| blob | d03422e5f188368f8df5283cedfd4e32845e64df |
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 */
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 */
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>
43 #include <linux/linkage.h>
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
51 .level LEVEL
53 .text
55 .import syscall_exit,code
56 .import syscall_exit_rfi,code
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 */
66 .align PAGE_SIZE
67 ENTRY(linux_gateway_page)
69 /* ADDRESS 0x00 to 0xb0 = 176 bytes / 4 bytes per insn = 44 insns */
70 .rept 44
71 KILL_INSN
72 .endr
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)
79 lws_entry:
80 gate lws_start, %r0 /* increase privilege */
81 depi 3, 31, 2, %r31 /* Ensure we return into user mode. */
83 /* Fill from 0xb8 to 0xe0 */
84 .rept 10
85 KILL_INSN
86 .endr
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 */
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
102 /* This address must remain fixed at 0x100 for glibc's syscalls to work */
103 .align 256
104 linux_gateway_entry:
105 gate .+8, %r0 /* become privileged */
106 mtsp %r0,%sr4 /* get kernel space into sr4 */
107 mtsp %r0,%sr5 /* get kernel space into sr5 */
108 mtsp %r0,%sr6 /* get kernel space into sr6 */
109 mfsp %sr7,%r1 /* save user sr7 */
110 mtsp %r1,%sr3 /* and store it in sr3 */
112 #ifdef CONFIG_64BIT
113 /* for now we can *always* set the W bit on entry to the syscall
114 * since we don't support wide userland processes. We could
115 * also save the current SM other than in r0 and restore it on
116 * exit from the syscall, and also use that value to know
117 * whether to do narrow or wide syscalls. -PB
118 */
119 ssm PSW_SM_W, %r1
120 extrd,u %r1,PSW_W_BIT,1,%r1
121 /* sp must be aligned on 4, so deposit the W bit setting into
122 * the bottom of sp temporarily */
123 or,ev %r1,%r30,%r30
124 b,n 1f
125 /* The top halves of argument registers must be cleared on syscall
126 * entry from narrow executable.
127 */
128 depdi 0, 31, 32, %r26
129 depdi 0, 31, 32, %r25
130 depdi 0, 31, 32, %r24
131 depdi 0, 31, 32, %r23
132 depdi 0, 31, 32, %r22
133 depdi 0, 31, 32, %r21
134 1:
135 #endif
136 mfctl %cr30,%r1
137 xor %r1,%r30,%r30 /* ye olde xor trick */
138 xor %r1,%r30,%r1
139 xor %r1,%r30,%r30
141 ldo THREAD_SZ_ALGN+FRAME_SIZE(%r30),%r30 /* set up kernel stack */
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 */
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
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)
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 */
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 */
187 ldo TASK_PT_FR0(%r1), %r27 /* save fpregs from the kernel */
188 save_fp %r27 /* or potential task switch */
190 mfctl %cr11, %r27 /* i.e. SAR */
191 STREG %r27, TASK_PT_SAR(%r1)
193 loadgp
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
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
212 /* Note! We cannot use the syscall table that is mapped
213 nearby since the gateway page is mapped execute-only. */
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
229 LDREGX %r20(%r19), %r19
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
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. */
253 .Lsyscall_nosys:
254 syscall_nosys:
255 ldil L%syscall_exit,%r1
256 be R%syscall_exit(%sr7,%r1)
257 ldo -ENOSYS(%r0),%r28 /* set errno */
260 /* Warning! This trace code is a virtual duplicate of the code above so be
261 * sure to maintain both! */
262 .Ltracesys:
263 tracesys:
264 /* Need to save more registers so the debugger can see where we
265 * are. This saves only the lower 8 bits of PSW, so that the C
266 * bit is still clear on syscalls, and the D bit is set if this
267 * full register save path has been executed. We check the D
268 * bit on syscall_return_rfi to determine which registers to
269 * restore. An interrupt results in a full PSW saved with the
270 * C bit set, a non-straced syscall entry results in C and D clear
271 * in the saved PSW.
