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1/*
2 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
3 *
4 * System call entry code Copyright (c) Matthew Wilcox 1999 <willy@bofh.ai>
5 * Licensed under the GNU GPL.
6 * thanks to Philipp Rumpf, Mike Shaver and various others
7 * sorry about the wall, puffin..
8 */
9
10#include <asm/asm-offsets.h>
11#include <asm/unistd.h>
12#include <asm/errno.h>
13#include <asm/page.h>
14#include <asm/psw.h>
15#include <asm/thread_info.h>
16#include <asm/assembly.h>
17#include <asm/processor.h>
18
19#include <linux/linkage.h>
20
21 /* We fill the empty parts of the gateway page with
22 * something that will kill the kernel or a
23 * userspace application.
24 */
25#define KILL_INSN break 0,0
26
27 .level LEVEL
28
29 .text
30
31 .import syscall_exit,code
32 .import syscall_exit_rfi,code
33
34 /* Linux gateway page is aliased to virtual page 0 in the kernel
35 * address space. Since it is a gateway page it cannot be
36 * dereferenced, so null pointers will still fault. We start
37 * the actual entry point at 0x100. We put break instructions
38 * at the beginning of the page to trap null indirect function
39 * pointers.
40 */
41
42 .align PAGE_SIZE
43ENTRY(linux_gateway_page)
44
45 /* ADDRESS 0x00 to 0xb0 = 176 bytes / 4 bytes per insn = 44 insns */
46 .rept 44
47 KILL_INSN
48 .endr
49
50 /* ADDRESS 0xb0 to 0xb8, lws uses two insns for entry */
51 /* Light-weight-syscall entry must always be located at 0xb0 */
52 /* WARNING: Keep this number updated with table size changes */
53#define __NR_lws_entries (2)
54
55lws_entry:
56 gate lws_start, %r0 /* increase privilege */
57 depi 3, 31, 2, %r31 /* Ensure we return into user mode. */
58
59 /* Fill from 0xb8 to 0xe0 */
60 .rept 10
61 KILL_INSN
62 .endr
63
64 /* This function MUST be located at 0xe0 for glibc's threading
65 mechanism to work. DO NOT MOVE THIS CODE EVER! */
66set_thread_pointer:
67 gate .+8, %r0 /* increase privilege */
68 depi 3, 31, 2, %r31 /* Ensure we return into user mode. */
69 be 0(%sr7,%r31) /* return to user space */
70 mtctl %r26, %cr27 /* move arg0 to the control register */
71
72 /* Increase the chance of trapping if random jumps occur to this
73 address, fill from 0xf0 to 0x100 */
74 .rept 4
75 KILL_INSN
76 .endr
77
78/* This address must remain fixed at 0x100 for glibc's syscalls to work */
79 .align 256
80linux_gateway_entry:
81 gate .+8, %r0 /* become privileged */
82 mtsp %r0,%sr4 /* get kernel space into sr4 */
83 mtsp %r0,%sr5 /* get kernel space into sr5 */
84 mtsp %r0,%sr6 /* get kernel space into sr6 */
85 mfsp %sr7,%r1 /* save user sr7 */
86 mtsp %r1,%sr3 /* and store it in sr3 */
87
88#ifdef CONFIG_64BIT
89 /* for now we can *always* set the W bit on entry to the syscall
90 * since we don't support wide userland processes. We could
91 * also save the current SM other than in r0 and restore it on
92 * exit from the syscall, and also use that value to know
93 * whether to do narrow or wide syscalls. -PB
94 */
95 ssm PSW_SM_W, %r1
96 extrd,u %r1,PSW_W_BIT,1,%r1
97 /* sp must be aligned on 4, so deposit the W bit setting into
98 * the bottom of sp temporarily */
99 or,ev %r1,%r30,%r30
100 b,n 1f
101 /* The top halves of argument registers must be cleared on syscall
102 * entry from narrow executable.
103 */
104 depdi 0, 31, 32, %r26
105 depdi 0, 31, 32, %r25
106 depdi 0, 31, 32, %r24
107 depdi 0, 31, 32, %r23
108 depdi 0, 31, 32, %r22
109 depdi 0, 31, 32, %r21
1101:
111#endif
112 mfctl %cr30,%r1
113 xor %r1,%r30,%r30 /* ye olde xor trick */
114 xor %r1,%r30,%r1
115 xor %r1,%r30,%r30
116
117 ldo THREAD_SZ_ALGN+FRAME_SIZE(%r30),%r30 /* set up kernel stack */
118
119 /* N.B.: It is critical that we don't set sr7 to 0 until r30
120 * contains a valid kernel stack pointer. It is also
121 * critical that we don't start using the kernel stack
122 * until after sr7 has been set to 0.
