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