272 */
273 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
274 LDREG TI_TASK(%r1), %r1
275 ssm 0,%r2
276 STREG %r2,TASK_PT_PSW(%r1) /* Lower 8 bits only!! */
277 mfsp %sr0,%r2
278 STREG %r2,TASK_PT_SR0(%r1)
279 mfsp %sr1,%r2
280 STREG %r2,TASK_PT_SR1(%r1)
281 mfsp %sr2,%r2
282 STREG %r2,TASK_PT_SR2(%r1)
283 mfsp %sr3,%r2
284 STREG %r2,TASK_PT_SR3(%r1)
285 STREG %r2,TASK_PT_SR4(%r1)
286 STREG %r2,TASK_PT_SR5(%r1)
287 STREG %r2,TASK_PT_SR6(%r1)
288 STREG %r2,TASK_PT_SR7(%r1)
289 STREG %r2,TASK_PT_IASQ0(%r1)
290 STREG %r2,TASK_PT_IASQ1(%r1)
291 LDREG TASK_PT_GR31(%r1),%r2
292 STREG %r2,TASK_PT_IAOQ0(%r1)
293 ldo 4(%r2),%r2
294 STREG %r2,TASK_PT_IAOQ1(%r1)
295 ldo TASK_REGS(%r1),%r2
296 /* reg_save %r2 */
297 STREG %r3,PT_GR3(%r2)
298 STREG %r4,PT_GR4(%r2)
299 STREG %r5,PT_GR5(%r2)
300 STREG %r6,PT_GR6(%r2)
301 STREG %r7,PT_GR7(%r2)
302 STREG %r8,PT_GR8(%r2)
303 STREG %r9,PT_GR9(%r2)
304 STREG %r10,PT_GR10(%r2)
305 STREG %r11,PT_GR11(%r2)
306 STREG %r12,PT_GR12(%r2)
307 STREG %r13,PT_GR13(%r2)
308 STREG %r14,PT_GR14(%r2)
309 STREG %r15,PT_GR15(%r2)
310 STREG %r16,PT_GR16(%r2)
311 STREG %r17,PT_GR17(%r2)
312 STREG %r18,PT_GR18(%r2)
313 /* Finished saving things for the debugger */
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
321 tracesys_next:
322 /* do_syscall_trace_enter either returned the syscallno, or -1L,
323 * so we skip restoring the PT_GR20 below, since we pulled it from
324 * task->thread.regs.gr[20] above.
325 */
326 copy %ret0,%r20
327 ldil L%sys_call_table,%r1
328 ldo R%sys_call_table(%r1), %r19
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
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
350 LDREGX %r20(%r19), %r19
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
364 .Ltracesys_nosys:
365 ldo -ENOSYS(%r0),%r28 /* set errno */
367 /* Do *not* call this function on the gateway page, because it
368 makes a direct call to syscall_trace. */
370 tracesys_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. */
383 ldil L%syscall_exit,%r1
384 be,n R%syscall_exit(%sr7,%r1)
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
392 tracesys_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
401 ldil L%syscall_exit_rfi,%r1
402 be,n R%syscall_exit_rfi(%sr7,%r1)
405 /*********************************************************
406 32/64-bit Light-Weight-Syscall ABI
408 * - Indicates a hint for userspace inline asm
409 implementations.
411 Syscall number (caller-saves)
412 - %r20
413 * In asm clobber.
415 Argument registers (caller-saves)
416 - %r26, %r25, %r24, %r23, %r22
417 * In asm input.
419 Return registers (caller-saves)
420 - %r28 (return), %r21 (errno)
421 * In asm output.
423 Caller-saves registers
424 - %r1, %r27, %r29
425 - %r2 (return pointer)
426 - %r31 (ble link register)
427 * In asm clobber.
