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/sched.h>
  13#include <linux/tick.h>
  14#include <linux/kernel.h>
  15#include <linux/mm.h>
  16#include <linux/stddef.h>
  17#include <linux/unistd.h>
  18#include <linux/export.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_idle_enter();
  60                rcu_idle_enter();
  61                while (!need_resched() && cpu_online(cpu)) {
  62#ifdef CONFIG_MIPS_MT_SMTC
  63                        extern void smtc_idle_loop_hook(void);
  64
  65                        smtc_idle_loop_hook();
  66#endif
  67
  68                        if (cpu_wait) {
  69                                /* Don't trace irqs off for idle */
  70                                stop_critical_timings();
  71                                (*cpu_wait)();
  72                                start_critical_timings();
  73                        }
  74                }
  75#ifdef CONFIG_HOTPLUG_CPU
  76                if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
  77                    (system_state == SYSTEM_RUNNING ||
  78                     system_state == SYSTEM_BOOTING))
  79                        play_dead();
  80#endif
  81                rcu_idle_exit();
  82                tick_nohz_idle_exit();
  83                preempt_enable_no_resched();
  84                schedule();
  85                preempt_disable();
  86        }
  87}
  88
  89asmlinkage void ret_from_fork(void);
  90
  91void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
  92{
  93        unsigned long status;
  94
  95        /* New thread loses kernel privileges. */
  96        status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
  97#ifdef CONFIG_64BIT
  98        status |= test_thread_flag(TIF_32BIT_REGS) ? 0 : ST0_FR;
  99#endif
 100        status |= KU_USER;
 101        regs->cp0_status = status;
 102        clear_used_math();
 103        clear_fpu_owner();
 104        if (cpu_has_dsp)
 105                __init_dsp();
 106        regs->cp0_epc = pc;
 107        regs->regs[29] = sp;
 108}
 109
 110void exit_thread(void)
 111{
 112}
 113
 114void flush_thread(void)
 115{
 116}
 117
 118int copy_thread(unsigned long clone_flags, unsigned long usp,
 119        unsigned long unused, struct task_struct *p, struct pt_regs *regs)
 120{
 121        struct thread_info *ti = task_thread_info(p);
 122        struct pt_regs *childregs;
 123        unsigned long childksp;
 124        p->set_child_tid = p->clear_child_tid = NULL;
 125
 126        childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
 127
 128        preempt_disable();
 129
 130        if (is_fpu_owner())
 131                save_fp(p);
 132
 133        if (cpu_has_dsp)
 134                save_dsp(p);
 135
 136        preempt_enable();
 137
 138        /* set up new TSS. */
 139        childregs = (struct pt_regs *) childksp - 1;
 140        /*  Put the stack after the struct pt_regs.  */
 141        childksp = (unsigned long) childregs;
 142        *childregs = *regs;
 143        childregs->regs[7] = 0; /* Clear error flag */
 144
 145        childregs->regs[2] = 0; /* Child gets zero as return value */
 146
 147        if (childregs->cp0_status & ST0_CU0) {
 148                childregs->regs[28] = (unsigned long) ti;
 149                childregs->regs[29] = childksp;
 150                ti->addr_limit = KERNEL_DS;
 151        } else {
 152                childregs->regs[29] = usp;
 153                ti->addr_limit = USER_DS;
 154        }
 155        p->thread.reg29 = (unsigned long) childregs;
 156        p->thread.reg31 = (unsigned long) ret_from_fork;
 157
 158        /*
 159         * New tasks lose permission to use the fpu. This accelerates context
 160         * switching for most programs since they don't use the fpu.
 161         */
 162        p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
 163        childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
 164
 165#ifdef CONFIG_MIPS_MT_SMTC
 166        /*
 167         * SMTC restores TCStatus after Status, and the CU bits
 168         * are aliased there.
