r20) 860 ssm PSW_SM_I, %r0 861 ldo 1(%r0),%r28 862 b lws_exit 863 ldo -EFAULT(%r0),%r21 /* set errno */ 864 nop 865 nop 866 nop 867 868 /* Exception table entries, for the load and store, return EFAULT. 869 Each of the entries must be relocated. */ 870 ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 22b-linux_gateway_page) 871 ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 22b-linux_gateway_page) 872 ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 22b-linux_gateway_page) 873 ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 22b-linux_gateway_page) 874 ASM_EXCEPTIONTABLE_ENTRY(8b-linux_gateway_page, 22b-linux_gateway_page) 875 ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 22b-linux_gateway_page) 876 ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 22b-linux_gateway_page) 877 ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 22b-linux_gateway_page) 878 ASM_EXCEPTIONTABLE_ENTRY(13b-linux_gateway_page, 22b-linux_gateway_page) 879 ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 22b-linux_gateway_page) 880 ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 22b-linux_gateway_page) 881 ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 22b-linux_gateway_page) 882 ASM_EXCEPTIONTABLE_ENTRY(17b-linux_gateway_page, 22b-linux_gateway_page) 883 ASM_EXCEPTIONTABLE_ENTRY(18b-linux_gateway_page, 22b-linux_gateway_page) 884 ASM_EXCEPTIONTABLE_ENTRY(19b-linux_gateway_page, 22b-linux_gateway_page) 885 ASM_EXCEPTIONTABLE_ENTRY(20b-linux_gateway_page, 22b-linux_gateway_page) 886#ifndef CONFIG_64BIT 887 ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 22b-linux_gateway_page) 888 ASM_EXCEPTIONTABLE_ENTRY(21b-linux_gateway_page, 22b-linux_gateway_page) 889#endif 890 891 /* Make sure nothing else is placed on this page */ 892 .align PAGE_SIZE 893END(linux_gateway_page) 894ENTRY(end_linux_gateway_page) 895 896 /* Relocate symbols assuming linux_gateway_page is mapped 897 to virtual address 0x0 */ 898 899#define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page) 900 901 .section .rodata,"a" 902 903 .align 8 904 /* Light-weight-syscall table */ 905 /* Start of lws table. */ 906ENTRY(lws_table) 907 LWS_ENTRY(compare_and_swap32) /* 0 - ELF32 Atomic 32bit CAS */ 908 LWS_ENTRY(compare_and_swap64) /* 1 - ELF64 Atomic 32bit CAS */ 909 LWS_ENTRY(compare_and_swap_2) /* 2 - ELF32 Atomic 64bit CAS */ 910END(lws_table) 911 /* End of lws table */ 912 913 .align 8 914ENTRY(sys_call_table) 915 .export sys_call_table,data 916#include "syscall_table.S" 917END(sys_call_table) 918 919#ifdef CONFIG_64BIT 920 .align 8 921ENTRY(sys_call_table64) 922#define SYSCALL_TABLE_64BIT 923#include "syscall_table.S" 924END(sys_call_table64) 925#endif 926 927 /* 928 All light-weight-syscall atomic operations 929 will use this set of locks 930 931 NOTE: The lws_lock_start symbol must be 932 at least 16-byte aligned for safe use 933 with ldcw. 934 */ 935 .section .data 936 .align L1_CACHE_BYTES 937ENTRY(lws_lock_start) 938 /* lws locks */ 939 .rept 16 940 /* Keep locks aligned at 16-bytes */ 941 .word 1 942 .word 0 943 .word 0 944 .word 0 945 .endr 946END(lws_lock_start) 947 .previous 948 949.end 950 951 952