429 Callee-saves registers
430 - %r3-%r18
431 - %r30 (stack pointer)
432 * Not in asm clobber.
434 If userspace is 32-bit:
435 Callee-saves registers
436 - %r19 (32-bit PIC register)
438 Differences from 32-bit calling convention:
439 - Syscall number in %r20
440 - Additional argument register %r22 (arg4)
441 - Callee-saves %r19.
443 If userspace is 64-bit:
444 Callee-saves registers
445 - %r27 (64-bit PIC register)
447 Differences from 64-bit calling convention:
448 - Syscall number in %r20
449 - Additional argument register %r22 (arg4)
450 - Callee-saves %r27.
452 Error codes returned by entry path:
454 ENOSYS - r20 was an invalid LWS number.
456 *********************************************************/
457 lws_start:
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
469 /* Clip LWS number to a 32-bit value always */
470 depdi 0, 31, 32, %r20
471 #endif
473 /* Is the lws entry number valid? */
474 comiclr,>> __NR_lws_entries, %r20, %r0
475 b,n lws_exit_nosys
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 */
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 */
487 /* Jump to lws, lws table pointers already relocated */
488 be,n 0(%sr2,%r21)
490 lws_exit_nosys:
491 ldo -ENOSYS(%r0),%r21 /* set errno */
492 /* Fall through: Return to userspace */
494 lws_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)
509 /***************************************************
510 Implementing 32bit CAS as an atomic operation:
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
518 If debugging is DISabled:
520 %r21 has the following meanings:
522 EAGAIN - CAS is busy, ldcw failed, try again.
523 EFAULT - Read or write failed.
525 If debugging is enabled:
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.
532 Scratch: r20, r28, r1
534 ****************************************************/
536 /* Do not enable LWS debugging */
537 #define ENABLE_LWS_DEBUG 0
539 /* ELF64 Process entry path */
540 lws_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
551 /* ELF32 Process entry path */
552 lws_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
560 lws_compare_and_swap:
561 /* Load start of lock table */
562 ldil L%lws_lock_start, %r20
563 ldo R%lws_lock_start(%r20), %r28
565 /* Extract four bits from r26 and hash lock (Bits 4-7) */
566 extru %r26, 27, 4, %r20
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
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
588 cas_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 */
593 cas_nocontend:
594 # endif
595 /* ENABLE_LWS_DEBUG */
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? */
601 cas_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 */
607 /*
608 prev = *addr;
609 if ( prev == old )
610 *addr = new;
611 return prev;
612 */
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 */
623 cas_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 */
630 1: ldw,ma 0(%sr3,%r26), %r28
631 sub,<> %r28, %r25, %r0
632 2: 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
645 3:
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
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)
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.
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
679 %r21 has the following meanings:
681 EAGAIN - CAS is busy, ldcw failed, try again.
682 EFAULT - Read or write failed.
684 Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only)
686 ****************************************************/
688 /* ELF32 Process entry path */
689 lws_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
698 /* Check the validity of the size pointer */
699 subi,>>= 4, %r23, %r0
700 b,n lws_exit_nosys
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
708 /* 8bit load */
709 4: ldb 0(%sr3,%r25), %r25
710 b cas2_lock_start
711 5: ldb 0(%sr3,%r24), %r24
712 nop
713 nop
714 nop
715 nop
716 nop
718 /* 16bit load */
719 6: ldh 0(%sr3,%r25), %r25
720 b cas2_lock_start
721 7: ldh 0(%sr3,%r24), %r24
722 nop
723 nop
724 nop
725 nop
726 nop
728 /* 32bit load */
729 8: ldw 0(%sr3,%r25), %r25
730 b cas2_lock_start
731 9: ldw 0(%sr3,%r24), %r24
732 nop
733 nop
734 nop
735 nop
736 nop
738 /* 64bit load */
739 #ifdef CONFIG_64BIT
740 10: ldd 0(%sr3,%r25), %r25
741 11: ldd 0(%sr3,%r24), %r24
742 #else
743 /* Load new value into r22/r23 - high/low */
744 10: ldw 0(%sr3,%r25), %r22
745 11: ldw 4(%sr3,%r25), %r23
746 /* Load new value into fr4 for atomic store later */
747 12: flddx 0(%sr3,%r24), %fr4
748 #endif
750 cas2_lock_start:
751 /* Load start of lock table */
752 ldil L%lws_lock_start, %r20
753 ldo R%lws_lock_start(%r20), %r28
755 /* Extract four bits from r26 and hash lock (Bits 4-7) */
756 extru %r26, 27, 4, %r20
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
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? */
768 cas2_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 */
774 /*
775 prev = *addr;
776 if ( prev == old )
777 *addr = new;
778 return prev;
779 */
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 */
790 cas2_action:
791 /* Jump to the correct function */
792 blr %r29, %r0
793 /* Set %r28 as non-zero for now */
794 ldo 1(%r0),%r28
796 /* 8bit CAS */
797 13: ldb,ma 0(%sr3,%r26), %r29
798 sub,= %r29, %r25, %r0
799 b,n cas2_end
800 14: stb,ma %r24, 0(%sr3,%r26)
801 b cas2_end
802 copy %r0, %r28
803 nop
804 nop
806 /* 16bit CAS */
807 15: ldh,ma 0(%sr3,%r26), %r29
808 sub,= %r29, %r25, %r0
809 b,n cas2_end
810 16: sth,ma %r24, 0(%sr3,%r26)
811 b cas2_end
812 copy %r0, %r28
813 nop
814 nop
816 /* 32bit CAS */
817 17: ldw,ma 0(%sr3,%r26), %r29
818 sub,= %r29, %r25, %r0
819 b,n cas2_end
820 18: stw,ma %r24, 0(%sr3,%r26)
821 b cas2_end
822 copy %r0, %r28
823 nop
824 nop
826 /* 64bit CAS */
827 #ifdef CONFIG_64BIT
828 19: ldd,ma 0(%sr3,%r26), %r29
829 sub,*= %r29, %r25, %r0
830 b,n cas2_end
831 20: std,ma %r24, 0(%sr3,%r26)
832 copy %r0, %r28
833 #else
834 /* Compare first word */
835 19: ldw,ma 0(%sr3,%r26), %r29
836 sub,= %r29, %r22, %r0
837 b,n cas2_end
838 /* Compare second word */
839 20: ldw,ma 4(%sr3,%r26), %r29
840 sub,= %r29, %r23, %r0
841 b,n cas2_end
842 /* Perform the store */
843 21: fstdx %fr4, 0(%sr3,%r26)
844 copy %r0, %r28
845 #endif
847 cas2_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
856 22:
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
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
891 /* Make sure nothing else is placed on this page */
892 .align PAGE_SIZE
893 END(linux_gateway_page)
894 ENTRY(end_linux_gateway_page)
896 /* Relocate symbols assuming linux_gateway_page is mapped
897 to virtual address 0x0 */
899 #define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page)
901 .section .rodata,"a"
903 .align 8
904 /* Light-weight-syscall table */
905 /* Start of lws table. */
906 ENTRY(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 */
910 END(lws_table)
911 /* End of lws table */
913 .align 8
914 ENTRY(sys_call_table)
915 .export sys_call_table,data
916 #include "syscall_table.S"
917 END(sys_call_table)
919 #ifdef CONFIG_64BIT
920 .align 8
921 ENTRY(sys_call_table64)
922 #define SYSCALL_TABLE_64BIT
923 #include "syscall_table.S"
924 END(sys_call_table64)
925 #endif
927 /*
928 All light-weight-syscall atomic operations
929 will use this set of locks
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
937 ENTRY(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
946 END(lws_lock_start)
947 .previous
949 .end