 169         */
 170        childregs->cp0_tcstatus &= ~(ST0_CU2|ST0_CU1);
 171#endif
 172        clear_tsk_thread_flag(p, TIF_USEDFPU);
 173
 174#ifdef CONFIG_MIPS_MT_FPAFF
 175        clear_tsk_thread_flag(p, TIF_FPUBOUND);
 176#endif /* CONFIG_MIPS_MT_FPAFF */
 177
 178        if (clone_flags & CLONE_SETTLS)
 179                ti->tp_value = regs->regs[7];
 180
 181        return 0;
 182}
 183
 184/* Fill in the fpu structure for a core dump.. */
 185int dump_fpu(struct pt_regs *regs, elf_fpregset_t *r)
 186{
 187        memcpy(r, &current->thread.fpu, sizeof(current->thread.fpu));
 188
 189        return 1;
 190}
 191
 192void elf_dump_regs(elf_greg_t *gp, struct pt_regs *regs)
 193{
 194        int i;
 195
 196        for (i = 0; i < EF_R0; i++)
 197                gp[i] = 0;
 198        gp[EF_R0] = 0;
 199        for (i = 1; i <= 31; i++)
 200                gp[EF_R0 + i] = regs->regs[i];
 201        gp[EF_R26] = 0;
 202        gp[EF_R27] = 0;
 203        gp[EF_LO] = regs->lo;
 204        gp[EF_HI] = regs->hi;
 205        gp[EF_CP0_EPC] = regs->cp0_epc;
 206        gp[EF_CP0_BADVADDR] = regs->cp0_badvaddr;
 207        gp[EF_CP0_STATUS] = regs->cp0_status;
 208        gp[EF_CP0_CAUSE] = regs->cp0_cause;
 209#ifdef EF_UNUSED0
 210        gp[EF_UNUSED0] = 0;
 211#endif
 212}
 213
 214int dump_task_regs(struct task_struct *tsk, elf_gregset_t *regs)
 215{
 216        elf_dump_regs(*regs, task_pt_regs(tsk));
 217        return 1;
 218}
 219
 220int dump_task_fpu(struct task_struct *t, elf_fpregset_t *fpr)
 221{
 222        memcpy(fpr, &t->thread.fpu, sizeof(current->thread.fpu));
 223
 224        return 1;
 225}
 226
 227/*
 228 * Create a kernel thread
 229 */
 230static void __noreturn kernel_thread_helper(void *arg, int (*fn)(void *))
 231{
 232        do_exit(fn(arg));
 233}
 234
 235long kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
 236{
 237        struct pt_regs regs;
 238
 239        memset(&regs, 0, sizeof(regs));
 240
 241        regs.regs[4] = (unsigned long) arg;
 242        regs.regs[5] = (unsigned long) fn;
 243        regs.cp0_epc = (unsigned long) kernel_thread_helper;
 244        regs.cp0_status = read_c0_status();
 245#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
 246        regs.cp0_status = (regs.cp0_status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
 247                          ((regs.cp0_status & (ST0_KUC | ST0_IEC)) << 2);
 248#else
 249        regs.cp0_status |= ST0_EXL;
 250#endif
 251
 252        /* Ok, create the new process.. */
 253        return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, &regs, 0, NULL, NULL);
 254}
 255
 256/*
 257 *
 258 */
 259struct mips_frame_info {
 260        void            *func;
 261        unsigned long   func_size;
 262        int             frame_size;
 263        int             pc_offset;
 264};
 265
 266static inline int is_ra_save_ins(union mips_instruction *ip)
 267{
 268        /* sw / sd $ra, offset($sp) */
 269        return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
 270                ip->i_format.rs == 29 &&
 271                ip->i_format.rt == 31;
 272}
 273
 274static inline int is_jal_jalr_jr_ins(union mips_instruction *ip)
 275{
 276        if (ip->j_format.opcode == jal_op)
 277                return 1;
 278        if (ip->r_format.opcode != spec_op)
 279                return 0;
 280        return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
 281}
 282
 283static inline int is_sp_move_ins(union mips_instruction *ip)
 284{
 285        /* addiu/daddiu sp,sp,-imm */
 286        if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
 287                return 0;
 288        if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
 289                return 1;
 290        return 0;
 291}
 292
 293static int get_frame_info(struct mips_frame_info *info)
 294{
 295        union mips_instruction *ip = info->func;
 296        unsigned max_insns = info->func_size / sizeof(union mips_instruction);
 297        unsigned i;
 298
 299        info->pc_offset = -1;
 300        info->frame_size = 0;
 301
 302        if (!ip)
 303                goto err;
 304
 305        if (max_insns == 0)
 306                max_insns = 128U;       /* unknown function size */
 307        max_insns = min(128U, max_insns);
 308
 309        for (i = 0; i < max_insns; i++, ip++) {
 310
 311                if (is_jal_jalr_jr_ins(ip))
 312                        break;
 313                if (!info->frame_size) {
 314                        if (is_sp_move_ins(ip))
 315                                info->frame_size = - ip->i_format.simmediate;
 316                        continue;
 317                }
 318                if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
 319                        info->pc_offset =
 320                                ip->i_format.simmediate / sizeof(long);
 321                        break;
 322                }
 323        }
 324        if (info->frame_size && info->pc_offset >= 0) /* nested */
 325                return 0;
 326        if (info->pc_offset < 0) /* leaf */
 327                return 1;
 328        /* prologue seems boggus... */
 329err:
 330        return -1;
 331}
 332
 333static struct mips_frame_info schedule_mfi __read_mostly;
 334
 335static int __init frame_info_init(void)
 336{
 337        unsigned long size = 0;
 338#ifdef CONFIG_KALLSYMS
 339        unsigned long ofs;
 340
 341        kallsyms_lookup_size_offset((unsigned long)schedule, &size, &ofs);
 342#endif
 343        schedule_mfi.func = schedule;
 344        schedule_mfi.func_size = size;
 345
 346        get_frame_info(&schedule_mfi);
 347
 348        /*
 349         * Without schedule() frame info, result given by
 350         * thread_saved_pc() and get_wchan() are not reliable.
