xref: /linux/arch/parisc/kernel/syscall.S (revision ca55b2fef3a9373fcfc30f82fd26bc7fccbda732) 
1/*
2 * Linux/PA-RISC Project (http://www.parisc-linux.org/)
3 *
4 * System call entry code / Linux gateway page
5 * Copyright (c) Matthew Wilcox 1999 <willy@bofh.ai>
6 * Licensed under the GNU GPL.
7 * thanks to Philipp Rumpf, Mike Shaver and various others
8 * sorry about the wall, puffin..
9 */
10
11/*
12How does the Linux gateway page on PA-RISC work?
13------------------------------------------------
14The Linux gateway page on PA-RISC is "special".
15It actually has PAGE_GATEWAY bits set (this is linux terminology; in parisc
16terminology it's Execute, promote to PL0) in the page map.  So anything
17executing on this page executes with kernel level privilege (there's more to it
18than that: to have this happen, you also have to use a branch with a ,gate
19completer to activate the privilege promotion).  The upshot is that everything
20that runs on the gateway page runs at kernel privilege but with the current
21user process address space (although you have access to kernel space via %sr2).
22For the 0x100 syscall entry, we redo the space registers to point to the kernel
23address space (preserving the user address space in %sr3), move to wide mode if
24required, save the user registers and branch into the kernel syscall entry
25point.  For all the other functions, we execute at kernel privilege but don't
26flip address spaces. The basic upshot of this is that these code snippets are
27executed atomically (because the kernel can't be pre-empted) and they may
28perform architecturally forbidden (to PL3) operations (like setting control
29registers).
30*/
31
32
33#include <asm/asm-offsets.h>
34#include <asm/unistd.h>
35#include <asm/errno.h>
36#include <asm/page.h>
37#include <asm/psw.h>
38#include <asm/thread_info.h>
39#include <asm/assembly.h>
40#include <asm/processor.h>
41#include <asm/cache.h>
42
43#include <linux/linkage.h>
44
45	/* We fill the empty parts of the gateway page with
46 	 * something that will kill the kernel or a
47 	 * userspace application.
48	 */
49#define KILL_INSN	break	0,0
50
51	.level          LEVEL
52
53	.text
54
55	.import syscall_exit,code
56	.import syscall_exit_rfi,code
57
58	/* Linux gateway page is aliased to virtual page 0 in the kernel
59	 * address space. Since it is a gateway page it cannot be
60	 * dereferenced, so null pointers will still fault. We start
61	 * the actual entry point at 0x100. We put break instructions
62	 * at the beginning of the page to trap null indirect function
63	 * pointers.
64	 */
65
66	.align PAGE_SIZE
67ENTRY(linux_gateway_page)
68
69        /* ADDRESS 0x00 to 0xb0 = 176 bytes / 4 bytes per insn = 44 insns */
70	.rept 44
71	KILL_INSN
72	.endr
73
74	/* ADDRESS 0xb0 to 0xb8, lws uses two insns for entry */
75	/* Light-weight-syscall entry must always be located at 0xb0 */
76	/* WARNING: Keep this number updated with table size changes */
77#define __NR_lws_entries (3)
78
79lws_entry:
80	gate	lws_start, %r0		/* increase privilege */
81	depi	3, 31, 2, %r31		/* Ensure we return into user mode. */
82
83	/* Fill from 0xb8 to 0xe0 */
84	.rept 10
85	KILL_INSN
86	.endr
87
88	/* This function MUST be located at 0xe0 for glibc's threading
89	mechanism to work. DO NOT MOVE THIS CODE EVER! */
90set_thread_pointer:
91	gate	.+8, %r0		/* increase privilege */
92	depi	3, 31, 2, %r31		/* Ensure we return into user mode. */
93	be	0(%sr7,%r31)		/* return to user space */
94	mtctl	%r26, %cr27		/* move arg0 to the control register */
95
96	/* Increase the chance of trapping if random jumps occur to this
97	address, fill from 0xf0 to 0x100 */
98	.rept 4
99	KILL_INSN
100	.endr
101
102/* This address must remain fixed at 0x100 for glibc's syscalls to work */
103	.align 256
104linux_gateway_entry:
105	gate	.+8, %r0			/* become privileged */
106	mtsp	%r0,%sr4			/* get kernel space into sr4 */
107	mtsp	%r0,%sr5			/* get kernel space into sr5 */
108	mtsp	%r0,%sr6			/* get kernel space into sr6 */
109	mfsp    %sr7,%r1                        /* save user sr7 */
110	mtsp    %r1,%sr3                        /* and store it in sr3 */
111
112#ifdef CONFIG_64BIT
113	/* for now we can *always* set the W bit on entry to the syscall
114	 * since we don't support wide userland processes.  We could
115	 * also save the current SM other than in r0 and restore it on
116	 * exit from the syscall, and also use that value to know
117	 * whether to do narrow or wide syscalls. -PB
118	 */
119	ssm	PSW_SM_W, %r1
120	extrd,u	%r1,PSW_W_BIT,1,%r1
121	/* sp must be aligned on 4, so deposit the W bit setting into
122	 * the bottom of sp temporarily */
123	or,ev	%r1,%r30,%r30
124	b,n	1f
125	/* The top halves of argument registers must be cleared on syscall
126	 * entry from narrow executable.
