Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph...
[linux-2.6.git] / arch / mips / kernel / process.c
1 /*
2  * This file is subject to the terms and conditions of the GNU General Public
3  * License.  See the file "COPYING" in the main directory of this archive
4  * for more details.
5  *
6  * Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
7  * Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
8  * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
9  * Copyright (C) 2004 Thiemo Seufer
10  */
11 #include <linux/errno.h>
12 #include <linux/module.h>
13 #include <linux/sched.h>
14 #include <linux/tick.h>
15 #include <linux/kernel.h>
16 #include <linux/mm.h>
17 #include <linux/stddef.h>
18 #include <linux/unistd.h>
19 #include <linux/ptrace.h>
20 #include <linux/mman.h>
21 #include <linux/personality.h>
22 #include <linux/sys.h>
23 #include <linux/user.h>
24 #include <linux/init.h>
25 #include <linux/completion.h>
26 #include <linux/kallsyms.h>
27 #include <linux/random.h>
28
29 #include <asm/asm.h>
30 #include <asm/bootinfo.h>
31 #include <asm/cpu.h>
32 #include <asm/dsp.h>
33 #include <asm/fpu.h>
34 #include <asm/pgtable.h>
35 #include <asm/system.h>
36 #include <asm/mipsregs.h>
37 #include <asm/processor.h>
38 #include <asm/uaccess.h>
39 #include <asm/io.h>
40 #include <asm/elf.h>
41 #include <asm/isadep.h>
42 #include <asm/inst.h>
43 #include <asm/stacktrace.h>
44
45 /*
46  * The idle thread. There's no useful work to be done, so just try to conserve
47  * power and have a low exit latency (ie sit in a loop waiting for somebody to
48  * say that they'd like to reschedule)
49  */
50 void __noreturn cpu_idle(void)
51 {
52         int cpu;
53
54         /* CPU is going idle. */
55         cpu = smp_processor_id();
56
57         /* endless idle loop with no priority at all */
58         while (1) {
59                 tick_nohz_stop_sched_tick(1);
60                 while (!need_resched() && cpu_online(cpu)) {
61 #ifdef CONFIG_MIPS_MT_SMTC
62                         extern void smtc_idle_loop_hook(void);
63
64                         smtc_idle_loop_hook();
65 #endif
66
67                         if (cpu_wait) {
68                                 /* Don't trace irqs off for idle */
69                                 stop_critical_timings();
70                                 (*cpu_wait)();
71                                 start_critical_timings();
72                         }
73                 }
74 #ifdef CONFIG_HOTPLUG_CPU
75                 if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
76                     (system_state == SYSTEM_RUNNING ||
77                      system_state == SYSTEM_BOOTING))
78                         play_dead();
79 #endif
80                 tick_nohz_restart_sched_tick();
81                 preempt_enable_no_resched();
82                 schedule();
83                 preempt_disable();
84         }
85 }
86
87 asmlinkage void ret_from_fork(void);
88
89 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
90 {
91         unsigned long status;
92
93         /* New thread loses kernel privileges. */
94         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
95 #ifdef CONFIG_64BIT
96         status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
97 #endif
98         status |= KU_USER;
99         regs->cp0_status = status;
100         clear_used_math();
101         clear_fpu_owner();
102         if (cpu_has_dsp)
103                 __init_dsp();
104         regs->cp0_epc = pc;
105         regs->regs[29] = sp;
106         current_thread_info()->addr_limit = USER_DS;
107 }
108
109 void exit_thread(void)
110 {
111 }
112
113 void flush_thread(void)
114 {
115 }
116
117 int copy_thread(unsigned long clone_flags, unsigned long usp,
118         unsigned long unused, struct task_struct *p, struct pt_regs *regs)
119 {
120         struct thread_info *ti = task_thread_info(p);
121         struct pt_regs *childregs;
122         unsigned long childksp;
123         p->set_child_tid = p->clear_child_tid = NULL;
124
125         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
126
127         preempt_disable();
128
129         if (is_fpu_owner())
130                 save_fp(p);
131
132         if (cpu_has_dsp)
133                 save_dsp(p);
134
135         preempt_enable();
136
137         /* set up new TSS. */
138         childregs = (struct pt_regs *) childksp - 1;
139         /*  Put the stack after the struct pt_regs.  */
140         childksp = (unsigned long) childregs;
141         *childregs = *regs;
142         childregs->regs[7] = 0; /* Clear error flag */
143
144         childregs->regs[2] = 0; /* Child gets zero as return value */
145
146         if (childregs->cp0_status & ST0_CU0) {
147                 childregs->regs[28] = (unsigned long) ti;
148                 childregs->regs[29] = childksp;
149                 ti->addr_limit = KERNEL_DS;
150         } else {
151                 childregs->regs[29] = usp;
152                 ti->addr_limit = USER_DS;
153         }
154         p->thread.reg29 = (unsigned long) childregs;
155         p->thread.reg31 = (unsigned long) ret_from_fork;
156
157         /*
158          * New tasks lose permission to use the fpu. This accelerates context
159          * switching for most programs since they don't use the fpu.
