MIPS: Yosemite, Emma: Fix off-by-two in arcs_cmdline buffer size check
[linux-2.6/linux-mips.git] / arch / mips / kernel / process.c
blobb30cb2573aaf8cc8a3edae6d8b0a70a1a564a867
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.
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
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>
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>
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)
50 void __noreturn cpu_idle(void)
52 int cpu;
54 /* CPU is going idle. */
55 cpu = smp_processor_id();
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);
64 smtc_idle_loop_hook();
65 #endif
67 if (cpu_wait) {
68 /* Don't trace irqs off for idle */
69 stop_critical_timings();
70 (*cpu_wait)();
71 start_critical_timings();
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();
87 asmlinkage void ret_from_fork(void);
89 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
91 unsigned long status;
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;
108 void exit_thread(void)
112 void flush_thread(void)
116 int copy_thread(unsigned long clone_flags, unsigned long usp,
117 unsigned long unused, struct task_struct *p, struct pt_regs *regs)
119 struct thread_info *ti = task_thread_info(p);
120 struct pt_regs *childregs;
121 unsigned long childksp;
122 p->set_child_tid = p->clear_child_tid = NULL;
124 childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
126 preempt_disable();
128 if (is_fpu_owner())
129 save_fp(p);
131 if (cpu_has_dsp)
132 save_dsp(p);
134 preempt_enable();
136 /* set up new TSS. */
137 childregs = (struct pt_regs *) childksp - 1;
138 /* Put the stack after the struct pt_regs. */
139 childksp = (unsigned long) childregs;
140 *childregs = *regs;
141 childregs->regs[7] = 0; /* Clear error flag */
143 childregs->regs[2] = 0; /* Child gets zero as return value */
145 if (childregs->cp0_status & ST0_CU0) {
146 childregs->regs[28] = (unsigned long) ti;
147 childregs->regs[29] = childksp;
148 ti->addr_limit = KERNEL_DS;
149 } else {
150 childregs->regs[29] = usp;
151 ti->addr_limit = USER_DS;
153 p->thread.reg29 = (unsigned long) childregs;
154 p->thread.reg31 = (unsigned long) ret_from_fork;
157 * New tasks lose permission to use the fpu. This accelerates context
158 * switching for most programs since they don't use the fpu.
160 p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
161 childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
163 #ifdef CONFIG_MIPS_MT_SMTC
165 * SMTC restores TCStatus after Status, and the CU bits
166 * are aliased there.
168 childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
169 #endif
170 clear_tsk_thread_flag(p, TIF_USEDFPU);
172 #ifdef CONFIG_MIPS_MT_FPAFF
173 clear_tsk_thread_flag(p, TIF_FPUBOUND);
174 #endif /* CONFIG_MIPS_MT_FPAFF */
176 if (clone_flags & CLONE_SETTLS)
177 ti->tp_value = regs->regs[7];
179 return 0;
182 /* Fill in the fpu structure for a core dump.. */
183 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
185 memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
187 return 1;
190 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
192 int i;
194 for (i = 0; i < EF_R0; i++)
195 gp[i] = 0;
196 gp[EF_R0] = 0;
197 for (i = 1; i <= 31; i++)
198 gp[EF_R0 + i] = regs->regs[i];
199 gp[EF_R26] = 0;
200 gp[EF_R27] = 0;
201 gp[EF_LO] = regs->lo;
202 gp[EF_HI] = regs->hi;
203 gp[EF_CP0_EPC] = regs->cp0_epc;
204 gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
205 gp[EF_CP0_STATUS] = regs->cp0_status;
206 gp[EF_CP0_CAUSE] = regs->cp0_cause;
207 #ifdef EF_UNUSED0
208 gp[EF_UNUSED0] = 0;
209 #endif
212 int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
214 elf_dump_regs(*regs, task_pt_regs(tsk));
215 return 1;
218 int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
220 memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
222 return 1;
226 * Create a kernel thread
228 static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
230 do_exit(fn(arg));
233 long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
235 struct pt_regs regs;
237 memset(&regs, 0, sizeof(regs));
239 regs.regs[4] = (unsigned long) arg;
240 regs.regs[5] = (unsigned long) fn;
241 regs.cp0_epc = (unsigned long) kernel_thread_helper;
242 regs.cp0_status = read_c0_status();
243 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
244 regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
245 ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
246 #else
247 regs.cp0_status |= ST0_EXL;
248 #endif
250 /* Ok, create the new process.. */
251 return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
257 struct mips_frame_info {
258 void *func;
259 unsigned long func_size;
260 int frame_size;
261 int pc_offset;
264 static inline int is_ra_save_ins(union mips_instruction *ip)
266 /* sw / sd $ra, offset($sp) */
267 return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
268 ip->i_format.rs == 29 &&
269 ip->i_format.rt == 31;
272 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
274 if (ip->j_format.opcode == jal_op)
275 return 1;
276 if (ip->r_format.opcode != spec_op)
277 return 0;
278 return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
281 static inline int is_sp_move_ins(union mips_instruction *ip)
283 /* addiu/daddiu sp,sp,-imm */
284 if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
285 return 0;
286 if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
287 return 1;
288 return 0;
291 static int get_frame_info(struct mips_frame_info *info)
293 union mips_instruction *ip = info->func;
294 unsigned max_insns = info->func_size / sizeof(union mips_instruction);
295 unsigned i;
297 info->pc_offset = -1;
298 info->frame_size = 0;
300 if (!ip)
301 goto err;
303 if (max_insns == 0)
304 max_insns = 128U; /* unknown function size */
305 max_insns = min(128U, max_insns);
307 for (i = 0; i < max_insns; i++, ip++) {
309 if (is_jal_jalr_jr_ins(ip))
310 break;
311 if (!info->frame_size) {
312 if (is_sp_move_ins(ip))
313 info->frame_size = - ip->i_format.simmediate;
314 continue;
316 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
317 info->pc_offset =
318 ip->i_format.simmediate / sizeof(long);
319 break;
322 if (info->frame_size && info->pc_offset >= 0) /* nested */
323 return 0;
324 if (info->pc_offset < 0) /* leaf */
325 return 1;
326 /* prologue seems boggus... */
327 err:
328 return -1;
331 static struct mips_frame_info schedule_mfi __read_mostly;
333 static int __init frame_info_init(void)
335 unsigned long size = 0;
336 #ifdef CONFIG_KALLSYMS
337 unsigned long ofs;
339 kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
340 #endif
341 schedule_mfi.func = schedule;
342 schedule_mfi.func_size = size;
344 get_frame_info(&schedule_mfi);
347 * Without schedule() frame info, result given by
348 * thread_saved_pc() and get_wchan() are not reliable.
