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/abi.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 #ifdef CONFIG_MIPS_MT_SMTC
  45 #include <asm/mipsmtregs.h>
  46 extern void smtc_idle_loop_hook(void);
  47 #endif /* CONFIG_MIPS_MT_SMTC */
  48
  49 /*
  50  * The idle thread. There's no useful work to be done, so just try to conserve
  51  * power and have a low exit latency (ie sit in a loop waiting for somebody to
  52  * say that they'd like to reschedule)
  53  */
  54 ATTRIB_NORET void cpu_idle(void)
  55 {
  56         /* endless idle loop with no priority at all */
  57         while (1) {
  58                 while (!need_resched()) {
  59 #ifdef CONFIG_MIPS_MT_SMTC
  60                         smtc_idle_loop_hook();
  61 #endif /* CONFIG_MIPS_MT_SMTC */
  62                         if (cpu_wait)
  63                                 (*cpu_wait)();
  64                 }
  65                 preempt_enable_no_resched();
  66                 schedule();
  67                 preempt_disable();
  68         }
  69 }
  70
  71 /*
  72  * Native o32 and N64 ABI without DSP ASE
  73  */
  74 struct mips_abi mips_abi = {
  75         .do_signal      = do_signal,
  76 #ifdef CONFIG_TRAD_SIGNALS
  77         .setup_frame    = setup_frame,
  78 #endif
  79         .setup_rt_frame = setup_rt_frame
  80 };
  81
  82 #ifdef CONFIG_MIPS32_O32
  83 /*
  84  * o32 compatibility on 64-bit kernels, without DSP ASE
  85  */
  86 struct mips_abi mips_abi_32 = {
  87         .do_signal      = do_signal32,
  88         .setup_frame    = setup_frame_32,
  89         .setup_rt_frame = setup_rt_frame_32
  90 };
  91 #endif /* CONFIG_MIPS32_O32 */
  92
  93 #ifdef CONFIG_MIPS32_N32
  94 /*
  95  * N32 on 64-bit kernels, without DSP ASE
  96  */
  97 struct mips_abi mips_abi_n32 = {
  98         .do_signal      = do_signal,
  99         .setup_rt_frame = setup_rt_frame_n32
 100 };
 101 #endif /* CONFIG_MIPS32_N32 */
 102
 103 asmlinkage void ret_from_fork(void);
 104
 105 void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
 106 {
 107         unsigned long status;
 108
 109         /* New thread loses kernel privileges. */
 110         status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|KU_MASK);
 111 #ifdef CONFIG_64BIT
 112         status &= ~ST0_FR;
 113         status |= (current->thread.mflags & MF_32BIT_REGS) ? 0 : ST0_FR;
 114 #endif
 115         status |= KU_USER;
 116         regs->cp0_status = status;
 117         clear_used_math();
 118         clear_fpu_owner();
 119         if (cpu_has_dsp)
 120                 __init_dsp();
 121         regs->cp0_epc = pc;
 122         regs->regs[29] = sp;
 123         current_thread_info()->addr_limit = USER_DS;
 124 }
 125
 126 void exit_thread(void)
 127 {
 128 }
 129
 130 void flush_thread(void)
 131 {
 132 }
 133
 134 int copy_thread(int nr, unsigned long clone_flags, unsigned long usp,
 135         unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 136 {
 137         struct thread_info *ti = task_thread_info(p);
 138         struct pt_regs *childregs;
 139         long childksp;
 140         p->set_child_tid = p->clear_child_tid = NULL;
 141
 142         childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 143
 144         preempt_disable();
 145
 146         if (is_fpu_owner())
 147                 save_fp(p);
 148
 149         if (cpu_has_dsp)
 150                 save_dsp(p);
 151
 152         preempt_enable();
 153
 154         /* set up new TSS. */
 155         childregs = (struct pt_regs *) childksp - 1;
 156         *childregs = *regs;
 157         childregs->regs[7] = 0; /* Clear error flag */
 158
 159 #if defined(CONFIG_BINFMT_IRIX)
 160         if (current->personality != PER_LINUX) {
 161                 /* Under IRIX things are a little different. */
 162                 childregs->regs[3] = 1;
 163                 regs->regs[3] = 0;
 164         }
 165 #endif
 166         childregs->regs[2] = 0; /* Child gets zero as return value */
 167         regs->regs[2] = p->pid;
 168
 169         if (childregs->cp0_status & ST0_CU0) {
 170                 childregs->regs[28] = (unsigned long) ti;
 171                 childregs->regs[29] = childksp;
 172                 ti->addr_limit = KERNEL_DS;
 173         } else {
 174                 childregs->regs[29] = usp;
 175                 ti->addr_limit = USER_DS;
 176         }
 177         p->thread.reg29 = (unsigned long) childregs;
 178         p->thread.reg31 = (unsigned long) ret_from_fork;
 179
 180         /*
 181          * New tasks lose permission to use the fpu. This accelerates context
 182          * switching for most programs since they don't use the fpu.
