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	.Ltracesys_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.Ltracesys_nosys:
363	ldo	-ENOSYS(%r0),%r28		/* set errno */
364
365	/* Do *not* call this function on the gateway page, because it
366	makes a direct call to syscall_trace. */
367
368tracesys_exit:
369	ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
370	LDREG	TI_TASK(%r1), %r1
371#ifdef CONFIG_64BIT
372	ldo	-16(%r30),%r29			/* Reference param save area */
373#endif
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. */
380
381	ldil	L%syscall_exit,%r1
382	be,n	R%syscall_exit(%sr7,%r1)
383
384.Ltrace_rt_sigreturn:
385	comib,<> 0,%r25,.Ltrace_in_syscall
386	ldil	L%tracesys_sigexit,%r2
387	be      0(%sr7,%r19)
388	ldo	R%tracesys_sigexit(%r2),%r2
389
390tracesys_sigexit:
391	ldo     -THREAD_SZ_ALGN-FRAME_SIZE(%r30),%r1      /* get task ptr */
392	LDREG	TI_TASK(%r1), %r1
393#ifdef CONFIG_64BIT
394	ldo	-16(%r30),%r29			/* Reference param save area */
395#endif
396	bl	do_syscall_trace_exit,%r2
397	ldo	TASK_REGS(%r1),%r26
398
399	ldil	L%syscall_exit_rfi,%r1
400	be,n	R%syscall_exit_rfi(%sr7,%r1)
401
402
403	/*********************************************************
404		32/64-bit Light-Weight-Syscall ABI
405
406		* - Indicates a hint for userspace inline asm
407		implementations.
408
409		Syscall number (caller-saves)
410	        - %r20
411	        * In asm clobber.
412
413		Argument registers (caller-saves)
414	        - %r26, %r25, %r24, %r23, %r22
415	        * In asm input.
416
417		Return registers (caller-saves)
418	        - %r28 (return), %r21 (errno)
419	        * In asm output.
420
421		Caller-saves registers
422	        - %r1, %r27, %r29
423	        - %r2 (return pointer)
424	        - %r31 (ble link register)
425	        * In asm clobber.
426
427		Callee-saves registers
428	        - %r3-%r18
429	        - %r30 (stack pointer)
430	        * Not in asm clobber.
431
432		If userspace is 32-bit:
433		Callee-saves registers
434	        - %r19 (32-bit PIC register)
435
436		Differences from 32-bit calling convention:
437		- Syscall number in %r20
438		- Additional argument register %r22 (arg4)
439		- Callee-saves %r19.
440
441		If userspace is 64-bit:
442		Callee-saves registers
443		- %r27 (64-bit PIC register)
444
445		Differences from 64-bit calling convention:
446		- Syscall number in %r20
447		- Additional argument register %r22 (arg4)
448		- Callee-saves %r27.
449
450		Error codes returned by entry path:
451
452		ENOSYS - r20 was an invalid LWS number.
453
454	*********************************************************/
455lws_start:
456
457#ifdef CONFIG_64BIT
458	/* FIXME: If we are a 64-bit kernel just
459	 *        turn this on unconditionally.
460	 */
461	ssm	PSW_SM_W, %r1
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 */
465	or,ev	%r1,%r30,%r30
466
467	/* Clip LWS number to a 32-bit value always */
468	depdi	0, 31, 32, %r20
469#endif
470
471        /* Is the lws entry number valid? */
472	comiclr,>>	__NR_lws_entries, %r20, %r0
473	b,n	lws_exit_nosys
474
475	/* WARNING: Trashing sr2 and sr3 */
476	mfsp	%sr7,%r1			/* get userspace into sr3 */
477	mtsp	%r1,%sr3
478	mtsp	%r0,%sr2			/* get kernel space into sr2 */
479
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 */
484
485	/* Jump to lws, lws table pointers already relocated */
486	be,n	0(%sr2,%r21)
487
488lws_exit_nosys:
489	ldo	-ENOSYS(%r0),%r21		   /* set errno */
490	/* Fall through: Return to userspace */
491
492lws_exit:
493#ifdef CONFIG_64BIT
494	/* decide whether to reset the wide mode bit
495	 *
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
499	rsm	PSW_SM_W, %r0
500	/* now reset the lowest bit of sp if it was set */
501	xor	%r30,%r1,%r30
502#endif
503	be,n	0(%sr7, %r31)
504
505
506
507	/***************************************************
508		Implementing 32bit CAS as an atomic operation:
509
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
515
516		If debugging is DISabled:
517
518		%r21 has the following meanings:
519
520		EAGAIN - CAS is busy, ldcw failed, try again.
521		EFAULT - Read or write failed.
522
523		If debugging is enabled:
524
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.
529
530		Scratch: r20, r28, r1
531
532	****************************************************/
533
534	/* Do not enable LWS debugging */
535#define ENABLE_LWS_DEBUG 0
536
537	/* ELF64 Process entry path */
538lws_compare_and_swap64:
539#ifdef CONFIG_64BIT
540	b,n	lws_compare_and_swap
541#else
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.