123 */
124
125 mtsp %r0,%sr7 /* get kernel space into sr7 */
126 STREGM %r1,FRAME_SIZE(%r30) /* save r1 (usp) here for now */
127 mfctl %cr30,%r1 /* get task ptr in %r1 */
128 LDREG TI_TASK(%r1),%r1
129
130 /* Save some registers for sigcontext and potential task
131 switch (see entry.S for the details of which ones are
132 saved/restored). TASK_PT_PSW is zeroed so we can see whether
133 a process is on a syscall or not. For an interrupt the real
134 PSW value is stored. This is needed for gdb and sys_ptrace. */
135 STREG %r0, TASK_PT_PSW(%r1)
136 STREG %r2, TASK_PT_GR2(%r1) /* preserve rp */
137 STREG %r19, TASK_PT_GR19(%r1)
138
139 LDREGM -FRAME_SIZE(%r30), %r2 /* get users sp back */
140#ifdef CONFIG_64BIT
141 extrd,u %r2,63,1,%r19 /* W hidden in bottom bit */
142#if 0
143 xor %r19,%r2,%r2 /* clear bottom bit */
144 depd,z %r19,1,1,%r19
145 std %r19,TASK_PT_PSW(%r1)
146#endif
147#endif
148 STREG %r2, TASK_PT_GR30(%r1) /* ... and save it */
149
150 STREG %r20, TASK_PT_GR20(%r1) /* Syscall number */
151 STREG %r21, TASK_PT_GR21(%r1)
152 STREG %r22, TASK_PT_GR22(%r1)
153 STREG %r23, TASK_PT_GR23(%r1) /* 4th argument */
154 STREG %r24, TASK_PT_GR24(%r1) /* 3rd argument */
155 STREG %r25, TASK_PT_GR25(%r1) /* 2nd argument */
156 STREG %r26, TASK_PT_GR26(%r1) /* 1st argument */
157 STREG %r27, TASK_PT_GR27(%r1) /* user dp */
158 STREG %r28, TASK_PT_GR28(%r1) /* return value 0 */
159 STREG %r28, TASK_PT_ORIG_R28(%r1) /* return value 0 (saved for signals) */
160 STREG %r29, TASK_PT_GR29(%r1) /* return value 1 */
161 STREG %r31, TASK_PT_GR31(%r1) /* preserve syscall return ptr */
162
163 ldo TASK_PT_FR0(%r1), %r27 /* save fpregs from the kernel */
164 save_fp %r27 /* or potential task switch */
165
166 mfctl %cr11, %r27 /* i.e. SAR */
167 STREG %r27, TASK_PT_SAR(%r1)
168
169 loadgp
170
171#ifdef CONFIG_64BIT
172 ldo -16(%r30),%r29 /* Reference param save area */
173 copy %r19,%r2 /* W bit back to r2 */
174#else
175 /* no need to save these on stack in wide mode because the first 8
176 * args are passed in registers */
177 stw %r22, -52(%r30) /* 5th argument */
178 stw %r21, -56(%r30) /* 6th argument */
179#endif
180
181 /* Are we being ptraced? */
182 mfctl %cr30, %r1
183 LDREG TI_TASK(%r1),%r1
184 ldw TASK_PTRACE(%r1), %r1
185 bb,<,n %r1,31,.Ltracesys
186
187 /* Note! We cannot use the syscall table that is mapped
188 nearby since the gateway page is mapped execute-only. */
189
190#ifdef CONFIG_64BIT
191 ldil L%sys_call_table, %r1
192 or,= %r2,%r2,%r2
193 addil L%(sys_call_table64-sys_call_table), %r1
194 ldo R%sys_call_table(%r1), %r19
195 or,= %r2,%r2,%r2
196 ldo R%sys_call_table64(%r1), %r19
197#else
198 ldil L%sys_call_table, %r1
199 ldo R%sys_call_table(%r1), %r19
200#endif
201 comiclr,>> __NR_Linux_syscalls, %r20, %r0
202 b,n .Lsyscall_nosys
203
204 LDREGX %r20(%r19), %r19
205
206 /* If this is a sys_rt_sigreturn call, and the signal was received
207 * when not in_syscall, then we want to return via syscall_exit_rfi,
208 * not syscall_exit. Signal no. in r20, in_syscall in r25 (see
209 * trampoline code in signal.c).
