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