127	 */
128	depdi	0, 31, 32, %r26
129	depdi	0, 31, 32, %r25
130	depdi	0, 31, 32, %r24
131	depdi	0, 31, 32, %r23
132	depdi	0, 31, 32, %r22
133	depdi	0, 31, 32, %r21
1341:
135#endif
136	mfctl   %cr30,%r1
137	xor     %r1,%r30,%r30                   /* ye olde xor trick */
138	xor     %r1,%r30,%r1
139	xor     %r1,%r30,%r30
140
141	ldo     THREAD_SZ_ALGN+FRAME_SIZE(%r30),%r30  /* set up kernel stack */
142
143	/* N.B.: It is critical that we don't set sr7 to 0 until r30
144	 *       contains a valid kernel stack pointer. It is also
145	 *       critical that we don't start using the kernel stack
146	 *       until after sr7 has been set to 0.
147	 */
148
149	mtsp	%r0,%sr7			/* get kernel space into sr7 */
150	STREGM	%r1,FRAME_SIZE(%r30)		/* save r1 (usp) here for now */
151	mfctl	%cr30,%r1			/* get task ptr in %r1 */
152	LDREG	TI_TASK(%r1),%r1
153
154	/* Save some registers for sigcontext and potential task
155	   switch (see entry.S for the details of which ones are
156	   saved/restored).  TASK_PT_PSW is zeroed so we can see whether
157	   a process is on a syscall or not.  For an interrupt the real
158	   PSW value is stored.  This is needed for gdb and sys_ptrace. */
159	STREG	%r0,  TASK_PT_PSW(%r1)
160	STREG	%r2,  TASK_PT_GR2(%r1)		/* preserve rp */
161	STREG	%r19, TASK_PT_GR19(%r1)
162
163	LDREGM	-FRAME_SIZE(%r30), %r2		/* get users sp back */
164#ifdef CONFIG_64BIT
165	extrd,u	%r2,63,1,%r19			/* W hidden in bottom bit */
166#if 0
167	xor	%r19,%r2,%r2			/* clear bottom bit */
168	depd,z	%r19,1,1,%r19
169	std	%r19,TASK_PT_PSW(%r1)
170#endif
171#endif
172	STREG	%r2,  TASK_PT_GR30(%r1)		/* ... and save it */
173
174	STREG	%r20, TASK_PT_GR20(%r1)		/* Syscall number */
175	STREG	%r21, TASK_PT_GR21(%r1)
176	STREG	%r22, TASK_PT_GR22(%r1)
177	STREG	%r23, TASK_PT_GR23(%r1)		/* 4th argument */
178	STREG	%r24, TASK_PT_GR24(%r1)		/* 3rd argument */
179	STREG	%r25, TASK_PT_GR25(%r1)		/* 2nd argument */
180	STREG	%r26, TASK_PT_GR26(%r1)	 	/* 1st argument */
181	STREG	%r27, TASK_PT_GR27(%r1)		/* user dp */
182	STREG   %r28, TASK_PT_GR28(%r1)         /* return value 0 */
183	STREG   %r0, TASK_PT_ORIG_R28(%r1)      /* don't prohibit restarts */
184	STREG	%r29, TASK_PT_GR29(%r1)		/* return value 1 */
185	STREG	%r31, TASK_PT_GR31(%r1)		/* preserve syscall return ptr */
186
187	ldo	TASK_PT_FR0(%r1), %r27		/* save fpregs from the kernel */
188	save_fp	%r27				/* or potential task switch  */
189
190	mfctl	%cr11, %r27			/* i.e. SAR */
191	STREG	%r27, TASK_PT_SAR(%r1)
192
193	loadgp
194
195#ifdef CONFIG_64BIT
196	ldo	-16(%r30),%r29			/* Reference param save area */
197	copy	%r19,%r2			/* W bit back to r2 */
198#else
199	/* no need to save these on stack in wide mode because the first 8
200	 * args are passed in registers */
201	stw     %r22, -52(%r30)                 /* 5th argument */
202	stw     %r21, -56(%r30)                 /* 6th argument */
203#endif
204
205	/* Are we being ptraced? */
206	mfctl	%cr30, %r1
207	LDREG	TI_FLAGS(%r1),%r1
208	ldi	_TIF_SYSCALL_TRACE_MASK, %r19
209	and,COND(=) %r1, %r19, %r0
210	b,n	.Ltracesys
211
212	/* Note!  We cannot use the syscall table that is mapped
213	nearby since the gateway page is mapped execute-only. */
214
215#ifdef CONFIG_64BIT
216	ldil	L%sys_call_table, %r1
217	or,=	%r2,%r2,%r2
218	addil	L%(sys_call_table64-sys_call_table), %r1
219	ldo	R%sys_call_table(%r1), %r19
220	or,=	%r2,%r2,%r2
221	ldo	R%sys_call_table64(%r1), %r19
222#else
223	ldil	L%sys_call_table, %r1
224	ldo     R%sys_call_table(%r1), %r19
225#endif
226	comiclr,>>	__NR_Linux_syscalls, %r20, %r0
227	b,n	.Lsyscall_nosys
228
229	LDREGX  %r20(%r19), %r19
230
231	/* If this is a sys_rt_sigreturn call, and the signal was received
232	 * when not in_syscall, then we want to return via syscall_exit_rfi,
233	 * not syscall_exit.  Signal no. in r20, in_syscall in r25 (see
234	 * trampoline code in signal.c).