210 */
211 ldi __NR_rt_sigreturn,%r2
212 comb,= %r2,%r20,.Lrt_sigreturn
213.Lin_syscall:
214 ldil L%syscall_exit,%r2
215 be 0(%sr7,%r19)
216 ldo R%syscall_exit(%r2),%r2
217.Lrt_sigreturn:
218 comib,<> 0,%r25,.Lin_syscall
219 ldil L%syscall_exit_rfi,%r2
220 be 0(%sr7,%r19)
221 ldo R%syscall_exit_rfi(%r2),%r2
222
223 /* Note! Because we are not running where we were linked, any
224 calls to functions external to this file must be indirect. To
225 be safe, we apply the opposite rule to functions within this
226 file, with local labels given to them to ensure correctness. */
227
228.Lsyscall_nosys:
229syscall_nosys:
230 ldil L%syscall_exit,%r1
231 be R%syscall_exit(%sr7,%r1)
232 ldo -ENOSYS(%r0),%r28 /* set errno */
233
234
235/* Warning! This trace code is a virtual duplicate of the code above so be
236 * sure to maintain both! */
237.Ltracesys:
238tracesys:
239 /* Need to save more registers so the debugger can see where we
240 * are. This saves only the lower 8 bits of PSW, so that the C
241 * bit is still clear on syscalls, and the D bit is set if this
242 * full register save path has been executed. We check the D
243 * bit on syscall_return_rfi to determine which registers to
244 * restore. An interrupt results in a full PSW saved with the
245 * C bit set, a non-straced syscall entry results in C and D clear
246 * in the saved PSW.
247 */
248 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
249 LDREG TI_TASK(%r1), %r1
250 ssm 0,%r2
251 STREG %r2,TASK_PT_PSW(%r1) /* Lower 8 bits only!! */
252 mfsp %sr0,%r2
253 STREG %r2,TASK_PT_SR0(%r1)
254 mfsp %sr1,%r2
255 STREG %r2,TASK_PT_SR1(%r1)
256 mfsp %sr2,%r2
257 STREG %r2,TASK_PT_SR2(%r1)
258 mfsp %sr3,%r2
259 STREG %r2,TASK_PT_SR3(%r1)
260 STREG %r2,TASK_PT_SR4(%r1)
261 STREG %r2,TASK_PT_SR5(%r1)
262 STREG %r2,TASK_PT_SR6(%r1)
263 STREG %r2,TASK_PT_SR7(%r1)
264 STREG %r2,TASK_PT_IASQ0(%r1)
265 STREG %r2,TASK_PT_IASQ1(%r1)
266 LDREG TASK_PT_GR31(%r1),%r2
267 STREG %r2,TASK_PT_IAOQ0(%r1)
268 ldo 4(%r2),%r2
269 STREG %r2,TASK_PT_IAOQ1(%r1)
270 ldo TASK_REGS(%r1),%r2
271 /* reg_save %r2 */
272 STREG %r3,PT_GR3(%r2)
273 STREG %r4,PT_GR4(%r2)
274 STREG %r5,PT_GR5(%r2)
275 STREG %r6,PT_GR6(%r2)
276 STREG %r7,PT_GR7(%r2)
277 STREG %r8,PT_GR8(%r2)
278 STREG %r9,PT_GR9(%r2)
279 STREG %r10,PT_GR10(%r2)
280 STREG %r11,PT_GR11(%r2)
281 STREG %r12,PT_GR12(%r2)
282 STREG %r13,PT_GR13(%r2)
283 STREG %r14,PT_GR14(%r2)
284 STREG %r15,PT_GR15(%r2)
285 STREG %r16,PT_GR16(%r2)
286 STREG %r17,PT_GR17(%r2)
287 STREG %r18,PT_GR18(%r2)
288 /* Finished saving things for the debugger */
289
290 copy %r2,%r26
291 ldil L%do_syscall_trace_enter,%r1
292 ldil L%tracesys_next,%r2
293 be R%do_syscall_trace_enter(%sr7,%r1)
294 ldo R%tracesys_next(%r2),%r2
295
296tracesys_next:
297 /* do_syscall_trace_enter either returned the syscallno, or -1L,
298 * so we skip restoring the PT_GR20 below, since we pulled it from
299 * task->thread.regs.gr[20] above.