 183          */
 184         p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 185         childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 186         clear_tsk_thread_flag(p, TIF_USEDFPU);
 187
 188 #ifdef CONFIG_MIPS_MT_FPAFF
 189         /*
 190          * FPU affinity support is cleaner if we track the
 191          * user-visible CPU affinity from the very beginning.
 192          * The generic cpus_allowed mask will already have
 193          * been copied from the parent before copy_thread
 194          * is invoked.
 195          */
 196         p->thread.user_cpus_allowed = p->cpus_allowed;
 197 #endif /* CONFIG_MIPS_MT_FPAFF */
 198
 199         if (clone_flags & CLONE_SETTLS)
 200                 ti->tp_value = regs->regs[7];
 201
 202         return 0;
 203 }
 204
 205 /* Fill in the fpu structure for a core dump.. */
 206 int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 207 {
 208         memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 209
 210         return 1;
 211 }
 212
 213 void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 214 {
 215         int i;
 216
 217         for (i = 0; i < EF_R0; i++)
 218                 gp[i] = 0;
 219         gp[EF_R0] = 0;
 220         for (i = 1; i <= 31; i++)
 221                 gp[EF_R0 + i] = regs->regs[i];
 222         gp[EF_R26] = 0;
 223         gp[EF_R27] = 0;
 224         gp[EF_LO] = regs->lo;
 225         gp[EF_HI] = regs->hi;
 226         gp[EF_CP0_EPC] = regs->cp0_epc;
 227         gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 228         gp[EF_CP0_STATUS] = regs->cp0_status;
 229         gp[EF_CP0_CAUSE] = regs->cp0_cause;
 230 #ifdef EF_UNUSED0
 231         gp[EF_UNUSED0] = 0;
 232 #endif
 233 }
 234
 235 int dump_task_regs (struct task_struct *tsk, elf_gregset_t *regs)
 236 {
 237         elf_dump_regs(*regs, task_pt_regs(tsk));
 238         return 1;
 239 }
 240
 241 int dump_task_fpu (struct task_struct *t, elf_fpregset_t *fpr)
 242 {
 243         memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 244
 245         return 1;
 246 }
 247
 248 /*
 249  * Create a kernel thread
 250  */
 251 ATTRIB_NORET void kernel_thread_helper(void *arg, int (*fn)(void *))
 252 {
 253         do_exit(fn(arg));
 254 }
 255
 256 long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 257 {
 258         struct pt_regs regs;
 259
 260         memset(&regs, 0, sizeof(regs));
 261
 262         regs.regs[4] = (unsigned long) arg;
 263         regs.regs[5] = (unsigned long) fn;
 264         regs.cp0_epc = (unsigned long) kernel_thread_helper;
 265         regs.cp0_status = read_c0_status();
 266 #if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 267         regs.cp0_status &= ~(ST0_KUP | ST0_IEC);
 268         regs.cp0_status |= ST0_IEP;
 269 #else
 270         regs.cp0_status |= ST0_EXL;
 271 #endif
 272
 273         /* Ok, create the new process.. */
 274         return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 275 }
 276
 277 /*
 278  *
 279  */
 280 struct mips_frame_info {
 281         void            *func;
 282         unsigned long   func_size;
 283         int             frame_size;
 284         int             pc_offset;
 285 };
 286
 287 static inline int is_ra_save_ins(union mips_instruction *ip)
 288 {
 289         /* sw / sd $ra, offset($sp) */
 290         return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 291                 ip->i_format.rs == 29 &&
 292                 ip->i_format.rt == 31;
 293 }
 294
 295 static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 296 {
 297         if (ip->j_format.opcode == jal_op)
 298                 return 1;
 299         if (ip->r_format.opcode != spec_op)
 300                 return 0;
 301         return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 302 }
 303
 304 static inline int is_sp_move_ins(union mips_instruction *ip)
 305 {
 306         /* addiu/daddiu sp,sp,-imm */
 307         if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 308                 return 0;
 309         if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 310                 return 1;
 311         return 0;
 312 }
 313
 314 static int get_frame_info(struct mips_frame_info *info)
 315 {
 316         union mips_instruction *ip = info->func;
 317         unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 318         unsigned i;
 319
 320         info->pc_offset = -1;
 321         info->frame_size = 0;
 322
 323         if (!ip)
 324                 goto err;
 325
 326         if (max_insns == 0)
 327                 max_insns = 128U;       /* unknown function size */
 328         max_insns = min(128U, max_insns);
 329
 330         for (i = 0; i < max_insns; i++, ip++) {
 331
 332                 if (is_jal_jalr_jr_ins(ip))
 333                         break;
 334                 if (!info->frame_size) {
 335                         if (is_sp_move_ins(ip))
 336                                 info->frame_size = - ip->i_format.simmediate;
 337                         continue;
 338                 }
 339                 if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 340                         info->pc_offset =
 341                                 ip->i_format.simmediate / sizeof(long);
 342                         break;
 343                 }
 344         }
 345         if (info->frame_size && info->pc_offset >= 0) /* nested */
 346                 return 0;
 347         if (info->pc_offset < 0) /* leaf */
 348                 return 1;
 349         /* prologue seems boggus... */
 350 err:
 351         return -1;
 352 }
 353
 354 static struct mips_frame_info schedule_mfi __read_mostly;
 355
 356 static int __init frame_info_init(void)
 357 {
 358         unsigned long size = 0;
 359 #ifdef CONFIG_KALLSYMS
 360         unsigned long ofs;
 361
 362         kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 363 #endif
 364         schedule_mfi.func = schedule;
 365         schedule_mfi.func_size = size;
 366
 367         get_frame_info(&schedule_mfi);
 368
 369         /*
 370          * Without schedule() frame info, result given by
 371          * thread_saved_pc() and get_wchan() are not reliable.
