2 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
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..
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
33 #include <asm/asm-offsets.h>
34 #include <asm/unistd.h>
35 #include <asm/errno.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.
49 #define KILL_INSN break 0,0
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
67 ENTRY(linux_gateway_page)
69 /* ADDRESS 0x00 to 0xb0 = 176 bytes / 4 bytes per insn = 44 insns */
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)
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 */
88 /* This function MUST be located at 0xe0 for glibc's threading
89 mechanism to work. DO NOT MOVE THIS CODE EVER! */
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 */
102 /* This address must remain fixed at 0x100 for glibc's syscalls to work */
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 */
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
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 */
125 /* The top halves of argument registers must be cleared on syscall
126 * entry from narrow executable.
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
137 xor %r1,%r30,%r30 /* ye olde xor trick */
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.
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 */
165 extrd,u %r2,63,1,%r19 /* W hidden in bottom bit */
167 xor %r19,%r2,%r2 /* clear bottom bit */
169 std %r19,TASK_PT_PSW(%r1)
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)
196 ldo -16(%r30),%r29 /* Reference param save area */
197 copy %r19,%r2 /* W bit back to r2 */
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 */
205 /* Are we being ptraced? */
207 LDREG TI_FLAGS(%r1),%r1
208 ldi _TIF_SYSCALL_TRACE_MASK, %r19
209 and,COND(=) %r1, %r19, %r0
212 /* Note! We cannot use the syscall table that is mapped
213 nearby since the gateway page is mapped execute-only. */
216 ldil L%sys_call_table, %r1
218 addil L%(sys_call_table64-sys_call_table), %r1
219 ldo R%sys_call_table(%r1), %r19
221 ldo R%sys_call_table64(%r1), %r19
223 ldil L%sys_call_table, %r1
224 ldo R%sys_call_table(%r1), %r19
226 comiclr,>> __NR_Linux_syscalls, %r20, %r0
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).
236 ldi __NR_rt_sigreturn,%r2
237 comb,= %r2,%r20,.Lrt_sigreturn
239 ldil L%syscall_exit,%r2
241 ldo R%syscall_exit(%r2),%r2
243 comib,<> 0,%r25,.Lin_syscall
244 ldil L%syscall_exit_rfi,%r2
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. */
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! */
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
273 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
274 LDREG TI_TASK(%r1), %r1
276 STREG %r2,TASK_PT_PSW(%r1) /* Lower 8 bits only!! */
278 STREG %r2,TASK_PT_SR0(%r1)
280 STREG %r2,TASK_PT_SR1(%r1)
282 STREG %r2,TASK_PT_SR2(%r1)
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)
294 STREG %r2,TASK_PT_IAOQ1(%r1)
295 ldo TASK_REGS(%r1),%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 */
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
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.
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_GR26(%r1), %r26 /* Restore the users args */
333 LDREG TASK_PT_GR25(%r1), %r25
334 LDREG TASK_PT_GR24(%r1), %r24
335 LDREG TASK_PT_GR23(%r1), %r23
336 LDREG TASK_PT_GR22(%r1), %r22
337 LDREG TASK_PT_GR21(%r1), %r21
339 ldo -16(%r30),%r29 /* Reference param save area */
341 stw %r22, -52(%r30) /* 5th argument */
342 stw %r21, -56(%r30) /* 6th argument */
345 comiclr,>>= __NR_Linux_syscalls, %r20, %r0
348 LDREGX %r20(%r19), %r19
350 /* If this is a sys_rt_sigreturn call, and the signal was received
351 * when not in_syscall, then we want to return via syscall_exit_rfi,
352 * not syscall_exit. Signal no. in r20, in_syscall in r25 (see
353 * trampoline code in signal.c).