300 */
301 copy %ret0,%r20
302 ldil L%sys_call_table,%r1
303 ldo R%sys_call_table(%r1), %r19
304
305 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
306 LDREG TI_TASK(%r1), %r1
307 LDREG TASK_PT_GR26(%r1), %r26 /* Restore the users args */
308 LDREG TASK_PT_GR25(%r1), %r25
309 LDREG TASK_PT_GR24(%r1), %r24
310 LDREG TASK_PT_GR23(%r1), %r23
311#ifdef CONFIG_64BIT
312 LDREG TASK_PT_GR22(%r1), %r22
313 LDREG TASK_PT_GR21(%r1), %r21
314 ldo -16(%r30),%r29 /* Reference param save area */
315#endif
316
317 comiclr,>>= __NR_Linux_syscalls, %r20, %r0
318 b,n .Lsyscall_nosys
319
320 LDREGX %r20(%r19), %r19
321
322 /* If this is a sys_rt_sigreturn call, and the signal was received
323 * when not in_syscall, then we want to return via syscall_exit_rfi,
324 * not syscall_exit. Signal no. in r20, in_syscall in r25 (see
325 * trampoline code in signal.c).
326 */
327 ldi __NR_rt_sigreturn,%r2
328 comb,= %r2,%r20,.Ltrace_rt_sigreturn
329.Ltrace_in_syscall:
330 ldil L%tracesys_exit,%r2
331 be 0(%sr7,%r19)
332 ldo R%tracesys_exit(%r2),%r2
333
334 /* Do *not* call this function on the gateway page, because it
335 makes a direct call to syscall_trace. */
336
337tracesys_exit:
338 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
339 LDREG TI_TASK(%r1), %r1
340#ifdef CONFIG_64BIT
341 ldo -16(%r30),%r29 /* Reference param save area */
342#endif
343 ldo TASK_REGS(%r1),%r26
344 bl do_syscall_trace_exit,%r2
345 STREG %r28,TASK_PT_GR28(%r1) /* save return value now */
346 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
347 LDREG TI_TASK(%r1), %r1
348 LDREG TASK_PT_GR28(%r1), %r28 /* Restore return val. */
349
350 ldil L%syscall_exit,%r1
351 be,n R%syscall_exit(%sr7,%r1)
352
353.Ltrace_rt_sigreturn:
354 comib,<> 0,%r25,.Ltrace_in_syscall
355 ldil L%tracesys_sigexit,%r2
356 be 0(%sr7,%r19)
357 ldo R%tracesys_sigexit(%r2),%r2
358
359tracesys_sigexit:
360 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
361 LDREG TI_TASK(%r1), %r1
362#ifdef CONFIG_64BIT
363 ldo -16(%r30),%r29 /* Reference param save area */
364#endif
365 bl do_syscall_trace_exit,%r2
366 ldo TASK_REGS(%r1),%r26
367
368 ldil L%syscall_exit_rfi,%r1
369 be,n R%syscall_exit_rfi(%sr7,%r1)
370
371
372 /*********************************************************
373 32/64-bit Light-Weight-Syscall ABI
374
375 * - Indicates a hint for userspace inline asm
376 implementations.
377
378 Syscall number (caller-saves)
379 - %r20
380 * In asm clobber.
381
382 Argument registers (caller-saves)
383 - %r26, %r25, %r24, %r23, %r22
384 * In asm input.
385
386 Return registers (caller-saves)
387 - %r28 (return), %r21 (errno)
388 * In asm output.
389
390 Caller-saves registers
391 - %r1, %r27, %r29
392 - %r2 (return pointer)
393 - %r31 (ble link register)
394 * In asm clobber.
395
396 Callee-saves registers
397 - %r3-%r18
398 - %r30 (stack pointer)
399 * Not in asm clobber.
400
401 If userspace is 32-bit:
402 Callee-saves registers
403 - %r19 (32-bit PIC register)
404
405 Differences from 32-bit calling convention:
406 - Syscall number in %r20
407 - Additional argument register %r22 (arg4)
408 - Callee-saves %r19.