160          */
161         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
162         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
163
164 #ifdef CONFIG_MIPS_MT_SMTC
165         /*
166          * SMTC restores TCStatus after Status, and the CU bits
167          * are aliased there.
168          */
169         childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
170 #endif
171         clear_tsk_thread_flag(p, TIF_USEDFPU);
172
173 #ifdef CONFIG_MIPS_MT_FPAFF
174         clear_tsk_thread_flag(p, TIF_FPUBOUND);
175 #endif /* CONFIG_MIPS_MT_FPAFF */
176
177         if (clone_flags & CLONE_SETTLS)
178                 ti->tp_value = regs->regs[7];
179
180         return 0;
181 }
182
183 /* Fill in the fpu structure for a core dump.. */
184 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
185 {
186         memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
187
188         return 1;
189 }
190
191 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
192 {
193         int i;
194
195         for (i = 0; i < EF_R0; i++)
196                 gp[i] = 0;
197         gp[EF_R0] = 0;
198         for (i = 1; i <= 31; i++)
199                 gp[EF_R0 + i] = regs->regs[i];
200         gp[EF_R26] = 0;
201         gp[EF_R27] = 0;
202         gp[EF_LO] = regs->lo;
203         gp[EF_HI] = regs->hi;
204         gp[EF_CP0_EPC] = regs->cp0_epc;
205         gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
206         gp[EF_CP0_STATUS] = regs->cp0_status;
207         gp[EF_CP0_CAUSE] = regs->cp0_cause;
208 #ifdef EF_UNUSED0
209         gp[EF_UNUSED0] = 0;
210 #endif
211 }
212
213 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
214 {
215         elf_dump_regs(*regs, task_pt_regs(tsk));
216         return 1;
217 }
218
219 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
220 {
221         memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
222
223         return 1;
224 }
225
226 /*
227  * Create a kernel thread
228  */
229 static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
230 {
231         do_exit(fn(arg));
232 }
233
234 long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
235 {
236         struct pt_regs regs;
237
238         memset(&regs, 0, sizeof(regs));
239
240         regs.regs[4] = (unsigned long) arg;
241         regs.regs[5] = (unsigned long) fn;
242         regs.cp0_epc = (unsigned long) kernel_thread_helper;
243         regs.cp0_status = read_c0_status();
244 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
245         regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
246                           ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
247 #else
248         regs.cp0_status |= ST0_EXL;
249 #endif
250
251         /* Ok, create the new process.. */
252         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
253 }
254
255 /*
256  *
257  */
258 struct mips_frame_info {
259         void            *func;
260         unsigned long   func_size;
261         int             frame_size;
262         int             pc_offset;
263 };
264
265 static inline int is_ra_save_ins(union mips_instruction *ip)
266 {
267         /* sw / sd $ra, offset($sp) */
268         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
269                 ip->i_format.rs == 29 &&
270                 ip->i_format.rt == 31;
271 }
272
273 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
274 {
275         if (ip->j_format.opcode == jal_op)
276                 return 1;
277         if (ip->r_format.opcode != spec_op)
278                 return 0;
279         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
280 }
281
282 static inline int is_sp_move_ins(union mips_instruction *ip)
283 {
284         /* addiu/daddiu sp,sp,-imm */
285         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
286                 return 0;
287         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
288                 return 1;
289         return 0;
290 }
291
292 static int get_frame_info(struct mips_frame_info *info)
293 {
294         union mips_instruction *ip = info->func;
295         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
296         unsigned i;
297
298         info->pc_offset = -1;
299         info->frame_size = 0;
300
301         if (!ip)
302                 goto err;
303
304         if (max_insns == 0)
305                 max_insns = 128U;       /* unknown function size */
306         max_insns = min(128U, max_insns);
307
308         for (i = 0; i < max_insns; i++, ip++) {
309
310                 if (is_jal_jalr_jr_ins(ip))
311                         break;
312                 if (!info->frame_size) {
313                         if (is_sp_move_ins(ip))
314                                 info->frame_size = - ip->i_format.simmediate;
315                         continue;
316                 }
317                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
318                         info->pc_offset =
319                                 ip->i_format.simmediate / sizeof(long);
320                         break;
321                 }
322         }
323         if (info->frame_size && info->pc_offset >= 0) /* nested */
324                 return 0;
325         if (info->pc_offset < 0) /* leaf */
326                 return 1;
327         /* prologue seems boggus... */
328 err:
329         return -1;
330 }
331
332 static struct mips_frame_info schedule_mfi __read_mostly;
333
334 static int __init frame_info_init(void)
335 {
336         unsigned long size = 0;
337 #ifdef CONFIG_KALLSYMS
338         unsigned long ofs;
339
340         kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
341 #endif
342         schedule_mfi.func = schedule;
343         schedule_mfi.func_size = size;
344
345         get_frame_info(&schedule_mfi);
346
347         /*
348          * Without schedule() frame info, result given by
349          * thread_saved_pc() and get_wchan() are not reliable.
