| blob | 23de307c3052aa9ecac21fd6c294657fb53de447 |
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 LINUX_GATEWAY_ADDR
104 linux_gateway_entry:
105 gate .+8, %r0 /* become privileged */
106 mtsp %r0,%sr4 /* get kernel space into sr4 */
107 mtsp %r0,%sr5 /* get kernel space into sr5 */
108 mtsp %r0,%sr6 /* get kernel space into sr6 */
110 #ifdef CONFIG_64BIT
111 /* for now we can *always* set the W bit on entry to the syscall
112 * since we don't support wide userland processes. We could
113 * also save the current SM other than in r0 and restore it on
114 * exit from the syscall, and also use that value to know
115 * whether to do narrow or wide syscalls. -PB
116 */
117 ssm PSW_SM_W, %r1
118 extrd,u %r1,PSW_W_BIT,1,%r1
119 /* sp must be aligned on 4, so deposit the W bit setting into
120 * the bottom of sp temporarily */
121 or,ev %r1,%r30,%r30
122 b,n 1f
123 /* The top halves of argument registers must be cleared on syscall
124 * entry from narrow executable.
125 */
126 depdi 0, 31, 32, %r26
127 depdi 0, 31, 32, %r25
128 depdi 0, 31, 32, %r24
129 depdi 0, 31, 32, %r23
130 depdi 0, 31, 32, %r22
131 depdi 0, 31, 32, %r21
132 1:
133 #endif
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 */
142 mfctl %cr30,%r1
143 xor %r1,%r30,%r30 /* ye olde xor trick */
144 xor %r1,%r30,%r1
145 xor %r1,%r30,%r30
147 ldo THREAD_SZ_ALGN+FRAME_SIZE(%r30),%r30 /* set up kernel stack */
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 */
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
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)
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 */
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 */
194 ldo TASK_PT_FR0(%r1), %r27 /* save fpregs from the kernel */
195 save_fp %r27 /* or potential task switch */
197 mfctl %cr11, %r27 /* i.e. SAR */
198 STREG %r27, TASK_PT_SAR(%r1)
200 loadgp
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
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
219 /* Note! We cannot use the syscall table that is mapped
220 nearby since the gateway page is mapped execute-only. */
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
236 LDREGX %r20(%r19), %r19
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
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. */
260 .Lsyscall_nosys:
261 syscall_nosys:
262 ldil L%syscall_exit,%r1
263 be R%syscall_exit(%sr7,%r1)
264 ldo -ENOSYS(%r0),%r28 /* set errno */
267 /* Warning! This trace code is a virtual duplicate of the code above so be
268 * sure to maintain both! */
269 .Ltracesys:
270 tracesys:
271 /* Need to save more registers so the debugger can see where we
272 * are. This saves only the lower 8 bits of PSW, so that the C
273 * bit is still clear on syscalls, and the D bit is set if this
274 * full register save path has been executed. We check the D
275 * bit on syscall_return_rfi to determine which registers to
276 * restore. An interrupt results in a full PSW saved with the
277 * C bit set, a non-straced syscall entry results in C and D clear
278 * in the saved PSW.