355 ldi __NR_rt_sigreturn,%r2
356 comb,= %r2,%r20,.Ltrace_rt_sigreturn
358 ldil L%tracesys_exit,%r2
360 ldo R%tracesys_exit(%r2),%r2
363 ldo -ENOSYS(%r0),%r28 /* set errno */
365 /* Do *not* call this function on the gateway page, because it
366 makes a direct call to syscall_trace. */
369 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
370 LDREG TI_TASK(%r1), %r1
372 ldo -16(%r30),%r29 /* Reference param save area */
374 ldo TASK_REGS(%r1),%r26
375 BL do_syscall_trace_exit,%r2
376 STREG %r28,TASK_PT_GR28(%r1) /* save return value now */
377 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
378 LDREG TI_TASK(%r1), %r1
379 LDREG TASK_PT_GR28(%r1), %r28 /* Restore return val. */
381 ldil L%syscall_exit,%r1
382 be,n R%syscall_exit(%sr7,%r1)
384 .Ltrace_rt_sigreturn:
385 comib,<> 0,%r25,.Ltrace_in_syscall
386 ldil L%tracesys_sigexit,%r2
388 ldo R%tracesys_sigexit(%r2),%r2
391 ldo -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1 /* get task ptr */
392 LDREG TI_TASK(%r1), %r1
394 ldo -16(%r30),%r29 /* Reference param save area */
396 BL do_syscall_trace_exit,%r2
397 ldo TASK_REGS(%r1),%r26
399 ldil L%syscall_exit_rfi,%r1
400 be,n R%syscall_exit_rfi(%sr7,%r1)
403 /*********************************************************
404 32/64-bit Light-Weight-Syscall ABI
406 * - Indicates a hint for userspace inline asm
409 Syscall number (caller-saves)
413 Argument registers (caller-saves)
414 - %r26, %r25, %r24, %r23, %r22
417 Return registers (caller-saves)
418 - %r28 (return), %r21 (errno)
421 Caller-saves registers
423 - %r2 (return pointer)
424 - %r31 (ble link register)
427 Callee-saves registers
429 - %r30 (stack pointer)
430 * Not in asm clobber.
432 If userspace is 32-bit:
433 Callee-saves registers
434 - %r19 (32-bit PIC register)
436 Differences from 32-bit calling convention:
437 - Syscall number in %r20
438 - Additional argument register %r22 (arg4)
441 If userspace is 64-bit:
442 Callee-saves registers
443 - %r27 (64-bit PIC register)
445 Differences from 64-bit calling convention:
446 - Syscall number in %r20
447 - Additional argument register %r22 (arg4)
450 Error codes returned by entry path:
452 ENOSYS - r20 was an invalid LWS number.
454 *********************************************************/
458 /* FIXME: If we are a 64-bit kernel just
459 * turn this on unconditionally.
462 extrd,u %r1,PSW_W_BIT,1,%r1
463 /* sp must be aligned on 4, so deposit the W bit setting into
464 * the bottom of sp temporarily */
467 /* Clip LWS number to a 32-bit value always */
468 depdi 0, 31, 32, %r20
471 /* Is the lws entry number valid? */
472 comiclr,>> __NR_lws_entries, %r20, %r0
475 /* WARNING: Trashing sr2 and sr3 */
476 mfsp %sr7,%r1 /* get userspace into sr3 */
478 mtsp %r0,%sr2 /* get kernel space into sr2 */
480 /* Load table start */
481 ldil L%lws_table, %r1
482 ldo R%lws_table(%r1), %r28 /* Scratch use of r28 */
483 LDREGX %r20(%sr2,r28), %r21 /* Scratch use of r21 */
485 /* Jump to lws, lws table pointers already relocated */
489 ldo -ENOSYS(%r0),%r21 /* set errno */
490 /* Fall through: Return to userspace */
494 /* decide whether to reset the wide mode bit
496 * For a syscall, the W bit is stored in the lowest bit
497 * of sp. Extract it and reset W if it is zero */
498 extrd,u,*<> %r30,63,1,%r1
500 /* now reset the lowest bit of sp if it was set */
507 /***************************************************
508 Implementing 32bit CAS as an atomic operation:
510 %r26 - Address to examine
511 %r25 - Old value to check (old)
512 %r24 - New value to set (new)
513 %r28 - Return prev through this register.
