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/kernel.h>
  15 #include <linux/mm.h>
  16 #include <linux/stddef.h>
  17 #include <linux/unistd.h>
  18 #include <linux/ptrace.h>
  19 #include <linux/slab.h>
  20 #include <linux/mman.h>
  21 #include <linux/personality.h>
  22 #include <linux/sys.h>
  23 #include <linux/user.h>
  24 #include <linux/a.out.h>
  25 #include <linux/init.h>
  26 #include <linux/completion.h>
  27 #include <linux/kallsyms.h>
  28
  29 #include <asm/bootinfo.h>
  30 #include <asm/cpu.h>
  31 #include <asm/dsp.h>
  32 #include <asm/fpu.h>
  33 #include <asm/pgtable.h>
  34 #include <asm/system.h>
  35 #include <asm/mipsregs.h>
  36 #include <asm/processor.h>
  37 #include <asm/uaccess.h>
  38 #include <asm/io.h>
  39 #include <asm/elf.h>
  40 #include <asm/isadep.h>
  41 #include <asm/inst.h>
  42 #include <asm/stacktrace.h>
  43
  44 /*
  45  * The idle thread. There's no useful work to be done, so just try to conserve
  46  * power and have a low exit latency (ie sit in a loop waiting for somebody to
  47  * say that they'd like to reschedule)
  48  */
  49 ATTRIB_NORET void cpu_idle(void)
  50 {
  51         /* endless idle loop with no priority at all */
  52         while (1) {
  53                 while (!need_resched()) {
  54 #ifdef CONFIG_SMTC_IDLE_HOOK_DEBUG
  55                         extern void smtc_idle_loop_hook(void);
  56
  57                         smtc_idle_loop_hook();
  58 #endif
  59                         if (cpu_wait)
  60                                 (*cpu_wait)();
  61                 }
  62                 preempt_enable_no_resched();
  63                 schedule();
  64                 preempt_disable();
  65         }
  66 }
  67
  68 asmlinkage void ret_from_fork(void);
  69
  70 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  71 {
  72         unsigned long status;
  73
  74         /* New thread loses kernel privileges. */
  75         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|KU_MASK);
  76 #ifdef CONFIG_64BIT
  77         status &= ~ST0_FR;
  78         status |= (current->thread.mflags & MF_32BIT_REGS) ? 0 : ST0_FR;
  79 #endif
  80         status |= KU_USER;
  81         regs->cp0_status = status;
  82         clear_used_math();
  83         clear_fpu_owner();
  84         if (cpu_has_dsp)
  85                 __init_dsp();
  86         regs->cp0_epc = pc;
  87         regs->regs[29] = sp;
  88         current_thread_info()->addr_limit = USER_DS;
  89 }
  90
  91 void exit_thread(void)
  92 {
  93 }
  94
  95 void flush_thread(void)
  96 {
  97 }
  98
  99 int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
 100         unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 101 {
 102         struct thread_info *ti = task_thread_info(p);
 103         struct pt_regs *childregs;
 104         long childksp;
 105         p->set_child_tid = p->clear_child_tid = NULL;
 106
 107         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 108
 109         preempt_disable();
 110
 111         if (is_fpu_owner())
 112                 save_fp(p);
 113
 114         if (cpu_has_dsp)
 115                 save_dsp(p);
 116
 117         preempt_enable();
 118
 119         /* set up new TSS. */
 120         childregs = (struct pt_regs *) childksp - 1;
 121         *childregs = *regs;
 122         childregs->regs[7] = 0; /* Clear error flag */
 123
 124 #if defined(CONFIG_BINFMT_IRIX)
 125         if (current->personality != PER_LINUX) {
 126                 /* Under IRIX things are a little different. */
 127                 childregs->regs[3] = 1;
 128                 regs->regs[3] = 0;
 129         }
 130 #endif
 131         childregs->regs[2] = 0; /* Child gets zero as return value */
 132         regs->regs[2] = p->pid;
 133
 134         if (childregs->cp0_status & ST0_CU0) {
 135                 childregs->regs[28] = (unsigned long) ti;
 136                 childregs->regs[29] = childksp;
 137                 ti->addr_limit = KERNEL_DS;
 138         } else {
 139                 childregs->regs[29] = usp;
 140                 ti->addr_limit = USER_DS;
 141         }
 142         p->thread.reg29 = (unsigned long) childregs;
 143         p->thread.reg31 = (unsigned long) ret_from_fork;
 144
 145         /*
 146          * New tasks lose permission to use the fpu. This accelerates context
 147          * switching for most programs since they don't use the fpu.