279 */
280 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
281 LDREG TI_TASK(%r1), %r1
282 ssm 0,%r2
283 STREG %r2,TASK_PT_PSW(%r1) /* Lower 8 bits only!! */
284 mfsp %sr0,%r2
285 STREG %r2,TASK_PT_SR0(%r1)
286 mfsp %sr1,%r2
287 STREG %r2,TASK_PT_SR1(%r1)
288 mfsp %sr2,%r2
289 STREG %r2,TASK_PT_SR2(%r1)
290 mfsp %sr3,%r2
291 STREG %r2,TASK_PT_SR3(%r1)
292 STREG %r2,TASK_PT_SR4(%r1)
293 STREG %r2,TASK_PT_SR5(%r1)
294 STREG %r2,TASK_PT_SR6(%r1)
295 STREG %r2,TASK_PT_SR7(%r1)
296 STREG %r2,TASK_PT_IASQ0(%r1)
297 STREG %r2,TASK_PT_IASQ1(%r1)
298 LDREG TASK_PT_GR31(%r1),%r2
299 STREG %r2,TASK_PT_IAOQ0(%r1)
300 ldo 4(%r2),%r2
301 STREG %r2,TASK_PT_IAOQ1(%r1)
302 ldo TASK_REGS(%r1),%r2
303 /* reg_save %r2 */
304 STREG %r3,PT_GR3(%r2)
305 STREG %r4,PT_GR4(%r2)
306 STREG %r5,PT_GR5(%r2)
307 STREG %r6,PT_GR6(%r2)
308 STREG %r7,PT_GR7(%r2)
309 STREG %r8,PT_GR8(%r2)
310 STREG %r9,PT_GR9(%r2)
311 STREG %r10,PT_GR10(%r2)
312 STREG %r11,PT_GR11(%r2)
313 STREG %r12,PT_GR12(%r2)
314 STREG %r13,PT_GR13(%r2)
315 STREG %r14,PT_GR14(%r2)
316 STREG %r15,PT_GR15(%r2)
317 STREG %r16,PT_GR16(%r2)
318 STREG %r17,PT_GR17(%r2)
319 STREG %r18,PT_GR18(%r2)
320 /* Finished saving things for the debugger */
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
328 tracesys_next:
329 /* do_syscall_trace_enter either returned the syscallno, or -1L,
330 * so we skip restoring the PT_GR20 below, since we pulled it from
331 * task->thread.regs.gr[20] above.
332 */
333 copy %ret0,%r20
334 ldil L%sys_call_table,%r1
335 ldo R%sys_call_table(%r1), %r19
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
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
357 LDREGX %r20(%r19), %r19
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
371 .Ltracesys_nosys:
372 ldo -ENOSYS(%r0),%r28 /* set errno */
374 /* Do *not* call this function on the gateway page, because it
375 makes a direct call to syscall_trace. */
377 tracesys_exit:
378 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
379 LDREG TI_TASK(%r1), %r1
380 #ifdef CONFIG_64BIT
381 ldo -16(%r30),%r29 /* Reference param save area */
382 #endif
383 ldo TASK_REGS(%r1),%r26
384 BL do_syscall_trace_exit,%r2
385 STREG %r28,TASK_PT_GR28(%r1) /* save return value now */
386 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
387 LDREG TI_TASK(%r1), %r1
388 LDREG TASK_PT_GR28(%r1), %r28 /* Restore return val. */
390 ldil L%syscall_exit,%r1
391 be,n R%syscall_exit(%sr7,%r1)
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
399 tracesys_sigexit:
400 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
401 LDREG TI_TASK(%r1), %r1
402 #ifdef CONFIG_64BIT
403 ldo -16(%r30),%r29 /* Reference param save area */
404 #endif
405 BL do_syscall_trace_exit,%r2
406 ldo TASK_REGS(%r1),%r26
408 ldil L%syscall_exit_rfi,%r1
409 be,n R%syscall_exit_rfi(%sr7,%r1)
412 /*********************************************************
413 32/64-bit Light-Weight-Syscall ABI
415 * - Indicates a hint for userspace inline asm
416 implementations.
418 Syscall number (caller-saves)
419 - %r20
420 * In asm clobber.
422 Argument registers (caller-saves)
423 - %r26, %r25, %r24, %r23, %r22
424 * In asm input.
426 Return registers (caller-saves)
427 - %r28 (return), %r21 (errno)
428 * In asm output.
430 Caller-saves registers
431 - %r1, %r27, %r29
432 - %r2 (return pointer)
433 - %r31 (ble link register)
434 * In asm clobber.
436 Callee-saves registers
437 - %r3-%r18
438 - %r30 (stack pointer)
439 * Not in asm clobber.
441 If userspace is 32-bit:
442 Callee-saves registers
443 - %r19 (32-bit PIC register)
445 Differences from 32-bit calling convention:
446 - Syscall number in %r20
447 - Additional argument register %r22 (arg4)
448 - Callee-saves %r19.
450 If userspace is 64-bit:
451 Callee-saves registers
452 - %r27 (64-bit PIC register)
454 Differences from 64-bit calling convention:
455 - Syscall number in %r20
456 - Additional argument register %r22 (arg4)
457 - Callee-saves %r27.