545	 */
546	b,n	lws_exit_nosys
547#endif
548
549	/* ELF32 Process entry path */
550lws_compare_and_swap32:
551#ifdef CONFIG_64BIT
552	/* Clip all the input registers */
553	depdi	0, 31, 32, %r26
554	depdi	0, 31, 32, %r25
555	depdi	0, 31, 32, %r24
556#endif
557
558lws_compare_and_swap:
559	/* Load start of lock table */
560	ldil	L%lws_lock_start, %r20
561	ldo	R%lws_lock_start(%r20), %r28
562
563	/* Extract four bits from r26 and hash lock (Bits 4-7) */
564	extru  %r26, 27, 4, %r20
565
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. */
569	shlw	%r20, 4, %r20
570	add	%r20, %r28, %r20
571
572# if ENABLE_LWS_DEBUG
573	/*
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.
579	*/
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
586cas_lock:
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 */
591cas_nocontend:
592# endif
593/* ENABLE_LWS_DEBUG */
594
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? */
599cas_wouldblock:
600	ldo	2(%r0), %r28				/* 2nd case */
601	ssm	PSW_SM_I, %r0
602	b	lws_exit				/* Contended... */
603	ldo	-EAGAIN(%r0), %r21			/* Spin in userspace */
604
605	/*
606		prev = *addr;
607		if ( prev == old )
608		  *addr = new;
609		return prev;
610	*/
611
612	/* NOTES:
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
619		perspective
620	*/
621cas_action:
622#if defined CONFIG_SMP && ENABLE_LWS_DEBUG
623	/* DEBUG */
624	mfctl	%cr27, %r1
625	stw	%r1, 4(%sr2,%r20)
626#endif
627	/* The load and store could fail */
6281:	ldw,ma	0(%sr3,%r26), %r28
629	sub,<>	%r28, %r25, %r0
6302:	stw,ma	%r24, 0(%sr3,%r26)
631	/* Free lock */
632	stw,ma	%r20, 0(%sr2,%r20)
633#if ENABLE_LWS_DEBUG
634	/* Clear thread register indicator */
635	stw	%r0, 4(%sr2,%r20)
636#endif
637	/* Enable interrupts */
638	ssm	PSW_SM_I, %r0
639	/* Return to userspace, set no error */
640	b	lws_exit
641	copy	%r0, %r21
642
6433:
644	/* Error occurred on load or store */
645	/* Free lock */
646	stw	%r20, 0(%sr2,%r20)
647#if ENABLE_LWS_DEBUG
648	stw	%r0, 4(%sr2,%r20)
649#endif
650	ssm	PSW_SM_I, %r0
651	b	lws_exit
652	ldo	-EFAULT(%r0),%r21	/* set errno */
653	nop
654	nop
655	nop
656	nop
657
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)
663
664
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.
669
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
676
677		%r21 has the following meanings:
678
679		EAGAIN - CAS is busy, ldcw failed, try again.
680		EFAULT - Read or write failed.
681
682		Scratch: r20, r22, r28, r29, r1, fr4 (32bit for 64bit CAS only)
683
684	****************************************************/
685
686	/* ELF32 Process entry path */
687lws_compare_and_swap_2:
688#ifdef CONFIG_64BIT
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
694#endif
695
696	/* Check the validity of the size pointer */
697	subi,>>= 4, %r23, %r0
698	b,n	lws_exit_nosys
699
700	/* Jump to the functions which will load the old and new values into
701	   registers depending on the their size */
702	shlw	%r23, 2, %r29
703	blr	%r29, %r0
704	nop
705
706	/* 8bit load */
7074:	ldb	0(%sr3,%r25), %r25
708	b	cas2_lock_start
7095:	ldb	0(%sr3,%r24), %r24
710	nop
711	nop
712	nop
713	nop
714	nop
715
716	/* 16bit load */
7176:	ldh	0(%sr3,%r25), %r25
718	b	cas2_lock_start
7197:	ldh	0(%sr3,%r24), %r24
720	nop
721	nop
722	nop
723	nop
724	nop
725
726	/* 32bit load */
7278:	ldw	0(%sr3,%r25), %r25
728	b	cas2_lock_start
7299:	ldw	0(%sr3,%r24), %r24
730	nop
731	nop
732	nop
733	nop
734	nop
735
736	/* 64bit load */
737#ifdef CONFIG_64BIT
73810:	ldd	0(%sr3,%r25), %r25
73911:	ldd	0(%sr3,%r24), %r24
740#else
741	/* Load new value into r22/r23 - high/low */
74210:	ldw	0(%sr3,%r25), %r22
74311:	ldw	4(%sr3,%r25), %r23
744	/* Load new value into fr4 for atomic store later */
74512:	flddx	0(%sr3,%r24), %fr4
746#endif
747
748cas2_lock_start:
749	/* Load start of lock table */