235	 */
236	ldi	__NR_rt_sigreturn,%r2
237	comb,=	%r2,%r20,.Lrt_sigreturn
238.Lin_syscall:
239	ldil	L%syscall_exit,%r2
240	be      0(%sr7,%r19)
241	ldo	R%syscall_exit(%r2),%r2
242.Lrt_sigreturn:
243	comib,<> 0,%r25,.Lin_syscall
244	ldil	L%syscall_exit_rfi,%r2
245	be      0(%sr7,%r19)
246	ldo	R%syscall_exit_rfi(%r2),%r2
247
248	/* Note!  Because we are not running where we were linked, any
249	calls to functions external to this file must be indirect.  To
250	be safe, we apply the opposite rule to functions within this
251	file, with local labels given to them to ensure correctness. */
252
253.Lsyscall_nosys:
254syscall_nosys:
255	ldil	L%syscall_exit,%r1
256	be	R%syscall_exit(%sr7,%r1)
257	ldo	-ENOSYS(%r0),%r28		   /* set errno */
258
259
260/* Warning! This trace code is a virtual duplicate of the code above so be
261 * sure to maintain both! */
262.Ltracesys:
263tracesys:
264	/* Need to save more registers so the debugger can see where we
265	 * are.  This saves only the lower 8 bits of PSW, so that the C
266	 * bit is still clear on syscalls, and the D bit is set if this
267	 * full register save path has been executed.  We check the D
268	 * bit on syscall_return_rfi to determine which registers to
269	 * restore.  An interrupt results in a full PSW saved with the
270	 * C bit set, a non-straced syscall entry results in C and D clear
271	 * in the saved PSW.
272	 */
273	ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
274	LDREG	TI_TASK(%r1), %r1
275	ssm	0,%r2
276	STREG	%r2,TASK_PT_PSW(%r1)		/* Lower 8 bits only!! */
277	mfsp	%sr0,%r2
278	STREG	%r2,TASK_PT_SR0(%r1)
279	mfsp	%sr1,%r2
280	STREG	%r2,TASK_PT_SR1(%r1)
281	mfsp	%sr2,%r2
282	STREG	%r2,TASK_PT_SR2(%r1)
283	mfsp	%sr3,%r2
284	STREG	%r2,TASK_PT_SR3(%r1)
285	STREG	%r2,TASK_PT_SR4(%r1)
286	STREG	%r2,TASK_PT_SR5(%r1)
287	STREG	%r2,TASK_PT_SR6(%r1)
288	STREG	%r2,TASK_PT_SR7(%r1)
289	STREG	%r2,TASK_PT_IASQ0(%r1)
290	STREG	%r2,TASK_PT_IASQ1(%r1)
291	LDREG	TASK_PT_GR31(%r1),%r2
292	STREG	%r2,TASK_PT_IAOQ0(%r1)
293	ldo	4(%r2),%r2
294	STREG	%r2,TASK_PT_IAOQ1(%r1)
295	ldo	TASK_REGS(%r1),%r2
296	/* reg_save %r2 */
297	STREG	%r3,PT_GR3(%r2)
298	STREG	%r4,PT_GR4(%r2)
299	STREG	%r5,PT_GR5(%r2)
300	STREG	%r6,PT_GR6(%r2)
301	STREG	%r7,PT_GR7(%r2)
302	STREG	%r8,PT_GR8(%r2)
303	STREG	%r9,PT_GR9(%r2)
304	STREG	%r10,PT_GR10(%r2)
305	STREG	%r11,PT_GR11(%r2)
306	STREG	%r12,PT_GR12(%r2)
307	STREG	%r13,PT_GR13(%r2)
308	STREG	%r14,PT_GR14(%r2)
309	STREG	%r15,PT_GR15(%r2)
310	STREG	%r16,PT_GR16(%r2)
311	STREG	%r17,PT_GR17(%r2)
312	STREG	%r18,PT_GR18(%r2)
313	/* Finished saving things for the debugger */
314
315	copy	%r2,%r26
316	ldil	L%do_syscall_trace_enter,%r1
317	ldil	L%tracesys_next,%r2
318	be	R%do_syscall_trace_enter(%sr7,%r1)
319	ldo	R%tracesys_next(%r2),%r2
320
321tracesys_next:
322	/* do_syscall_trace_enter either returned the syscallno, or -1L,
323	 *  so we skip restoring the PT_GR20 below, since we pulled it from
324	 *  task->thread.regs.gr[20] above.