409
410 If userspace is 64-bit:
411 Callee-saves registers
412 - %r27 (64-bit PIC register)
413
414 Differences from 64-bit calling convention:
415 - Syscall number in %r20
416 - Additional argument register %r22 (arg4)
417 - Callee-saves %r27.
418
419 Error codes returned by entry path:
420
421 ENOSYS - r20 was an invalid LWS number.
422
423 *********************************************************/
424lws_start:
425
426#ifdef CONFIG_64BIT
427 /* FIXME: If we are a 64-bit kernel just
428 * turn this on unconditionally.
429 */
430 ssm PSW_SM_W, %r1
431 extrd,u %r1,PSW_W_BIT,1,%r1
432 /* sp must be aligned on 4, so deposit the W bit setting into
433 * the bottom of sp temporarily */
434 or,ev %r1,%r30,%r30
435
436 /* Clip LWS number to a 32-bit value always */
437 depdi 0, 31, 32, %r20
438#endif
439
440 /* Is the lws entry number valid? */
441 comiclr,>> __NR_lws_entries, %r20, %r0
442 b,n lws_exit_nosys
443
444 /* WARNING: Trashing sr2 and sr3 */
445 mfsp %sr7,%r1 /* get userspace into sr3 */
446 mtsp %r1,%sr3
447 mtsp %r0,%sr2 /* get kernel space into sr2 */
448
449 /* Load table start */
450 ldil L%lws_table, %r1
451 ldo R%lws_table(%r1), %r28 /* Scratch use of r28 */
452 LDREGX %r20(%sr2,r28), %r21 /* Scratch use of r21 */
453
454 /* Jump to lws, lws table pointers already relocated */
455 be,n 0(%sr2,%r21)
456
457lws_exit_nosys:
458 ldo -ENOSYS(%r0),%r21 /* set errno */
459 /* Fall through: Return to userspace */
460
461lws_exit:
462#ifdef CONFIG_64BIT
463 /* decide whether to reset the wide mode bit
464 *
465 * For a syscall, the W bit is stored in the lowest bit
466 * of sp. Extract it and reset W if it is zero */
467 extrd,u,*<> %r30,63,1,%r1
468 rsm PSW_SM_W, %r0
469 /* now reset the lowest bit of sp if it was set */
470 xor %r30,%r1,%r30
471#endif
472 be,n 0(%sr7, %r31)
473
474
475
476 /***************************************************
477 Implementing CAS as an atomic operation:
478
479 %r26 - Address to examine
480 %r25 - Old value to check (old)
481 %r24 - New value to set (new)
482 %r28 - Return prev through this register.
483 %r21 - Kernel error code
484
485 If debugging is DISabled:
486
487 %r21 has the following meanings:
488
489 EAGAIN - CAS is busy, ldcw failed, try again.
490 EFAULT - Read or write failed.
491
492 If debugging is enabled:
493
494 EDEADLOCK - CAS called recursively.
495 EAGAIN && r28 == 1 - CAS is busy. Lock contended.
496 EAGAIN && r28 == 2 - CAS is busy. ldcw failed.
497 EFAULT - Read or write failed.
498
499 Scratch: r20, r28, r1
500
501 ****************************************************/
502
503 /* Do not enable LWS debugging */
504#define ENABLE_LWS_DEBUG 0
505
506 /* ELF64 Process entry path */
507lws_compare_and_swap64:
508#ifdef CONFIG_64BIT
509 b,n lws_compare_and_swap
510#else
511 /* If we are not a 64-bit kernel, then we don't
512 * have 64-bit input registers, and calling
513 * the 64-bit LWS CAS returns ENOSYS.
514 */
515 b,n lws_exit_nosys
516#endif
517
518 /* ELF32 Process entry path */
519lws_compare_and_swap32:
520#ifdef CONFIG_64BIT
521 /* Clip all the input registers */
522 depdi 0, 31, 32, %r26
523 depdi 0, 31, 32, %r25
524 depdi 0, 31, 32, %r24
525#endif
526
527lws_compare_and_swap:
528 /* Load start of lock table */
529 ldil L%lws_lock_start, %r20
530 ldo R%lws_lock_start(%r20), %r28
531
532 /* Extract four bits from r26 and hash lock (Bits 4-7) */
533 extru %r26, 27, 4, %r20
534
535 /* Find lock to use, the hash is either one of 0 to
536 15, multiplied by 16 (keep it 16-byte aligned)
537 and add to the lock table offset. */
538 shlw %r20, 4, %r20
539 add %r20, %r28, %r20
540
541# if ENABLE_LWS_DEBUG
542 /*
543 DEBUG, check for deadlock!
544 If the thread register values are the same
545 then we were the one that locked it last and
546 this is a recurisve call that will deadlock.
