LXR linux/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/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>
  28
  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>
  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 */
  50void __noreturn cpu_idle(void)
  51{
  52        int cpu;
  53
  54        /* CPU is going idle. */
  55        cpu = smp_processor_id();
  56
  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);
  63
  64                        smtc_idle_loop_hook();
  65#endif
  66
  67                        if (cpu_wait) {
  68                                /* Don't trace irqs off for idle */
  69                                stop_critical_timings();
  70                                (*cpu_wait)();
  71                                start_critical_timings();
  72                        }
  73                }
  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();
  84        }
  85}
  86
  87asmlinkage void ret_from_fork(void);
  88
  89void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  90{
  91        unsigned long status;
  92
  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;
 106        current_thread_info()->addr_limit = USER_DS;
 107}
 108
 109void exit_thread(void)
 110{
 111}
 112
 113void flush_thread(void)
 114{
 115}
 116
 117int copy_thread(unsigned long clone_flags, unsigned long usp,
 118        unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 119{
 120        struct thread_info *ti = task_thread_info(p);
 121        struct pt_regs *childregs;
 122        unsigned long childksp;
 123        p->set_child_tid = p->clear_child_tid = NULL;
 124
 125        childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 126
 127        preempt_disable();
 128
 129        if (is_fpu_owner())
 130                save_fp(p);
 131
 132        if (cpu_has_dsp)
 133                save_dsp(p);
 134
 135        preempt_enable();
 136
 137        /* set up new TSS. */
 138        childregs = (struct pt_regs *) childksp - 1;
 139        /*  Put the stack after the struct pt_regs.  */
 140        childksp = (unsigned long) childregs;
 141        *childregs = *regs;
 142        childregs->regs[7] = 0; /* Clear error flag */
 143
 144        childregs->regs[2] = 0; /* Child gets zero as return value */
 145
 146        if (childregs->cp0_status & ST0_CU0) {
 147                childregs->regs[28] = (unsigned long) ti;
 148                childregs->regs[29] = childksp;
 149                ti->addr_limit = KERNEL_DS;
 150        } else {
 151                childregs->regs[29] = usp;
 152                ti->addr_limit = USER_DS;
 153        }
 154        p->thread.reg29 = (unsigned long) childregs;
 155        p->thread.reg31 = (unsigned long) ret_from_fork;
 156
 157        /*
 158         * New tasks lose permission to use the fpu. This accelerates context
 159         * switching for most programs since they don't use the fpu.
 160         */
 161        p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 162        childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 163
 164#ifdef CONFIG_MIPS_MT_SMTC
 165        /*
 166         * SMTC restores TCStatus after Status, and the CU bits
 167         * are aliased there.
 168         */
 169        childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 170#endif
 171        clear_tsk_thread_flag(p, TIF_USEDFPU);
 172
 173#ifdef CONFIG_MIPS_MT_FPAFF
 174        clear_tsk_thread_flag(p, TIF_FPUBOUND);
 175#endif /* CONFIG_MIPS_MT_FPAFF */
 176
 177        if (clone_flags & CLONE_SETTLS)
 178                ti->tp_value = regs->regs[7];
 179
 180        return 0;
 181}
 182
 183/* Fill in the fpu structure for a core dump.. */
 184int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 185{
 186        memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 187
 188        return 1;
 189}
 190
 191void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 192{
 193        int i;
 194
 195        for (i = 0; i < EF_R0; i++)
 196                gp[i] = 0;
 197        gp[EF_R0] = 0;
 198        for (i = 1; i <= 31; i++)
 199                gp[EF_R0 + i] = regs->regs[i];
 200        gp[EF_R26] = 0;
 201        gp[EF_R27] = 0;
 202        gp[EF_LO] = regs->lo;
 203        gp[EF_HI] = regs->hi;
 204        gp[EF_CP0_EPC] = regs->cp0_epc;
 205        gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 206        gp[EF_CP0_STATUS] = regs->cp0_status;
 207        gp[EF_CP0_CAUSE] = regs->cp0_cause;