459 Error codes returned by entry path:
461 ENOSYS - r20 was an invalid LWS number.
463 *********************************************************/
464 lws_start:
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
476 /* Clip LWS number to a 32-bit value always */
477 depdi 0, 31, 32, %r20
478 #endif
480 /* Is the lws entry number valid? */
481 comiclr,>> __NR_lws_entries, %r20, %r0
482 b,n lws_exit_nosys
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 */
489 /* Jump to lws, lws table pointers already relocated */
490 be,n 0(%sr2,%r21)
492 lws_exit_nosys:
493 ldo -ENOSYS(%r0),%r21 /* set errno */
494 /* Fall through: Return to userspace */
496 lws_exit:
497 #ifdef CONFIG_64BIT
498 /* decide whether to reset the wide mode bit
499 *
500 * For a syscall, the W bit is stored in the lowest bit
501 * of sp. Extract it and reset W if it is zero */
502 extrd,u,*<> %r30,63,1,%r1
503 rsm PSW_SM_W, %r0
504 /* now reset the lowest bit of sp if it was set */
505 xor %r30,%r1,%r30
506 #endif
507 be,n 0(%sr7, %r31)
511 /***************************************************
512 Implementing 32bit CAS as an atomic operation:
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
520 If debugging is DISabled:
522 %r21 has the following meanings:
524 EAGAIN - CAS is busy, ldcw failed, try again.
525 EFAULT - Read or write failed.
527 If debugging is enabled:
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.
534 Scratch: r20, r28, r1
536 ****************************************************/
538 /* Do not enable LWS debugging */
539 #define ENABLE_LWS_DEBUG 0
541 /* ELF64 Process entry path */
542 lws_compare_and_swap64:
543 #ifdef CONFIG_64BIT
544 b,n lws_compare_and_swap
545 #else
546 /* If we are not a 64-bit kernel, then we don't
547 * have 64-bit input registers, and calling
548 * the 64-bit LWS CAS returns ENOSYS.
549 */
550 b,n lws_exit_nosys
551 #endif
553 /* ELF32 Process entry path */
554 lws_compare_and_swap32:
555 #ifdef CONFIG_64BIT
556 /* Clip all the input registers */
557 depdi 0, 31, 32, %r26
558 depdi 0, 31, 32, %r25
559 depdi 0, 31, 32, %r24
560 #endif
562 lws_compare_and_swap:
563 /* Load start of lock table */
564 ldil L%lws_lock_start, %r20
565 ldo R%lws_lock_start(%r20), %r28
567 /* Extract four bits from r26 and hash lock (Bits 4-7) */
568 extru %r26, 27, 4, %r20
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
576 # if ENABLE_LWS_DEBUG
577 /*
578 DEBUG, check for deadlock!
579 If the thread register values are the same
580 then we were the one that locked it last and
581 this is a recurisve call that will deadlock.
582 We *must* giveup this call and fail.
583 */
584 ldw 4(%sr2,%r20), %r28 /* Load thread register */
585 /* WARNING: If cr27 cycles to the same value we have problems */
586 mfctl %cr27, %r21 /* Get current thread register */
587 cmpb,<>,n %r21, %r28, cas_lock /* Called recursive? */
588 b lws_exit /* Return error! */
589 ldo -EDEADLOCK(%r0), %r21
590 cas_lock:
591 cmpb,=,n %r0, %r28, cas_nocontend /* Is nobody using it? */
592 ldo 1(%r0), %r28 /* 1st case */
593 b lws_exit /* Contended... */
594 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
595 cas_nocontend:
596 # endif
597 /* ENABLE_LWS_DEBUG */
599 rsm PSW_SM_I, %r0 /* Disable interrupts */
600 /* COW breaks can cause contention on UP systems */
601 LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */
602 cmpb,<>,n %r0, %r28, cas_action /* Did we get it? */
603 cas_wouldblock:
604 ldo 2(%r0), %r28 /* 2nd case */
605 ssm PSW_SM_I, %r0
606 b lws_exit /* Contended... */
607 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
609 /*
610 prev = *addr;
611 if ( prev == old )
612 *addr = new;
613 return prev;
614 */
616 /* NOTES:
617 This all works becuse intr_do_signal
618 and schedule both check the return iasq
619 and see that we are on the kernel page
620 so this process is never scheduled off
621 or is ever sent any signal of any sort,
622 thus it is wholly atomic from usrspaces
623 perspective
624 */
625 cas_action:
626 #if defined CONFIG_SMP && ENABLE_LWS_DEBUG
627 /* DEBUG */
628 mfctl %cr27, %r1
629 stw %r1, 4(%sr2,%r20)
630 #endif
631 /* The load and store could fail */
632 1: ldw,ma 0(%r26), %r28
633 sub,<> %r28, %r25, %r0
634 2: stw,ma %r24, 0(%r26)
635 /* Free lock */
636 stw,ma %r20, 0(%sr2,%r20)
637 #if ENABLE_LWS_DEBUG
638 /* Clear thread register indicator */
639 stw %r0, 4(%sr2,%r20)
640 #endif
641 /* Enable interrupts */
642 ssm PSW_SM_I, %r0
643 /* Return to userspace, set no error */
644 b lws_exit
645 copy %r0, %r21
647 3:
648 /* Error occurred on load or store */
649 /* Free lock */
650 stw %r20, 0(%sr2,%r20)
651 #if ENABLE_LWS_DEBUG
652 stw %r0, 4(%sr2,%r20)
653 #endif
654 ssm PSW_SM_I, %r0
655 b lws_exit
656 ldo -EFAULT(%r0),%r21 /* set errno */
657 nop
658 nop
659 nop
660 nop
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)
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.
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
681 %r21 has the following meanings:
683 EAGAIN - CAS is busy, ldcw failed, try again.
684 EFAULT - Read or write failed.
686 Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only)
688 ****************************************************/
690 /* ELF32 Process entry path */
691 lws_compare_and_swap_2:
692 #ifdef CONFIG_64BIT
693 /* Clip the input registers */
694 depdi 0, 31, 32, %r26
695 depdi 0, 31, 32, %r25
696 depdi 0, 31, 32, %r24
697 depdi 0, 31, 32, %r23
698 #endif
700 /* Check the validity of the size pointer */
701 subi,>>= 4, %r23, %r0
702 b,n lws_exit_nosys
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
710 /* 8bit load */
711 4: ldb 0(%r25), %r25
712 b cas2_lock_start
713 5: ldb 0(%r24), %r24
714 nop
715 nop
716 nop
717 nop
718 nop
720 /* 16bit load */
721 6: ldh 0(%r25), %r25
722 b cas2_lock_start
723 7: ldh 0(%r24), %r24
724 nop
725 nop
726 nop
727 nop
728 nop
730 /* 32bit load */
731 8: ldw 0(%r25), %r25
732 b cas2_lock_start
733 9: ldw 0(%r24), %r24
734 nop
735 nop
736 nop
737 nop
738 nop
740 /* 64bit load */
741 #ifdef CONFIG_64BIT
742 10: ldd 0(%r25), %r25
743 11: ldd 0(%r24), %r24
744 #else
745 /* Load new value into r22/r23 - high/low */
746 10: ldw 0(%r25), %r22
747 11: ldw 4(%r25), %r23
748 /* Load new value into fr4 for atomic store later */
749 12: flddx 0(%r24), %fr4
750 #endif
752 cas2_lock_start:
753 /* Load start of lock table */
754 ldil L%lws_lock_start, %r20
755 ldo R%lws_lock_start(%r20), %r28
757 /* Extract four bits from r26 and hash lock (Bits 4-7) */
758 extru %r26, 27, 4, %r20
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
766 rsm PSW_SM_I, %r0 /* Disable interrupts */
767 /* COW breaks can cause contention on UP systems */
768 LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */
769 cmpb,<>,n %r0, %r28, cas2_action /* Did we get it? */
770 cas2_wouldblock:
771 ldo 2(%r0), %r28 /* 2nd case */
772 ssm PSW_SM_I, %r0
773 b lws_exit /* Contended... */