325	 */
326	copy	%ret0,%r20
327	ldil	L%sys_call_table,%r1
328	ldo     R%sys_call_table(%r1), %r19
329
330	ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
331	LDREG	TI_TASK(%r1), %r1
332	LDREG   TASK_PT_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
338#ifdef CONFIG_64BIT
339	ldo	-16(%r30),%r29			/* Reference param save area */
340#else
341	stw     %r22, -52(%r30)                 /* 5th argument */
342	stw     %r21, -56(%r30)                 /* 6th argument */
343#endif
344
345	comiclr,>>=	__NR_Linux_syscalls, %r20, %r0
346	b,n	.Lsyscall_nosys
347
348	LDREGX  %r20(%r19), %r19
349
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).
354	 */
355	ldi	__NR_rt_sigreturn,%r2
356	comb,=	%r2,%r20,.Ltrace_rt_sigreturn
357.Ltrace_in_syscall:
358	ldil	L%tracesys_exit,%r2
359	be      0(%sr7,%r19)
360	ldo	R%tracesys_exit(%r2),%r2
361
362	/* Do *not* call this function on the gateway page, because it
363	makes a direct call to syscall_trace. */
364
365tracesys_exit:
366	ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
367	LDREG	TI_TASK(%r1), %r1
368#ifdef CONFIG_64BIT
369	ldo	-16(%r30),%r29			/* Reference param save area */
370#endif
371	ldo	TASK_REGS(%r1),%r26
372	bl	do_syscall_trace_exit,%r2
373	STREG   %r28,TASK_PT_GR28(%r1)          /* save return value now */
374	ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
375	LDREG	TI_TASK(%r1), %r1
376	LDREG   TASK_PT_GR28(%r1), %r28		/* Restore return val. */
377
378	ldil	L%syscall_exit,%r1
379	be,n	R%syscall_exit(%sr7,%r1)
380
381.Ltrace_rt_sigreturn:
382	comib,<> 0,%r25,.Ltrace_in_syscall
383	ldil	L%tracesys_sigexit,%r2
384	be      0(%sr7,%r19)
385	ldo	R%tracesys_sigexit(%r2),%r2
386
387tracesys_sigexit:
388	ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
389	LDREG	TI_TASK(%r1), %r1
390#ifdef CONFIG_64BIT
391	ldo	-16(%r30),%r29			/* Reference param save area */
392#endif
393	bl	do_syscall_trace_exit,%r2
394	ldo	TASK_REGS(%r1),%r26
395
396	ldil	L%syscall_exit_rfi,%r1
397	be,n	R%syscall_exit_rfi(%sr7,%r1)
398
399
400	/*********************************************************
401		32/64-bit Light-Weight-Syscall ABI
402
403		* - Indicates a hint for userspace inline asm
404		implementations.
405
406		Syscall number (caller-saves)
407	        - %r20
408	        * In asm clobber.
409
410		Argument registers (caller-saves)
411	        - %r26, %r25, %r24, %r23, %r22
412	        * In asm input.
413
414		Return registers (caller-saves)
415	        - %r28 (return), %r21 (errno)
416	        * In asm output.
417
418		Caller-saves registers
419	        - %r1, %r27, %r29
420	        - %r2 (return pointer)
421	        - %r31 (ble link register)
422	        * In asm clobber.
423
424		Callee-saves registers
425	        - %r3-%r18
426	        - %r30 (stack pointer)
427	        * Not in asm clobber.
428
429		If userspace is 32-bit:
430		Callee-saves registers
431	        - %r19 (32-bit PIC register)
432
433		Differences from 32-bit calling convention:
434		- Syscall number in %r20
435		- Additional argument register %r22 (arg4)
436		- Callee-saves %r19.
437
438		If userspace is 64-bit:
439		Callee-saves registers
440		- %r27 (64-bit PIC register)
441
442		Differences from 64-bit calling convention:
443		- Syscall number in %r20
444		- Additional argument register %r22 (arg4)
445		- Callee-saves %r27.