 208#ifdef EF_UNUSED0
 209        gp[EF_UNUSED0] = 0;
 210#endif
 211}
 212
 213int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 214{
 215        elf_dump_regs(*regs, task_pt_regs(tsk));
 216        return 1;
 217}
 218
 219int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 220{
 221        memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 222
 223        return 1;
 224}
 225
 226/*
 227 * Create a kernel thread
 228 */
 229static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
 230{
 231        do_exit(fn(arg));
 232}
 233
 234long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 235{
 236        struct pt_regs regs;
 237
 238        memset(&regs, 0, sizeof(regs));
 239
 240        regs.regs[4] = (unsigned long) arg;
 241        regs.regs[5] = (unsigned long) fn;
 242        regs.cp0_epc = (unsigned long) kernel_thread_helper;
 243        regs.cp0_status = read_c0_status();
 244#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 245        regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 246                          ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
 247#else
 248        regs.cp0_status |= ST0_EXL;
 249#endif
 250
 251        /* Ok, create the new process.. */
 252        return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 253}
 254
 255/*
 256 *
 257 */
 258struct mips_frame_info {
 259        void            *func;
 260        unsigned long   func_size;
 261        int             frame_size;
 262        int             pc_offset;
 263};
 264
 265static inline int is_ra_save_ins(union mips_instruction *ip)
 266{
 267        /* sw / sd $ra, offset($sp) */
 268        return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 269                ip->i_format.rs == 29 &&
 270                ip->i_format.rt == 31;
 271}
 272
 273static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 274{
 275        if (ip->j_format.opcode == jal_op)
 276                return 1;
 277        if (ip->r_format.opcode != spec_op)
 278                return 0;
 279        return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 280}
 281
 282static inline int is_sp_move_ins(union mips_instruction *ip)
 283{
 284        /* addiu/daddiu sp,sp,-imm */
 285        if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 286                return 0;
 287        if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 288                return 1;
 289        return 0;
 290}
 291
 292static int get_frame_info(struct mips_frame_info *info)
 293{
 294        union mips_instruction *ip = info->func;
 295        unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 296        unsigned i;
 297
 298        info->pc_offset = -1;
 299        info->frame_size = 0;
 300
 301        if (!ip)
 302                goto err;
 303
 304        if (max_insns == 0)
 305                max_insns = 128U;       /* unknown function size */
 306        max_insns = min(128U, max_insns);
 307
 308        for (i = 0; i < max_insns; i++, ip++) {
 309
 310                if (is_jal_jalr_jr_ins(ip))
 311                        break;
 312                if (!info->frame_size) {
 313                        if (is_sp_move_ins(ip))
 314                                info->frame_size = - ip->i_format.simmediate;
 315                        continue;
 316                }
 317                if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 318                        info->pc_offset =
 319                                ip->i_format.simmediate / sizeof(long);
 320                        break;
 321                }
 322        }
 323        if (info->frame_size && info->pc_offset >= 0) /* nested */
 324                return 0;
 325        if (info->pc_offset < 0) /* leaf */
 326                return 1;
 327        /* prologue seems boggus... */
 328err:
 329        return -1;
 330}
 331
 332static struct mips_frame_info schedule_mfi __read_mostly;
 333
 334static int __init frame_info_init(void)
 335{
 336        unsigned long size = 0;
 337#ifdef CONFIG_KALLSYMS
 338        unsigned long ofs;
 339
 340        kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 341#endif
 342        schedule_mfi.func = schedule;
 343        schedule_mfi.func_size = size;
 344
 345        get_frame_info(&schedule_mfi);
 346
 347        /*
 348         * Without schedule() frame info, result given by
 349         * thread_saved_pc() and get_wchan() are not reliable.