750	ldil	L%lws_lock_start, %r20
751	ldo	R%lws_lock_start(%r20), %r28
752
753	/* Extract four bits from r26 and hash lock (Bits 4-7) */
754	extru  %r26, 27, 4, %r20
755
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. */
759	shlw	%r20, 4, %r20
760	add	%r20, %r28, %r20
761
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? */
766cas2_wouldblock:
767	ldo	2(%r0), %r28			/* 2nd case */
768	ssm	PSW_SM_I, %r0
769	b	lws_exit			/* Contended... */
770	ldo	-EAGAIN(%r0), %r21		/* Spin in userspace */
771
772	/*
773		prev = *addr;
774		if ( prev == old )
775		  *addr = new;
776		return prev;
777	*/
778
779	/* NOTES:
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
786		perspective
787	*/
788cas2_action:
789	/* Jump to the correct function */
790	blr	%r29, %r0
791	/* Set %r28 as non-zero for now */
792	ldo	1(%r0),%r28
793
794	/* 8bit CAS */
79513:	ldb,ma	0(%sr3,%r26), %r29
796	sub,=	%r29, %r25, %r0
797	b,n	cas2_end
79814:	stb,ma	%r24, 0(%sr3,%r26)
799	b	cas2_end
800	copy	%r0, %r28
801	nop
802	nop
803
804	/* 16bit CAS */
80515:	ldh,ma	0(%sr3,%r26), %r29
806	sub,=	%r29, %r25, %r0
807	b,n	cas2_end
80816:	sth,ma	%r24, 0(%sr3,%r26)
809	b	cas2_end
810	copy	%r0, %r28
811	nop
812	nop
813
814	/* 32bit CAS */
81517:	ldw,ma	0(%sr3,%r26), %r29
816	sub,=	%r29, %r25, %r0
817	b,n	cas2_end
81818:	stw,ma	%r24, 0(%sr3,%r26)
819	b	cas2_end
820	copy	%r0, %r28
821	nop
822	nop
823
824	/* 64bit CAS */
825#ifdef CONFIG_64BIT
82619:	ldd,ma	0(%sr3,%r26), %r29
827	sub,*=	%r29, %r25, %r0
828	b,n	cas2_end
82920:	std,ma	%r24, 0(%sr3,%r26)
830	copy	%r0, %r28
831#else
832	/* Compare first word */
83319:	ldw,ma	0(%sr3,%r26), %r29
834	sub,=	%r29, %r22, %r0
835	b,n	cas2_end
836	/* Compare second word */
83720:	ldw,ma	4(%sr3,%r26), %r29
838	sub,=	%r29, %r23, %r0
839	b,n	cas2_end
840	/* Perform the store */
84121:	fstdx	%fr4, 0(%sr3,%r26)
842	copy	%r0, %r28
843#endif
844
845cas2_end:
846	/* Free lock */
847	stw,ma	%r20, 0(%sr2,%r20)
848	/* Enable interrupts */
849	ssm	PSW_SM_I, %r0
850	/* Return to userspace, set no error */
851	b	lws_exit
852	copy	%r0, %r21
853
85422:
855	/* Error occurred on load or store */
856	/* Free lock */
857	stw	%r20, 0(%sr2,%r20)
858	ssm	PSW_SM_I, %r0
859	ldo	1(%r0),%r28
860	b	lws_exit
861	ldo	-EFAULT(%r0),%r21	/* set errno */
862	nop
863	nop
864	nop
865
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)
884#ifndef CONFIG_64BIT
885	ASM_EXCEPTIONTABLE_ENTRY(12b-linux_gateway_page, 22b-linux_gateway_page)
886	ASM_EXCEPTIONTABLE_ENTRY(21b-linux_gateway_page, 22b-linux_gateway_page)
887#endif
888
889	/* Make sure nothing else is placed on this page */
890	.align PAGE_SIZE
891END(linux_gateway_page)
892ENTRY(end_linux_gateway_page)
893
894	/* Relocate symbols assuming linux_gateway_page is mapped
895	   to virtual address 0x0 */
896
897#define LWS_ENTRY(_name_) ASM_ULONG_INSN (lws_##_name_ - linux_gateway_page)
898
899	.section .rodata,"a"
900
901	.align 8
902	/* Light-weight-syscall table */
903	/* Start of lws table. */
904ENTRY(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 */
908END(lws_table)
909	/* End of lws table */
910
911	.align 8
912ENTRY(sys_call_table)
913#include "syscall_table.S"
914END(sys_call_table)
915
916#ifdef CONFIG_64BIT
917	.align 8
918ENTRY(sys_call_table64)
919#define SYSCALL_TABLE_64BIT
920#include "syscall_table.S"
921END(sys_call_table64)
922#endif
923
924	/*
925		All light-weight-syscall atomic operations
926		will use this set of locks
927
928		NOTE: The lws_lock_start symbol must be
929		at least 16-byte aligned for safe use
930		with ldcw.
931	*/
932	.section .data
933	.align	L1_CACHE_BYTES
934ENTRY(lws_lock_start)
935	/* lws locks */
936	.rept 16
937	/* Keep locks aligned at 16-bytes */
938	.word 1
939	.word 0
940	.word 0
941	.word 0
942	.endr
943END(lws_lock_start)
944	.previous
945
946.end
947
948
949