514 %r21 - Kernel error code
516 If debugging is DISabled:
518 %r21 has the following meanings:
520 EAGAIN - CAS is busy, ldcw failed, try again.
521 EFAULT - Read or write failed.
523 If debugging is enabled:
525 EDEADLOCK - CAS called recursively.
526 EAGAIN && r28 == 1 - CAS is busy. Lock contended.
527 EAGAIN && r28 == 2 - CAS is busy. ldcw failed.
528 EFAULT - Read or write failed.
530 Scratch: r20, r28, r1
532 ****************************************************/
534 /* Do not enable LWS debugging */
535 #define ENABLE_LWS_DEBUG 0
537 /* ELF64 Process entry path */
538 lws_compare_and_swap64:
540 b,n lws_compare_and_swap
542 /* If we are not a 64-bit kernel, then we don't
543 * have 64-bit input registers, and calling
544 * the 64-bit LWS CAS returns ENOSYS.
549 /* ELF32 Process entry path */
550 lws_compare_and_swap32:
552 /* Clip all the input registers */
553 depdi 0, 31, 32, %r26
554 depdi 0, 31, 32, %r25
555 depdi 0, 31, 32, %r24
558 lws_compare_and_swap:
559 /* Load start of lock table */
560 ldil L%lws_lock_start, %r20
561 ldo R%lws_lock_start(%r20), %r28
563 /* Extract four bits from r26 and hash lock (Bits 4-7) */
564 extru %r26, 27, 4, %r20
566 /* Find lock to use, the hash is either one of 0 to
567 15, multiplied by 16 (keep it 16-byte aligned)
568 and add to the lock table offset. */
572 # if ENABLE_LWS_DEBUG
574 DEBUG, check for deadlock!
575 If the thread register values are the same
576 then we were the one that locked it last and
577 this is a recurisve call that will deadlock.
578 We *must* giveup this call and fail.
580 ldw 4(%sr2,%r20), %r28 /* Load thread register */
581 /* WARNING: If cr27 cycles to the same value we have problems */
582 mfctl %cr27, %r21 /* Get current thread register */
583 cmpb,<>,n %r21, %r28, cas_lock /* Called recursive? */
584 b lws_exit /* Return error! */
585 ldo -EDEADLOCK(%r0), %r21
587 cmpb,=,n %r0, %r28, cas_nocontend /* Is nobody using it? */
588 ldo 1(%r0), %r28 /* 1st case */
589 b lws_exit /* Contended... */
590 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
593 /* ENABLE_LWS_DEBUG */
595 rsm PSW_SM_I, %r0 /* Disable interrupts */
596 /* COW breaks can cause contention on UP systems */
597 LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */
598 cmpb,<>,n %r0, %r28, cas_action /* Did we get it? */
600 ldo 2(%r0), %r28 /* 2nd case */
602 b lws_exit /* Contended... */
603 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
613 This all works becuse intr_do_signal
614 and schedule both check the return iasq
615 and see that we are on the kernel page
616 so this process is never scheduled off
617 or is ever sent any signal of any sort,
618 thus it is wholly atomic from usrspaces
622 #if defined CONFIG_SMP && ENABLE_LWS_DEBUG
625 stw %r1, 4(%sr2,%r20)
627 /* The load and store could fail */
628 1: ldw,ma 0(%sr3,%r26), %r28
629 sub,<> %r28, %r25, %r0
630 2: stw,ma %r24, 0(%sr3,%r26)
632 stw,ma %r20, 0(%sr2,%r20)
634 /* Clear thread register indicator */
635 stw %r0, 4(%sr2,%r20)
637 /* Enable interrupts */
639 /* Return to userspace, set no error */
644 /* Error occurred on load or store */
646 stw %r20, 0(%sr2,%r20)
648 stw %r0, 4(%sr2,%r20)
652 ldo -EFAULT(%r0),%r21 /* set errno */
658 /* Two exception table entries, one for the load,
659 the other for the store. Either return -EFAULT.