350          */
351         if (schedule_mfi.pc_offset < 0)
352                 printk("Can't analyze schedule() prologue at %p\n", schedule);
353
354         return 0;
355 }
356
357 arch_initcall(frame_info_init);
358
359 /*
360  * Return saved PC of a blocked thread.
361  */
362 unsigned long thread_saved_pc(struct task_struct *tsk)
363 {
364         struct thread_struct *t = &tsk->thread;
365
366         /* New born processes are a special case */
367         if (t->reg31 == (unsigned long) ret_from_fork)
368                 return t->reg31;
369         if (schedule_mfi.pc_offset < 0)
370                 return 0;
371         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
372 }
373
374
375 #ifdef CONFIG_KALLSYMS
376 /* generic stack unwinding function */
377 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
378                                               unsigned long *sp,
379                                               unsigned long pc,
380                                               unsigned long *ra)
381 {
382         struct mips_frame_info info;
383         unsigned long size, ofs;
384         int leaf;
385         extern void ret_from_irq(void);
386         extern void ret_from_exception(void);
387
388         if (!stack_page)
389                 return 0;
390
391         /*
392          * If we reached the bottom of interrupt context,
393          * return saved pc in pt_regs.
394          */
395         if (pc == (unsigned long)ret_from_irq ||
396             pc == (unsigned long)ret_from_exception) {
397                 struct pt_regs *regs;
398                 if (*sp >= stack_page &&
399                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
400                         regs = (struct pt_regs *)*sp;
401                         pc = regs->cp0_epc;
402                         if (__kernel_text_address(pc)) {
403                                 *sp = regs->regs[29];
404                                 *ra = regs->regs[31];
405                                 return pc;
406                         }
407                 }
408                 return 0;
409         }
410         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
411                 return 0;
412         /*
413          * Return ra if an exception occurred at the first instruction
414          */
415         if (unlikely(ofs == 0)) {
416                 pc = *ra;
417                 *ra = 0;
418                 return pc;
419         }
420
421         info.func = (void *)(pc - ofs);
422         info.func_size = ofs;   /* analyze from start to ofs */
423         leaf = get_frame_info(&info);
424         if (leaf < 0)
425                 return 0;
426
427         if (*sp < stack_page ||
428             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
429                 return 0;
430
431         if (leaf)
432                 /*
433                  * For some extreme cases, get_frame_info() can
434                  * consider wrongly a nested function as a leaf
435                  * one. In that cases avoid to return always the
436                  * same value.
437                  */
438                 pc = pc != *ra ? *ra : 0;
439         else
440                 pc = ((unsigned long *)(*sp))[info.pc_offset];
441
442         *sp += info.frame_size;
443         *ra = 0;
444         return __kernel_text_address(pc) ? pc : 0;
445 }
446 EXPORT_SYMBOL(unwind_stack_by_address);
447
448 /* used by show_backtrace() */
449 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
450                            unsigned long pc, unsigned long *ra)
451 {
452         unsigned long stack_page = (unsigned long)task_stack_page(task);
453         return unwind_stack_by_address(stack_page, sp, pc, ra);
454 }
455 #endif
456
457 /*
458  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
459  */
460 unsigned long get_wchan(struct task_struct *task)
461 {
462         unsigned long pc = 0;
463 #ifdef CONFIG_KALLSYMS
464         unsigned long sp;
465         unsigned long ra = 0;
466 #endif
467
468         if (!task || task == current || task->state == TASK_RUNNING)
469                 goto out;
470         if (!task_stack_page(task))
471                 goto out;
472
473         pc = thread_saved_pc(task);
474
475 #ifdef CONFIG_KALLSYMS
476         sp = task->thread.reg29 + schedule_mfi.frame_size;
477
478         while (in_sched_functions(pc))
479                 pc = unwind_stack(task, &sp, pc, &ra);
480 #endif
481
482 out:
483         return pc;
484 }
485
486 /*
487  * Don't forget that the stack pointer must be aligned on a 8 bytes
488  * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
489  */
490 unsigned long arch_align_stack(unsigned long sp)
491 {
492         if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
493                 sp -= get_random_int() & ~PAGE_MASK;
494
495         return sp & ALMASK;
496 }