547 We *must* giveup this call and fail.
548 */
549 ldw 4(%sr2,%r20), %r28 /* Load thread register */
550 /* WARNING: If cr27 cycles to the same value we have problems */
551 mfctl %cr27, %r21 /* Get current thread register */
552 cmpb,<>,n %r21, %r28, cas_lock /* Called recursive? */
553 b lws_exit /* Return error! */
554 ldo -EDEADLOCK(%r0), %r21
555cas_lock:
556 cmpb,=,n %r0, %r28, cas_nocontend /* Is nobody using it? */
557 ldo 1(%r0), %r28 /* 1st case */
558 b lws_exit /* Contended... */
559 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
560cas_nocontend:
561# endif
562/* ENABLE_LWS_DEBUG */
563
564 LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */
565 cmpb,<>,n %r0, %r28, cas_action /* Did we get it? */
566cas_wouldblock:
567 ldo 2(%r0), %r28 /* 2nd case */
568 b lws_exit /* Contended... */
569 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
570
571 /*
572 prev = *addr;
573 if ( prev == old )
574 *addr = new;
575 return prev;
576 */
577
578 /* NOTES:
579 This all works becuse intr_do_signal
580 and schedule both check the return iasq
581 and see that we are on the kernel page
582 so this process is never scheduled off
583 or is ever sent any signal of any sort,
584 thus it is wholly atomic from usrspaces
585 perspective
586 */
587cas_action:
588#if defined CONFIG_SMP && ENABLE_LWS_DEBUG
589 /* DEBUG */
590 mfctl %cr27, %r1
591 stw %r1, 4(%sr2,%r20)
592#endif
593 /* The load and store could fail */
5941: ldw 0(%sr3,%r26), %r28
595 sub,<> %r28, %r25, %r0
5962: stw %r24, 0(%sr3,%r26)
597 /* Free lock */
598 stw %r20, 0(%sr2,%r20)
599#if ENABLE_LWS_DEBUG
600 /* Clear thread register indicator */
601 stw %r0, 4(%sr2,%r20)
602#endif
603 /* Return to userspace, set no error */
604 b lws_exit
605 copy %r0, %r21
606
6073:
608 /* Error occurred on load or store */
609 /* Free lock */
610 stw %r20, 0(%sr2,%r20)
611#if ENABLE_LWS_DEBUG
612 stw %r0, 4(%sr2,%r20)
613#endif
614 b lws_exit
615 ldo -EFAULT(%r0),%r21 /* set errno */
616 nop
617 nop
618 nop
619 nop
620
621 /* Two exception table entries, one for the load,
622 the other for the store. Either return -EFAULT.
623 Each of the entries must be relocated. */
624 .section __ex_table,"aw"
625 ASM_ULONG_INSN (1b - linux_gateway_page), (3b - linux_gateway_page)
626 ASM_ULONG_INSN (2b - linux_gateway_page), (3b - linux_gateway_page)
627 .previous
628
629
630 /* Make sure nothing else is placed on this page */
631 .align PAGE_SIZE
632END(linux_gateway_page)
633ENTRY(end_linux_gateway_page)
634
635 /* Relocate symbols assuming linux_gateway_page is mapped
636 to virtual address 0x0 */
637
638#define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page)
639
640 .section .rodata,"a"
641
642 .align PAGE_SIZE
643 /* Light-weight-syscall table */
644 /* Start of lws table. */
645ENTRY(lws_table)
646 LWS_ENTRY(compare_and_swap32) /* 0 - ELF32 Atomic compare and swap */
647 LWS_ENTRY(compare_and_swap64) /* 1 - ELF64 Atomic compare and swap */
648END(lws_table)
649 /* End of lws table */
650
651 .align PAGE_SIZE
652ENTRY(sys_call_table)
653#include "syscall_table.S"
654END(sys_call_table)
655
656#ifdef CONFIG_64BIT
657 .align PAGE_SIZE
658ENTRY(sys_call_table64)
659#define SYSCALL_TABLE_64BIT
660#include "syscall_table.S"
661END(sys_call_table64)
662#endif
663
664 /*
665 All light-weight-syscall atomic operations
666 will use this set of locks
667
668 NOTE: The lws_lock_start symbol must be
669 at least 16-byte aligned for safe use
670 with ldcw.