660 Each of the entries must be relocated. */
661 ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 3b-linux_gateway_page)
662 ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 3b-linux_gateway_page)
665 /***************************************************
666 New CAS implementation which uses pointers and variable size
667 information. The value pointed by old and new MUST NOT change
668 while performing CAS. The lock only protect the value at %r26.
670 %r26 - Address to examine
671 %r25 - Pointer to the value to check (old)
672 %r24 - Pointer to the value to set (new)
673 %r23 - Size of the variable (0/1/2/3 for 8/16/32/64 bit)
674 %r28 - Return non-zero on failure
675 %r21 - Kernel error code
677 %r21 has the following meanings:
679 EAGAIN - CAS is busy, ldcw failed, try again.
680 EFAULT - Read or write failed.
682 Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only)
684 ****************************************************/
686 /* ELF32 Process entry path */
687 lws_compare_and_swap_2:
689 /* Clip the input registers */
690 depdi 0, 31, 32, %r26
691 depdi 0, 31, 32, %r25
692 depdi 0, 31, 32, %r24
693 depdi 0, 31, 32, %r23
696 /* Check the validity of the size pointer */
697 subi,>>= 4, %r23, %r0
700 /* Jump to the functions which will load the old and new values into
701 registers depending on the their size */
707 4: ldb 0(%sr3,%r25), %r25
709 5: ldb 0(%sr3,%r24), %r24
717 6: ldh 0(%sr3,%r25), %r25
719 7: ldh 0(%sr3,%r24), %r24
727 8: ldw 0(%sr3,%r25), %r25
729 9: ldw 0(%sr3,%r24), %r24
738 10: ldd 0(%sr3,%r25), %r25
739 11: ldd 0(%sr3,%r24), %r24
741 /* Load new value into r22/r23 - high/low */
742 10: ldw 0(%sr3,%r25), %r22
743 11: ldw 4(%sr3,%r25), %r23
744 /* Load new value into fr4 for atomic store later */
745 12: flddx 0(%sr3,%r24), %fr4
749 /* Load start of lock table */
750 ldil L%lws_lock_start, %r20
751 ldo R%lws_lock_start(%r20), %r28
753 /* Extract four bits from r26 and hash lock (Bits 4-7) */
754 extru %r26, 27, 4, %r20
756 /* Find lock to use, the hash is either one of 0 to
757 15, multiplied by 16 (keep it 16-byte aligned)
758 and add to the lock table offset. */
762 rsm PSW_SM_I, %r0 /* Disable interrupts */
763 /* COW breaks can cause contention on UP systems */
764 LDCW 0(%sr2,%r20), %r28 /* Try to acquire the lock */
765 cmpb,<>,n %r0, %r28, cas2_action /* Did we get it? */
767 ldo 2(%r0), %r28 /* 2nd case */
769 b lws_exit /* Contended... */
770 ldo -EAGAIN(%r0), %r21 /* Spin in userspace */
780 This all works becuse intr_do_signal
781 and schedule both check the return iasq
782 and see that we are on the kernel page
783 so this process is never scheduled off
784 or is ever sent any signal of any sort,
785 thus it is wholly atomic from usrspaces
789 /* Jump to the correct function */
791 /* Set %r28 as non-zero for now */
795 13: ldb,ma 0(%sr3,%r26), %r29
796 sub,= %r29, %r25, %r0
798 14: stb,ma %r24, 0(%sr3,%r26)
805 15: ldh,ma 0(%sr3,%r26), %r29
806 sub,= %r29, %r25, %r0
808 16: sth,ma %r24, 0(%sr3,%r26)
815 17: ldw,ma 0(%sr3,%r26), %r29
816 sub,= %r29, %r25, %r0
818 18: stw,ma %r24, 0(%sr3,%r26)