446
447		Error codes returned by entry path:
448
449		ENOSYS - r20 was an invalid LWS number.
450
451	*********************************************************/
452lws_start:
453
454#ifdef CONFIG_64BIT
455	/* FIXME: If we are a 64-bit kernel just
456	 *        turn this on unconditionally.
457	 */
458	ssm	PSW_SM_W, %r1
459	extrd,u	%r1,PSW_W_BIT,1,%r1
460	/* sp must be aligned on 4, so deposit the W bit setting into
461	 * the bottom of sp temporarily */
462	or,ev	%r1,%r30,%r30
463
464	/* Clip LWS number to a 32-bit value always */
465	depdi	0, 31, 32, %r20
466#endif
467
468        /* Is the lws entry number valid? */
469	comiclr,>>	__NR_lws_entries, %r20, %r0
470	b,n	lws_exit_nosys
471
472	/* WARNING: Trashing sr2 and sr3 */
473	mfsp	%sr7,%r1			/* get userspace into sr3 */
474	mtsp	%r1,%sr3
475	mtsp	%r0,%sr2			/* get kernel space into sr2 */
476
477	/* Load table start */
478	ldil	L%lws_table, %r1
479	ldo	R%lws_table(%r1), %r28	/* Scratch use of r28 */
480	LDREGX	%r20(%sr2,r28), %r21	/* Scratch use of r21 */
481
482	/* Jump to lws, lws table pointers already relocated */
483	be,n	0(%sr2,%r21)
484
485lws_exit_nosys:
486	ldo	-ENOSYS(%r0),%r21		   /* set errno */
487	/* Fall through: Return to userspace */
488
489lws_exit:
490#ifdef CONFIG_64BIT
491	/* decide whether to reset the wide mode bit
492	 *
493	 * For a syscall, the W bit is stored in the lowest bit
494	 * of sp.  Extract it and reset W if it is zero */
495	extrd,u,*<>	%r30,63,1,%r1
496	rsm	PSW_SM_W, %r0
497	/* now reset the lowest bit of sp if it was set */
498	xor	%r30,%r1,%r30
499#endif
500	be,n	0(%sr7, %r31)
501
502
503
504	/***************************************************
505		Implementing 32bit CAS as an atomic operation:
506
507		%r26 - Address to examine
508		%r25 - Old value to check (old)
509		%r24 - New value to set (new)
510		%r28 - Return prev through this register.
511		%r21 - Kernel error code
512
513		If debugging is DISabled:
514
515		%r21 has the following meanings:
516
517		EAGAIN - CAS is busy, ldcw failed, try again.
518		EFAULT - Read or write failed.
519
520		If debugging is enabled:
521
522		EDEADLOCK - CAS called recursively.
523		EAGAIN && r28 == 1 - CAS is busy. Lock contended.
524		EAGAIN && r28 == 2 - CAS is busy. ldcw failed.
525		EFAULT - Read or write failed.
526
527		Scratch: r20, r28, r1
528
529	****************************************************/
530
531	/* Do not enable LWS debugging */
532#define ENABLE_LWS_DEBUG 0
533
534	/* ELF64 Process entry path */
535lws_compare_and_swap64:
536#ifdef CONFIG_64BIT
537	b,n	lws_compare_and_swap
538#else
539	/* If we are not a 64-bit kernel, then we don't
540	 * have 64-bit input registers, and calling
541	 * the 64-bit LWS CAS returns ENOSYS.
542	 */
543	b,n	lws_exit_nosys
544#endif
545
546	/* ELF32 Process entry path */
547lws_compare_and_swap32:
548#ifdef CONFIG_64BIT
549	/* Clip all the input registers */
550	depdi	0, 31, 32, %r26
551	depdi	0, 31, 32, %r25
552	depdi	0, 31, 32, %r24
553#endif
554
555lws_compare_and_swap:
556	/* Load start of lock table */
557	ldil	L%lws_lock_start, %r20
558	ldo	R%lws_lock_start(%r20), %r28
559
560	/* Extract four bits from r26 and hash lock (Bits 4-7) */
561	extru  %r26, 27, 4, %r20
562
563	/* Find lock to use, the hash is either one of 0 to
564	   15, multiplied by 16 (keep it 16-byte aligned)
565	   and add to the lock table offset. */
566	shlw	%r20, 4, %r20
567	add	%r20, %r28, %r20
568
569# if ENABLE_LWS_DEBUG
570	/*
571		DEBUG, check for deadlock!
572		If the thread register values are the same
573		then we were the one that locked it last and
574		this is a recurisve call that will deadlock.