 351         */
 352        if (schedule_mfi.pc_offset < 0)
 353                printk("Can't analyze schedule() prologue at %p\n", schedule);
 354
 355        return 0;
 356}
 357
 358arch_initcall(frame_info_init);
 359
 360/*
 361 * Return saved PC of a blocked thread.
 362 */
 363unsigned long thread_saved_pc(struct task_struct *tsk)
 364{
 365        struct thread_struct *t = &tsk->thread;
 366
 367        /* New born processes are a special case */
 368        if (t->reg31 == (unsigned long) ret_from_fork)
 369                return t->reg31;
 370        if (schedule_mfi.pc_offset < 0)
 371                return 0;
 372        return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
 373}
 374
 375
 376#ifdef CONFIG_KALLSYMS
 377/* generic stack unwinding function */
 378unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
 379                                              unsigned long *sp,
 380                                              unsigned long pc,
 381                                              unsigned long *ra)
 382{
 383        struct mips_frame_info info;
 384        unsigned long size, ofs;
 385        int leaf;
 386        extern void ret_from_irq(void);
 387        extern void ret_from_exception(void);
 388
 389        if (!stack_page)
 390                return 0;
 391
 392        /*
 393         * If we reached the bottom of interrupt context,
 394         * return saved pc in pt_regs.
 395         */
 396        if (pc == (unsigned long)ret_from_irq ||
 397            pc == (unsigned long)ret_from_exception) {
 398                struct pt_regs *regs;
 399                if (*sp >= stack_page &&
 400                    *sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
 401                        regs = (struct pt_regs *)*sp;
 402                        pc = regs->cp0_epc;
 403                        if (__kernel_text_address(pc)) {
 404                                *sp = regs->regs[29];
 405                                *ra = regs->regs[31];
 406                                return pc;
 407                        }
 408                }
 409                return 0;
 410        }
 411        if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
 412                return 0;
 413        /*
 414         * Return ra if an exception occurred at the first instruction
 415         */
 416        if (unlikely(ofs == 0)) {
 417                pc = *ra;
 418                *ra = 0;
 419                return pc;
 420        }
 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        *ra = 0;
 445        return __kernel_text_address(pc) ? pc : 0;
 446}
 447EXPORT_SYMBOL(unwind_stack_by_address);
 448
 449/* used by show_backtrace() */
 450unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
 451                           unsigned long pc, unsigned long *ra)
 452{
 453        unsigned long stack_page = (unsigned long)task_stack_page(task);
 454        return unwind_stack_by_address(stack_page, sp, pc, ra);
 455}
 456#endif
 457
 458/*
 459 * get_wchan - a maintenance nightmare^W^Wpain in the ass ...
 460 */
 461unsigned long get_wchan(struct task_struct *task)
 462{
 463        unsigned long pc = 0;
 464#ifdef CONFIG_KALLSYMS
 465        unsigned long sp;
 466        unsigned long ra = 0;
 467#endif
 468
 469        if (!task || task == current || task->state == TASK_RUNNING)
 470                goto out;
 471        if (!task_stack_page(task))
 472                goto out;
 473
 474        pc = thread_saved_pc(task);
 475
 476#ifdef CONFIG_KALLSYMS
 477        sp = task->thread.reg29 + schedule_mfi.frame_size;
 478
 479        while (in_sched_functions(pc))
 480                pc = unwind_stack(task, &sp, pc, &ra);
 481#endif
 482
 483out:
 484        return pc;
 485}
 486
 487/*
 488 * Don't forget that the stack pointer must be aligned on a 8 bytes
 489 * boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
 490 */
 491unsigned long arch_align_stack(unsigned long sp)
 492{
 493        if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
 494                sp -= get_random_int() & ~PAGE_MASK;
 495
 496        return sp & ALMASK;
 497}
 498