826 19: ldd,ma 0(%sr3,%r26), %r29
827 sub,*= %r29, %r25, %r0
829 20: std,ma %r24, 0(%sr3,%r26)
832 /* Compare first word */
833 19: ldw,ma 0(%sr3,%r26), %r29
834 sub,= %r29, %r22, %r0
836 /* Compare second word */
837 20: ldw,ma 4(%sr3,%r26), %r29
838 sub,= %r29, %r23, %r0
840 /* Perform the store */
841 21: fstdx %fr4, 0(%sr3,%r26)
847 stw,ma %r20, 0(%sr2,%r20)
848 /* Enable interrupts */
850 /* Return to userspace, set no error */
855 /* Error occurred on load or store */
857 stw %r20, 0(%sr2,%r20)
861 ldo -EFAULT(%r0),%r21 /* set errno */
866 /* Exception table entries, for the load and store, return EFAULT.
867 Each of the entries must be relocated. */
868 ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 22b-linux_gateway_page)
869 ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 22b-linux_gateway_page)
870 ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 22b-linux_gateway_page)
871 ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 22b-linux_gateway_page)
872 ASM_EXCEPTIONTABLE_ENTRY(8b-linux_gateway_page, 22b-linux_gateway_page)
873 ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 22b-linux_gateway_page)
874 ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 22b-linux_gateway_page)
875 ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 22b-linux_gateway_page)
876 ASM_EXCEPTIONTABLE_ENTRY(13b-linux_gateway_page, 22b-linux_gateway_page)
877 ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 22b-linux_gateway_page)
878 ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 22b-linux_gateway_page)
879 ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 22b-linux_gateway_page)
880 ASM_EXCEPTIONTABLE_ENTRY(17b-linux_gateway_page, 22b-linux_gateway_page)
881 ASM_EXCEPTIONTABLE_ENTRY(18b-linux_gateway_page, 22b-linux_gateway_page)
882 ASM_EXCEPTIONTABLE_ENTRY(19b-linux_gateway_page, 22b-linux_gateway_page)
883 ASM_EXCEPTIONTABLE_ENTRY(20b-linux_gateway_page, 22b-linux_gateway_page)
885 ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 22b-linux_gateway_page)
886 ASM_EXCEPTIONTABLE_ENTRY(21b-linux_gateway_page, 22b-linux_gateway_page)
889 /* Make sure nothing else is placed on this page */
891 END(linux_gateway_page)
892 ENTRY(end_linux_gateway_page)
894 /* Relocate symbols assuming linux_gateway_page is mapped
895 to virtual address 0x0 */
897 #define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page)
902 /* Light-weight-syscall table */
903 /* Start of lws table. */
905 LWS_ENTRY(compare_and_swap32) /* 0 - ELF32 Atomic 32bit CAS */
906 LWS_ENTRY(compare_and_swap64) /* 1 - ELF64 Atomic 32bit CAS */
907 LWS_ENTRY(compare_and_swap_2) /* 2 - ELF32 Atomic 64bit CAS */
909 /* End of lws table */
912 ENTRY(sys_call_table)
913 #include "syscall_table.S"
918 ENTRY(sys_call_table64)
919 #define SYSCALL_TABLE_64BIT
920 #include "syscall_table.S"
921 END(sys_call_table64)
925 All light-weight-syscall atomic operations
926 will use this set of locks
928 NOTE: The lws_lock_start symbol must be
929 at least 16-byte aligned for safe use
933 .align L1_CACHE_BYTES
934 ENTRY(lws_lock_start)
937 /* Keep locks aligned at 16-bytes */