575		We *must* giveup this call and fail.
576	*/
577	ldw	4(%sr2,%r20), %r28			/* Load thread register */
578	/* WARNING: If cr27 cycles to the same value we have problems */
579	mfctl	%cr27, %r21				/* Get current thread register */
580	cmpb,<>,n	%r21, %r28, cas_lock		/* Called recursive? */
581	b	lws_exit				/* Return error! */
582	ldo	-EDEADLOCK(%r0), %r21
583cas_lock:
584	cmpb,=,n	%r0, %r28, cas_nocontend	/* Is nobody using it? */
585	ldo	1(%r0), %r28				/* 1st case */
586	b	lws_exit				/* Contended... */
587	ldo	-EAGAIN(%r0), %r21			/* Spin in userspace */
588cas_nocontend:
589# endif
590/* ENABLE_LWS_DEBUG */
591
592	rsm	PSW_SM_I, %r0				/* Disable interrupts */
593	/* COW breaks can cause contention on UP systems */
594	LDCW	0(%sr2,%r20), %r28			/* Try to acquire the lock */
595	cmpb,<>,n	%r0, %r28, cas_action		/* Did we get it? */
596cas_wouldblock:
597	ldo	2(%r0), %r28				/* 2nd case */
598	ssm	PSW_SM_I, %r0
599	b	lws_exit				/* Contended... */
600	ldo	-EAGAIN(%r0), %r21			/* Spin in userspace */
601
602	/*
603		prev = *addr;
604		if ( prev == old )
605		  *addr = new;
606		return prev;
607	*/
608
609	/* NOTES:
610		This all works becuse intr_do_signal
611		and schedule both check the return iasq
612		and see that we are on the kernel page
613		so this process is never scheduled off
614		or is ever sent any signal of any sort,
615		thus it is wholly atomic from usrspaces
616		perspective
617	*/
618cas_action:
619#if defined CONFIG_SMP && ENABLE_LWS_DEBUG
620	/* DEBUG */
621	mfctl	%cr27, %r1
622	stw	%r1, 4(%sr2,%r20)
623#endif
624	/* The load and store could fail */
6251:	ldw,ma	0(%sr3,%r26), %r28
626	sub,<>	%r28, %r25, %r0
6272:	stw,ma	%r24, 0(%sr3,%r26)
628	/* Free lock */
629	stw,ma	%r20, 0(%sr2,%r20)
630#if ENABLE_LWS_DEBUG
631	/* Clear thread register indicator */
632	stw	%r0, 4(%sr2,%r20)
633#endif
634	/* Enable interrupts */
635	ssm	PSW_SM_I, %r0
636	/* Return to userspace, set no error */
637	b	lws_exit
638	copy	%r0, %r21
639
6403:
641	/* Error occurred on load or store */
642	/* Free lock */
643	stw	%r20, 0(%sr2,%r20)
644#if ENABLE_LWS_DEBUG
645	stw	%r0, 4(%sr2,%r20)
646#endif
647	ssm	PSW_SM_I, %r0
648	b	lws_exit
649	ldo	-EFAULT(%r0),%r21	/* set errno */
650	nop
651	nop
652	nop
653	nop
654
655	/* Two exception table entries, one for the load,
656	   the other for the store. Either return -EFAULT.
657	   Each of the entries must be relocated. */
658	ASM_EXCEPTIONTABLE_ENTRY(1b-linux_gateway_page, 3b-linux_gateway_page)
659	ASM_EXCEPTIONTABLE_ENTRY(2b-linux_gateway_page, 3b-linux_gateway_page)
660
661
662	/***************************************************
663		New CAS implementation which uses pointers and variable size
664		information. The value pointed by old and new MUST NOT change
665		while performing CAS. The lock only protect the value at %r26.
666
667		%r26 - Address to examine
668		%r25 - Pointer to the value to check (old)
669		%r24 - Pointer to the value to set (new)
670		%r23 - Size of the variable (0/1/2/3 for 8/16/32/64 bit)
671		%r28 - Return non-zero on failure
672		%r21 - Kernel error code
673
674		%r21 has the following meanings:
675
676		EAGAIN - CAS is busy, ldcw failed, try again.
677		EFAULT - Read or write failed.
678
679		Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only)
680
681	****************************************************/
682
683	/* ELF32 Process entry path */
684lws_compare_and_swap_2:
685#ifdef CONFIG_64BIT
686	/* Clip the input registers */
687	depdi	0, 31, 32, %r26
688	depdi	0, 31, 32, %r25
689	depdi	0, 31, 32, %r24
690	depdi	0, 31, 32, %r23
691#endif
692
693	/* Check the validity of the size pointer */
694	subi,>>= 4, %r23, %r0
695	b,n	lws_exit_nosys
696
697	/* Jump to the functions which will load the old and new values into
698	   registers depending on the their size */
699	shlw	%r23, 2, %r29
700	blr	%r29, %r0
701	nop
702
703	/* 8bit load */
7044:	ldb	0(%sr3,%r25), %r25
705	b	cas2_lock_start
7065:	ldb	0(%sr3,%r24), %r24
707	nop
708	nop
709	nop
710	nop
711	nop
712
713	/* 16bit load */
7146:	ldh	0(%sr3,%r25), %r25
715	b	cas2_lock_start
7167:	ldh	0(%sr3,%r24), %r24
717	nop
718	nop
719	nop
720	nop
721	nop
722
723	/* 32bit load */
7248:	ldw	0(%sr3,%r25), %r25
725	b	cas2_lock_start
7269:	ldw	0(%sr3,%r24), %r24
727	nop
728	nop
729	nop
730	nop
731	nop
732
733	/* 64bit load */
734#ifdef CONFIG_64BIT
73510:	ldd	0(%sr3,%r25), %r25
73611:	ldd	0(%sr3,%r24), %r24
737#else
738	/* Load new value into r22/r23 - high/low */
73910:	ldw	0(%sr3,%r25), %r22
74011:	ldw	4(%sr3,%r25), %r23
741	/* Load new value into fr4 for atomic store later */
74212:	flddx	0(%sr3,%r24), %fr4
743#endif
744
745cas2_lock_start:
746	/* Load start of lock table */
747	ldil	L%lws_lock_start, %r20
748	ldo	R%lws_lock_start(%r20), %r28
749
750	/* Extract four bits from r26 and hash lock (Bits 4-7) */
751	extru  %r26, 27, 4, %r20
752
753	/* Find lock to use, the hash is either one of 0 to
754	   15, multiplied by 16 (keep it 16-byte aligned)
755	   and add to the lock table offset. */
756	shlw	%r20, 4, %r20
757	add	%r20, %r28, %r20
758
759	rsm	PSW_SM_I, %r0			/* Disable interrupts */
760	/* COW breaks can cause contention on UP systems */
761	LDCW	0(%sr2,%r20), %r28		/* Try to acquire the lock */
762	cmpb,<>,n	%r0, %r28, cas2_action	/* Did we get it? */
763cas2_wouldblock:
764	ldo	2(%r0), %r28			/* 2nd case */
765	ssm	PSW_SM_I, %r0
766	b	lws_exit			/* Contended... */
767	ldo	-EAGAIN(%r0), %r21		/* Spin in userspace */
768
769	/*
770		prev = *addr;
771		if ( prev == old )
772		  *addr = new;
773		return prev;
774	*/
775
776	/* NOTES:
777		This all works becuse intr_do_signal
778		and schedule both check the return iasq
779		and see that we are on the kernel page
780		so this process is never scheduled off
781		or is ever sent any signal of any sort,
782		thus it is wholly atomic from usrspaces
783		perspective
784	*/
785cas2_action:
786	/* Jump to the correct function */
787	blr	%r29, %r0
788	/* Set %r28 as non-zero for now */
789	ldo	1(%r0),%r28
790
791	/* 8bit CAS */
79213:	ldb,ma	0(%sr3,%r26), %r29
793	sub,=	%r29, %r25, %r0
794	b,n	cas2_end
79514:	stb,ma	%r24, 0(%sr3,%r26)
796	b	cas2_end
797	copy	%r0, %r28
798	nop
799	nop
800
801	/* 16bit CAS */
80215:	ldh,ma	0(%sr3,%r26), %r29
803	sub,=	%r29, %r25, %r0
804	b,n	cas2_end
80516:	sth,ma	%r24, 0(%sr3,%r26)
806	b	cas2_end
807	copy	%r0, %r28
808	nop
809	nop
810
811	/* 32bit CAS */
81217:	ldw,ma	0(%sr3,%r26), %r29
813	sub,=	%r29, %r25, %r0
814	b,n	cas2_end
81518:	stw,ma	%r24, 0(%sr3,%r26)
816	b	cas2_end
817	copy	%r0, %r28
818	nop
819	nop
820
821	/* 64bit CAS */
822#ifdef CONFIG_64BIT
82319:	ldd,ma	0(%sr3,%r26), %r29
824	sub,*=	%r29, %r25, %r0
825	b,n	cas2_end
82620:	std,ma	%r24, 0(%sr3,%r26)
827	copy	%r0, %r28
828#else
829	/* Compare first word */
83019:	ldw,ma	0(%sr3,%r26), %r29
831	sub,=	%r29, %r22, %r0
832	b,n	cas2_end
833	/* Compare second word */
83420:	ldw,ma	4(%sr3,%r26), %r29
835	sub,=	%r29, %r23, %r0
836	b,n	cas2_end
837	/* Perform the store */
83821:	fstdx	%fr4, 0(%sr3,%r26)
839	copy	%r0, %r28
840#endif
841
842cas2_end:
843	/* Free lock */
844	stw,ma	%r20, 0(%sr2,%r20)
845	/* Enable interrupts */
846	ssm	PSW_SM_I, %r0
847	/* Return to userspace, set no error */
848	b	lws_exit
849	copy	%r0, %r21
850
85122:
852	/* Error occurred on load or store */
853	/* Free lock */
854	stw	%r20, 0(%sr2,%r20)
855	ssm	PSW_SM_I, %r0
856	ldo	1(%r0),%r28
857	b	lws_exit
858	ldo	-EFAULT(%r0),%r21	/* set errno */
859	nop
860	nop
861	nop
862
863	/* Exception table entries, for the load and store, return EFAULT.