671 */
672 .section .data
673 .align PAGE_SIZE
674ENTRY(lws_lock_start)
675 /* lws locks */
676 .rept 16
677 /* Keep locks aligned at 16-bytes */
678 .word 1
679 .word 0
680 .word 0
681 .word 0
682 .endr
683END(lws_lock_start)
684 .previous
685
686.end
687
688
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 LINUX_GATEWAY_ADDR
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
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
1321:
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:
261syscall_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:
270tracesys:
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
328tracesys_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
377tracesys_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
399tracesys_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 *********************************************************/
464lws_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
492lws_exit_nosys:
493 ldo -ENOSYS(%r0),%r21 /* set errno */
494 /* Fall through: Return to userspace */
495
496lws_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 */
542lws_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 */
554lws_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
562lws_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
590cas_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 */
595cas_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? */
603cas_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 */
625cas_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 */
6321: ldw,ma 0(%r26), %r28
633 sub,<> %r28, %r25, %r0
6342: 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
6473:
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 */
691lws_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 */
7114: ldb 0(%r25), %r25
712 b cas2_lock_start
7135: ldb 0(%r24), %r24
714 nop
715 nop
716 nop
717 nop
718 nop
719
720 /* 16bit load */
7216: ldh 0(%r25), %r25
722 b cas2_lock_start
7237: ldh 0(%r24), %r24
724 nop
725 nop
726 nop
727 nop
728 nop
729
730 /* 32bit load */
7318: ldw 0(%r25), %r25
732 b cas2_lock_start
7339: ldw 0(%r24), %r24
734 nop
735 nop
736 nop
737 nop
738 nop
739
740 /* 64bit load */
741#ifdef CONFIG_64BIT
74210: ldd 0(%r25), %r25
74311: ldd 0(%r24), %r24
744#else
745 /* Load new value into r22/r23 - high/low */
74610: ldw 0(%r25), %r22
74711: ldw 4(%r25), %r23
748 /* Load new value into fr4 for atomic store later */
74912: flddx 0(%r24), %fr4
750#endif
751
752cas2_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? */
770cas2_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 */
792cas2_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 */
79913: ldb,ma 0(%r26), %r29
800 sub,= %r29, %r25, %r0
801 b,n cas2_end
80214: stb,ma %r24, 0(%r26)
803 b cas2_end
804 copy %r0, %r28
805 nop
806 nop
807
808 /* 16bit CAS */
80915: ldh,ma 0(%r26), %r29
810 sub,= %r29, %r25, %r0
811 b,n cas2_end
81216: sth,ma %r24, 0(%r26)
813 b cas2_end
814 copy %r0, %r28
815 nop
816 nop
817
818 /* 32bit CAS */
81917: ldw,ma 0(%r26), %r29
820 sub,= %r29, %r25, %r0
821 b,n cas2_end
82218: 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
83019: ldd,ma 0(%r26), %r29
831 sub,*= %r29, %r25, %r0
832 b,n cas2_end
83320: std,ma %r24, 0(%r26)
834 copy %r0, %r28
835#else
836 /* Compare first word */
83719: ldw,ma 0(%r26), %r29
838 sub,= %r29, %r22, %r0
839 b,n cas2_end
840 /* Compare second word */
84120: ldw,ma 4(%r26), %r29
842 sub,= %r29, %r23, %r0
843 b,n cas2_end
844 /* Perform the store */
84521: fstdx %fr4, 0(%r26)
846 copy %r0, %r28
847#endif
848
849cas2_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
85822:
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
895END(linux_gateway_page)
896ENTRY(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. */
908ENTRY(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 */
912END(lws_table)
913 /* End of lws table */
914
915 .align 8
916ENTRY(sys_call_table)
917 .export sys_call_table,data
918#include "syscall_table.S"
919END(sys_call_table)
920
921#ifdef CONFIG_64BIT
922 .align 8
923ENTRY(sys_call_table64)
924#define SYSCALL_TABLE_64BIT
925#include "syscall_table.S"
926END(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
939ENTRY(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
948END(lws_lock_start)
949 .previous
950
951.end
952
953