 148          */
 149         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 150         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 151         clear_tsk_thread_flag(p, TIF_USEDFPU);
 152
 153 #ifdef CONFIG_MIPS_MT_FPAFF
 154         /*
 155          * FPU affinity support is cleaner if we track the
 156          * user-visible CPU affinity from the very beginning.
 157          * The generic cpus_allowed mask will already have
 158          * been copied from the parent before copy_thread
 159          * is invoked.
 160          */
 161         p->thread.user_cpus_allowed = p->cpus_allowed;
 162 #endif /* CONFIG_MIPS_MT_FPAFF */
 163
 164         if (clone_flags & CLONE_SETTLS)
 165                 ti->tp_value = regs->regs[7];
 166
 167         return 0;
 168 }
 169
 170 /* Fill in the fpu structure for a core dump.. */
 171 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 172 {
 173         memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 174
 175         return 1;
 176 }
 177
 178 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 179 {
 180         int i;
 181
 182         for (i = 0; i < EF_R0; i++)
 183                 gp[i] = 0;
 184         gp[EF_R0] = 0;
 185         for (i = 1; i <= 31; i++)
 186                 gp[EF_R0 + i] = regs->regs[i];
 187         gp[EF_R26] = 0;
 188         gp[EF_R27] = 0;
 189         gp[EF_LO] = regs->lo;
 190         gp[EF_HI] = regs->hi;
 191         gp[EF_CP0_EPC] = regs->cp0_epc;
 192         gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 193         gp[EF_CP0_STATUS] = regs->cp0_status;
 194         gp[EF_CP0_CAUSE] = regs->cp0_cause;
 195 #ifdef EF_UNUSED0
 196         gp[EF_UNUSED0] = 0;
 197 #endif
 198 }
 199
 200 int dump_task_regs (struct task_struct *tsk, elf_gregset_t *regs)
 201 {
 202         elf_dump_regs(*regs, task_pt_regs(tsk));
 203         return 1;
 204 }
 205
 206 int dump_task_fpu (struct task_struct *t, elf_fpregset_t *fpr)
 207 {
 208         memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 209
 210         return 1;
 211 }
 212
 213 /*
 214  * Create a kernel thread
 215  */
 216 static ATTRIB_NORET void kernel_thread_helper(void *arg, int (*fn)(void *))
 217 {
 218         do_exit(fn(arg));
 219 }
 220
 221 long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 222 {
 223         struct pt_regs regs;
 224
 225         memset(&regs, 0, sizeof(regs));
 226
 227         regs.regs[4] = (unsigned long) arg;
 228         regs.regs[5] = (unsigned long) fn;
 229         regs.cp0_epc = (unsigned long) kernel_thread_helper;
 230         regs.cp0_status = read_c0_status();
 231 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 232         regs.cp0_status &= ~(ST0_KUP | ST0_IEC);
 233         regs.cp0_status |= ST0_IEP;
 234 #else
 235         regs.cp0_status |= ST0_EXL;
 236 #endif
 237
 238         /* Ok, create the new process.. */
 239         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 240 }
 241
 242 /*
 243  *
 244  */
 245 struct mips_frame_info {
 246         void            *func;
 247         unsigned long   func_size;
 248         int             frame_size;
 249         int             pc_offset;
 250 };
 251
 252 static inline int is_ra_save_ins(union mips_instruction *ip)
 253 {
 254         /* sw / sd $ra, offset($sp) */
 255         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 256                 ip->i_format.rs == 29 &&
 257                 ip->i_format.rt == 31;
 258 }
 259
 260 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 261 {
 262         if (ip->j_format.opcode == jal_op)
 263                 return 1;
 264         if (ip->r_format.opcode != spec_op)
 265                 return 0;
 266         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 267 }
 268
 269 static inline int is_sp_move_ins(union mips_instruction *ip)
 270 {
 271         /* addiu/daddiu sp,sp,-imm */
 272         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 273                 return 0;
 274         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 275                 return 1;
 276         return 0;
 277 }
 278
 279 static int get_frame_info(struct mips_frame_info *info)
 280 {
 281         union mips_instruction *ip = info->func;
 282         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 283         unsigned i;
 284
 285         info->pc_offset = -1;
 286         info->frame_size = 0;
 287
 288         if (!ip)
 289                 goto err;
 290
 291         if (max_insns == 0)
 292                 max_insns = 128U;       /* unknown function size */
 293         max_insns = min(128U, max_insns);
 294
 295         for (i = 0; i < max_insns; i++, ip++) {
 296
 297                 if (is_jal_jalr_jr_ins(ip))
 298                         break;
 299                 if (!info->frame_size) {
 300                         if (is_sp_move_ins(ip))
 301                                 info->frame_size = - ip->i_format.simmediate;
 302                         continue;
 303                 }
 304                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 305                         info->pc_offset =
 306                                 ip->i_format.simmediate / sizeof(long);
 307                         break;
 308                 }
 309         }
 310         if (info->frame_size && info->pc_offset >= 0) /* nested */
 311                 return 0;
 312         if (info->pc_offset < 0) /* leaf */
 313                 return 1;
 314         /* prologue seems boggus... */
 315 err:
 316         return -1;
 317 }
 318
 319 static struct mips_frame_info schedule_mfi __read_mostly;
 320
 321 static int __init frame_info_init(void)
 322 {
 323         unsigned long size = 0;
 324 #ifdef CONFIG_KALLSYMS
 325         unsigned long ofs;
 326
 327         kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 328 #endif
 329         schedule_mfi.func = schedule;
 330         schedule_mfi.func_size = size;
 331
 332         get_frame_info(&schedule_mfi);
 333
 334         /*
 335          * Without schedule() frame info, result given by
 336          * thread_saved_pc() and get_wchan() are not reliable.