774 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
776 /*
777 prev = *addr;
778 if ( prev == old )
779 *addr = new;
780 return prev;
781 */
783 /* NOTES:
784 This all works becuse intr_do_signal
785 and schedule both check the return iasq
786 and see that we are on the kernel page
787 so this process is never scheduled off
788 or is ever sent any signal of any sort,
789 thus it is wholly atomic from usrspaces
790 perspective
791 */
792 cas2_action:
793 /* Jump to the correct function */
794 blr %r29, %r0
795 /* Set %r28 as non-zero for now */
796 ldo 1(%r0),%r28
798 /* 8bit CAS */
799 13: ldb,ma 0(%r26), %r29
800 sub,= %r29, %r25, %r0
801 b,n cas2_end
802 14: stb,ma %r24, 0(%r26)
803 b cas2_end
804 copy %r0, %r28
805 nop
806 nop
808 /* 16bit CAS */
809 15: ldh,ma 0(%r26), %r29
810 sub,= %r29, %r25, %r0
811 b,n cas2_end
812 16: sth,ma %r24, 0(%r26)
813 b cas2_end
814 copy %r0, %r28
815 nop
816 nop
818 /* 32bit CAS */
819 17: ldw,ma 0(%r26), %r29
820 sub,= %r29, %r25, %r0
821 b,n cas2_end
822 18: stw,ma %r24, 0(%r26)
823 b cas2_end
824 copy %r0, %r28
825 nop
826 nop
828 /* 64bit CAS */
829 #ifdef CONFIG_64BIT
830 19: ldd,ma 0(%r26), %r29
831 sub,*= %r29, %r25, %r0
832 b,n cas2_end
833 20: std,ma %r24, 0(%r26)
834 copy %r0, %r28
835 #else
836 /* Compare first word */
837 19: ldw,ma 0(%r26), %r29
838 sub,= %r29, %r22, %r0
839 b,n cas2_end
840 /* Compare second word */
841 20: ldw,ma 4(%r26), %r29
842 sub,= %r29, %r23, %r0
843 b,n cas2_end
844 /* Perform the store */
845 21: fstdx %fr4, 0(%r26)
846 copy %r0, %r28
847 #endif
849 cas2_end:
850 /* Free lock */
851 stw,ma %r20, 0(%sr2,%r20)
852 /* Enable interrupts */
853 ssm PSW_SM_I, %r0
854 /* Return to userspace, set no error */
855 b lws_exit
856 copy %r0, %r21
858 22:
859 /* Error occurred on load or store */
860 /* Free lock */
861 stw %r20, 0(%sr2,%r20)
862 ssm PSW_SM_I, %r0
863 ldo 1(%r0),%r28
864 b lws_exit
865 ldo -EFAULT(%r0),%r21 /* set errno */
866 nop
867 nop
868 nop
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
893 /* Make sure nothing else is placed on this page */
894 .align PAGE_SIZE
895 END(linux_gateway_page)
896 ENTRY(end_linux_gateway_page)
898 /* Relocate symbols assuming linux_gateway_page is mapped
899 to virtual address 0x0 */
901 #define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page)
903 .section .rodata,"a"
905 .align 8
906 /* Light-weight-syscall table */
907 /* Start of lws table. */
908 ENTRY(lws_table)
909 LWS_ENTRY(compare_and_swap32) /* 0 - ELF32 Atomic 32bit CAS */
910 LWS_ENTRY(compare_and_swap64) /* 1 - ELF64 Atomic 32bit CAS */
911 LWS_ENTRY(compare_and_swap_2) /* 2 - ELF32 Atomic 64bit CAS */
912 END(lws_table)
913 /* End of lws table */
915 .align 8
916 ENTRY(sys_call_table)
917 .export sys_call_table,data
918 #include "syscall_table.S"
919 END(sys_call_table)
921 #ifdef CONFIG_64BIT
922 .align 8
923 ENTRY(sys_call_table64)
924 #define SYSCALL_TABLE_64BIT
925 #include "syscall_table.S"
926 END(sys_call_table64)
927 #endif
929 /*
930 All light-weight-syscall atomic operations
931 will use this set of locks
933 NOTE: The lws_lock_start symbol must be
934 at least 16-byte aligned for safe use
935 with ldcw.
936 */
937 .section .data
938 .align L1_CACHE_BYTES
939 ENTRY(lws_lock_start)
940 /* lws locks */
941 .rept 16
942 /* Keep locks aligned at 16-bytes */
943 .word 1
944 .word 0
945 .word 0
946 .word 0
947 .endr
948 END(lws_lock_start)
949 .previous
951 .end