 350         */
 351        if (schedule_mfi.pc_offset < 0)
 352                printk("Can't analyze schedule() prologue at %p\n", schedule);
 353
 354        return 0;
 355}
 356
 357arch_initcall(frame_info_init);
 358
 359/*
 360 * Return saved PC of a blocked thread.
 361 */
 362unsigned long thread_saved_pc(struct task_struct *tsk)
 363{
 364        struct thread_struct *t = &tsk->thread;
 365
 366        /* New born processes are a special case */
 367        if (t->reg31 == (unsigned long) ret_from_fork)
 368                return t->reg31;
 369        if (schedule_mfi.pc_offset < 0)
 370                return 0;
 371        return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 372}
 373
 374
 375#ifdef CONFIG_KALLSYMS
 376/* used by show_backtrace() */
 377unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 378                           unsigned long pc, unsigned long *ra)
 379{
 380        unsigned long stack_page;
 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);
 386
 387        stack_page = (unsigned long)task_stack_page(task);
 388        if (!stack_page)
 389                return 0;
 390
 391        /*
 392         * If we reached the bottom of interrupt context,
 393         * return saved pc in pt_regs.
 394         */
 395        if (pc == (unsigned long)ret_from_irq ||
 396            pc == (unsigned long)ret_from_exception) {
 397                struct pt_regs *regs;
 398                if (*sp >= stack_page &&
 399                    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 400                        regs = (struct pt_regs *)*sp;
 401                        pc = regs->cp0_epc;
 402                        if (__kernel_text_address(pc)) {
 403                                *sp = regs->regs[29];
 404                                *ra = regs->regs[31];
 405                                return pc;
 406                        }
 407                }
 408                return 0;
 409        }
 410        if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 411                return 0;
 412        /*
 413         * Return ra if an exception occurred at the first instruction
 414         */
 415        if (unlikely(ofs == 0)) {
 416                pc = *ra;
 417                *ra = 0;
 418                return pc;
 419        }
 420
 421        info.func = (void *)(pc - ofs);
 422        info.func_size = ofs;   /* analyze from start to ofs */
 423        leaf = get_frame_info(&info);
 424        if (leaf < 0)
 425                return 0;
 426
 427        if (*sp < stack_page ||
 428            *sp + info.frame_size > stack_page + THREAD_SIZE - 32)
 429                return 0;
 430
 431        if (leaf)
 432                /*
 433                 * For some extreme cases, get_frame_info() can
 434                 * consider wrongly a nested function as a leaf
 435                 * one. In that cases avoid to return always the
 436                 * same value.
 437                 */
 438                pc = pc != *ra ? *ra : 0;
 439        else
 440                pc = ((unsigned long *)(*sp))[info.pc_offset];
 441
 442        *sp += info.frame_size;
 443        *ra = 0;
 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 */
 451unsigned long get_wchan(struct task_struct *task)
 452{
 453        unsigned long pc = 0;
 454#ifdef CONFIG_KALLSYMS
 455        unsigned long sp;
 456        unsigned long ra = 0;
 457#endif
 458
 459        if (!task || task == current || task->state == TASK_RUNNING)
 460                goto out;
 461        if (!task_stack_page(task))
 462                goto out;
 463
 464        pc = thread_saved_pc(task);
 465
 466#ifdef CONFIG_KALLSYMS
 467        sp = task->thread.reg29 + schedule_mfi.frame_size;
 468
 469        while (in_sched_functions(pc))
 470                pc = unwind_stack(task, &sp, pc, &ra);
 471#endif
 472
 473out:
 474        return pc;
 475}
 476
 477/*
 478 * Don't forget that the stack pointer must be aligned on a 8 bytes
 479 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 480 */
 481unsigned long arch_align_stack(unsigned long sp)
 482{
 483        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 484                sp -= get_random_int() & ~PAGE_MASK;
 485
 486        return sp & ALMASK;
 487}
 488