 337          */
 338         if (schedule_mfi.pc_offset < 0)
 339                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 340
 341         return 0;
 342 }
 343
 344 arch_initcall(frame_info_init);
 345
 346 /*
 347  * Return saved PC of a blocked thread.
 348  */
 349 unsigned long thread_saved_pc(struct task_struct *tsk)
 350 {
 351         struct thread_struct *t = &tsk->thread;
 352
 353         /* New born processes are a special case */
 354         if (t->reg31 == (unsigned long) ret_from_fork)
 355                 return t->reg31;
 356         if (schedule_mfi.pc_offset < 0)
 357                 return 0;
 358         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 359 }
 360
 361
 362 #ifdef CONFIG_KALLSYMS
 363 /* used by show_backtrace() */
 364 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 365                            unsigned long pc, unsigned long *ra)
 366 {
 367         unsigned long stack_page;
 368         struct mips_frame_info info;
 369         unsigned long size, ofs;
 370         int leaf;
 371         extern void ret_from_irq(void);
 372         extern void ret_from_exception(void);
 373
 374         stack_page = (unsigned long)task_stack_page(task);
 375         if (!stack_page)
 376                 return 0;
 377
 378         /*
 379          * If we reached the bottom of interrupt context,
 380          * return saved pc in pt_regs.
 381          */
 382         if (pc == (unsigned long)ret_from_irq ||
 383             pc == (unsigned long)ret_from_exception) {
 384                 struct pt_regs *regs;
 385                 if (*sp >= stack_page &&
 386                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 387                         regs = (struct pt_regs *)*sp;
 388                         pc = regs->cp0_epc;
 389                         if (__kernel_text_address(pc)) {
 390                                 *sp = regs->regs[29];
 391                                 *ra = regs->regs[31];
 392                                 return pc;
 393                         }
 394                 }
 395                 return 0;
 396         }
 397         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 398                 return 0;
 399         /*
 400          * Return ra if an exception occured at the first instruction
 401          */
 402         if (unlikely(ofs == 0)) {
 403                 pc = *ra;
 404                 *ra = 0;
 405                 return pc;
 406         }
 407
 408         info.func = (void *)(pc - ofs);
 409         info.func_size = ofs;   /* analyze from start to ofs */
 410         leaf = get_frame_info(&info);
 411         if (leaf < 0)
 412                 return 0;
 413
 414         if (*sp < stack_page ||
 415             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 416                 return 0;
 417
 418         if (leaf)
 419                 /*
 420                  * For some extreme cases, get_frame_info() can
 421                  * consider wrongly a nested function as a leaf
 422                  * one. In that cases avoid to return always the
 423                  * same value.
 424                  */
 425                 pc = pc != *ra ? *ra : 0;
 426         else
 427                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 428
 429         *sp += info.frame_size;
 430         *ra = 0;
 431         return __kernel_text_address(pc) ? pc : 0;
 432 }
 433 #endif
 434
 435 /*
 436  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 437  */
 438 unsigned long get_wchan(struct task_struct *task)
 439 {
 440         unsigned long pc = 0;
 441 #ifdef CONFIG_KALLSYMS
 442         unsigned long sp;
 443         unsigned long ra = 0;
 444 #endif
 445
 446         if (!task || task == current || task->state == TASK_RUNNING)
 447                 goto out;
 448         if (!task_stack_page(task))
 449                 goto out;
 450
 451         pc = thread_saved_pc(task);
 452
 453 #ifdef CONFIG_KALLSYMS
 454         sp = task->thread.reg29 + schedule_mfi.frame_size;
 455
 456         while (in_sched_functions(pc))
 457                 pc = unwind_stack(task, &sp, pc, &ra);
 458 #endif
 459
 460 out:
 461         return pc;
 462 }