864	   Each of the entries must be relocated. */
865	ASM_EXCEPTIONTABLE_ENTRY(4b-linux_gateway_page, 22b-linux_gateway_page)
866	ASM_EXCEPTIONTABLE_ENTRY(5b-linux_gateway_page, 22b-linux_gateway_page)
867	ASM_EXCEPTIONTABLE_ENTRY(6b-linux_gateway_page, 22b-linux_gateway_page)
868	ASM_EXCEPTIONTABLE_ENTRY(7b-linux_gateway_page, 22b-linux_gateway_page)
869	ASM_EXCEPTIONTABLE_ENTRY(8b-linux_gateway_page, 22b-linux_gateway_page)
870	ASM_EXCEPTIONTABLE_ENTRY(9b-linux_gateway_page, 22b-linux_gateway_page)
871	ASM_EXCEPTIONTABLE_ENTRY(10b-linux_gateway_page, 22b-linux_gateway_page)
872	ASM_EXCEPTIONTABLE_ENTRY(11b-linux_gateway_page, 22b-linux_gateway_page)
873	ASM_EXCEPTIONTABLE_ENTRY(13b-linux_gateway_page, 22b-linux_gateway_page)
874	ASM_EXCEPTIONTABLE_ENTRY(14b-linux_gateway_page, 22b-linux_gateway_page)
875	ASM_EXCEPTIONTABLE_ENTRY(15b-linux_gateway_page, 22b-linux_gateway_page)
876	ASM_EXCEPTIONTABLE_ENTRY(16b-linux_gateway_page, 22b-linux_gateway_page)
877	ASM_EXCEPTIONTABLE_ENTRY(17b-linux_gateway_page, 22b-linux_gateway_page)
878	ASM_EXCEPTIONTABLE_ENTRY(18b-linux_gateway_page, 22b-linux_gateway_page)
879	ASM_EXCEPTIONTABLE_ENTRY(19b-linux_gateway_page, 22b-linux_gateway_page)
880	ASM_EXCEPTIONTABLE_ENTRY(20b-linux_gateway_page, 22b-linux_gateway_page)
881#ifndef CONFIG_64BIT
882	ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 22b-linux_gateway_page)
883	ASM_EXCEPTIONTABLE_ENTRY(21b-linux_gateway_page, 22b-linux_gateway_page)
884#endif
885
886	/* Make sure nothing else is placed on this page */
887	.align PAGE_SIZE
888END(linux_gateway_page)
889ENTRY(end_linux_gateway_page)
890
891	/* Relocate symbols assuming linux_gateway_page is mapped
892	   to virtual address 0x0 */
893
894#define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page)
895
896	.section .rodata,"a"
897
898	.align 8
899	/* Light-weight-syscall table */
900	/* Start of lws table. */
901ENTRY(lws_table)
902	LWS_ENTRY(compare_and_swap32)		/* 0 - ELF32 Atomic 32bit CAS */
903	LWS_ENTRY(compare_and_swap64)		/* 1 - ELF64 Atomic 32bit CAS */
904	LWS_ENTRY(compare_and_swap_2)		/* 2 - ELF32 Atomic 64bit CAS */
905END(lws_table)
906	/* End of lws table */
907
908	.align 8
909ENTRY(sys_call_table)
910#include "syscall_table.S"
911END(sys_call_table)
912
913#ifdef CONFIG_64BIT
914	.align 8
915ENTRY(sys_call_table64)
916#define SYSCALL_TABLE_64BIT
917#include "syscall_table.S"
918END(sys_call_table64)
919#endif
920
921	/*
922		All light-weight-syscall atomic operations
923		will use this set of locks
924
925		NOTE: The lws_lock_start symbol must be
926		at least 16-byte aligned for safe use
927		with ldcw.
928	*/
929	.section .data
930	.align	L1_CACHE_BYTES
931ENTRY(lws_lock_start)
932	/* lws locks */
933	.rept 16
934	/* Keep locks aligned at 16-bytes */
935	.word 1
936	.word 0
937	.word 0
938	.word 0
939	.endr
940END(lws_lock_start)
941	.previous
942
943.end
944
945
946