350 if (schedule_mfi.pc_offset < 0)
351 printk("Can't analyze schedule() prologue at %p\n", schedule);
353 return 0;
356 arch_initcall(frame_info_init);
359 * Return saved PC of a blocked thread.
361 unsigned long thread_saved_pc(struct task_struct *tsk)
363 struct thread_struct *t = &tsk->thread;
365 /* New born processes are a special case */
366 if (t->reg31 == (unsigned long) ret_from_fork)
367 return t->reg31;
368 if (schedule_mfi.pc_offset < 0)
369 return 0;
370 return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
374 #ifdef CONFIG_KALLSYMS
375 /* generic stack unwinding function */
376 unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
377 unsigned long *sp,
378 unsigned long pc,
379 unsigned long *ra)
381 struct mips_frame_info info;
382 unsigned long size, ofs;
383 int leaf;
384 extern void ret_from_irq(void);
385 extern void ret_from_exception(void);
387 if (!stack_page)
388 return 0;
391 * If we reached the bottom of interrupt context,
392 * return saved pc in pt_regs.
394 if (pc == (unsigned long)ret_from_irq ||
395 pc == (unsigned long)ret_from_exception) {
396 struct pt_regs *regs;
397 if (*sp >= stack_page &&
398 *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
399 regs = (struct pt_regs *)*sp;
400 pc = regs->cp0_epc;
401 if (__kernel_text_address(pc)) {
402 *sp = regs->regs[29];
403 *ra = regs->regs[31];
404 return pc;
407 return 0;
409 if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
410 return 0;
412 * Return ra if an exception occurred at the first instruction
414 if (unlikely(ofs == 0)) {
415 pc = *ra;
416 *ra = 0;
417 return pc;
420 info.func = (void *)(pc - ofs);
421 info.func_size = ofs; /* analyze from start to ofs */
422 leaf = get_frame_info(&info);
423 if (leaf < 0)
424 return 0;
426 if (*sp < stack_page ||
427 *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
428 return 0;
430 if (leaf)
432 * For some extreme cases, get_frame_info() can
433 * consider wrongly a nested function as a leaf
434 * one. In that cases avoid to return always the
435 * same value.
437 pc = pc != *ra ? *ra : 0;
438 else
439 pc = ((unsigned long *)(*sp))[info.pc_offset];
441 *sp += info.frame_size;
442 *ra = 0;
443 return __kernel_text_address(pc) ? pc : 0;
445 EXPORT_SYMBOL(unwind_stack_by_address);
447 /* used by show_backtrace() */
448 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
449 unsigned long pc, unsigned long *ra)
451 unsigned long stack_page = (unsigned long)task_stack_page(task);
452 return unwind_stack_by_address(stack_page, sp, pc, ra);
454 #endif
457 * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
459 unsigned long get_wchan(struct task_struct *task)
461 unsigned long pc = 0;
462 #ifdef CONFIG_KALLSYMS
463 unsigned long sp;
464 unsigned long ra = 0;
465 #endif
467 if (!task || task == current || task->state == TASK_RUNNING)
468 goto out;
469 if (!task_stack_page(task))
470 goto out;
472 pc = thread_saved_pc(task);
474 #ifdef CONFIG_KALLSYMS
475 sp = task->thread.reg29 + schedule_mfi.frame_size;
477 while (in_sched_functions(pc))
478 pc = unwind_stack(task, &sp, pc, &ra);
479 #endif
481 out:
482 return pc;
486 * Don't forget that the stack pointer must be aligned on a 8 bytes
487 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
489 unsigned long arch_align_stack(unsigned long sp)
491 if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
492 sp -= get_random_int() & ~PAGE_MASK;
494 return sp & ALMASK;