 372          */
 373         if (schedule_mfi.pc_offset < 0)
 374                 printk("Can't analyze schedule() prologue at %p\n", schedule);
 375
 376         return 0;
 377 }
 378
 379 arch_initcall(frame_info_init);
 380
 381 /*
 382  * Return saved PC of a blocked thread.
 383  */
 384 unsigned long thread_saved_pc(struct task_struct *tsk)
 385 {
 386         struct thread_struct *t = &tsk->thread;
 387
 388         /* New born processes are a special case */
 389         if (t->reg31 == (unsigned long) ret_from_fork)
 390                 return t->reg31;
 391         if (schedule_mfi.pc_offset < 0)
 392                 return 0;
 393         return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 394 }
 395
 396
 397 #ifdef CONFIG_KALLSYMS
 398 /* used by show_backtrace() */
 399 unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 400                            unsigned long pc, unsigned long *ra)
 401 {
 402         unsigned long stack_page;
 403         struct mips_frame_info info;
 404         unsigned long size, ofs;
 405         int leaf;
 406         extern void ret_from_irq(void);
 407         extern void ret_from_exception(void);
 408
 409         stack_page = (unsigned long)task_stack_page(task);
 410         if (!stack_page)
 411                 return 0;
 412
 413         /*
 414          * If we reached the bottom of interrupt context,
 415          * return saved pc in pt_regs.
 416          */
 417         if (pc == (unsigned long)ret_from_irq ||
 418             pc == (unsigned long)ret_from_exception) {
 419                 struct pt_regs *regs;
 420                 if (*sp >= stack_page &&
 421                     *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 422                         regs = (struct pt_regs *)*sp;
 423                         pc = regs->cp0_epc;
 424                         if (__kernel_text_address(pc)) {
 425                                 *sp = regs->regs[29];
 426                                 *ra = regs->regs[31];
 427                                 return pc;
 428                         }
 429                 }
 430                 return 0;
 431         }
 432         if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 433                 return 0;
 434         /*
 435          * Return ra if an exception occured at the first instruction
 436          */
 437         if (unlikely(ofs == 0)) {
 438                 pc = *ra;
 439                 *ra = 0;
 440                 return pc;
 441         }
 442
 443         info.func = (void *)(pc - ofs);
 444         info.func_size = ofs;   /* analyze from start to ofs */
 445         leaf = get_frame_info(&info);
 446         if (leaf < 0)
 447                 return 0;
 448
 449         if (*sp < stack_page ||
 450             *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 451                 return 0;
 452
 453         if (leaf)
 454                 /*
 455                  * For some extreme cases, get_frame_info() can
 456                  * consider wrongly a nested function as a leaf
 457                  * one. In that cases avoid to return always the
 458                  * same value.
 459                  */
 460                 pc = pc != *ra ? *ra : 0;
 461         else
 462                 pc = ((unsigned long *)(*sp))[info.pc_offset];
 463
 464         *sp += info.frame_size;
 465         *ra = 0;
 466         return __kernel_text_address(pc) ? pc : 0;
 467 }
 468 #endif
 469
 470 /*
 471  * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 472  */
 473 unsigned long get_wchan(struct task_struct *task)
 474 {
 475         unsigned long pc = 0;
 476 #ifdef CONFIG_KALLSYMS
 477         unsigned long sp;
 478         unsigned long ra = 0;
 479 #endif
 480
 481         if (!task || task == current || task->state == TASK_RUNNING)
 482                 goto out;
 483         if (!task_stack_page(task))
 484                 goto out;
 485
 486         pc = thread_saved_pc(task);
 487
 488 #ifdef CONFIG_KALLSYMS
 489         sp = task->thread.reg29 + schedule_mfi.frame_size;
 490
 491         while (in_sched_functions(pc))
 492                 pc = unwind_stack(task, &sp, pc, &ra);
 493 #endif
 494
 495 out:
 496         return pc;
 497 }